Selection for resistance to yellow vein mosaic virus disease of okra by induced mutation

Yellow vein mosaic virus disease (YVMD) caused by a begomovirus is the most serious factor affecting okra (Abelmochus esculentus) production for both export and domestic consumption in Thailand. Seeds of Annie and Okura okra varieties were gamma-irradiated at doses of 400 and 600 Gy and planted at Huaysai King's Project in Petchaburi Province. M3 plants were screened for OYVMD (Okra YVMD) resistance under field conditions at Huaysai King's Project and Phichit Horticultural Research Center (PHRC) in Phichit Province. In addition, M4 plants were screened for OYVMD resistance under greenhouse conditions at Crop Protection Research and Development Office using whitefly transmission. None of Annie was found resistant but one plant of Okura (B-21) irradiated at 400 Gy was found to be highly resistant. Ten resistant lines obtained through rescreening of B-21 descendants up to M7 generation were selected for yield trial observations at PHRC and Chiengmai Horticultural Research Station (CHRS). The mutants had good stature and fruit shape but the fruits have spines on the ridges. Selections for OYVMD resistance and spineless fruits were performed at PHRC in three generations and seven of the lines were chosen for yield trial at PHRC. Three of the mutant lines were also screened for OYVMD resistance at Kanchanaburi Horticultural Research Center (KHRC) in Kanchanaburi Province, okra growing area, where OYVMD was seriously widespread. All mutant lines showed resistance against the local OYVMV isolates up to a month before they started showing signs of the disease. Seeds were collected from resistant individuals and planted in farmers's fields for further selection. The farmers were very satisfied with the stature and fruit shape of the mutants when tested against a commercial variety. (author)