Molecular Plant Breeding 2016, Vol.7, No.29, 1
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2010), prevents obesity by effecting energy balance (Whiting et al., 2012). Furthermore, TRPV1 works as a
regulator of growth factor signaling in the suppression of tumorigenesis (De Jong et al., 2014), and its anti-cancer
effects are also confirmed (Ramos-Torres et al., 2015; Anandakumar et at., 2015). More than 80% of capsaicin is
passively absorbed in the stomach and upper portion of the small intestine and is also circulated in the blood by
albumin (Kawada et al., 1984), therefore, it may extensively activate local TRPV1 channels in different organs or
tissues to initiate aforementioned physiological effects.
Chili is invariably used in almost every Bangladeshi cuisine. Introduced diverse chili germplasms are cultivated
for centuries and adapted to various agro-ecological zones of Bangladesh (Hasanuzzaman and Golam, 2011). Low
and medium pungent chili varieties cultivated on a field scale in Bangladesh mainly belong to
Capsicum annuum
L. (Farhad et al. 2010). Chili cultivars are grown based on its size, shape, appealing color, pungency and
consumer's preference in various parts of Bangladesh (Hasan et al., 2014). However, despite its huge medicinal
value and rich genetic variability, the average yield of chili is low (1.3 ton/ha) in Bangladesh compared to the
neighboring countries like India (1.74 ton/ha) and China (6.82) (FAOSTAT, 2013). The prime constrain in
achieving good production of chili in Bangladesh is the lack of high yielding chili varieties with multiple
resistance against biotic and abiotic stresses. Therefore, it is desirable to develop improved varieties through
systematic breeding programme.
To carry out any successful breeding programme, it is necessary to select suitable parental lines from available
indigenous germplasms. The study of genetic divergence is a popular method in parent selection for researchers
involved in breeding programs of several crops, leading to reduce the number of crosses (Guerra
et al.
1999). The
progenies derived from diverse parents are expected to show a broad spectrum of genetic variability and provide
better scope to isolate superior recombinants. Therefore, genetically diverse genotypes should be used in a
hybridization program to get superior recombinants. The multivariate analysis is the most widely used statistical
tools to quantify the genetic divergence. Among the various methods developed to study the genetic divergence in
the genotypes/accessions, the Mahalanobis D
2
(Mahalanobis, 1936) is the most reliable and widely used statistical
tools to quantify the degree of genetic divergence by assessing the relative contribution of different characters to
the total divergence. It is a very useful technique and has been used by several workers in case of self-pollinated
crops (Bashar et al., 2016; Hasan et al., 2015; Huque et al., 2012; Natarajan et al., 1988; Shidhu et al., 1989).
Relative contribution of different traits to the total divergence helps to select a particular trait or a combination of
traits for intercrossing which avoids wastage to time and labor. Principal component analysis (PCA) is also a
powerful technique which allows the visualization of natural grouping of the genotypes and is precise indicator of
differences among genotypes (Huque et al., 2012). Ranking of parents based on their variance will be promising
as it gives an idea about more stable genotypes for a particular location. More stable genotypes are believed to
generate superior recombinants through crossing as there is less environmental influence on them. The
genotype-by trait (GT) biplot analysis, proposed by Yan and Rajcan (2002), is another powerful statistical tool for
studying relationships among traits, evaluating cultivars based on multiple traits and for identifying those
genotypes that are superior in certain traits. The GT analysis allows visual display of the genetic correlation
among traits, thus, helps detect less important (redundant) traits, and identify those that are appropriate for indirect
selection for a target trait.
Keeping these points in mind, the present investigation was undertaken to evaluate the genetic diversity among
the chili genotypes collected from diverse location and to identify superior genotypes for future use.
1 Results and Discussion
1.1 Cluster analysis
On the basis of Mahalanobis D
2
values, the 30 genotypes were grouped into six divergent clusters (Table 1),
indicating adequate genetic diversity for selecting superior and diverse parents which can be exploited for any
breeding program. Cluster I was the largest group containing 9 genotypes, followed by cluster III, cluster IV and
cluster III containing 7, 6 and 5 genotypes, respectively. Cluster VI had 2 genotypes while cluster V possessed
