eChapters

India, one of the largest food producer countries (I in milk production, II in fruit and vegetable production and III in food grain production at world level), possesses the potential of being the biggest with the food and agricultural sector contributing around 26 percent of the Gross Domestic Product (GDP). It is a paradox that people of the country producing such huge quantities of food including fruits, vegetables, milk, cereals grains etc. are still suffering from many nutritional deficiencies in their diet, and even in some places, the stomachs of people remain unfilled for the want of food. The credit of this would predominantly go to the poor postharvest infrastructure as well as knowhow and accessibility to the facilities. All this makes us one among those countries having largest postharvest losses. The reduction of losses occuring during food handling, processing, storage, distribution and use would be an indirect way of increasing the food production and making the country self-sufficient in nutritional requirements.

Physiological Development

Fruits and vegetables can be divided into 3 stages based n their physiological development i.e. growth, maturation and senescence.

Growth: This generally refers to cell division, enlargement and differentiation ultimately giving a particular size, weight and volume to the commodity.

Maturation: It is initiated before the ceasation of growth and lasts till the onset of senescence.

Senescence: The stage when anabolic (synthetic) processes almost terminate and catabolic (degradative) processes are initiated and speeded up causing ageing and finally death of tissues.

Ripening: Stage that begins with the last stages of maturation and lasts till the beginning (first stage) of senescence. Ripening is a very important event in the life of a plant as it transforms a physiologically mature but inedible (or not preferred to be eaten) plant part into an edible, visually and olfactorily attractive and tasty commodity. Ripening marks the completion of developmental phase and is an irrevessible event.

Maturity Standards and Harvesting Indices

Harvesting : Harvesting is detaching a commodity from the point of its origin. This point of origin may be an above ground plant part i.e. shoot eg. apple, tomato etc. or an underground plant part eg potato, carrot, etc. or in water i.e. harvesting of fish from a pond (not to be covered in this book).

Storage : It can be defined as keeping the commodity fresh or processed in safe condition with minimum of deteriorative changes for later use.

Reasons of Deterioration During Storage

Packaging : Packaging of fruits, vegetables, flowers or any other commodity is chiefly done to assemble the produce in convenient units of different sizes, shapes & types for storage, transportation, marketing and distribution. The size of units may vary depending on the requirement e.g for retail marketing smaller units are preferred and for bulk transportation and storage, large units would be more convenient.

Why do we Require Packaging?

Imagine there is no packaging material and technology available. How we are going to transport apple, mango etc. to distant markets? Definitely as loose. Then how can we weigh or count the fruits being transported or marketed? This would be very difficult. Had there been no packaging the commodity would have suffered great physical, chemical and microbiological losses. It would have been very difficult to handle, manage, transport and market the produce as loose and unpacked. Therefore, the packaging of fresh as well as processed commodities was needed to contain, unitize and protect the produce.

Nature has made such a beautiful system that a fruit does not spoil unless its outer covering is removed and till it is there on the plant. For example banana will not spoil for long time if we do not remove its peel. Similar is the case with apple, guava, mango and many other fruits and vegetables. But as soon as the outer covering is removed the damage begins and the commodity is spoilt very soon.

Preservation is extending shelf life of fresh or processed food by using various methods and prevention or reduction of spoilage. Better the preservation, lesser the spoilage, more the spoilage poorer and inefficient is the preservation.

Therefore, in order to prevent or reduce the spoilage, we have to first identify and understand the causes of spoilage. There are chiefly 3 agencies that cause spoilage in fruits and vegetables i.e. (i) microorganisms, (ii) enzymes & chemical changes and (iii) man, animals, rodents, insects, etc. For effective preservation we have to check the growth and activity of these spoilage causing agencies. So, in order to prevent spoilage and preserve a perishable commodity for long time the following principles and methods are to be followed.

Essentials for Quality Product Preparation

Plant ripened red tomatoes should be selected. Yellow and green fruits on processing yield dull colour and turn brown due to oxidation.

Never use iron equipment for processing. Lycopene oxidizes and turns brown when comes in contact with iron. It also forms black compounds with the tannins present in tomatoes or the spices which are used for product preparation.

Avoid prolonged heating and cool immediately to avoid over-cooking.

Pickles known to be good appetizers, aid digestion and pallate are edible products preserved and flavoured in a solution of common salt and vinegar. Spices and oil may also be added. There are a number of pickles very popular in India i.e. mango pickle, cauliflower pickle, lime and lemon pickles, ginger chilli pickle etc. But, some pickles like Sauerkraut are not very common in India but are very popular in European countries.

Jam : It is a product prepared by boiling to a suitable consistency, fruit pulp with sufficient quantity of sugar, acid and pectin so as to set and become firm enough to hold the tissues in position. About 45 parts of pulp are used with every 55 parts of sugar. The finished product should not contain less than 68 per cent total soluble solids.

Jelly : Jelly is prepared by boiling the fruit pectin extract with sugar in the presence of appropriate amounts of acid so as to set into a clear gel. A perfect jelly is transparent, devoid of haziness or any suspended material well set, but not too stiff and should have original flavour of the fruit. When cut it should retain its shape and show a smooth cut surface.

Marmalade : It is a fruit jelly like product in which slices of fruit or peel are suspended in the set gel. Mostly they are prepared from citrus fruits like oranges, lemons etc.

Canning : Process of preservation of various food stuffs including fruits and vegetables whole or in pieces, in sugar syrup or brine by heat processing them in hermetically sealed containers.

Drying/ Dehydration means the process of removal of water.

