Chapter I: General Introduction-

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1 Human civilization has begun with agricultural practices that played an important role in the global system. Agriculture is the main source of employment for a majority of the world s poorer population and it shares total employment in developing countries which constitutes about 60% of the total workforce in (FAOSTAT, 2011). India has a strong agriculture-based economy and 43% of its territory remains employed in agricultural activities. Agriculture contributes 30% of the countries gross domestic product (GDP) and 20% of total exports. In India, the existence of diverse agro-climatic conditions has enabled the production of a wide array of horticultural crops. Horticultural crops contribute about 18% to the gross agricultural output in the country and occupy hardly 7% of the cropped area. India is the second largest producer of vegetables in the world next only to Brazil and China, producing 66 Mt of vegetables contributing 8.6% of the world production (FAOSTAT, 2008). Vegetables are the fresh and edible portions of herbaceous plants; which includes edible roots, stems, leaves, fruits or seeds, each contributing to diet in its own way (Robinson, 1990), and are valued mainly for their high content of carbohydrate, minerals, vitamins and fiber. They contain valuable food ingredients which can be successfully utilized to build and repair the body. 1.1 Chilli Chilli pepper or Chilli are the fruits or berries of plants belonging to the genus of the nightshade family, Solanaceae, cultivated in temperate and tropical regions (Pozzobon et al., 2005). Chilli is considered to be a native of South America having a secondary centre of diversity and origin in Guatemala. Capsicum is derived from the Greek word "Kapsimo" meaning "to bite (Basu and De, 2003). It is an indispensable spice in the food habits of most people in the world over. Chillies are known as capsicum, paprika, pimento, sweet pepper, hot pepper, red pepper, bird pepper etc. Capsicum has at least about 30 species, from which five have become domesticated: Capsicum annuum, C. frutescens, C. chinense, C. pubescens and C. baccatum (Lanteri, 1993; Pozzobon et al., 2005; De Teodoro-Pardo et al., 2007). In India only two species viz., C. annuum and C. frutescens are the most cultivated varieties (Bosland and Votava, 2003; Kallupurackal and Ravindran, 2004). Chilli is classified under, 1

2 Kingdom : Plantae Division : Spermatophyta Class : Magnoliopsida Order : Solanales Family : Solanaceae Genus : Capsicum Species : Capsicum annuum (L.) Common names: capsicum, paprika, pimento, sweet pepper, hot pepper, red pepper, bird pepper Figure 1.1 Healthy chilli plant a) b) Figure 1.2 a) Chilli growing field near Gadag district of Karnataka; b) Drying of chilli fruits after harvest 2

3 Chilli (Capsicum annuum) is the fourth most important vegetable in the World and the first in Asia (FAOSTAT, 2008). It is an annual herbaceous crop and appears rich in diversity for size, shape, color and quality of fruit. Optimum temperature range required is C and prefers annual rainfall of cm. Normally, chilli is raised by transplanting seedlings but in some regions direct seed sowing is also practiced. Chilli prefers frost free climate and relatively dry weather during fruit maturity. It can be grown in wide range of soils but well drained fertile loam soil is ideal. Chilli cannot withstand water logging condition for more than a day. The ideal ph range is 6-7 but it is grown on soils with ph 5-9 in India. Harvesting of green chilli crop is done when the fruits are green and matured. For the harvesting of red chilli crop, it is to be harvested late when 80% of them become red in color and dry up (Kallupurchal and Ravindran, 2004). The fruit shape may be elongated, round, distal and pointed, blunt or sucked, with skin corrugated, leathery or smooth. Color varies from green, orange, red, yellow, violet and cream to near black. 1.2 International scenario: The world area and production of chilli is around 15 lakh ha and 70 lakh tonne respectively. The major chilli producing countries with their percentage share in world total production are India (41.8%), China (8.2%), Pakistan (5.9%), Bangladesh (5.10%), Peru (4%), Thailand (4%) and others (18.6%) (Fig.1.3a). India is the world leader in chilli production followed by China and Pakistan. The major consumers of chilli in the world are India, China, Mexico, Thailand, United States of America, United Kingdom, Germany and Sweden. The world trade in chilli accounts for 16% of the total spice trade of the world, occupying second position after black pepper. The major chilli importing countries of the world are United Arab Emirates, European Union, Sri Lanka, Malaysia, Japan and Korea (Sources: Spices Board of India and FAOSTAT, 2011). 1.3 Indian scenario: India is the world s largest producer, as well as consumer and exporter of chilli. India also has the largest area under chilli cultivation in the world. Chilli production is spread throughout the length and breadth of the country with almost all the states producing this crop. It can also be grown round the year at one or the other part of the country. However, the major arrival season extends from February to April and market remains active till May. The crop planting starts from August and extends till October. The harvesting begins from December with 5% of the arrivals usually reported in this month. The major producers are Andhra Pradesh, 3

