Abstract
Anthracnose disease is one of the major economic constraints to chilli (Capsicum spp.) production in tropical and subtropical regions, which significantly affects the yield and fruit quality of chilli. This study aimed to screen forty one to sixty germplasms of chilli against anthracnose on the basis of morpho-molecular characters. In first experiment, genetic variability including mean, genotypic and phenotypic variances, heritability, genetic advance and phenotypic divergence were investigated among fifty chilli germplasms. Significant differences were observed among the genotypes for all the traits. BD2011 outperformed for plant height and number of branches plant1, Srilanka and one unknown germplasm outperformed for fruit length, BD2043 outperformed for number of fruit plant1, Ramu outperformed for dry fruit weight and yield plant1 on the basis of mean performance. The phenotypic and genotypic coefficient of variations were high for all agronomic traits indicating that these traits had wide genetic variability and would respond better to selection. High heritability and high genetic advance recorded for fruit yield plant1, number of fruits plant1, fruit length and plant height indicating the role of additive gene action for the inheritance of these traits. The germplasms grouped into six clusters based on their degree of phenotypic divergence. Cluster I had higher intracluster distance. Germplasms between cluster I and II had the highest intercluster distance. Genetic relationships among sixty chilli germplasms collected from different places of Bangladesh were analyzed using five RAPD and three SSR primers. Clustering based on the generated markers was done using NTSYS software. The RAPD primers produced a total of 54 bands of which 44 were polymorphic with a mean value of 8.800 polymorphic bands per primer, while the SSR primers produced 28 SSR loci with a mean of 9.333 alleles per SSR locus. The values of pair-wise comparisons of Nei's (1972) genetic distance ranged from 0 to 1.045 (RAPD) and 0 to 1 (SSR) with mean of 0.218 and 0.138, respectively. Polymorphic Information Content (PIC) values of the SSR primers ranged from 0.622 to 0.844 with an average value of 0.749. Both RAPD and SSR markers showed genetic variability in the studied chilli germplasms and they emerged as powerful tools for estimating genetic similarities and diversity. Ten isolates of Colletotrichum capsici causing chilli anthracnose were isolated from infected chillies collected from different area of Bangladesh. Molecular identification of the isolates was carried out by two SSR primers (CcapF/CcapR and CC1F1/CC2R2) that amplified products of 394bp and 447bp, respectively. Experiments were conducted to identify anthracnose resistant/susceptible germplasms of chilli by pathogen inoculation on mature fruits. A set of disease scales, with 0 to 10 scores, were used to assess the degree of anthracnose resistance/susceptibility of the forty one chilli germplasms. Infection was induced in all germplasms except Comilla morich, where no infection was detected. BD-2035, BD- 9737, BD-2064 and BD-2006 had very slight disease symptoms. Highly susceptible germplasms were Dhani morich, BD-2091, Angoor, BD-2048 and Naga. Nine morphological data and per cent of infection area were recorded and multivariate analysis was used to identify the genetic variations among the forty one germplasms by using Euclidean distance following Ward's method. Gemplasms were significantly correlated in number of fruits plant1 and dry fruit weight and yield plant1. Principal component analysis showed that percentage of infected area and yield plant1 was the traits responsible for major variation among the genotypes. In cluster analysis, different chilli genotypes produced six distinct groups. Gerplasms with remarkable higher yield and anthracnose resistance of the cluster VI (BD2035, Comilla, BD2006, BD2064) have the potential use in future breeding programs for the improvement of chilli to produce anthracnose resistant hybrids in Bangladesh.