Drying : Removal of water (moisture) by using non conventional energy sources like Sun or wind.

Dehydration : Process of removal of moisture by the application of artificial heat under controlled conditions of temperature and / or humidity and air flow.

Freezing : Freezing is a process where temperature of food (fruits, vegetable etc.) is lowered down considerably below freezing point so that the water present inside the food undergoes change in state from liquid to solid (ice) and gets frozen immediately eg Frozen Pea. Water is immobilized and solutes are concentrated to reduce the water activity.

Principles of preservation : Combination of low temperature, low water activity, and pre-treatments like blanching, dipping in sugar syrup etc. stop (reduce) the growth and activity of microorganisms.

Theory of freezing : Freezing takes place in two main steps

Beverage: It includes all drinks whether they are fermented or unfermented, prepared from fruits or non-fruit, sweetened or unsweetened eg. tea, coffee, coca cola, cider, maaza are all beverages.

Fruit Beverages : Beverage which is prepared partly or fully from fruit juice or pulps with or without additives eg. pure fruit juice, squash, cordial, RTS beverage etc.

Non-fruit Beverage : Beverage which does not contain any fruit part eg. Coca cola, pepsi, sherbet etc.

Unfermented Juice or Pure Fruit Juice: This is the natural juice pressed out of the fruit and practically its composition remains unaltered during preparation and preservation. No additives like sugar, acid, water etc. are added. eg apple juice, orange juice.

Fruit Juice Beverage: This is the fruit juice that has been considerably altered in composition by adding water, sugar, acid, flavour, colours, preservatives etc. before consumption. It may or may not be diluted before it is served as a drink eg. squashes, nectars, appetizers etc.

Alcoholic Beverages

These are the beverages which are prepared after alcoholic fermentation of sugars by yeast, contain varying amounts of ethyl alcohol (5-42%), and are consumed directly or after dilution in water.

Wine : Product made by alcoholic fermentation of grapes or grape juice unless otherwise specified, by yeast (Saccharomyces cerevisiae and a subsequent ageing process. Alcohol content is 11-14 %, but may be as low as 7%.

Enzymes are biocatalysts that change the rate of reaction without being changed themselves. All (Most) enzymes are proteins but all proteins are not enzymes. Ribonuclease is the enzyme which is non- protein in nature.

Properties of Enzymes

Spoilage may be defined as the deteriorative process which renders the food inedible or results into reduction of quality.

Spoilage is Mainly of Two Types

Abiotic Spoilage: Less potential for causing health hazards to consumers. Occurs due to

In a commercial horticultural enterprise, if the product is not marketed properly, safely and beneficially, all the investment, inputs, hard work goes in vain. Basically every commodity that is produced should reach the consumer and marketing is all about how the commodity reaches the consumer. There is no fun of producing any commodity if it does not reach the consumer.

The word market has been derived form Latin word “marcatus” meaning merchandise, where people conduct business. Market therefore refers to place where goods/ commodity and services are bought and sold.

Marketing is a sum total of business activities through which the goods and services are either bought or sold. Cundiff and Still defined marketing as “the business process by which products are matched with markets and through which transfer of ownership are affected.

Why Marketing of Fruits and Vegetables is Complex and Risky as Compared to Other Goods

Before beginning the actual work on the establishment of a Fruit and Vegetable Processing Industry the following points should be considered:

Availability and possibilities of obtaining Funds: Investment of own money or obtaining loans from banks etc.

The scale of industry (Large, Small, Cottage or Home): Has to be decided based on availability of raw material, funds availability, land, labour and other resources.

The location: The processing unit should be located near to the actual production site of raw material so that the transportation costs of high bulk raw materials is reduced. There is no fun or justification of establishing apple processing industry in Lucknow or Bangalore and mango processing industry in Shimla as the related raw materials would have to be transported through long distances.

Site: Site selected in the location should be sunny area free from dampness and sufficient space for waste disposal should be ensured.

With the increasing health consciousness of consumers, there has been an increasing concern over the use of thermal processing methods like blanching, pasteurization, sterilization etc. for enhancing the shelf life of foods as these methods fail to preserve the fresh like nutritional, therapeutical and sensory qualities of the food. With the increased consumer demand for fresh and fresh-like foods, interest in minimal processing of foods is increasing. The trend is also shifting from the traditional heat processing to those technologies that employ no or minimum heat application, thereby retaining the quality to a maximum level. One of the ways to accomplish this is via use of non-thermal processes. Over the past few years a number of non-thermal processes or cold preservation methods have been invented and developed. These methods are being evaluated in pasteurization and sterilization of various foods or in the extension of shelf life of various packaged foods. Some of such novel technologies and the products prepared, have been discussed here under.

1. Extrusion

Extrusion is a size enlargement process wherein small granular food or powdered particles are re-formed into larger pieces with different shapes, textures, colours and flavours from the basic ingredients. In extrusion food is compressed and forced to pass through a fine opening (die). As soon as it comes out of the opening, the outside pressure is very less as compared to the pressure inside the screw of extruder and the food expands instantaneously. If the food is heated the process is called as extrusion cooking. It is a process which combines several unit operations including cooking, mixing, kneading, shearing, compressing, shaping and forming. Extrusion adds a variety to the products by changing shape, size, texture and even some of the minor ingredients of the food and at a reduced cost than most of the other processing methods. Extrusion cooking (not extrusion) is a high temperature short time (HTST) process that reduces microbial contamination and inactivates enzymes.

