eChapters

Pattern of Growth Flushes in a Bearing Tree

Two or three peak periods of growth are usually observed in a bearing cashew tree, even though under favourable conditions the stray shoot growth may occur almost every month. The pattern of growth of a bearing tree consists of a generative flower flush (reproductive) and a vegetative flush. The vegetative flush, consisting of lateral shoots, always develops soon after the main crop has matured. Flowering is terminal and is universally preceded by the vegetative flush.

There are two types of branching in cashew, intensive and extensive.

Cashew being a highly cross pollinated crop, planting of seedling is not recommended. In the past seed propagation was in vogue, which has resulted into large variation in plants due to highly heterozygous nature. However, it is seldom practiced now-a-days except to raise the rootstock materials. Selection of seed is very important for raising rootstock material. Seed nuts which are heavy and sink in water should be selected for raising seedling. Seed nuts should be collected from high yielding trees. Seed nuts collected from the current season’s crop during March, April and May are the best for seed production as they have been found to give high percentage of seed germination. Studies conducted to investigate the time taken and germination percentage revealed that heavy nuts (sunken in water) gave 92 per cent germination on 14-17 days, whereas floating nuts took 14-22 days and gave 64 per cent germination (Krishnamurthy et al., 1985).

Cashew research in India dates back to 1950’s when Indian Council of Agricultural Research sanctioned ad-hoc schemes in the then composite Madras, Travancore, Cochin and Bombay States. Thus, Kottarakkara (Kerala) in 1952; Ullal (Karnataka in 1953 and Vengurla (Maharashtra) in 1957 came into being as pioneering cashew centres in the country. More research schemes were started with ICAR’s assistance in 1955 at Bapatla (Andhra Pradesh) and in 1956 at Deragaon (now shifted to Kothiali) in Assam. During the period, Central Food Technological Research Institute, Mysore and National Chemical Laboratory, Pune were also engaged in developing technologies for economic utilisation of cashew apple and Cashew Nut Shell Liquid (CNSL). In the second phase of strengthening cashew research in India, the ICAR started All India Spices and Cashewnut Improvement Project in 1971 linking countrywide network among different research centres. Collection, conservation and evaluation of germplasm, hybridization and selection, vegetative propagation, and nutritional studies were the primary areas under this programme.

Maharashtra, the first state was to release cashew variety under the name Vengurla-1 through Dr. Balasaheb Sawant Konkan Krishi Vidyapeeth, Dapoli in the year 1974. So far, 8 varieties have been released from Regional Fruit Research Station, Vengurla (M.S.), of which, Vengurla-4, Vengurla-6, Vengurla-7 and Vengurla-8 are widely accepted for commercial plantation.

Anacardium occidentale is a medium-sized tree, spreading, and evergreen, much branched; grows to a height of 12 m. When grown on lateritic, gravelly, coastal sandy areas, it rarely exceeds 6 m and develops a spreading habit and globose shape with crown diameter to 12 m but, if grown inland on loams; it reaches 15 m tall and is much branched, with a smaller (4-6 m) crown diameter. The root system of a mature A. occidentale, when grown from the seed, consists of a very prominent taproot and a well developed and extensive network of lateral and sinker roots. Leaves simple, alternate, coriaceous, glabrous, obovate, rounded at ends, 10-18 x 8-15 cm, with short petiole, pale green or reddish when young and dark green at mature. Rai and Vatsala (1985) studied the dermal morphology and stomatal ontogeny of Spondias pinnata Kurz., Lannea coromandelica (Houtt.) Merr., Anacardium occidentale L., Holigarna arnottiana Hook. F. and Mangifera indica L. are studied. The cuticle is thick in H. arnottiana, A. occidentale and M. indica, but is thin in S. pinnata and L. coromandelica. Based on the shape of epidermal cells, the five species are categorised into three: cells in both upper and lower epidermis sinuous (A. occidentale, H. arnottiana, S. pinnata); upper sinuous and lower polygonal (M. indica) and upper polygonal and lower sinuous (L. coromandelica). Stomatal ontogeny aperigenous (L. coromandelica), paramesoperigenous (A. occidentale) and anisomesogenous (M. indica, H. arnottiana). S. pinnata is peculiar in that it possesses three different types of stomata, aperigenous, hemiparamesoperigenous and paramesoperigenous; whereas, in all the other four species, only one type of stomatal ontogenesis exists. Except S. pinnata, all the other species possess epidermal appendages. Unicellular trichomes occur in A. occidentale and H. arnottiana, and multicellular glandular trichomes in A. occidentale, M. indica and L. coromandelica. The multicellular hairs are found in A. occidentale in specialized pockets in two rows on either side of the major veins - a unique feature which is reported for the first time.

