eChapters

Introduction

Plant pathogens induce diverse reactions in the body of their hosts. This result in creation of abnormalities which become visible on the plants. A visible or otherwise detectable expression of abnormal physiology, development, or behaviour in a plant resulting from disease is called symptoms. Normally, a distinction is made between symptoms and signs A symptom of disease is expressed as a reaction of the host to a causal agent, whereas, a sign is evidence of disease other than that expressed by the host. Signs are usually the structures of the pathogen. A disease is first noticed by the presence of symptoms and /or signs, and recognition of specific type of symptoms or sign aid in the eventual diagnosis of the disease.

Taxonomy

Taxonomy is the science that deals with the identification, nomenclature and classification of organisms.

Systematics

It is scientific study of organisms with the ultimate object of characterizing and arranging them in an orderly manner.

Classification

Classification is the ordering of organisms into groups and systems, based on their morphological, phylogenetic and physiological relationships.

Nomenclature

It is the system of assigning names to the taxonomic groups or organism according to international rules.

Bacteria

Definition

Bacteria belong to prokaryota which encompasses organisms with a primitive type of nucleus lacking a clearly defined membrane. The bacteria are smaller than fungi and measure about 0.5 to 1.0 x 2.0 to 5.0µ.

Definition of Virus

According to Luria and Darnell (1968), Viruses are entities whose genome is a nucleic acid, either DNA or RNA, which reproduce inside living cells and use their synthetic machinery to direct the synthesis of specialized particles- the virions, which contain the viral genome and transfer it to other cells.

Nature of Virus

The physical and chemical nature of viruses eluded scientists until the 1930s. Stanley (1935) announced crystallization of Tobacco mosaic viruses, a feat for which he got a Nobel Prize. Stanley thought the crystals to be pure proteins. It was the pioneer work of F.C. Bawden and N.W. Pirie of England which showed that the viruses consists of proetein and nucleic acid. The chemical nature of viruses was settled. It consisted of nucleic acid and protein. The viruses chemically were proved to be nucleic acid. The mature particle of a plant virus is generally called virion and the whole infective particle is called as Nuclcocapsid.

The parasitic flowering plants are also important pathogens. There are few seed plants, which are parasitic on living plants and are called parasitic higher plants or Phanerogamic parasites. These parasitic higher plants attack some valuable crops and trees causing considerable losses. They produce flowers and seeds and belongs to several widely separated botanical families they differ to each other on their dependency on host plants. These parasites have haustoria as absorbing organ, which sent deep into the vascular bundle of the host to draw water and nutrients. More than 2500 species of higher plants are known to live parasitically on other plants.

Definition

Neamtode may be defined as triploblastic, bilaterally symmetrical, unsegmented, pseudocoelomate individual invertebrate, with 4 main hypodermal chords, a triradiate oesophagus, circum oesophageal nerve ring, and lacking specialized organs for respiration and circulation.They have tubular gonads which open separately in females but join alimentary canal in males to open through a cloacal aperture.

Definition

To make a healthy plant sick or diseased, primary requirement of a pathogen is spread of its inoculums from the source of survival to the susceptible host. The spread of a plant pathogen within the common area in which it is already established is called dispersal or dissemination. Moving the inoculum only a few inches and transporting it for hundreds of kilometers both represent its dispersal. Nevertheless, the pathogen dispersal is not necessarily only for spread of diseases but also for continuity of the life cycle and development of the pathogen. A detail knowledge of pathogen dispersal is necessary to find out effective control measures for diseases because the possibilities of preventing dispersal and thereby breaking the infection chain always exist.

Definition

The availability of a plant pathogens in given area depends upon its ability to survive not only during its parasitic relations with hosts but also during those seasons in which the hosts are not growing. The latter part of continued existence of plant pathogens in which they remain in dormant condition to overcome the unfavourable condition of non availability of hosts is called “survival”. Pathogens may survive between crop seasons by means of specialized resting structures , by functioning as saprophyte in or on the soil or in diseased plant debris, or by living in some intimate association with living plants or other organism.

A. Types of parasitism

An organism that lives within or upon another living organism from which it derives nourishment and in which it may cause various degrees of injury is called as parasite. The removal of food by a parasite from its host is called parasitism. Among the parasite one can distinguish different degree of parasitism

Pathogenesis: Role of enzymes

The chain of metabolic events that bring about the disease is pathogenesis. It involves the virulence of the pathogen, susceptibility of the plant and impact of the environment. It is called disease triangle. Penetration infection, invasion, colonization and reproduction are the events that occur during pathogenesis, and lead to development of disease.

