Yellow Vein Mosaic Virus Disease in Okra (Abelmoschus esculentus L. Monech): Its genetic control and relationship with the biochemical parameters.

Abstract

The yellow vein mosaic virus (YVMV) is one of the most serious diseases in okra production, often causing severe losses in commercial fields. Identifying and deploying resistant genotypes and understanding the inheritance of YVMV disease resistance are essential for the okra geneticists to develop an effective breeding strategy. Genetic control of the host resistance to YVMV disease of okra was studied employing six generations (P1, P2, F1, F2, BC1, BC2) of three selected crosses: Tolerant × Tolerant (T × T), Tolerant × Susceptible (T × S) and Susceptible × Susceptible (S × S) among two tolerant and susceptible genotypes. Relationship between disease reaction and different biochemical parameters of the parents and hybrids at three phenological stages (Pre-flowering, flowering and post-flowering) was studied. The inheritance study amply indicated that tolerance to YVMV disease was conditioned by two duplicate dominant genes in Tolerant × Tolerant cross, and by two complementary dominant genes in Tolerant × Susceptible cross. The significant scaling tests and joint scaling test also indicated the presence of digenic epistasis for both the disease reaction characters. The study also suggested that tolerant genotypes appeared in the progeny of even Tolerant × Susceptible cross. Some of the enzyme activities (peroxidase and polyphenol oxidase) and proximate compositions (total phenol and ascorbic acid) in okra leaf exhibited consistent and significant negative correlation with PDI of YVMV disease even over the growth stages suggesting their implication as selection indices for identification of genotype tolerant to YVMV disease. The results suggested modified bulk method of breeding through deferred selection after attaining homozygosity for maximum heterozygous loci.