Soil
Cashew is grown on a wide variety of soils in India. It comes up well in all types of soils at an altitude up to 700 m. It cannot stand in water logged or saline soils. It can come up in very sandy soils also. Adoption of cashew has been found in wide variety of soils from coastal sands to degraded laterites. The worst soils, not suited to other crops, are normally allotted for cashew. In Sri Lanka and Philippines, it is grown in alluvial soils. Cashew comes up well even in volcanic soils of Indonesia, Fiji and some part of Philippines. Cashew is not suitable in heavy clays, water logged conditions and ill drained soils. It is grown abundantly in loose sandy soils particularly in South India, East Africa and Brazil. In Karnataka and Kerala, it grows well in poor laterite soils. Cashew prefers well-drained aerated sandy loam soils with adequate moisture. Coastal plains and plateau are very good for cashew cultivation.

In India, cashew is mostly grown on laterite and red soils and coastal sands. The tree has an extensive root system, which helps it to tolerate a wide range of moisture levels and soil types, but commercial production is only advisable in well-drained, sandy loam or red soils with slight acidic pH (4.5-6). The cashew tree can flourish in the sand of open beaches, but it grows poorly in heavy clay or limestone.

Though cashew can be grown on a variety of soils, a well-drained 1-1.5 m deep soil having a water table between 2 and 10 m depth and pH of 5.6 to 7.0 is preferred. Laterites, red and coastal soils rich with organic matter are best for cashew growing. Even the marginal soils can be used for cashew cultivation but the waterlogged condition should be avoided as the cashew is very susceptible to it (Farooki and Sreeramu, 1999).

Global Scenario

Globally, India’s share in the cashew area and production is 20 per cent and 16 per cent, respectively. India occupies the largest area followed by Ivory Coast (19%), Brazil (16%), Indonesia (12%), Vietnam (7%), Nigeria (7%), Benin (5%), Guinea-Bissau (5%), Mozambique (2%) and Philippines (1%). The highest production was from Vietnam (30%) followed by Nigeria (19%), India (16%), Ivory Coast (11%), Brazil (5%), Indonesia (3%), Philippines (3%), Guinea-Bissau (3%), Benin (2%) and Mozambique (2%). Sometimes back, India was credited as largest producer, processor and exporter of cashew in the world but as other cashew producing countries also acquired the know-how of processing and entered in the international market, currently the India’s share in the International market has shrank to 30 per cent only. On the other hand, the domestic consumption in India has increased considerably, owing to largest consumption of cashew kernel. Every year, over 7-8 lakh tonnes of raw cashew nut are imported mainly from African countries and exporting cashew kernel to USA and UK after processing (Saroj, 2013).

Cashew has a long history as a useful tree but only in the current century, it became an important tropical horticultural crop. Small-scale local exploitation of cashew for its nuts and cashew apples is the pattern for more than 300 years in Asia and Africa. It was not until early years of 20^th century that international trade in cashew kernels began with first exports from India. Although with slow beginning, cashew became an important commercial crop in the last couple of years. In India, use of cashew apples and nuts was started by local people, and accounts from Africa are similar; making cashew wine/liquor possessing a common practice in both Asia and Africa (Johnson, 1973).

Cashew, an evergreen tree, produces both nuts and apples, has become a crop of importance owing to the highly valued kernel and wide adaptability to varying agro-climatic conditions. India is one of the largest producer, exporter and consumer of cashew in the world. Today, cashew has become a crop of high economy and has moved from a crop of waste lands to commercial crop, even in organized sector (Singh, 1998).