1. Multiple Choice Questions

1.1 THE IMPORTANCE OF SOILS

Soils are the medium in which crops grow, and so they are essential to the provision of the food and fibre to sustain mankind. But besides the immense importance of this role they are an essential component to life as we know it because of their action as a buffer to control the flow of water between sky, land and sea. They are also a sink, and usually a safe sink, for many of the chemicals that might otherwise make life difficult or unpleasant.

As with other natural resources, it is important that soils are used conservatively, so that the advantages we enjoy from them now can continue to be enjoyed in the future. To do this we need to understand them, to understand the flow of nutrients from soil to plants, and back to the soil or the sea in food chains and water flow. We need to understand the processes by which rocks alter to form soils, and how fast or how slowly the process occurs in different conditions. We need to understand the decay of plant materials in the soil, and how the products of decay help to make the soil a better place for plants to grow.

The chemistry of the constituents of soils, and of the processes by which changes occur, is not simple. Nevertheless we have learnt much about it, and can apply that knowledge to ensure that soils continue their important functions, and are not exploited so that they become infertile, nor used in such a way that the fertile topsoil is lost by erosion by wind or water.

2.1 INTRODUCTION

Textural assessment has long been used to indicate quality in agricultural soil and although it contains an element of subjective judgement, a skilled surveyor can differentiate many grades of texture. Soil texture correlates with the distribution of particle size in the soil, though this is not the only component in texture. Although particle size distribution is an objective attribute of soils and can, in principle, be measured with accuracy, the determination is in practice quite difficult and certainly laborious, so that it is customary in soil mechanical analysis to divide the soil into several broad fractions: sand, silt and clay are the principal categories. The clay fraction, which comprises the smallest particles in the soil, is generally defined as the fraction smaller than a nominal diameter of 2 jam. The practical division is, however, based on the velocity of fall of soil particles through a fluid, calculating the diameter of the particles from the equation of Stokes

3.1 INTRODUCTION

The complete soil organic fraction is made up of live organisms, and their undecomposed, partly decomposed and completely transformed remains. Soil organic matter is the term used to refer more specifically to the non-living components which are a heterogeneous mixture composed largely of products resulting from microbial and chemical transformations of organic debris. These transformations, known collectively as the humification process, give rise to humus, a mixture of substances which have a degree of resistance to further microbial attack.

4.1 INTRODUCTION

It has been suggested that the relationship of surface chemistry to soil science is similar to that of biochemistry to biology. Certainly the fact that surfaces of soil particles are extensive and reactive leads to a dominance of surface chemistry in soil behaviour, but it is not an exclusive relationship, because many precipitation reactions, oxidation and reduction processes, and biological reactions take place more or less independently of the surface processes. Nevertheless it is difficult to understand soil properties fully without an appreciation of the nature and extent of the surfaces of the soil constituents, and this chapter is devoted to a discussion of this topic.

5.1 INTRODUCTION: THE PHYSICAL CHEMISTRY OF COLLOIDAL SUSPENSIONS

This chapter is concerned with understanding the factors which influence the partition of ions between solid surfaces and aqueous solutions. There are many aspects of soil science such as some of those concerned with soil formation, transfer of nutrient ions from soil particles to plant roots, soil pollutant interaction and soil management which are critically dependent on what happens in the space of the order of 1 nm wide between solid and equilibrium solution. A broad survey of the development of ideas on soil-electrolyte interaction shows that there have been two main avenues of approach. One views the soil as an electrically charged surface with its adsorbed hydrated ions as one phase in equilibrium with solution, which is seen as the second phase. The other approach focuses on the electrical double layer extending from the charged solid surface out into the solution. In the latter approach the solid surface, the outer equilibrium solution and the make up of the transition zone between these two phases must all be involved in any detailed consideration of the micro structure of the system. For a full and proper understanding of soil-electrolyte interaction anything less than a detailed analysis of the micro-structure is likely to be inadequate and in this it must be remembered that the interaction between electrical double layers which overlap with one another is likely to be important.

6.1 INTRODUCTION

Water in soils is essential to plant growth, being the medium through which inorganic nutrients are translocated to the root surface and carried through the plant. Most of the water in soils at or near field saturation can be considered as equivalent to bulk water, and only bulk properties need be considered in discussing its movement through soil interstices and its retention in soil capillaries; this is the field with which soil physics deals. But, in the first molecular layer in contact with soil particles, and perhaps for several molecular layers beyond, the behaviour of water molecules is very different from that in the bulk. Strong adsorptive forces can reduce the volatility of these molecules and restrict their mobility. Such an adsorbed layer of water competes with other polar molecules for adsorption sites, and so has an important role in determining the release and retention of fertilizers and pesticides. Such strongly adsorbed layers confer wettability on soils, but hydrophobic surfaces can also be present and these lead to non-wettable soils with serious consequences in run off and inefficient use of precipitation. This region of distinctive molecular interactions between water and soil particles falls within the field of soil chemistry.

