Combining Ability Analysis of Late Leaf Spot Resistance and Other Agronomic Traits in Nine Groundnut Genotypes

Abstract

Late leaf spot (LLS) Phaeoisariopsis personata (Berk. and Curtis) Deighton is one of the most important foliar diseases of groundnut worldwide including Nigeria. The genotypes were used to estimate the general combining ability (GCA) and specific combining ability (SCA) for yield components and late leaf spot (LLS) resistance. Four susceptible genotypes (SAMNUT 23, SAMNUT 24, SAMNUT 25 and SAMNUT 26) were used as females and five resistant genotypes (ICGV 12991, ICGV 7878, FDR-F7 82, FDR-F7 67 and FDR-F7 61) were used as males using line x tester mating design with three replications. The parents and progenies were evaluated for late leaf spot resistance. Highly significant negative general combing ability (GCA) effects were recorded for disease incidence in SAMNUT 25 (-0.05), indicating the genotype is a good general combiner for late leaf spot (LLS) and SAMNUT 26 (-5.90) is a good general combiner for LLS disease severity. ICGV 12991 (-12.00), FDR-F7 67 (-.68) and FDR-F7 61 (-2.23) genotypes are good general combiner for late leaf spot (LLS) disease resistance (disease incidence and severity), among the crosses, significant and negative SCA effects were obtained for most of the crosses i.e SAMNUT 24 x FDR-F7 67 and SAMNUT 24 x FDR-F7 61 for late leaf spot (LLS) resistance indicating that they are good specific combiners for late leaf spot (LLS) resistance. The ratio of the general combining ability (GCA) and specific combing ability (SCA) variances indicated the preponderance of specific combining ability (SCA) variance over general combining ability (GCA) variance for disease incidence and severity, indicating the role of non-additive gene effect and it may be due to difference in genotypes used as parents.