The cashew nut (Anacardium occidentale L.) belongs to Anacardiaceae family which also includes the mango, pistachio and poison ivy (Nakasone and Paull, 1998). Anacardium contains 8 species all of which are native to the coastal parts of north eastern Brazil (Azam-Ali and Judge, 2001). Cashew nut tree provides food, employment, income and the wood is used for carpentry mainly in the construction of boats and ferries while other products derived from it include firewood and charcoal (Akinwale, 2000). Cashew resins are also used in the manufacture of insect repellents and natural insecticides, while different tree parts have medicinal value as they are used to cure various diseases (Cavalcante et al., 2003). The cashew tree is a sprawling broad-leafed evergreen, well adapted to poor soils and dry sandy locations, drought resistant, but grows best on well drained sandy soils with pH of 4.5 to 6.5 (Aliyu, 2004). It favours temperatures between 15 to 35°C and rainfall over 400 mm with elevation of up to 1000 m above sea level.

Horticulture includes fruits, vegetables, floriculture, spices, tubers, plantation crops, medicinal and aromatic plants and mushrooms. The sector has established its importance in improving land use, promoting crop diversification, generating employment and above all providing nutritional security to the people. Even though India is the second largest producer of horticulture produces in the world, our per capita consumption of fruits and vegetables are very low.

Borer pests cause significant yield losses and are one of the most serious production constraints in tropical vegetable production. For instance, eggplant fruit and shoot borer (EFSB), Leucinodes orbonalis Guenée (Lepidoptera: Pyralidae) reduces yield as much as 70% (Dhandapani et al., 2003). Tomato fruit borer, Helicoverpa armigera Hubner (Lepidoptera: Noctuidae) causes about 5 to 55% loss in almost all the tomato producing areas in the world (Kashyap and Batra, 1987). Up to 80% yield losses have been reported in various vegetable and grain legumes due to legume pod borer (LPB), Maruca vitrata F. (Lepidoptera: Pyralidae) damage (Singh et al., 1990; Sharma, 1998; Gressel et al., 2004; Hammig et al., 2008; Zahid et al., 2008). Due to higher yield losses, growers tend to apply extremely high quantities of chemical pesticides to control borer pests on vegetable crops. Because the borer larvae are exposed on external plant parts only for a brief time after hatching, the window for effective pesticide application is very brief; vegetable farmers spray throughout the growing season, but without satisfactory results. A survey of pesticide use in Bangladesh indicated that farmers spray up to 180 times with chemical insecticides during a year to protect their eggplant crop against EFSB (SUSVEGAsia, 2007). Pesticide application often exceeded 50 sprays per tomato crop season in south India (Nagaraju et al., 2002). In Bangladesh, country bean (Lablab purpureus) is being sprayed at weekly or biweekly intervals—sometimes every day—to control LPB (Hoque et al., 2001). On average, farmers used 10-24 kg/ha of pesticides in cabbage and cauliflower in India to manage the diamondback moth, Plutella xylostella (Lepidoptera: Plutellidae) and other pests (Weinberger and Srinivasan, 2009).

Ash gourd (syn:wax gourd, winter melon, white gourd, white pumpkin, ash pumpkin, Chinese preserving melon and hairy melon) is a vegetable belonging to family Cucurbitaceae and genus Benincasa with only one cultivated species, Benincasa hispida (Thunb.) Cogn. (2n=2x=24). Ash gourd is an important vegetable especially in the Indo-China region, which is also the major producer of ash gourd (Rubatzky and Yamaguchi, 1997), but it is also a potential crop of tropical Africa and America (Sirohiet al., 2005).

Spices are defined as a strongly flavored or aromatic substance of vegetable origin, obtained from tropical plants, commonly used as a condiment. India is known as ‘land of spices’. Chilli (Capsicum annuum L.) also known as hot peppers and Capsicums also referred as bell peppers or sweet peppers belong to the genus Capsicum which is a member of the Solanaceae family. The native home of chilli is considered to New Mexico with secondary origin at Guatemala. They are known from pre-historic remains of Peru. Chilli was introduced into India by Portuguese in 16th century. Chilli is considered as one of the major commercial crops of the world. Both green and dried chillies are the important components of our routine diet. Chilli also contains vitamin A, C and E. It will give the required pungency, colour, taste and flavour to our dishes. The presence of capsaicin in chilli is responsible for its pungency and it has medicinal value. The extracted capsaicin is used in pain balms, cosmetics and medicines related to heart diseases. Capsanthin, a pigment in chilli is used for natural colouration to Jams, Jellies and squashes, since it is a natural pigment and no harmful or side effects on human health. Oleoresin is used in pain balms, vapours, etc. Hence, there is lot of demand for chilli oleoresin in the world market. The largest producer of chillies in the world is India contributing 52 per cent of world production, accounting for 11.67 lakh tonnes of production from an area of 7.5 lakh ha with 1550 kg/ha of productivity followed by Nigeria (17%), China (16%), Peru and Bangladesh (6%). India exported 1.8 million tonnes of chilli during 2009 (Reddy, 2010).

