Hybrid purity assessment in F1 hybrids segregating for phytophthora root rot resistance genes of chili pepper (Capsicum annuum L.)

Abstract

Root rot caused by Phytophthora capsici is the most devastating disease in Indonesia causing up to 100% yield loss. Breeding resistant cultivars is the most effective strategy to reduce losses caused by this disease. This study aimed to (1) determine the parentage confirmation and genetic relatedness of the parents, (2) genotype two F1 populations using a subset of six markers, and (3) measure the horticultural characteristics of two F1 populations. Tanjung-2 and Ciko varieties were used as recurrent parent (RP) in a cross with donor parent (DP) CM334 having Phytophthora root rot resistance gene. Molecular analysis of the parents was done using 33 markers linked to the resistance genes of which 17 markers demonstrated clear polymorphism. The phylogenetic tree classified the parents into two groups, i.e. group 1 consisted of two RPs (Ciko and Tanjung-2) and group 2 consisted of CM334. Clustering analysis clearly revealed that genetic materials used in this study were not closely related. Genotyping using six polymorphic markers showed that the marker-hybrid purity index ranged from 47.17 to 100% for F1 Tanjung-2/CM334 and 80 to 100% for F1 Ciko/CM334. The selected F1 was self-hybridized to develop F2 population. Horticulture characterization showed that branch number per plant, fruit diameter, fruit weight, and total fruit weight per plant of F1 Ciko/CM334 were higher than F1 Tanjung- 2/CM334. Meanwhile, for plant height, canopy diameter, flowering time, and harvesting time the F1 Tanjung-2/CM334 demonstrated better performances than the F1 Ciko/CM334. The populations developed from this study can be used in genetic linkage mapping of genes conferring resistance to P. capsici.