Assessment of Plant Genetic Resources of Chili Germplasm

ANUPAM DAS, SUBRATA KUNDU, and BISWAJIT GHOSH*

Plant Biotechnology Laboratory, Department of Botany, Ramakrishna Mission Vivekananda Centenary College, Rahara, Kolkata 700118, India

'Corresponding author. E-mail: This email address is being protected from spam bots, you need Javascript enabled to view it

ABSTRACT

The capsicum species, commonly known as chili peppers are pharmaceutically and economically important plants belonging to the Solanaceae family. Although domesticated in the Americas, the peppers have been distributed throughout the world and integrated into the world cuisine and food products. The chili fruits are vital to the human being as they are commonly used as vegetables, spices, and for therapeutic purposes. It possesses a wide range of pharmacologically important secondary metabolites including carotenoids, flavonoids, and vitamins that are beneficial to human health. These compounds have been reported to possess anticancer, antioxidant, anti-inflammatory, and antimicrobial properties. The exclusive metabolites present within the capsicum are the alkaloids capsaicinoids that make peppers pungent and are sequestered mainly in the placenta of the fruits. The nutritional content, as well as pungency of pepper, exhibit incredible diversity among different pepper types. The analysis of plethora of genetic resources of capsicum is pivotal for screening beneficial traits present within the enormous size of germplasm as well as for improved utilization in breeding programs. Therefore, in this chapter, we have emphasized on morphological, chemical, genetic, as well as disease diversity in different capsicum species cultivated in diverse geographical locations.

INTRODUCTION

Chili, a perennial shrub belonging to the Solanaceae family, originated in the tropical South American region and considered as an important dietary component since its domestication (Khan et al., 2014). As per estimates for 2011, about 3.8 million hectares of land was utilized for peppers cultivation, out of which 2.5 m ha is in Asia and 0.8 in ha in Africa (Faostat, 2013). It has been reported that only five genera of capsicum have been cultivated amongst twenty-seven genus (Onus and Pickersgill 2004; Olmstead et al., 2008). The five cultivated species of Capsicum are C. annuum L., C. chinense Jacq., C. frutescens L., C. baccatum L., and C. pubescens, and are recognized as economically important vegetable crops throughout the world due to their multipurpose and advanced application in food and therapeutic industries (Kellie et al., 2012; Kothari et al., 2010). C. annuum is found to be widespread, economically important and exploited maximum in commercial breeding programs. The fruit of Capsicum has immense etlmopharma- cological importance and has been traditionally used throughout the world in cuisine and food products due to its distinctive flavor and color (Andrews, 1995; Kothari et al., 2010). It contains a variety of vital nutrients and bioactive compounds that exhibit a wide array of activities, including free radical scavenging, antimicrobial, antiviral, anti-inflammatory, and anticancer properties (Saidu and Garba, 2011; Luo et al., 2011). Chili possesses unique pharmacologically important secondary metabolite capsaicinoids that is a major class of alkaloid found in chili fruits. More than 22 different capsaicinoids have been reported in chili peppers, capsaicin and dihydrocapsaicin being the most common ones (Bosland and Votava, 2012). Among different capsaicinoids, capsaicin dihydrocapsaicin, nordihydrocapsaicin, homodihy- drocapsaicin, and homocapsaicin were found to be predominant (Bosland 1996; Kozukue et al., 2005; Wahyuni et al., 2011; Davis et al., 2007). In the pericaip of chili fruits, capsaicin and dihydrocapsaicin that differ only in the acyl group existed for about 90% of total capsaicinoids (Bernal et al., 1993, Walpole et al., 1996, Kobata et al., 1998). It has been reported that capsaicinoids have versatile pharmaceuticals activities including against mutagenesis or tumorigenesis (Yoshitani et al., 2001, Sanchez et al., 2007), potent antimicrobials (Cichewicz 1996, Careaga et al., 2003), antioxidants (Henderson et al., 1999), and analgesic (Kaale et al., 2002, Caterina et al., 2000). They are found to be effective in the neuronal pain transmission and neurogenic inflammation (Szolcsanyi, 2004, Demirbilek et al., 2004) and possess anticancer effect that is closely associated with the prevention of cell proliferation and migration and induction of apoptosis (Luo et al., 2011).

Capsaicin has been proven effective in inhibiting platelet aggregation (Hogaboam and Wallace, 1991) and expansion of cancer cells (Min et al., 2004, Zhang et al., 2008). It has been reported that capsaicin also decreases membrane lipid peroxidation in human erythrocytes exposed to oxidative stress (Luqman and Rizvi, 2006).

The implementation of modern plant breeding resulted in swiping of heterogeneous traditional cultivars by commercial hybrid varieties with consistent yields including various disease resistance traits (Lanteri et al., 2003). This phenomenon led to a significant reduction in genetic diversity in Capsicum and leading to the extinction of some important germplasm (Hammer et al., 2003; Votava et al., 2005). Under such circumstances, the evaluation of genetic resources of Capsicum spp. is upmost essential to detect important accessions for commercial breeding and development of conservation policies. Therefore, the major objective of the present chapter includes the assessment of morphological, chemical, and genetic diversity corroborated with disease diversity existing in the different Capsicum species.

ASSESSMENT OF MORPHOLOGICAL DIVERSITY

Morphological identification and characterization are the principal phase in the description and classification of germplasm (Smith and Smith 1989). The variation in morphological traits within plant populations could exhibit as adaptations to different selection pressures (Morrison and Weston, 1985, Hageman and Fahselt, 1990). Consequently, methodical classification and assessment of plant genetic resources (PGR) is essential for effective use of germplasm for conventional or modern breeding techniques (Mehmood et al., 2008; Padilha et al., 2016). The future use of the collected germplasm is completely dependent on the proper characterization of PGR. Accurate characterization of the accessions facilitates their conservation and allow their proper utilization in breeding programs (Padilha et al., 2016). According to “The protection of plant varieties and Farmer’s Rights” (Government of India, 2001) act, a registrable cultivar needs to qualify the criteria of distinctiveness, uniformity, and stability (DUS) that can be validated by stipulating the characterization of important qualitative traits (Ramanna, 2003). Throughout the world, the grant of Plant Breeders’ Rights depends on the qualification of the DUS criteria (Cooke et al., 2003). Characterization of accessions is the only way to stop biopiracy, thereby, helpful in solving many social and ethical issues (Esquinas-Alcazar 2005). The key benefits of phenotypic characterization are quick, easy scoring, and cost efficient (Ganguly et al., 2012). The chili fruit of the wild progenitor was found to be small, red-colored, pungent, and deciduous with soft fleshed but domestication and successive artificial selections resulted in significant discrepancy in size, form, color, and level of pungency (Ortiz et al., 2010; Paran and van der Knaap, 2007). A large phenotypic diversity is exhibited among the cultivated peppers due to human preferences at the diverse regions. The phenotypic variance in chili fruits is measured based on some important morphological characteristics including average yield per plant, number of fruits per plant, average fruit length, fresh weight (g), seeds per fruit, and pulp/seeds ratio. The wide range of distribution in different morphological parameters of chili fruits cultivated in different geographic locations is represented in Table 16.1 and Figure 16.1.

 
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