[01] Medagam Thirupathi Reddy, Vegetable Research Station, Sri Konda Laxman Telangana State Horticultural University, Rajendranagar, Hyderabad, Telangana, India.

Okra (Abelmoschus esculentus L. Moench) is an important vegetable commercially cultivated in tropical and sub-tropical regions of the world mainly for its immature fruits. Yellow vein mosaic virus (YVMV) transmitted by white fly (Bemisia tabaci Gen.) is the most serious disease of okra affecting both fruit yield and quality, for which source of resistance is not available in cultivated okra. Interspecific hybridization followed by backcrossing and selection in the segregating generations is an effective method for developing YVMV resistant varieties. Characterization and evaluation of 28 inbred lines of cultivated okra (RNOYR-1 to RNOYR-28) and two wild species (A. manihot subsp. manihot and A. manihot subsp. tetraphyllus) in two separate field trials was undertaken at Vegetable Research Station, Rajendranagar during summer 2013. From these field trials, the horticulturally superior but YVMV susceptible cultivated okra RNOYR-19 and YVMV resistant A. manihot subsp. tetraphyllus were selected as parental lines for interspecific hybridization, which were crossed during summer 2013. Upon one-way crossing, the species A. esculentus (RNOYR-19) as female parent and A. manihot subsp. tetraphyllus as male parent were freely crossable and thus self-reproducing. The interspecific F1 hybrid plants of the above one-way cross were absolutely free from hybrid lethality and hybrid breakdown. Complete sterility was observed in the F1 hybrid plants of A. esculentus and A. manihot subsp. tetraphyllus. Hence, we were not able to advance or develop them further by direct backcrossing with the A. esculentus. A restoration of partial fertility in the F1 hybrid plants was achieved by treating the seedlings of the interspecific F1 plants at two leaf (pseudocotyledonary) stage with 0.1% colchicine on apical meristem through cotton swab method from 4th¬-7th day after germination 4 times a day at 3 h interval from 6.00 a.m. to 6.00 p.m., resulting in the production of raw colchiploids (C1). A restoration of complete fertility in the raw colchiploids (C1) was achieved by single cycle of selfing resulting in the production of stabilized colchiploids (C2).

Colchicines, Colchiploids, Crossability, Hybrid Sterility, Interspecific Hybridization

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