The establishment of pathogen in the host and consequent development of disease involves a chemical interaction between the host and the pathogen. The pathogen employs offensive chemical weapons to break host barriers, which the host resists with all its might. Parasitism and disease resistance run parallel and are inseparable, A biochemical ‘tug of war’ ensures between the host and the pathogen, in which one tries to outwit the other. Enzyme, toxins and growth regulators are the important chemical weapons of the pathogen. Viruses, however, because of their basic nature, do not produce any of these chemicals.

Pathogens produce these substances either in normal course of their activities (constitutively) or when, they grow on certain substrates such as their host plants (Inducible). Plant pathogenic enzymes disintegrate the structural components of host cells, breakdown inert food materials in the cell, or affect components of the protoplast directly and interfare with its functioning system. Toxins seem to act directly on protoplast component and interfare with the permeability of its membrane and with its function. Growth regulators exert a hormonal effect on the cells and either increase or decrease their ability to divide and enlarge. Polysaccharides seem to play a role only in the vascular diseases, in which they passively interfere with the translocation of water in the plants or they may also be toxic.

Introduction

Resistance to disease in a host plants is a condition in which the plant conquer the pathogen’s attack and thus suffers small or no injury. Resistant hosts prevent or slow the development and reproduction of the majority of pathogen propagules that they come into contact with. Different plants defend themselves in different ways. Each kind of plant, probably, employs different defense mechanism against each of the pathogens that attack it. The defense barriers erected by plants are a co-ordinated system of molecular, cellular and tissue-based responses to pathogen attack.

Epidemiology

Vanderplank has called epidemiology the science of disease in population. Epidemiology puts its emphasis on population phenomena. The important populations are those of the host, on the one hand, and of the pathogen, on the other. But further, epidemiology is concerned with host-pathogen interactions that lead to disease and crop losses. These interactions are often environmentally dependent. So epidemiology deals with effects of the biotic and abiotic environments. Finally , man has had important effects on hosts, pathogens and the environments, effect that today are increasing in magnitude and scale of importance. Epidemiology therefore also deals with the effects of man on disease and sometimes with the effects of plant disease on mankind. All of this can be symbolized by the disease tetrahedron.

Disease Forecasting

Definition

Forecasting involves all the activities in ascertaining and notifying the grower of community that conditions are sufficiently favourable for certain diseases, that application of control measures will result in economic gain or on the other hand, and just as important that the amount expected is unlikely to be enough to justify the expenditure of time, energy and money for control. The above statement made explicit distinction between positive forecast and negative forecast and both have value for growers as well as society in general.

Positive forecast: Employs need based chemical sprays, provides adequate protection to crop and reduces damage to environment.

Negative forecast: Avoids unnecessary chemical sprays, no risk to the crop health and no disruption of environment.

The techniques used in disease management mainly based on two principles: Prevention or prophylaxis and cure. The first principle prevention includes disease management tactics applied before infection i.e., the plant is protected from disease. It includes: avoidance, exclusion, eradication, resistant & protection. Second principle curative action: functions with any measure applied after the plant is infected i.e., the plant is treated for the disease. It includes therapy.

Defintion

Management of plant diseases using physical means is called physical management.

Also called physical therapy or thermotherapy.

It is mostly curative in nature.

Introduction

Cultural management is defined as manipulation /or adjustment of crop production techniques for management of plant diseases. Cultural practices have been as old as possibly agriculture itself. In early stage of agriculture development, the growers through their experiences and observations had known that repeated cultivation of a particular crop species or variety on a piece of land often resulted in crop sickness. As a matter of fact, in the present day agriculture, cultural practices are being considered as essential backup methods for management of plant diseases. Adequate adjustment in crop production techniques can modify the environment in such a manner that it becomes unfavorable for the pathogen and pathogenesis. Based on this the disease control affected by cultural practices are preventive, these practices aim at reducing the activity and density of inoculum. It offer the opportunity to alter the environment, the condition of the host, behavior of the causal agent to achieve economic management of disease.