4 Karnataka, Madhya Pradesh, Orissa, Maharashtra and Tamil Nadu (Fig.1.3b). Andhra Pradesh alone commands around 80% of chilli production in India (Source: Spices Board, India). The major chilli growing districts of Andhra Pradesh are Guntur, Warangal, Khammam, Krishna and Prakasham. Chilli has well established spot markets. Guntur, Warangal and Khammam in Andhra Pradesh; Raichur and Bellary in Karnataka are the major spot markets at the production centers. Chilli is known by its quality which differs from state to state. Karnataka chilli quality is known for its high oil content, Gujarat chilli is known for its sharp color, Rajasthan chilli is loved by pickle makers, Assam chilli is famous for its hard taste and Andhra Pradesh chilli is preferred for its hotness. China is the only competitor for India in this commodity. Chilli production and yield around the world and in India during are presented in Table 1.1. Table 1.1 Chilli production around World and India during World India Variety Green chillies Red chillies Green chillies Red chillies Year Area Yield harvested (ha) (hg/ha) Production (t) ha-hectare; hg/ha-hectogram/hectare; t-tonne. (Source: 4

5 World scenario of chilli production India 19% China Pakistan 2% 3% 3% 4% 4% 42% Bangladesh Peru Thailand Burma Ethiopia a. 4% 5% 6% 8% Vietnam Ghana Others Indian scenario of chilli production 18% 27% Andra Pradesh Karnataka Mahdya Pradesh 8% 2% 9% 19% Maharastra Orrisa Uttar Pradesh Tamil Nadu b. 12% 5% Others (Sources: Spices Board of India and FAOSTAT, 2011) Figure 1.3 a) Percentage of chilli production across World b) Percentage of chilli production across India 5

6 1.4 Nutritional significance Chilli fruit contains impressive list of plant derived chemical compounds that are known to have disease preventing and health promoting properties. Chillies have strong spicy taste that comes from the active alkaloid compounds capsaicin, capsanthin and capsorubin. Chilli has amazingly high levels of vitamins and minerals. Fresh chilli peppers, red or green, are rich source of vitamin-c and pro-vitamin-a. Vitamin-C is a potent water-soluble antioxidant, which is required for the collagen synthesis in the body. Collagen is the main structural protein in the body required for maintaining the integrity of blood vessels, skin, organs and bones. Regular consumption of foods rich in vitamin-c protects body from scurvy; promotes development of resistance against infectious agents and scavenges harmful pro-inflammatory free radicals from the body. High vitamin-c content food can also substantially increase the uptake of non-heme iron from other ingredients in a meal such as beans and grains and also assist digestion (Kallupurackal and Ravindran, 2004). Chillies are also good in other antioxidants like vitamin-a, flavonoids, β-carotene, α-carotene, lutein, zeaxanthin and cryptoxanthin. These antioxidant substances in chilli help to protect body from injurious effects of free radicals generated during stress and disease conditions. Chillies also contain substantial amounts of minerals like potassium, manganese, iron and magnesium. Potassium is an important component of cell and body fluids that helps controlling heart rate and blood pressure. Manganese is used by the body as a co-factor for the antioxidant enzyme, superoxide dismutase. Chillies are also good in B-complex group of vitamins such as niacin, pyridoxine (vitamin-b6), riboflavin and thiamin (vitamin-b1). Nutritional details of chilli along with percentage Recommended Dietary Allowance (RDA) are furnished in Table