Recently people are moving towards newer trends in food diversification for value addition. The beneficial effects could be either maintenance, promotion or well being of health or reduction of the risk of a pathogenic process or a disease. Genetically modified (GM) crops / foods, algae, mushrooms and probiotics are among the important functional foods which apart from improving health also protect against infections and/or stimulate immune systems. The interactive research between physiology, microbiology, food technology and molecular biology may produce many healthful, diversified value based food products for human consumption. The concept of value addition in food is changing significantly. Earlier the emphasis was on survival through hunger satisfaction but today it is aiming towards food safety and food sciences at developing foods which promote good health and reduce the risk of major diseases. With these efforts, these products have come into the market and are identified as functional foods. These include foods containing phytochemicals, dietary fibre, structural lipids, bioactive peptides, polyunsaturated fatty acids.

Recent awareness of consumers towards innovative probiotic fermented food products containing friendly bacteria and healthier foods has coined the term functional foods. Food development in the world is taking place mainly in three strategic directions as functional foods, organic foods and national foods. Every year the global demand is increasing at the rate of 15–20 %.

Fermentation by newer technologies involves specific strain of lactic acid bacteria. This brings specific fermentation under controlled conditions resulting in a specific fermented product with enhanced organoleptic, nutritional and therapeutic qualities.

Pomegranate is one of the oldest known edible fruits and is associated with ancient civilizations of the Middle East. From its origin in the area now occupied by Iran and Afghanistan, the pomegranate spread east to India and China and west to Mediterranean countries (Turkey, Egypt, Tunisia, Morocco, and Spain). Spanish missionaries brought the pomegranate to the Americas in the 1500s (Hodgson, 1917; LaRue, 1980). The primary commercial pomegranate growing regions of the world are the Near East, India and surrounding countries, and southern Europe. The fruit is consumed fresh or processed into juice, syrup, jams, or wine (Fig. 1) (LaRue, 1980; Adsule and Patil, 1995; Kumar, 1990; Patil and Karale, 2001; Roy and Wasker, 1997).

The potato (Solanum tuberosum L.) is one of the four most important food crops of the world, the other three being rice, wheat and maize. It is a high yielding and nutritive crop and produces highest dry matter, carbohydrates, edible protein, minerals and vitamin C and B per unit of area and time. In view of the shrinking cultivable land area and increasing population of India, the potato has a high potential to solve the problems of hunger and malnutrition in our country. But, potato is a perishable commodity and its harvest time (February/March) in Indo-Gangetic plains (which account for nearly 87% of the country’s potato production) coincides with steep rise in ambient temperatures. From April onwards, temperatures start shooting up and the produce has either to be consumed within a short period of time or is required to be preserved in the cold stores. Due to inadequate, expensive and unevenly distributed refrigerated storage facilities in the country, there have been frequent gluts in the market causing substantial economic losses to farmers and wastage of precious food. Such gluts occur every 3 to 5 years. The glut years are followed by a reduction in potato area and production leading to high potato prices in alternate years which again encourage farmers to increase potato area in subsequent years resulting again in a glut situation and price crashes. This boom and bust cycle has thus continued for long (Pandey et al., 2009).

