Evaluation of diversity in Bulgarian pepper cultivars by agronomical traits and ISSR markers
Information about the genetic variation among cultivars of vegetable crops is of vital importance for improvement of plant breeding programmes worldwide. The objectives of this study were to group 19 pepper (Capsicum annuum L.) cultivars from the collection of Maritsa Vegetable Crops Research Institute, Plovdiv, Bulgariainto clusters according to their distances as estimated by agronomic traits and 9 di-and tri -nucleotide inter simple sequence repeat polymorphism (ISSR) markers and to assess the relationships between them. The phenotypic characterization during 3 consecutive years revealed significant differences among Bulgarian cultivars for the studied 13 phenotypic traits. The biplot analysis of quantitative traits showed that the most strongly correlating traits with the first axis (55.6% of variance) were fruit width, fruit weight and pericarp thickness (in the negative direction of the axis), and plant height (PH) (in the positive direction). The most discriminative traits, considering the second axis (22.6% of variance) were fruit length (FL) and to a lesser extent the stem height (StH). The correspondence analysis of the qualitative traits showed that the intensity of the colour of the fruit (before and at maturity), fruit colourbefore maturity and fruit shape in longitudinal section were the most discriminative characteristics for the first two dimensions. The agronomic traits data and 7 dinucleotide ISSR primers were used to estimate the pairwise genetic distances. Higher mean phenotypic distance (0.414) in comparison to the genotypic ones (0.214) among the cultivars was observed, indicating higher phenotypic diversity among them. A highly signi?cant, positive correlation between the agronomic data and ISSR marker-based matrices (r=0.41, p=0.001)was detected. This indicates that ISSR distance tended to re?ect that of the agronomics ones. However, additional molecular studies and large collection of highly diverse genotypes are needed to reveal associations between the marker loci and specific QTLs. The research initiated is a base for more precise estimation of genetic distances between pepper genotypes from the available large collection of landraces, local and modern cultivars including large number of highly polymorphic markers.