Genetic relatedness among interspecific hybrids in the genus Capsicum and their implications in breeding King chilli

Abstract

The present study explores the potentiality of interspecific crosses using three different Capsicum species, comprising of two C. annuum (Krishna and Capsicum), five C. chinense (King chilli A1, A5, A18, A19, A20) and one C. frutescens (Mem) genotypes, with the objective to identify the incompatibility barriers, accomplish the morpho-molecular characterization of parents and hybrids and assess the genetic relatedness between the genotypes.Amongst the three species used for the crossing programme, 'Krishna' (C. annuum) and 'Mem' (C. frutescens) are local cultivars of Assam (India) and possess excellent adaptability. Guinness World Records certified King chilli, or 'Bhut Jolokia' (C. chinense), as the world's hottest chilli (10,001,304 SHU) in September 2007. King chilli has tremendous export potential but is prone to viral diseases, thereby necessitating the transfer of desirable disease resistance from local cultivars.It was observed from the study that the reciprocal crosses involving C. chinense and C. frutescens were compatible, but C. frutescens (Mem) was crossable with only accession A5, suggesting genotype specificity in the interspecific crosses. The usual Euclidean distance between Mem and A5 was 716.605Similarly reciprocal crosses involving C. annuum and C. chinense were partially incompatible. Both the C. annuum (Krishna, Capsicum) genotypes successfully crossed with King chilli accession A18 thereby exhibiting genotype specificity. It was observed that in the cross A18 x Krishna the F1 seeds failed to germinate and in the cross A18 x Capsicum the F1 plants exhibited dwarfism. Hence, unilateral incompatibility was observed when King chilli accession A18 was used as the female parent. In the reciprocal crosses, germination and plant development was normal.The pollen viability ranged from 72.64 to 94.92 % for parents and 23.55 to 81.02 % for the hybrids. Thus, hybrids exhibited lower pollen viability compared to their parents. Significant morphological differences were visible between the parents and their combinations; some features were similar to the male or female parent, and others were either intermediate or novel.Parental polymorphism was detected using thirty random SSR primers, and the markers showing polymorphic bands were used to confirm the hybridity of F1s. Therefore, an attempt was made in this study to assess the possibility of interspecific crosses to transfer disease resistance from the related species to enhance the quality of King chilli, thus improving its commercial valve.