Introduction

Cultural management is defined as manipulation /or adjustment of crop production techniques for management of plant diseases. Cultural practices have been as old as possibly agriculture itself. In early stage of agriculture development, the growers through their experiences and observations had known that repeated cultivation of a particular crop species or variety on a piece of land often resulted in crop sickness. As a matter of fact, in the present day agriculture, cultural practices are being considered as essential backup methods for management of plant diseases. Adequate adjustment in crop production techniques can modify the environment in such a manner that it becomes unfavorable for the pathogen and pathogenesis. Based on this the disease control affected by cultural practices are preventive, these practices aim at reducing the activity and density of inoculum. It offer the opportunity to alter the environment, the condition of the host, behavior of the causal agent to achieve economic management of disease.

1. Biosecurity

Biosecurity is strategic and integrated approach encompasses policy frameworks to analyze and manage risks for food safety, animal life and health and plant life and health including environment.

Definition

Garret (1970) defined biological control as any condition under which or practice whereby survival or activity of a pathogen is reduced through the agency of any other living organism (except man) with the result that there is a reduction in the incidence of the disease caused by that pathogen.

Baker and Cook (1974) stated that the biological control is the reduction of inoculum density or disease producing activities of a pathogen or parasite in its active or dormant stage, by one or more organisms, accomplished naturally or through manipulation of the environment, host or antagonists, or by mass introduction of one or more antagonists.

Biocontrol can be simply defined as the application of living organism to control diseases.

Definition

Those characters that enable a plant to avoid tolerate or recover from attacks of pathogens under conditions that would cause greater injury to other plants of the same species.

Introduction and Concept

The word fungicide has originated from two Latin words: viz. fungus and caedo (to kill). So literally, a fungicide would be any physical or chemical agency which kills a fungus. However, the word is restricted to chemicals. Hence, the word fungicide should mean a chemical capable of killing fungi. However, there are a number of compounds which do not kill the fungus. They simply inhibit growth or spore germination temporarily. If the fungus is freed from such substances, it would revive. Such a chemical is called a fungistat. and the phenomenon as fungistasis. Some other chemicals, like certain phenantherene derivatives and bordeaux mixture may inhibit spore production without affecting vegetative growth. These are called antisporulants. There are other groups of chemicals which exhibit very poor or no antifungal activity in vitro condition but provide protection to the plants either by inhibiting the penetration of host surface by the fungi or by inducing the host defense system. The former type of chemicals are termed as antipenetrants and later as antipathic agents. Even though fungistats, antisporulants, antipenentrants, and antipathic agents do not kill fungi, they are included under the broad term fungicide because by common usage, the word fungicide has been defined as chemical substance which has ability to prevent damage caused by fungi to plants and their products. Fungicide which is effective only if applied prior to fungal infection is called protectants. On the other hand, fungicide which is capable of eradicating a fungus after it has caused infection, and thereby curing the plant, is called therapeutant.

Fungicide Formulation

Fungicide formulation is the process by which the fungicide is put into a form which can be easily produced, stored, transported and applied by practical methods in order to achieve a safe, convenient economic and effective method of disease control.The mixture of active ingredient and inert (inactive) ingredients is called a fungicide formulation.

Proper selection of a fungicide and its application at the correct dose and the proper time are highly essential for the management of plant diseases. The basic requirement of an application method is that it delivers the fungicide to the site where the active compound will prevent the fungus damaging the plant. The fungicidal application varies according to the nature of the host part diseased and nature of survival and spread of the pathogen. The method which are commonly adopted in the application of the fungicides are discussed

Definitions

Selection, integration and implementation of disease control means on predicted economic, ecological, and sociological consequences.

A comprehensive approach to disease control that uses combined means to reduce the status of diseases to tolerable levels while maintaining a quality environment.

The optimization of disease control in an economically and ecologically sound manner, accomplished by the coordinated use of multiple tactics to assure stable crop production and to maintain disease loss below the economic injury level while minimizing risks to man and the environment.

A sustainable approach to manage diseases by combining biological, cultural, physical and chemical tools in a way that minimizes economic, health and environmental risks.

I. Definition of wasteland

Wasteland include degraded forest, overgrazed pastures, drought- struck pastures, eroded valley, hill slopes, water logged marshy lands, barren lands etc.

Different authors have defined wastelands as:

Land which is lying unproductive or which is not being utilized to its potential.

Land which is incapable of producing material or services of value (American Society of Soil science).

Land which has been abandoned and for which there is no further use (Mine spoils).

Land which produces less than 20% of economic potential. e) Land where no greenery can be sustained.