7 Table 1.2 Nutrient values of chilli (Capsicum annuum) Principle Nutrient Value for (100 g) RDA* (%) Principle Nutrient Value for (100 g) RDA* (%) Energy 40 Kcal 2 Electrolytes Carbohydrates 8.81 g 7 Sodium 9 mg 0.5 Protein 1.87 g 3 Potassium 322 mg 7 Total Fat 0.44 g 2 Minerals Cholesterol 0 mg 0 Calcium 14 mg 1.5 Dietary Fiber 1.5 g 3 Copper mg 14 Vitamins Iron 1.03 mg 13 Folates 23 µg 6 Magnesium 23 mg 6 Niacin mg 8 Manganese mg 8 Pantothenic acid mg 4 Phosphorus 43 mg 6 Pyridoxine mg 39 Selenium 0.5 µg 1 Riboflavin mg 6.5 Zinc 0.26 mg 2 Thiamin 0.72 mg 6 Phyto-nutrients Vitamin A mg 32 β-carotene 534 µg -- Vitamin C mg 240 α-carotene 36 µg -- Vitamin E 0.69 mg 4.5 β-cryptoxanthin 40 µg -- Vitamin K 14 µg 11.5 Lutein-zeaxanthin 709 µg -- (Source: USDA National Nutrient data base) *Note: RDA-Recommended Dietary Allowance 1.5 Applications of Chilli Chilli is an important ingredient in the curries, pickles and chutneys. Oleoresin, sauce and essence are prepared from chillies. The color and pungency differentiates chillies from other spices. Apart from culinary purposes, chillies are also used in medicinal applications and beverages. Early laboratory studies on experimental mammals suggested that capsaicin has anti-bacterial, anti-carcinogenic, analgesic and anti-diabetic properties. It was also found to reduce low density lipoproteins (LDL) cholesterol level in obese individuals (Joe and Lokesh, 1997; Wachtel, 1999). 7

8 Chilli also contains phytochemicals known collectively as capsaicinoids. Chilli alkaloids are used in the preparation of ointments, rubs and tinctures for their astringent, counter-irritant and analgesic properties (Daood et al., 1996; Mori et al., 2006). These are proven treatments for skin ailments. They are the primary active ingredients of over-the-counter topical ointments intended to alleviate a wide range of joint and muscle pain, including the pain from arthritis. They have also been shown, in laboratory settings to shrink carcinogenic tumors with minimal side-effects. They are known to control or even eliminate certain parasites from the gastro-intestinal tract. Chilli might have cardiovascular benefits, although proven benefits appear to be limited to increased myocardial perfusion in men (Ahuja et al., 2007). Some sources also claim weight loss properties by inducing thermogenesis. Canadian researchers believe that chillies might play a vital role in treating diabetes (Kallupurackal and Ravindran, 2004). Chillies have been used in the treatment of arthritic pain, postherpetic neuropathic pain, sore muscles, etc. 1.6 Chilli anthracnose Chilli plants are been attacked by more than 100 different types of pathogens during their growth and development. These include fungi, bacteria, virus, nematode and mycoplasma like organisms (Table 1.3). Fortunately, only a few of them cause economic losses. Three species of Colletotrichum including C. capsici, C. acutatum and C. gloeosporioides have been identified as the most important pathogens causing anthracnose of chilli (Than et al., 2008c). However, C. capsici is predominant and appeared to be virulent compared to C. gloeosporioides (Montri, 2008). Colletotrichum capsici is known to infect leaves, stems and fruit, which are serious in chilli growing areas of India. Sydow (1913) reported the disease for the first time in India, the disease sometimes causes up to 84% loss in yield (Thind and Jhooty, 1985). The disease has been observed to occur in three phases, which includes seedlings blight or damping off stage, leaf spot or die back and anthracnose or fruit rot. During die-back the fungus causes necrosis of tender twigs from the tip to backwards (Siddique et al., 1977). Infection usually begins during flowering stage and flowers dry up. This drying up spreads from the flower stalks to the stem and subsequently causes die-back of the branches and stem. The entire branch or the entire top portion of the plant may withers away and partially affected plants bear fruits which are few 8