Consumption of fruit and vegetables has dramatically increased globally during the past a few decades. These are living perishable biological entities which perform a number of metabolic functions and have a short life span. Once the fruit is harvested, respiration and transpiration continue, but only for as long as the fruit can draw on its own food reserves and moisture. It is this limited ability to continue vital metabolic functions which define fruit as perishable. It is also estimated that about 20% of all fruits and vegetables produced are lost each year due to spoilage. The process of the fruit spoilage is just the decomposition of the fruit itself. Once harvested, this begins to deteriorate until eventually it becomes unfit for consumption. This deterioration is known as decay and that leads to spoilage. Latter may be defined as “any sensory change (physical, visual, olfactory or flavour) which the consumer considers to be unacceptable. The gradual changes which cause deterioration and decay in fruits are due to certain organisms and chemicals present in the food and outside the food. Carbohydrates play a major role in the fruit spoilage process (Prasanna et al., 2007) by way of depolymerization leading to decreased molecular size with concomitant increase in the levels of ripening inducing specific enzymes, whose target differ from fruit to fruit. The major classes of cell wall polysaccharides that undergo modifications during ripening are pectins, cellulose, starch, and hemicelluloses (Hallet et al., 2005). The focus of this chapter is to provide information about carbohydrate metabolism during fruit spoilage.

Sustainability refers to productive performance of a system over time. It implies use of natural resources to meet the present needs without jeopardizing the future potential. The Technical Advisory Committee of the Consultative Group of International Agricultural Research has defined sustainability as “Successful management of resources for agriculture to satisfy changing human needs while maintaining or enhancing the quality of the environment and conserving natural resources” (TAC, 1989). A sustainable system must be sustainable both ecologically and economically.

During the past several decades, production of horticultural crops has undergone a tremendous change in both developed and developing countries due to the development and use of fertilizers, pesticides, mechanization, soil fumigation, container production in soil-less media, breeding, micropropagation, pathogen elimination and a number of other innovations for attaining its future stability and sustainability. Recently, in modern horticulture, enhanced productivity depends heavily on inputs of fertilizers and pesticides to maintain an economic level of productivity. On the other hand, social and economic pressures are demanding that agricultural/horticultural practices, that have a damaging impact on the environment and pose risk to health of mankind, be curtailed. Thus throughout the world, agriculture including horticulture is at crossroads in terms of its future stability and sustainability. The solution for the above lies in developing new technology with reduced use of fertilizer and pesticides besides maintaining a sustainable level of productivity. The increased concern about the sustainability and undesirable side-effects of chemistry-based agriculture is prompting many researchers to more seriously evaluate alternative approaches. One such effort was put forth in the management of microbes that live in the rhizosphere soil around the roots of nearly all terrestrial plants. It has been believed that the main orchestrators of microbial activity in the rhizosphere are mycorrhizal fungi.

The harmony between human beings and plants is one of the evergreen reasons that maintains and supports life on earth. This fact clearly explains why any hazard to the life of plants prominently affects man. One important feature distinguishing plants from other complex multicellular organisms is that plants are sessile and thus have to endure environmental challenges (Zhu, 2001).

Crop productivity is limited by stress factors. The stresses which pose major threats to survival of plants belong to two categories- abiotic and biotic stress. Drought, salinity, high or low temperatures, light, deficient or excess nutrients, heavy metals, pollutants etc., either individually or in combination causes abiotic stresses. Biotic stress refers to any stress provided by living organisms, be it unicellular or multicellular. Plants facing a variety of biotic and abiotic stresses are able to protect themselves by means of tolerance mechanisms which result from changes at the molecular level. They are often confronted by a multitude of stresses in their natural environment. To overcome this, plants have evolved various defence strategies, which involve comprehensive reprogramming of the cellular metabolism.

Understanding biology and genetics at molecular level has become very important for better understanding and manipulation of genome architecture and this creates new opportunities to streamline plant breeding. Breeding is simply defined as the selective mating of individuals of a population to isolate or combine desired morphological, physiological or genetic traits such as appearance, yield, and disease resistance. This is performed with the assistance of identifiable traits.

Molecular markers have contributed significantly in this respect and have been widely used in plant science in a number of ways, including genetic fingerprinting, diagnostics, identification of duplicates and selecting core collections, determination of genetic distances, genome analysis, identification of markers associated with desirable breeding traits which are useful in marker assisted breeding, genomics and development of transgenics. Use of these markers also significantly reduces breeding time and cycles required for crop improvement. This is reflected in the fact that complete molecular and genetic maps have now been constructed for at least 20 major crop species and many more have been characterized at less defined level and the genomes of a few model plant species were completely sequenced.