Land which is neither under forest cover or agricultural cover or assigned for specific purposes such as National park or National hydro power projects.

The Technical Task Group Report of the National Wasteland Board defines the wasteland due to different constraints.

Crusting soils

What is soil crusting?

Soil crusting refers to formation of a compact thin layer having high bulk density and high penetration resistance at the soil surface when dries after dispersion of fine particles and clogging of pores due to beating action of rain drop and slaking of irrigation water.

In arid and semiarid regions, crust formation occurs due to the destruction of soil aggregates. Crust formation occurs in all types of soils except sand. It is characterized by high bulk density, low non capillary pores, low hydraulic conductivity and aeration and high penetration resistance.

Calcareous soils

In arid regions, calcareous soils are developed from limestone or marl parent materials. The content of calcium and magnesium carbonate may be as high as 60 to 70 per cent of the total soil mass. In calcareous soil lime content may vary from a small amount in some places in the profile to appreciable amounts throughout the profile.

Calcium carbonate coatings occur in sand, silt and clay size fractions of calcareous soils. In sub soil, large amounts of lime forms hardpan under high water tables.

In general, pH of the soil increases to alkaline pH with increasing the proportion of water to soil ratio. This may happen in part from a reduction of CO₂ pressure. The dilution of salts in soil solution also permits greater hydrolysis of calcium clay. The dilution of calcium carbonate with production of hydroxyl ions may lead to higher pH as:

Iron Toxic Soils

Lowland rice is being cultivated on approximately 128 million hectares of either irrigated or rainfed land out of which 100 million hectares suffer due to nutrient deficiency or toxicities. Among the toxicities, iron toxicity is well recognized as a nutritional disorder in low land rice production. Iron toxicity is a syndrome of disorder associated with high concentration of Fe²⁺ in soil solution. A wide range of soil types show iron toxicity problem including acid sulphate soils, acid clay soils, peat soil and valley bottom soil. During monsoon rains in the wet season, soluble iron (Fe²⁺) migrate to the surface and its iron content increases to subtoxic or toxic levels.

In rolling topography and with heavy monsoon downpour there is considerable lateral flow of iron containing water from the adjacent uplands to mid – and low lands. This increases the iron content to toxic levels. Poorly drained sandy soils in valleys receiving interflow water from adjacent uplands with laterite horizon (Plinthudults) showed iron toxicity in Srilanka and Kerala and Odisha in India. These soil groups come under the taxonomic orders Alfisols, Ultisols and Oxisols occurring in association with Entisols and Inceptisols. The iron concentration (Fe²⁺) in soil solution that affect low land rice yield ranges from 10 to > 2000 mg L^-1 Iron toxicity induced yield reduction which is associated with poor nutrients . status (deficiency of P, K and Zn) and H₂S toxicities.

Soil erosion refers to detachment and transport of soil and soil particles from one place to other by the action of water, wind or gravity. Soil erosion consists of (i) detachment of soil particles from surface (ii) their transport from one place to other and (iii) deposition in another place.

Soil erosion are of two types: Natural erosion and accelerated erosion. The natural or geological erosion is steady, nondestructive and slow process of nature. On the contrary the accelerated erosion caused due to human activities like cutting of forest, intensive cropping, construction of roads and building is very rapid and destructive. Surface one inch of soil which is formed in thousand years can be lost within one year due to accelerated erosion.

In India, out of total 175 million hectares of degraded land, soil erosion due to water and wind accounts for 150 million hectare. Soil erosion due to shifting cultivation, salinity, alkalinity, water logging and shifting of water courses account for 25 million hectare.

Average soil loss from various land surfaces in India has been estimated to be 5334 million tonnes per year out of which 29 percent is permanently lost to sea, 10 percent is deposited in reservoirs and 61 percent is transported from one place to other. The plant nutrients lost through 5334 million tonnes of eroded soils was estimated to be 8.4 million tonnes which includes 2.5 million tonnes of N, 3.3 million tonnes of P and 2.6 million tonnes of K.

Siltation of reservoirs through water erosion is a major concern in India. This accelerated silting has considerably reduced the estimated life span of major reservoirs. The rate of siltation depends on the catchment area, soil erodability, topography and rainfall pattern. Larger the catchment area, smaller is the siltation load in the reservoirs because, the coarse fraction of eroded particles may be settle down in the stream valley before the water enters into the reservoir.