9 Chapter I: General Introductionand are of low quality. The dead twigs look water soaked to brown, becoming grayish white or straw colored in advanced stage of the disease. A large number of black dots (acervuli) are seen scattered all over the necrotic surfaces of the affected twigs. Sometimes the necrotic areas get separated from the healthy area by a dark brown to black band. Die-back usually appears after the stoppage of rain and when there is prolonged deposition of dew on the plants (Rajeshwari et al., 2004; Sharma et al., 2005). Conidia from acervuli and microsclerotia get dispersed in water splash and thus spread to the foliage and fruit (Bailey and Jeger, 1992). Anthracnose is mainly a disease of mature fruits, causing severe losses due to both pre- and post-harvest fruit decay (Bosland and Votava, 2003). In anthracnose, the ripe fruits turning red get affected by this disease, whereas green fruits are not generally attacked. Symptoms on the fruit first appear as sunken, water-soaked lesions that expand rapidly on the fruit (Voorrips et al., 2004). Fully expanded lesions are soft, sunken and range in color from dark red to tan black, generally described as anthracnose disease (Wharton and Dieguezuribeondo, 2004). A small, black, circular spot initially appears on the skin of fruits and it then spreads in the direction of the long axis of the fruit, thus becoming more or less elliptical. As the infection progresses, the spots get either diffused becoming black, greenish or grey in color or they are markedly delimited by a thick and sharp black outline enclosing a lighter black or straw colored area. On this discolored area numerous black acervuli are found scattered. When a diseased fruit is cut open the lower surface of the skin is found covered with minute, spherical, black stromatic masses or sclerotia of the fungus. Seeds are also covered by a mat of fungal hyphae. Such seeds turn rusty in color. Affected fruits are deformed in shape and lose their pungency. Ultimately the diseased fruits shrivel and dry up. Once the lesion develops, the fungus produces the conidia within 3 to 5 days at 30 C and at 90% relative humidity. A dark growth of the fungus may be visible in these lesions with tan to pink concentric circles of spores evident in some cases. Disease symptoms occur only on ripened fruits occasionally appears on leaf as leaf spot and also on mature green fruits (Borua and Das, 2000). Chilli fruit rot incidence varies with changes in climatic factors such as temperature, humidity and rainfall and also with stages of fruit development, location and season of cultivation (Basak et al., 1996). 9

10 Table 1.3 Major diseases of chilli Fungal diseases Anthracnose Disease Damping-off and root rot Phytophthora blight, Phytophthora crown, Rot and Aerial blight Pythium damping off Fusarium wilt Fusarium rot Cercospora leaf spot/frog eye spot Charcoal rot Aspergillus rot (Black mold rot) Black spot of pepper Downy mildew Ghost spot of pepper Gray leaf spot Sclerotinia stem rot/white rot of pepper Stem canker of pepper Wet rot Bacterial diseases Bacterial spot Bacterial wilt Viral diseases Alfalfa mosaic Andean potato mottle Chilli leaf curl Tobacco mosaic and Tomato mosaic Cucumber mosaic Nematode diseases Causal organism Colletotrichum capsici, C. gloeosporioieds, C. graminicola, C. acutatum, C. piperatum, C. indicum, C. nigrum Rhizoctonia solani, Phytophtora spp., Fusarium spp., Pythium spp. Phytophthora capsici, Phytophthora parasitica Pythium debaryanum, Pythium spp. Fusarium oxysporum f. sp. capsici Fusarium moniliforme Cercospora capsici Macrophomina phaseolina Aspergillus niger Alternaria solani Peronospora tabicini Botrytis cinerea Stemphylium solani Sclerotinia sclerotiorum Sclerotinia sclerotiorum, Rhizoctonia solani, F. solani Choanephora cucurbitarum Xanthomonas campestris pv. vesicatoria Ralstonia solanacearum Alfalfa mosaic virus Andean potato mottle virus-pepper strain Tobacco leaf curl virus, Begomovirus Tobacco and Tomato mosaic virus, Cucumber mosaic virus Root knot Meloidogyne incognita, Belonolaimus longicaduatus Source: 10