Historical Account on Vegetable Cultivation in India

The vegetables have chequered history in India which dates back to prehistoric period before the arrival of Aryans in India (c. 1500-1000 BC). During the pre-historic times before the arrival of Aryans in India, the Proto-Australoids (Nisada) used brinjal, bottle gourd and watermelon as vegetables. Pea existed in India much before the Aryans came to the country and it was already present in Western Asia prior to its cultivation. The pea, most likely the field pea (Pisum sativum subsp. sativum var. arvense L.) was eaten during the Harappan civilization as evidenced from the archaeological excavations of Mohenjo-daro and Harappa (2500-1750 B.C.) in which carbonized pea seeds were discovered. Pea seeds were also found from Neolithic site (last stage of the Stone age) of Chirand in Bihar (situated 10 Km south-east of Chapra), Chacolithic site (period or Copper Age) of Maheshwar Nevdatoli (c. 1200 BC.) in Madhya Pradesh and part of Osmanabad district in Maharashtra. The presence of seeds of melon along with wheat was also recorded from the Harappan excavation. Plant remains of Chenopodium album, Portulaca oleracea and a few species of Solanaceae, Polygonaceae and Labiatae family during Mesolithic times (Middle Stone Age) were found at Mesolithic site of Damdama, Uttar Pradesh (c. 7000-6000 BC). Wood charcoals of plant remains of Lablab purpureus were found from the early phase of Indus-Saraswati (Sarasvati) or Indus Ghaggar-Hakra civilization (c. 3100-2800 BC). Kundru (Coccinia indica), cowpea and field pea were recorded from Hulas in Saharanpur district, Uttar Pradesh, late Indus valley civilization archeological site. Carbonized seeds of hyacinth bean (dolichos bean), peas, Phaseolus, Vigna and melon from Rojdi in Gujarat and Chenopodium and amaranth from Surkotada, Gujarat (c. 2300-1800 BC), both being the archaeological sites belonging to the Indus valley civilization also suggested the existence of vegetables in India in the pre-historic times. Among the vegetables eaten during the pre-historic period, like brinjal, bottle gourd, watermelon, peas and melon as mentioned earlier, only brinjal has its origin in India while the other were brought from other countries much before the arrival of the Aryans. It is difficult to understand how a few important Indian native vegetables, like cucumber, Luffa (smooth and ridge gourd), pointed gourd and Dolichos bean (Lablab purpureus) were not known at that time. Similarly okra which has a secondary centre of origin in India has not been mentioned in any ancient literature. However, Abelmoschus moschatus called “Lata kasturika” in Sanskrit as a source of perfume has been recorded in Carak Samhita. The use of bottle gourd, which is not a native vegetable, is known from pre-historic times. Its dried fruit-shell is used as a hand jug (utensils) by saints and monks and in musical string instruments, like ektara, tamboora, tanpura, sitar and veena. Even mythological paintings have always delineated Naradmuni with tamboora in his hand and the goddess Saraswati with Veena which suggest the antiquity of bottle gourd in India. However, its date of introduction and the place from where it came remain unrecorded. It is also not mentioned in any iconography of the Medieval period (9^th and 10^th Century AD).

Food, at the fundamental level, is viewed as a source of nutrition to meet daily requirements at a minimum in order to survive but with an ever greater focus on the desire to thrive. Nutritional security denotes the consumption and physiological use of adequate quantities of safe and nutritious food by every member of the family and encompasses the process of equitable distribution among members of household and communities. This would entail the need to ensure a varied food intake, comprising all the essential macro- and micronutrients (protein, carbohydrates, minerals and vitamins), plant pigments (lycopene, β- carotene, anthocianin, lutein, capsanthin, zeaxanthin, etc.) and other functional phytochemicals (secondary metabolites, like flavonoids, isothiocyanates, glucosinolates, etc.) through a diversified diet. The growing awareness in recent years of the health promoting food has directed increased attention to vegetables as vital components of daily diets.

Main Nutrient Components of Vegetables

Nutrient components of our food can be grouped into five main divisions, namely, (i) Carbohydrate, (ii) Protein, (iii) Fat, (iv) Vitamins and (v) Minerals. Balanced diet is the food containing all these nutrient components in balanced form to run the physiological process in good tune. So, only eating to one’s heart’s content may not be the criterion of a balanced diet. Our dietary constitution which is mostly cereal based is really alarming. Cereals, which supply chiefly carbohydrate, constitute only a part of the diet. Moreover, the present average carbohydrate supply through cereals is also not adequate. Chief deficiencies in our diet are calories, protein, vitamin A and riboflavin. According to the studies of Indian Council of Medical Research, New Delhi and National Institute of Nutrition, Hyderabad, meager intake of vegetables, the low cost protective foods, is largely responsible for malnutrition among the majority of our population. The dieticians advocate intake of 125g leafy vegetables, 75g other vegetables and 100g root and tuber vegetables (total 300g) everyday to make our diet balanced. In households below the poverty line, per capita vegetable consumption is very low, apprehended to be even lower than 40g per day.

Classification of Vegetable Crops

Vegetables are defined as herbaceous plant origin product with no calorific value and providing micronutrients, vitamins, antioxidants, fibre and alkaline reaction inside human body. Vegetable crops are not only botanically different but also their cultural and climatic adaptation also shows wide variability. It is, therefore, necessary to classify the vegetable crops for their easy recognition. Vegetable crops can conveniently be classified “Botanically” for the purpose of vegetable breeding and according to “Method of culture” from the point of crop husbandry.

Botanical Classification

Botanical classification involves grouping of plants into kingdom, division, sub-division, phylum, sub-phylum, class, sub-class, order, family, genera, species, sub-species and variety. The broadest group in which vegetables are discussed is family. The genus and species constitute the scientific name. Scientific names are accepted worldwide and there cannot be any confusion as per their nomenclature. All vegetable crops belong to the division Angiospermae. The division Angiospermae has two classes: Monocotyledoneae and Dicotyledoneae.