Acid soils occupy about 30 percent of the land area of the world out of which 67% acid soils support forests and wood lands and 18 percent are covered by grassland vegetation. Only 4.2 per cent (179 million hectare) of the acid soils across the globe is used for arable crops.

Soil acidity is a major constraint in crop production. The removal of basic cations especially Ca and Mg by leaching and their replacement by acidic cations, H, Al and Fe on exchange complex leads to soil acidity. Soil developed from granite parent material are more acidic than those developed from basalt, shale or lime stone. In acid soils, low pH leading to toxic concentration of H⁺, Al³⁺, Mn²⁺ influences nutrient availability, organic matter decomposition and microbial activity.

Efficient soil amelioration and nutrient management practices are necessary for crops susceptible to soil acidity.

Saline and alkali soils occur commonly under arid climate due either to the presence of an excess of soluble sodium salts or to the predominance of sodium among the exchangeable bases.

Saline and alkali soils have been classified as follows

1. Saline soils

Saline soils were originally called “White alkali” soils. Russians term them as “Solonchak” soils.

The soils are classified as saline if the electrical conductivity of saturated soil paste is more than 4 dS /m at 25⁰C, exchangeable sodium is less than 15 percent and pH is less than 8.5.

2. Alkali soils

The soils have been classified as alkali if the electrical conductivity of saturated soil paste is less than 4 dS/m, exchangeable sodium is more than 15 percent and pH is 8.5 to 10.0.

Water used for irrigation contain some salts, but quantities and kinds vary greatly depending on the source of water. Since sodic status of soils can be greatly influenced by salts in irrigation waters, successful irrigation practices require the evaluation system to judge irrigation water quality and methods employed. The actual damage done by salt to plants or soils depends on the concentration in soil solution rather than the quality of irrigation water applied. Thus, the use of some water source for irrigation might lead to severe salt problem in soils where drainage is restricted.

Criteria for evaluation of irrigation water

Various criteria considered in evaluating the quality of irrigation water are:

1. Salinity hazard

The most satisfactory method for rating the salt content of irrigation water involves measuring electrical conductivity. Various conductivity limits have been proposed to indicate the degree of salinity problems that might be anticipated with use of irrigation water on crops. There are four classes of salinity hazard such as C₁, C₂, C₃, and C₄.

In India rice is cultivated under two land situations. In uplands, rice is grown under rainfed conditions and the yield is normally low. In medium or low land conditions rice is grown under wet condition where plenty of rain water or irrigation water is available. Here an intensive tillage is practiced in wet to create a soft puddle condition and then paddy is transplanted. Land submergence is thus an essential condition for successful rice cultivation.

Rice soils are not necessarily soils with water at or near the surface. Many soils have a fairly deep water table, but their surface is kept under submergence maintaining depth of 3-5 cm water. This condition is maintained either by puddling when wet or by having a compacted layer in the sub surface.

A rice soil is characterized by reducing conditions, when it is cropped with rice during wet season and oxidizing conditions during dry season, when the land remained fallow or planted with dry season crops if, irrigation water is available.

Pollution

Pollution is an undesirable change in physical, chemical or biological characteristics of air, water or land caused by excessive accumulation of pollutants (substances causing pollution).

Kind of pollution

Pollution can be classified in many ways:

Soil health

Soil health is defined as the continued capacity of soil to function as a vital living system, by recognizing that it contains biological elements that are keys to ecosystem function within land use-boundaries. These functions are able to sustain biological activity of soil, maintain the quality of air and water as well as promote plant, animal and human health.

The characteristics of a healthy soil depends on the physical, chemical and biological properties of soils which directly or indirectly influence crop production.

Soil quality and soil health are terms that are discussed in agricultural community. Both these terms encompass a complex, dynamic concept, different to define and hard to measure. The term soil quality and soil health are often used interchangeably in the scientific literature, with scientists in general preferring soil quality and producers preferring soil health. Soil health may be considered as the state of soil at a particular time equivalent to the dynamic properties in short term. In contrast, soil quality may be considered for a particular purpose over a longer time scale, equivalent to static soil quality. In a broader way soil quality may refer to both permanent and static soil properties. (Fig. 11.1).

A static soil property relates to natural characteristic of soil (texture) which are derived from pedogenic processes. These properties cannot be easily amended. The dynamic properties are readily related to management practices. The dynamic component is of most important for the growers because it allows the soil to come to its full potential.