11 1.7 Colletotrichum capsici (Syd.) Butler & Bisby Colletotrichum capsici is one of the most economically important plant pathogen i.e., fungus causing anthracnose disease in a wide range of hosts worldwide, especially in tropical and subtropical crops, reducing yield and quality of the plant products. Colletotrichum was first reported by Tode (1790) in Vermicularia, but was later redescribed by Corda (1831). Colletotrichum species comprise imperfect or asexual taxa which have a Glomerella teleomorph stage (Sutton, 1992). The fungus is classified as, Kingdom Phylum : Fungi : Ascomycota Subphylum : Pezizomycotina Class Order Family Genus Species : Sordariomycetes : Glomerellales : Glomerellaceae : Colletotrichum : Colletotrichum capsici The above-ground parts of plants including fruits get affected by C. capsici anthracnose and fruit infection, results in reduction in quantity and/or quality and post harvest losses (Phoulivong et al., 2010). Colletotrichum species are cosmopolitan and it has been shown that multiple species can infect a single host while a single species can infect multiple hosts (Cai et al., 2009; Hyde et al., 2009). The lifestyle of Colletotrichum species is called hemibiotrophic because of initial short biotrophic phase, during which the host cell remains alive, and that is followed by necrotrophic developmental stage, which is highly destructive characterized by extended areas of died host tissues (Bailey and Jeger, 1992; Kim et al., 2004; Munch et al., 2008). Colletotrichum capsici has a septate mycelium which is inter and intracellular in host cells, acervuli and stroma on the stem are hemispherical and µm in diameter. Setae are scattered, dark brown, tips light brown, several septate and up to 15 µm long. Conidia in mass appear pinkish to orange. They are borne singly at the tip of conidiophores. Individually, they are falcate, hyaline and unicellular curved with narrow ends. The fungus is seed borne; secondary spread is by airborne conidia and also by rain. The optimum temperature for conidia germination is C (Voorrips et al., 2004). a. b. Figure 1.4 a) Colletotrichum capsici infected chilli seed under stereo microscope (arrow indicates acervuli); b) Acervuli along with setae and conidia under compound microscope. 11

12 1.8 Epidemiology The environmental factors play a major role in the development of disease epidemics. The relationships between intensity and duration of rainfall, crop geometry and the dispersal of inoculum possibly lead to different levels of disease severity (Dodd et al., 1992). The duration of the surface wetness appears to have the most direct influence on the sporulation, spread of infection and growth of the pathogen on the host. Generally infection occurs during warm and wet weather, where the temperature is around 28 C with high humidity of 80% content, which is considered optimum for the anthracnose disease development (Roberts et al., 2001). Colletotrichum species produce a series of specialized infection structures such as germ tubes, appressoria, intracellular hyphae and secondary necrotrophic hyphae (Perfect et al., 1999). Adhesive appressoria serve as survival structure until an infection peg penetrates the surface (Ratanacherdchai et al., 2010). The pathogen is sub-cuticular, intramural, grows entirely beneath the cuticle and within the peri-clinical walls of the epidermal cells, causing the dissolution of the wall structure, (O Connell et al., 1985; Bailey and Jeger, 1992; Pring et al., 1995). 1.9 Disease management Effective control measures for C. capsici disease usually involve the use of one or a combination of the following practices: using disease resistant cultivars, cultural control, chemical control (fungicide and abiotic inducers) and biological control [biotic elicitor and plant growth promoting rhizobacteria (PGPR)]. Use of resistant varieties, crop rotation and mixed cropping is undoubtedly the best ways of eliminating this pathogen (Kaur and Singh, 1985; Singh and Kaur, 1986) Cultural control refers to tactics aimed at disease avoidance through phytosanitation, manipulation of cropping patterns or enhancing resistance and avoiding predisposition. Proper plant spacing should be maintained which helps in reducing the severity of foliar diseases (Agrios, 2005). Only seeds and seedlings that are pathogen free should be used and crucial cultural control for minimizing disease is to harvest fruits as soon as they ripen (Kefialew and Ayalew, 2008). If disease is already present in the field, then, chilli plants should be rotated with crops other than potato, soybean, beans, tomato, eggplant and cucurbits for three years (Pernezny et al., 2003; AVRDC, 2003). 12