The crops used for vegetable purpose in the world belong to 1200 species under 78 families and of them, more than 860 species under 59 families belong to dicotyledoneae and about 340 species under 19 families belong to monocotyledoneae. In the tropical and subtropical parts of the world, about 90 species of vegetable crops are cultivated, but hardly 25 of them are commercially important in terms of market demand, development of variety/hybrid and seed production. In the present botanical classification, over 140 different kinds of vegetable crops under 7 monocotyledoneae and 20 dicotyledoneae families have been included.

Development can be defined as the process and timing of differentiation of the component events causing qualitative changes in form and function of the plant and therefore, manifestation of economic plant parts. Sowing is the beginning of the process, after which plants emerge, grow and develop with or without transplanting and may be harvested in vegetative (e.g., cole, bulb, tuber, root, salad crops) or reproductive phase (solanaceous fruits, peas and beans, cucurbits, okra, etc.). Growth and development of plants is dependent on abiotic (physical) and biotic (biological) factors. Abiotic factors include the physical environmental conditions and biotic factors include animals, insects, and diseases. Each plant has certain environmental requirements. To attain the highest potential yields a crop must be grown in an environment that meets these requirements. A crop can be grown with minimal adjustments if it is well matched with its climate or growing condition. Unfavourable environmental conditions can produce a stress on plants resulting in lower yield. In such cases the environment can be artificially modified, as done in protected structures like poly house, shade net house, etc. to meet the crop requirements.

Different abiotic environmental factors viz., light, temperature, water and soil greatly influence plant growth and geographic distribution. These factors determine the suitability of a crop for a particular location, cropping pattern, management practices, and levels of inputs needed. A crop performs best and is least costly to produce if it is grown under the most favourable environmental conditions. To maximize the production of any crop, it is important to understand how these environmental factors affect plant growth and development.

The term ‘Phyto-hormone’ was coined by Thimann in 1948. Phyto-hormones are organic compounds, which are produced naturally in plants, synthesised in one part and usually translocated to the other part where in every small quantity affect the growth and other physiological function of the plants. Auxin was the first hormone to be discovered in plants. At one time, auxin was considered to be the only naturally occurring plant growth hormone however, four other classes of phyto-hormone viz., gibberellins, cytokinin, ethylene and abscisic acid was later discovered. Plant growth regulators include both five specified classes of phyto-hormones (auxin, gibberellins, cytokinin, ethylene and abscisic acid) and other synthetic organic compounds (for example, polyethylene glycol, dinoseb-2-sec butyl 4,6dinitrophenol, proteins and/or amino acids, carboxylic, phenolic acid, humic acids, etc.) having properties of bio-stimulants or bio-inhibitors. Plant growth regulators (PGRs) modify plant physiological processes either by stimulating or inhibiting specific enzymes or enzyme systems to help regulate plant metabolism and thereby enhance yield and product quality. They normally are active at very low concentrations in plants.

Importance of PGRs was first recognized in the 1930s. Since then, wide array of natural and synthetic compounds that alter function, shape and size of crop plants have been discovered. Of the many uses of PGRs, effects on yield are often indirect. A wide range of beneficial effects of PGRs on crop growth and yields are: 1. promotion of germination and/or emergence, 2. stimulation of root growth, 3. promotion, mobilization and translocation of nutrients within plants, 4. modification of flowering, 5. increase in stress tolerance and improvement of water relations in plants, 6. promotion of early maturity, 7. increase in disease resistance, 8. retardation of senescence and 9. improvement of crop yields and/or quality.

It is said that “Success of any production system depends on the kind of seed which are sowing”. It is true for the seedlings also beacause healthy seedlings grown in a well managed nursery will decide the yield and consequently the profit.

Definition of Vegetable Nursery

A vegetable nursery is a place or an establishment for raising or handling of young vegetable seedlings until they are ready for more permanent planting.

Why vegetable nursery is needed

Some vegetable crops require special cares during their early growth period. There are some vegetables with very small sized seeds. Seedlings of many seed propagated vegetable crops like, tomato, brinjal, chillies, sweet pepper, cauliflower, cabbage, knolkhol, broccoli, Brussels sprout, kale, endive, chicory, celery, lettuce, parsley, onion, etc. are first raised in the nursery beds before transplanted in the main field. Many seed propagated vegetable crops viz., okra, peas, beans, radish, carrot, beet, turnip and all the cucurbits (e.g. bitter gourd, bottle gourd, pumpkin, cucumber, watermelon, muskmelon, snake gourd, sponge gourd, ridge gourd, etc.) are conventionally grown through direct seeding in the main field. However, many cucurbits, particularly in the early season are also grown in India using the seedlings raised in polythene packets.

Plant nutrition is the study of the chemical elements and compounds necessary for plant growth, plant metabolism and their external supply. In 1972, Emanuel Epstein defined two criteria for an element to be essential for plant growth:

In its absence the plant is unable to complete a normal life cycle.

The element is part of some essential plant constituent or metabolite.

This is in accordance with Justus von Liebig’s law of the minimum. The essential plant nutrients include carbon, oxygen and hydrogen which are absorbed from the air, whereas other nutrients including nitrogen are typically obtained from the soil.

