STUDIES ON DEVELOPMENTAL STAGES OF MICROSPOROGENESIS TO INDUCE MALE STERILITY USING MALE GAMETOCIDES IN OKRA [Abelmoschus esculentus (L.) MOENCH]
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Date
2016-08
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University of Horticultural Sciences, Bagalkot
Abstract
Okra hybrid seeds are produced using hand emasculation and pollination technique
commercially. To skip tedious and labour consuming hand emasculation an experiment was
formulated to assess the specific flowering stage for application of male gametocides. The
lab and field experiment was conducted during Kharif and summer season of 2015- 2016 at
Seed Testing Laboratory, Seed Unit, Main campus, University of Horticultural Sciences,
Bagalkot. Developmental stages of microsporogenesis to induce effective male sterility
using different male gametocides in okra was conducted with different flower bud sizes
ranging from 3 mm (at the time of bud initiation) to 50 mm (at the time of anthesis). The
study reveals that the formation of microspore from PMC is between 3 mm to 5 mm bud
size. Clear meiosis was recorded by observing the formation of triads and tetrads during
different stage. Meiosis was completed at 5 mm bud stage and further growth and
development of pollen was seen between 10 mm to 45 mm buds. This was confirmed by
pollen viability test and opined that pollen are non-viable till bud reaches 45 mm size.
Further, pollen attains maturity just before flower anthesis between 45 mm to 50 mm bud
size. However, maximum pollen fertility is between an hour before and an hour after
opening of the flower. This observation has made a way to select a pre-meiotic and post
meiotic stage for effective application of gametocides to induce complete male sterility.
Earlier studies revealed that the spraying of gametocides at pre-meiotic stages
induced only 51.77 per cent pollen sterility. Hence, present work was conducted to test the
effect of gametocides with higher concentrations at post-meiotic stages. In laboratory
experiment, the results indicated that malic hydrazide @ 450 ppm treated at 45 mm bud size
stage induced higher pollen sterility of 93.40 per cent and 90.77 per cent under in vitro
pollen germination test and acetocarmine test respectively. In field experiment,
the maximum pollen sterility of 86.16 per cent was found by foliar application of
MH @ 450 ppm at 45 mm bud size.
Further the technique developed was validated by conducting Grow Out Test of the
hybrids seeds produced. Maximum genetic purity was obtained in 45 mm bud size stage
treated with MH at the rate of 450 ppm concentration. Hence among the gametocides (MH,
Ethrel and 2, 4- D) used, MH at a concentration of 450 ppm sprayed at 45 mm bud size
(before flowering) found to be more effective for inducing male sterility in Okra.
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