Constraints of hybrid seed production in upland and cultivated diploid cottons : Will different male sterility systems rescue? A review

摘要

Cotton fibre is an important raw material for the textile industry. Upland cottons (Gossypium hirsutum L.) account for over 90 per cent of lint production because of their high productivity and it is corner stone of the textile industries worldwide. In addition, in India Asiatic cottons (G. arboreum and G. herbaceum) are known as desi were grown on about 98 per cent area around 1947 and the G. hirsutum on just around 2. Presently, the situation is now exactly the reverse. The diploids and their hybrids are cultivated on very less(0.50 lakh ha) area in which desi cotton hybrid contributes only 1 per cent in production.However, now a day even short and coarse staple of diploid cotton is in great demand, particularly in fabrics like denim and upholstery, filling and medical purpose as well as fetches attractive price also. So, why not promote desi cottons, which are resistant to drought, water logging, diseses and pests especially cotton leaf curl disease, a dread disease of G. hirsutum, well adaptedto the climatic aberrations, suitable under rainfed conditions, wider adaptability and low cost of management? Thus desi cotton is to the rescue of Indian cotton growers.However, they are inherently low yielders and hence need to improve their genetic yield potential. Heterosis breeding (developing superior hybrids) is a good approach in these directions. The first ever success story of heterosis breeding in tetraploid cotton encouraged cotton breeders to explore the possibility of similar attempts in diploid cotton, that resulted in released hybrids viz., G.Cot.DH7 and G.Cot.DH9, which have not covered sizable area, due to the problem of seed production, the high costof conventional hybrid seed, which are limiting factors for poor/ marginal farmers to grow hybrids. Hence, the systems of male sterilities are of great significance in practical, as it avoids laborious process of emasculation and it can add in productionof hybrid seed. However, with the availability of genetic male sterility (GMS), photoperiod-sensitive genie male sterility (PGMS), thermo sensitive genie male sterility (TGMS) and environmental male sterilities (EGMS) lines in G. arboreum seed production cost can be reduced with increased purity. Therefore, these sterilities were thought to be a best, economical and alternative method for hybrid seed production technique in cotton and especially in diploid. Merits and demerits of these sterilities arereviewed and discussed.A remarkable heterosis for growth and yield reported in upland and diploid GMS based hybrids. Based on the earlier reviews on different aspects viz., genetic effects of heterosis, inheritance of GMS, cytological aspects of microsporogenesis breakdown, physiological and biochemical indices associated with GMS, environmental effects on expression of GMS, development of GMS and their utilization in producing hybrid seeds, practical problems of their utilization etc., future line ofresearch needs etc. are proposed.