Relationship Between Plant and Water

Water is the most vital component of the living cells and the basis of plant feeding. Water is also characterized with extraordinary physical properties: it has high specific heat, biggest latent heat of vaporization, very high thermal conductivity and greatest surface tension. Large amounts of heat are tied up with water because of very high specific heat, which contribute to both climatic stability and to heat budgets of the plants and other organisms. Water molecules are integral part of living systems being the solvent for metabolites and structural component of proteins and nucleic acids. In fact, biological macro-molecules cannot exist in their complicated secondary folding or spiralled helixes without the support of hydrogen bonding within their water matrix. The water matrix is also critical for metabolic activity because its properties of hydration permit ready reactivity between molecules in solution as well as between enzymes and their substrates, and the biochemical processes are sensitive to tissue hydration. A reduction of only 20-25 per cent below maximum hydration is sufficient to cause metabolic malfunctioning of many enzymes. It is the substrate for photosynthesis and a product of respiration. Water also helps to buffer plant tissue against fluctuations in the external environment. Plant growth including leaf expansion, organ enlargement, reproductive development and stomata function are all clearly associated with moisture status. Hormonal changes (abscisic acid and cytokinins) in plant body occur with brief reduction in water potential. Water is the also major force in shaping the climatic patterns.

Most of the insect pest and disease (insects, mites, diseases, nematodes, etc.) management problems arise from relying entirely on pesticides for control. Integrated pest management (IPM) is a strategy that draws on a range of management tools with the goal of using the least ecologically disruptive techniques to manage pests within economically acceptable levels. IPM considers the production system in a holistic manner and looks at all aspects of the farming enterprise as potentially increasing or decreasing pest numbers and, where possible, enhancing the activities that reduce these pest populations.

Strategy for Integrated Pest and Disease Management

The basic IPM strategy involves routine crop monitoring to ensure that pesticides are only applied when needed, as well as to ensure appropriate timing of pesticide applications. The most developed bio-intensive IPM relies primarily on beneficial organisms to manage insect pests. When greater pest control is needed, interventions chosen are complementary to the survival of these beneficial organisms. As other pests are incorporated more and more prevention strategies are adopted which reduces the need for direct control practices.

Weeds are unwanted and undesirable plants which interfere with the utilization of land and water resources and thus adversely affect crop production.

Classification of Weeds

Weeds can be classified in three different manner based on morphology, life cycle, habitat and origin.

Green revolution technologies such as greater use of synthetic agrochemicals like fertilizers and pesticides, adoption of nutrient-responsive, high-yielding varieties of crops, greater exploitation of irrigation potentials etc. has boosted the production output in most cases. However, continuous use of these high energy inputs indiscriminately now leads to decline in production and productivity of various crops as well as deterioration of soil health and environments.

Protected cultivation can be defined as a cropping technique wherein the micro-climate surrounding the plant is controlled partially or fully as per the requirement of the plant species during their growth period. This cropping technique is the most modern approach to grow different horticultural crops mainly, vegetable crops and flowers for enhancement of both productivity and product quality. This technology has spread extensively the world over in the last few decades. This technology involves the cultivation of different crops particularly, horticultural crops in a controlled environment wherein the environmental parameters like the temperature, humidity, light, soil, water, plant nutrition, etc. are manipulated for enhancement of production as well as product quality even during off-season which ensures additional return to the growers.

Potato

Potato, Solanum tuberosum L. under the family Solanaceae (Chromosome No. 2n = 4x = 48) is the most important non-grain food crop in the world, ranking 3rd in terms of total production with over 381 million tonnes per year in (FAOSTAT, 2017), after rice and wheat. It is grown in 150 countries spread across both temperate and tropical regions and at elevations from sea level to 4,000 m. It is extensively cultivated in China, Russian Federation, Ukarine, Poland, Ireland, Great Britain, Germany, Netherlands, France, Spain, South America, India and USA. Potato was brought from Peru to Spain by the Spaniards in 1565 when it was widely grown in Spain and Italy. They were probably brought to England in 1586 by Sir Francis Drake. Potato was introduced in India in early 17^th century probably by the Portuguese. Now it is one of the principal cash crops of India.

The crop

The subsection Potato is distinguished from all other subsections within the genus Solanum by “true potatoes whose tubers are borne on underground stolons, which are true stems, not roots”. The series tuberosa is characterised by “imparipinnate or simple leaves, forked peduncle, rotate to pentagonal corolla and round berries”.

The species S.tuberosum is characterised by “pedicel articulation placed in the middle third, short calyx lobes arranged regularly, leaves often slightly arched, leaflets always ovate to lanceolate, about twice as long as broad, tubers with well marked dormancy period”

Potato is an annual herbaceous plant and growth habit varies between and within species. The plant has a rosette or semi-rosette habit. The stem is erect in the early stage but becomes spreading and prostrate later on. The leaves are compound and alternate, irregularly odd pinnate. The tuber is an enlarged portion of an underground stem or stolon. Tuber eyes are the buds from which next season’s growth will emerge. Eyes are concentrated near the apical end of the tuber, with fewer near the stolon or basal end. Eye number and distribution are characteristic of the variety.

Potato is mainly propagated vegetatively by means of tubers and sometimes by botanical seeds, i.e., true potato seeds. Potato has a terminal inflorescence consisting of 1-30 (but usually 7-15) flowers, depending on the cultivar. The five petals give the open flower a star shape. A flower also has a pistil that generally protrudes above a cluster of five large, bright yellow anthers. The corolla colour varies from white to complex range of blue, red and purple. Flowers are self-pollinated but also cross pollination take place by insect. Seeds are produced in the fruit which is botanically called berry. Potato fruits, stems and leaves contain glycoalkaloids, the toxic compounds, of which the most prevalent are solanine and chaconine.

Cropping system is defined as the cropping pattern followed on a farm and its interactions with farm resources, other farm enterprises and production technology. The yearly sequence and spatial arrangement of crops and fallow on a given area is termed as cropping pattern.