Sustainable management of soil resources is essential for food, nutritional and economic security of the country. The continued degradation of soil resources is considered an important factor in lowering the total and partial factor productivity of agriculture in the country. The process like soil erosion, nutrient loss, water logging, desertification, acidification, compaction, crusting, salinization and soil contamination affect food and environmental security in most parts of the country. The future agricultural growth at higher rate cannot be sustained with a deteriorating soil resource base. We need to monitor the quality of soil resources and devise appropriate management strategies for sustainable crop production without deteriorating the environment.

In India, several agencies like National Commission on Agriculture (NCA), Ministry of Agriculture (Soil and Water conservation Division), Society for Promotion of Waste lands Development (SPWD), NBSS&LUP, Nagpur have been constantly inventorizing and characterizing soil resource for drawing up land use and development plans at National and State levels. However, there is a great variance in estimates due to differences in approaches and criteria for assessment. For an example,the total degraded land as estimated by NCA is 148.09 Mha as against, 175.0 Mha by Ministry of Agriculture (Soil and water conservation Division), 129.58 Mha by SPWD and 187.7 Mha by NBSS&LUP, Nagpur.

In soil profile development, we focused on vertical variability in soils - the differences among soil horizons. In this chapter we focused on horizontal variability- how soils differ from place to place across the landscape. Spatial variations in soil properties occurs across distances having geographic meaning for land management-from a few meters to many kilometers. We need to monitor regularly the status of our soil resources employing modern technologies to refine our understanding about them and renew our commitment to their preservation. The applications of Remote Sensing (RS), Geographical Information Systems (GIS) and Global Positioning System (GPS) have greater opportunities to offer in this regard.

Sustainable management of soil and water resources is essential for food, nutritional and environmental security of the country. The total and partial factor productivity of agricultures in India declined over years because of continued degradation of natural resources. The process leading to land degradation are generally triggered by excessive use of land and water resources to meet the growing demand of population for food, fibre and fodder. Various anthropogenic activities leading to accelerated land degradation through salinization, flooding, water logging, erosion of water and nutrients, drought reduced agricultural productivity and nutritional security in the country. These problems can be overcome by optimum utilization of land adopting suitable management practices. For effective land management practices, the soils should be interpreted in forms of their land capability, suitability for irrigation and crop growth. This will not only help the farming community and extension specialists, but also to the administrators and policy makers for using soils for sustainable agricultural production.

Trees are an integral and indispensable constituents of our natural surroundings. The trees keep the environment clean, make the soil healthy and provide food, fibre and shelter to mankind and wild animals. Trees help in stabilizing the soil, a vital natural resource, prevention of soil and water erosion, control run off water in the catchment areas, acts as a shelter belt against wind erosion in arid zone, act as a wind breaker to protect the coastal region during storm and cyclone besides contributing substantially to economic development. The National Commission on Agriculture stress the need for afforestation of about 40 million ha of land presently lying barren because of salinity, sodicity, waterloggings, ravines, coastal sandy areas, stony and gravelly lands, high altitude and slopping lands. Several agencies in various parts of the country are engaged in afforestation of these degraded lands.

Soil conservation in hilly areas

Soil erosion is a major problem on hills because of steep slopes. It has been estimated that about 6 million ha of land requires intensive conservation measures in Himalayan and sub-Himalayan regions of Uttar Pradesh, Uttarakhand, Punjab and Himachal Pradesh. Anthropogenic activities like shifting cultivation, deforestation, over grazing accelerate soil erosion in hilly ecosystem.

1. FOOD AND ITS SIGNIFICANCE

Food is the basic necessity of all the living world and the man is no exception to this. The basic purpose of food is to provide energy for the routine body functions and protect the body from various diseases. Life cannot be sustained without adequate nourishment for a healthy and active life, diets should therefore, be planned and consumed on sound nutritional principles (Fig. 1). For want of nutritious foods, consequence is the prevalence of malnutrition. There are several diseases that are related with deficiency of nutrition food, if not consumed. Such diseases include Kwashiorkor that can develop in children consuming insufficient protein even if total calories are sufficient. Marasmus is often due to the cessation of breast feeding and the attempt to replace it with foods, inadequate in protein such as rice broth. Other nutritional diseases still found particularly in the developing world are childhood blindness (vitamin A deficiency), rickets (vitamin D deficiency), beri-beri and infantile beri-beri (inadequate thiamin intake), pellagra (inadequate niacin intake), anemia (iron deficiency), goiter (iodine deficiency), etc. To cope up with this, the diet needs to be supplemented with nutritious food components including fruits and vegetables to make it more suitable for the growth and development of body.