13 1.9.2 Chemical control is the most common and practical method, which has widely been used for controlling anthracnose disease. Treating the seeds with synthetic chemicals reduces the seed-borne infection of C. capsici (Ahmed, 1982). Chemical control involves frequent application of fungicides such as mancozeb, carbendazim, dipheconasol, dicolad, benomyl, strobilurin, azoxystrobin, trifloxystrobin and pyraclostrobin. For successful chemical control, timing and placement of chemicals are of critical significance. Poorly timed fungicide applications may enhance the severity of disease Resistant cultivars not only overcome losses from diseases, but also eliminate chemical and mechanical expenses of disease control (Agrios, 2005; Than et al., 2008b and 2008c). It is effective because of its ease of use and lack of potential negative effects on the environment. Recent days, research is underway to identify resistant sources, to evaluate these sources for purity of resistance, and to introgress the resistance traits into cultivated chilli plants (Roberts et al., 2001). Only five accessions of peppers (C. chinense: CO4554, PBC932, C. baccatum: PBC880, PBC81, PBC133) are reported to have resistance to three species of Colletotrichum, i.e., C. acutatum, C. gloeosporioides and C. capsici. However, so far no commercial cultivars of C. annuum resistant to the pathogen C. capsici that cause anthracnose have been developed (Than et al., 2008b) Abiotic inducers are synthetic chemicals which do not show a direct antagonistic effect by themselves against the plant pathogens, but are capable of protecting various types of plant species against a wide range of pathogens by inducing systemic resistance. Induced resistance may be expressed either locally at the infection site or systemically, where it is called systemic acquired resistance (SAR). SAR offers resistance to broad-spectrum of pathogens which includes viruses, bacteria and fungi. SAR is evident when the plant is treated with chemical compounds like salicylic acid (SA), jasmonic acid (JA), 2,6-dichloroisonicotinic acid (INA), β-amino butyric acid (BABA) and acibenzalor-s-methyl (ASM) (Kessmann et al., 1994; Oostendorp et al., 2001) Biotic inducer acquired resistance is an ecofriendly concept in plant disease management and has regularly been demonstrated against various host-pathogen interaction system. These inducible reactions in plants are obtained by plant-derived 13

14 (endogenous) or pathogen-derived (exogenous) signal molecules (Veit et al., 2001). These resistance-inducing agents may be proteins, peptides, glycoproteins, lipids or oligosaccharides (Nurnberger, 1999), which elicit the host resistance at very low concentrations and this response is related to the presence of receptors in the plasma membrane and to a downstream signal cascade (Ebel and Cosio, 1994) Biological control of seed-borne disease can offer as a potential alternative and is promising as compared to chemical fungicides. Antagonistic bacterial strains are found to effectively control C. capsici (Intanoo and Chamswarng, 2007). Apart from a direct antagonistic effect on pathogen, some plant growth promoting rhizobacteria (PGPR) strains are also able to reduce disease in above-ground plant parts through induced systemic resistance (ISR). PGPR-mediated ISR has been demonstrated in many plant species against a wide range of pathogens including fungi, bacteria and viruses (Van Loon et al., 1998). Managing anthracnose disease of chilli is still a challenge ahead us. Though chemicals are the most common method used to control this disease, but they resulted in many undesirable problems including adverse health effects and toxic contamination to the environment. So far no single specific management practice has been reported to be effective in complete elimination of this disease. 14