India has over 17% of world’s population living on 2.4% of the world’s geographical area. Per capita agricultural land has reduced by 67% from 0.48 ha in 1951 to 0.16 ha in 2008 due to explosive increase in population. In this situation, it is very difficult to get horizontal expansion in vegetable cultivation. Hence, total production per unit area can be increased by increasing the productivity per unit area through (a) growing improved high yielding varieties and hybrids, (b) adequate and scientific crop management practices and (c) increasing cropping intensities following different cropping patterns.

Quality Components of the Produce

Various components of quality are used to evaluate the products in relation to specific grades and standards and responses to various environmental factors and post-harvest treatments. The relative importance of each factor depends upon the commodity and its intended use, fresh or processed. The main quality components of vegetables are mentioned below

Marketing is one of the most important factors in determining the success of any vegetable farming enterprise. Marketing includes all the operations and decisions taken by the producers. These decisions range from determining the most marketable crops for production to deciding how to best deliver quality produce to the consumers at a profit. However, contrary to popular belief, marketing does not begin after a crop is produced. Instead, marketing alternatives need to be considered even before the start of production.

However, vegetable marketing in India has not yet been organised so far. The long route from the grower to the retailer and ultimately to the consumer involves a chain of middlemen, transport contractors and wholesale merchants. Very often, there arises stagnation of the produce in the peak season or in the year of good production. The large number of intermediaries in the vegetable marketing channel grab maximum share of the consumer’s price and as a result, the producers’ profit becomes marginal. Vegetable cultivation is a capital intensive venture, and huge production alone cannot fetch profit for the growers. Organised marketing, storage and transport facilities are the key factors for making vegetable farming profitable which ultimatily boost vegetable cultivation.

Human beings, considered to be the highly evolved living organisms, have been making consistent and constant efforts to lead comfortable life without much concern for the conservation of nature and adversities to other living and nonliving entities existing in the universe. To meet the requirements of food, feed, fibre, timber and other needs, the plants that could supply the above were selected and domesticated. When the useful plant species were cultivated over large areas repeatedly year after year, the problems afflicting plants that were not recognized earlier as constraints for crop cultivation, assumed monstrous proportions wiping out entire crops and ruining the livelihood of the people of that geographical location/country. World history is replete with numerous instances of huge crop losses caused by microbial plant pathogens resulting in malnutrition, hunger and death. Migration of millions of people to other countries for their survival, became unavoidable. Such historical evidences threatening the existence of humans necessitated to investigate the causes of destructive diseases like late blight and heliminthosporiose diseases affecting respectively potato and rice, the staple food of the largest populations of the world. In order to take appropriate measures for minimizing losses due to crop diseases and to mitigate the sufferings of man and the animals, application of various short- and long-term disease management strategies has become indispensable for the profitable cultivation of crops

Occurrence of various diseases affecting agricultural and horticultural crop is known for several centuries. However, critical examination of crop diseases to understand the nature of the causative agents and extent of losses induced by diseases and development of effective disease management systems were possible much later. Any deviation from normal form and function of plants is considered as ‘disease’. Both pathogenic (biotic) and physiogenic (abiotic) causes are involved in diseases of plants. Adverse environmental conditions such as extremes of temperature, light and oxygen, soil moisture, pH and polluted air may alter the physiological conditions of the plants. Nutritional deficiencies also affect various crops leading to considerable losses. Microbial plant pathogens–fungus-like oomycetes, fungi, bacteria, phytoplasmas, viruses and viroids–form the major group of biotic agents that induce different diseases of crop plants in the field as well as during transport and storage (Narayanasamy 2002,2006). Presentation of information in this book is confined to various aspects of the microbial plant pathogens and the diseases caused by them.

Microbial pathogens may induce symptoms that may be visible externally and also in the deep-seated internal tissues which have to be examined using light or electron microscope. In the case of some diseases, the symptoms may be localized in different plant parts such as roots, leaves, stems, floral parts or seeds / fruits / vegetables. Such infections are known as local infection. On the other hand, the pathogen may spread from the point of entry into the host to other plant parts which exhibit characteristic symptoms. These diseases are termed as systemic diseases. In some cases, no recognizable visible symptom is produced although the pathogen is able to develop without inconveniencing the host plant species which are called as carriers and the infection is designated latent infection. Plant viruses are carried symptomlessly by many weed plant species which may serve as sources of infection for crop plants.

Detection and identification of the causes and diagnosis of the diseases rapidly and precisely are the basic requirements for developing effective crop disease management systems suitable for different ecosystems. Incorrect diagnosis leads to failure to contain the disease spread and consequent additional expenditure to the growers. Hence, it is essential that proper diagnostic procedures are followed to achieve the goal of reducing both quantitative and qualitative losses of agricultural and horticultural produce. Morphological, biological, biochemical, physiological, immunological and genomic characteristics of microbial plant pathogens have been carefully considered to develop rapid, sensitive and reliable methods of detection and identification of cause(s) of newly observed disease (s) in the locations concerned. Various methods of establishing the nature of microbial plant pathogens are discussed in detail in earlier publications

Plants are exposed to microbial pathogens at all growth stages from seeds to harvested produce. But they are resistant to numerous pathogens that are present in the environment and susceptible only to some of them. In other words, a plant species has built-in resistance mechanism to avoid or resist the invasion by many microbial pathogens. A pathogen may reach several plant species, but it can infect only a few plant species in the particular location or region. The process of pathogenesis or disease development is initiated when the pathogen reaches the plant surface that allows the initiation of infection. An organism is able to derive its nutrition from the susceptible host plant and becomes pathogenic. The physiological functions of such infected plants deviate from those of the healthy (normal) plants and suffer irreversibly to different magnitudes. The organism adversely affecting the plant growth and other functions to obtain nutrition is the pathogen. It develops rapidly or slowly in proportion to the levels of susceptibility / resistance of the host plant to the pathogen species concerned. Thus a plant species may be susceptible to some pathogens, while remains resistant / immune to other organisms that may be pathogenic to some other plant species. Depletion of compounds from the plants to meet the nutritional requirement of the pathogen leads to different kinds of external symptoms and internal changes due to derangement of normal metabolic functions of the host plant. The process of disease development in a susceptible host plant species is known as pathogenesis.