Out of different types of foods, the fruits and vegetables constitute an important component of the food. Horticultural crops occupy a prominent position both in the importance and production in the world. The temperate fruits and vegetables are an important part of the horticultural crops, in terms of production and role in human health. These crops assume all the more importance due to their antioxidant activity, and presence of minerals and vitamins. Both fresh and processed fruits and vegetable, their different products are consumed. They are also called as protective foods. Fruits and vegetables are major sources of important vitamins like B and C and minerals such as Ca, Fe, P and K.

1. INTRODUCTION

India produces a large variety of fruits and vegetable due to varied agro-climatic conditions. These include mango, citrus, banana, apple grapes, strawberry, pineapple, litchi, guava, papaya, plum, peach, pear apricot etc. Astonishingly, it may appear but it is a fact that postharvest losses of fruits and vegetables in India are staggering. Infact the postharvest losses of fruits and vegetables are equivalent to the annual consumption of fruits and vegetables in U.K. In this article, a focus is made on the causes of postharvest losses of fruits, overview of various techniques used to prevent the postharvest losses constrains in postharvest technology and future strategies.

1. INTRODUCTION

Every fruit or vegetable is harvested keeping in view, its intended use. At what stage it should be harvested, is indicated by the maturity index. The chapter focuses on these and postharvest quality of fruits and vegetables.

2. FRUIT MATURITY

"Maturity of a fruit can be defined as that stage at which a commodity has reached a sufficient stage of development that after harvesting and postharvest handling, its quality will be at least the minimum acceptable to the ultimate consumer”. Maturity is of two types:

1. INTRODUCTION

When the fruits and vegetables are ready for the intended purpose, these have to be harvested. What is meant by harvesting and how the produce is harvested, what are the harvesting methods, how these are packaged in what type of packages have been discussed in this chapter.

2. HARVESTING

Harvesting of produce at proper maturity is of paramount importance for maintaining quality during storage and marketing. When the produce is harvested immature or over-mature, it will affect the quality and storage life adversely. After the proper maturity stage has reached, the produce needs to be harvested for various markets. While harvesting, it must however, be kept in mind that all horticultural produce (with the exception of some dry fruits/nuts) is very delicate and mishandling at harvesting may lead to mechanical injury, compression injury that is irretrievable. The injury on fruits/vegetables enhances ethylene production, moisture loss and serves as an entry point for a wide range of pathogens, hence causing quick loss in quality and storability of produce. The injury caused to the produce during harvesting not only spoils the commodity but also makes it unfit for long-term storage or long-distance transportation. Proper training to the labour engaged in harvesting on what to harvest, and how to harvest and the use of proper harvesting tools can reduce considerably the postharvest losses.

1. INTRODUCTION

Fruits and Vegetables are heighly perishable crops and have to be handled carefully after harvest. Postharvest handling of these perishables is essential to prevent the post harvest losses and maintain the quality of the fruits and vegetables. Various treatments (chemical, physical and biological agents) have been standardised and used for retaining the storage quality of different horticultural commodities. All these aspects have been discussed in this chapter.

1. INTRODUCTION

To over come the problem of glut of perishables and to regulate the market, storage of such commodities is a 'common' practice. Storage of fruits and vegetables also makes available these commodities in the off-season. Needless to say, storage is a powerful tool in the prevention of postharvest losses and to give remunerative prices to the farmers. The management of temperature and relative humidity are the most important factors determining storage life of horticultural produce. The natural means like ice, cold water, night temperature have been used for long time for protecting food materials from spoilage and these are still common. However, with the development of innovative technologies, it is possible to achieve optimal environments in the insulated stores. All these aspects are discribed in this chapter.

1. INTRODUCTION

In the changing global scenario, food nutrition, health care and livelihood security are the matter of great concern to human, social and economic development. Fruits and vegetables is one of the most important and fast growing sub-sectors as they form an indispensable part of healthy diet. The current trend shows that dietary habits are changing with increasing income, from cereal based diet to nutritious diet. Resultantly, there is a growing demand for horticultural produce.