Climate Change: Understanding our Earth and Atmosphere

Our Mother Earth is the fifth largest planet in the solar system and the third from the sun. It is also the sole planet whose name comes from old English language only, and not from names of any other celestial bodies, whose names originated mostly from Greek/Roman mythology. Earth has a diameter of 6378 km, of which the earth crust (uppermost skin) is only 24 km. Earth is the only planet where water exists as liquid and 71% of its surface is covered by water. The earth’s atmosphere is made up mostly of nitrogen (77%) and oxygen (21%) gases. CO₂ consists of a very small (trace) fraction (0.03%) of atmosphere, but is most vital for the life cycle. When earth was created, it has got much higher CO₂ than today, and all of them have been sequestered in rocks as carbonates and dissolved in oceans and a negligible amount is distributed in plant communities. This extremely small quantity of CO₂ is keeping life on earth, by maintaining earth’s temperature at a comfortable 14°C (without CO₂, earth’s temperature would have been -21°C). This effect is called the ‘greenhouse effect’, revolving which all issues of climate change exist. It is also to be noted that water vapour is also an important greenhouse gas (GHG). It is to also to be noted that in spite of substantial increase in solar constant, earth’s average temperature has remained stable for billions of years. It is understood that this was possible through variation in CO₂, and it is the biological processes (Earth biosphere) that controlled the environment over years (Gaia hypothesis).

In this era of molecular markers in genetic studies, genome analysis encompasses several stages of increasing resolution and sophistication, leading to the generation of high resolution chromosome maps. Since the entire plant kingdom cannot be covered under sequencing projects, molecular markers and their correlation to phenotypes provide us with requisite landmarks for elucidation of genetic variation.

A molecular marker is a site of heterozygosity for some type of DNA variation. Such a DNA marker in mapping analysis is analogous to a conventional heterozygous allelic pair. When they are used for mapping the genome, the identity of this DNA fragment is not important, but is simply used as a reference point to arrange and order the genetic information along the length of a chromosome. The molecular markers provide landmarks along the length of chromosome that facilitate the manipulation of chromosome segments in breeding and chromosome engineering programs.

Delineating species boundaries correctly and also identifying species are crucial to the discovery of life’s diversity because it determines whether different individual organisms are members of the same entity or not (Dayrat, 2005). The identification of species depends on the knowledge held by taxonomists whose work cannot cover all taxon identification requested by non-specialists. To deal with these difficulties, the ‘DNA Barcode of Life’ project aims to develop a standardized, rapid and inexpensive species identification method accessible to non-taxonomists.

DNA barcoding is a technique in which species identification is performed by determining and comparing the sequences of several hundred base pairs of nucleotides from a small fragment of an identified gene, with the aim of contributing to a wide range of ecological and conservation studies in which traditional taxonomic identification is not practical (Krishnamurthy and Francis, 2012). The two main ambitions of DNA barcoding are to assign unknown specimens to species and to enhance the discovery of new species and facilitate identification, particularly in cryptic, microscopic and other organisms with complex or inaccessible morphology (Hebert et al., 2003a). Apart from these, identification of species previously defined by other criteria to also is an objective of barcoding. Another major objective could be the definition of operational units for ecological studies. This may also be used for forensic purposes by linking the specimens with already identified databases.

Ethylene is a primary plant hormone involved in the senescence of plant tissues including flowers and leaves. In carnation, inhibition of the synthesis or action of ethylene delays the onset of senescence symptoms and lengthens the vase life of flowers. Leaves of cut chrysanthemum of some cultivars frequently become yellow, sometimes prior to onset of flower senescence, in response to exogenous ethylene. Generation of transgenic plants with suppressed production or action of ethylene is an excellent way to lengthen the longevity of these ornamental plants. This paper reviews our studies on generation and characterization of carnations with reduced ethylene production and chrysanthemum with reduced sensitivity to ethylene.

Ethylene is a primary plant hormone involved in the senescence of cut flowers of many ornamentals such as carnation, sweetpea and delphinium. It is produced on a large amount at a later stage of flower senescence. The increased ethylene production accelerates withering and dropping of petals. Inhibition of synthesis or action of ethylene delays the onset of senescence symptoms and extends the vase life of flowers.