Although thousands of plant species exist on the earth, only those that were found to be useful for humans as food, feed, fiber, timber and other utility materials have been selected for domestication. When these plant species were affected by various biotic and abiotic causes, the necessity arose to determine the ways and means of protecting the valuable plants species and to understand the host plant defense mechanisms and pathogenic potential of the microbial pathogens causing enormous losses to the cultivators. All plant species have built-in resistance to most microbial plant pathogens existing in the environment. Susceptibility of plants to some of them is an exception, since they are endowed with genes which effectively nullify the possible adverse conditions created by the microorganism. Likewise, microbial pathogens possess genes for survival and pathogenicity to survive in the absence of susceptible plant species and to successfully establish infection in suitable plant species. The microbial pathogens have evolved highly specialized tactics to overcome the defense responses and to rapidly multiply in plants for their survival and perpetuation in a geographic location / ecosystem

Crops are grown with the primary aim of maximizing the profit for the cultivators. To achieve this goal, high yielding cultivars and suitable agricultural practices are selected. But due consideration is not given for the levels of susceptibility of the cultivars and some of the agricultural practices may enhance the chances of disease incidence and consequent losses. Hence, it becomes obligatory to determine the effects of crop cultivar and agricultural practices on the extent of disease incidence and to assess losses caused by microbial pathogens in different crops in an agroecosystem. Crop losses reflect the effects of various factors such as use of disease resistant cultivars, application of chemicals, biocontrol agents and preventive measures to reduce inoculum levels, introduction of new diseases and restriction of disease spread. Assessment of crop losses is essential to choose the most effective short- and long-term strategies of disease management. Disease assessment enables the plant pathologists is to gather quantitative information for evaluating disease management strategies, for undertaking surveys of losses and breeding for disease-resistant cultivars.

Various aspects of micorbial plant pathogens have been studied with the ultimate aim of gathering information that may be useful for development of effective disease management systems. Principles of management of crop diseases caused by microbial pathogens fall into three categories : exclusion, eradication and immunization.

7.1 Exclusion of Microbial Plant Pathogens

Exclusion of microbial pathogens may be expected to reduce the amount or efficacy of the initial population of pathogens that may be introduced into a geographical location / field. Exclusion is an important component of management of diseases, if the initial population of pathogen is large. This approach is particularly effective in the case of monocyclic pathogens that complete their life cycle only once during one cropping season. The methods with the aim of excluding the introduction of pathogens or to prevent the build up of inoculum required for disease spread are generally applied elsewhere. Hence, they have lower level of visibility compared to other approaches. Introduction of new pathogens present in plant and plant materials into another country or locations within a country may be effectively prevented by establishing plant quarantines. Build up of inoculum of microbial pathogens can be reduced considerably by the use of disease-free plants or planting materials supplied through certification agencies. These regulatory programmes have to be manned by trained technical personnel and supported by adequate infrastructure in terms of equipments and mobility (Chapter 8).

Management of crop diseases by various methods of exclusion in order to reduce the pathogen population in a geographical location / country may be achieved by either preventing introduction of pathogens or by growing disease-free seeds and planting materials. In addition, the inoculum of a pathogen reaching newly planted crops may be significantly reduced by adopting appropriate cultural practices also. The contributions of these factors for successful cultivation of crops are discussed hereunder.

8.1 Prevention of Introduction of Microbial Pathogens

Prevention of pathogen introduction is the primary responsibility of plant quarantines. Quarantines have been established by several countries by enacting appropriate laws that regulate the importation of plants, seeds and asexually propagated plant materials. These materials are placed in post-entry quarantines (PEQs) and examined by technical personnel for the presence of pathogens and pests. It is obligatory for the exporting countries to comply with the regulations of the importing countries. As the movement of plant products has increased enormously, following the adoption of the General Agreement on Tariffs and Trade (GATT), vigilant enforcement of sanitary and phytosanitary measures has become essential. The Food and Agriculture Organization (FAO) appointed an Expert Consultation on the Harmonization of Plant Quarantine Principles to formulate basic principles to determine standards for plant quarantine principles in relation to international trade (FAO 1991). According to the recommendations of the Expert Consultation, the sovereignty of the importing country is recognized and it has the right to implement the phytosanitary regulations deemed fit by that country. However, cooperation among countries was emphasized for the successful implementation of the recommendations by the member countries belonging to one of the eight regional plant protection organization set up after the International Plant Protection Convention (IPPC) held in 1951. A plant pathogen is recognized as of quarantine significance (QS), if its exclusion is considered to be essential to protect agriculture and natural vegetation of the importing country which has to be provide necessary infrastructure and trained personnel to prevent or delay its entry along possible routes. Lists of quarantine pathogens and the regulations to be followed are prepared by the importing country and made available to the exporting countries.