Genetic analysis of Okra Yellow Vein Mosaic Virus disease resistance in wild relative of okra Abelmoschus angulosus Wall. ex Wight & Arn

Abstract

Wild relative of okra, Abelmoschus angulosus Wall. ex Wight & Arn. was identified as a resistant germplasm for Okra Yellow Vein Mosaic Virus (OYVMV) which is the devastating disease for okra cultivation in Sri Lanka. The mode of resistance of OYVMV in A. angulosus was studied with the aim of tagging responsible genes for the disease resistance. Wide hybridization was performed between A. angulosus and highly virus susceptible A. esculentus variety, MI-7. Very poor seed setting was observed in F1 and F2 generations due to post zygotic abortion. Disease screening was carried out using F1 and F2:3 populations along with parents in the field under induced disease pressure. Disease severity index and area under disease progress curve were calculated to measure disease severity. Number of genes segregating for OYVMV disease resistance was calculated for the F2:3 generation. Modified Wright's formula was used to estimate the effective gene number and mode of inheritance by a quantitative method. A χ2 test was performed for qualitative analysis. Plants of A. angulosus were totally free of virus incidence while 100% disease incidence was observed in the variety MI-7. F2:3 population showed between and within progeny segregation for disease incidence. Results indicated that the disease susceptibility was dominant over resistance. χ2 analysis revealed that the segregation of disease severity was significantly fit to the gene model of 9:6:1 (χ2 = 0.1757 at P ≤ 0.05) suggesting the disease resistance in A. angulosus is governing by two recessive genes in an additive manner. Result was confirmed by the quantitative analysis.

Induced Systemic Resistance of Okra (Abelmoschus Esculentus L. Moench) Against Okra Yellow Vein Mosaic Virus Using Amino Acids and Algae Extracts

“…These were the treatments. OYVMV + Amino acids + Algal extract Screening for OYVMV under natural conditions: The plants were grown in an open field where they could be exposed to the virus freely, and the severity of the disease was measured using a standardized scoring system (Wasala et al, 2019). Because of this, the following grades have been given out (Table 2).…”