World production of vegetables amounts to 1169.45 million tonnes, while that of fruits is 689.39 million tonnes (NHB, 2017). India is the second major producer of fruits and vegetables in the world and ranks next to China. India produces 92.85 million tonnes of fruits from an area of 6.5 million hectares and 175.00 millions tonns of vegetables from an area of 9.2 million hectares annually. The productivity of vegetables in India is 17.6 tonnes per hectare. Potato (28.9%), tomato (11.3%), onion (10.3%) and brinjal (8.1%) are the 4 major vegetables contributing 58.6% of total vegetable production in our country. Other important vegetables are cabbage (5.4%), cauliflower (4.6%), okra (3.9%) and peas (2.4%)

1. INTRODUCTION

The Green Revolution and subsequent efforts through the application of science and technology for increasing food production in India, have brought self-reliance in food. The imputs given by the Government, State Agricultural Universities, State Departments of Agriculture and other organizations through the evolution and introduction of numerous hybrid varieties of fruits and vegetables and improved management practices have resulted in increased food production. However, the nation still faces the problem of the use of improper methods for the storage of food stuffs and their preservation leading to great wastage of the food produced. So, there is a urgent need for the application of food preservation and processing methods.

Food preservation involves all the processes used to maintain foods with the desired properties or nature for longer time. The process is has moved from an art to a highly interdisciplinary science. Food safety now the first priority of the food production and preservation industry, incorporating innovations and sustainability. The preservation and processing of food however, is not as simple or straight forward as it was in the past. A number of new preservation techniques have been developed to satisfy the current demands of economic preservation and consumer satisfaction in nutritional and sensory aspects, convenience, and safety, absence of chemical preservatives, and environmental safety. Understanding the effects of each preservation method on food has therefore, become critical in all the aspects.

1. INTRODUCTION

Fruits and vegetables represent highly perishable items of agricultural produce, mainly because of their high water content in the fresh form. Fruits and vegetables vary greatly in their protective covering, peel or rind, and also in shape, size, colour, texture and flavour. Their care starts from the field of harvest, including pre- harvest care to reduce postharvest infections and maintain quality. Because of the high rate of perishability in fresh form, fruits and vegetables are preserved by processing into several forms and choices, depending on the specific commodity to ensure reduction in mass, render storage stability for extension in storage life for both domestic and foreign trade over variable distance and time.

Food preservation can be defined as the science which deals with methods of prevention of decay or spoilage of food, thus allowing it to be stored in a fit condition for future use. In this chapter, food preservation and have been discussed in abroad way.

Thus, sugar serves as a preservative in jam and jelly, whereas salt is the major preservative for pickle. RTS (Ready-to-Serve) beverage under acidic conditions in pasteurized form can be stored at room temperature for approximately three months while dehydrated products with 5% residual moisture with suitable packages, depending on the low hygroscopicity can find storage life upto 12 months. Intermediate moisture product with 25% residual moisture is becoming popular to consume mango or papaya strips directly in ready-to-eat form. Storage quality of such forms assumes greater importance. The use of synthetic preservatives is highly questioned in the modern days. However, low concentrations of potassium meta-bisulfite and sodium benzoate are still in use. Formation of benzene under acidic conditions for example in products like RTS beverage by the use of sodium benzoate is said to be dangerous, as benzene is known to be carcinogenic. This takes us to a subject of food safety including hygiene and HACCP. Good manufacturing practices are practically the most useful form of product preparation to expect safety.

1. INTRODUCTION

Thermal processing means preservation by application of heat. It involves heating of foods in hermetically sealed containers for a specific time at a specific temperature to eliminate the microbial pathogens that endanger public health and that micro-organisms that deteriorate food during storage. The credit for invention of thermal processing (Canning) goes to a French Confectioner, Nichola Appert. The application of heat is an important method of preserving foods and is also a means of developing texture, flavour and colour in some foods.

1. INTRODUCTION

Preservation of foods by drying is perhaps the oldest method known to mankind. Drying is a thermo-physical action and its principles are governed by heat and mass transfer laws inside and outside the product. The weight of the product is reduced to the extent of 1/4^th to 1/9^th of its original fresh weight. Drying of foods and biological products is a widely applied process for different purposes such as increasing the shelf-life, reducing packaging costs, lowering shipping wastes, encapsulating flavours, making food available during off-season, adding value by changing the phase structure of the native material and maintaining nutritional value. Drying or dehydration of fruits and vegetables can be accomplished with low capital while maintaining high quality and obtaining less perishable food products.