GENETIC IMPROVEMENT OF YELLOW ONION {Allium cepa L.) FOR LATE KHARIF SEASON
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Date
2006-05-23
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MAHATMA PHULE KRISHI VIDYAPEETH, RAHURI-413 722, DIST. AHMEDNAGAR
Abstract
The present investigation entitled, "Genetic improvement of yellow onion for late kharif season" was undertaken with an object to develop new yellow onion genotypes [from parental population of cv. Phule Suvarna by open pollinated (OP) synthetic lines] on the basis of controlled vegetative growth coupled with rapid bulb development, early maturity with occurrence of natural foliage topfall and production of bigger size bulbs suitable for onion export. Hence, during late kharif of 2002-03, the parental bulb crop was raised and exclusive selection pressure was applied on seed bulbs. Initially on desirable plant characters, 250 bulbs were selected from one lakh parental plant population (0.25%) which finally reduced to 25 seed bulbs on the basis of bulb characteristics. Thus, eventually 0.025% selection pressure was applied on seed bulbs. However, to maintain wide genetic base and heterozygosity of onion crop, random mating of 250 seed bulbs was allowed in isolation but seeds of 25 selected seed bulbs were harvested separately during late rabi of 2003. The bulb crop was assessed during late kharif season of 2003-04 by raising 25 OP synthetic lines and compared with 5 lines of parental population of cv. Phule Suvarna. The selected and parental populations were compared each other for average performance and variability by t and F tests, respectively. While comparing selected seed bulbs with parental seed bulbs significant variation was recorded between two populations in average performance and variability for all the plant and bulb characters except polar bulb diameter. Thus, seed bulbs of two populations showed distinct difference in their crop performance and genetic variability. While evaluating seed crop raised from selected and parental seed bulbs during late rabi season of 2003, an adverse effect of late plantation noticed on seed crop. However, both populations showed distinct and significant variation in average performance and variability for all floral and seed characters under study. Selected seed bulbs showed superior mean values for all characters over parental one may be due to bigger bulb size and weight due to selection. While evaluating bulb crop during late kharif of 2003-04, it was noticed that plant growth was significantly varied between two populations by plant height and not due to number of leaves. Furthermore, rapid bulb development was noticed in selected population at all various crop stages (75-110 DAT) over parental population and showed significant difference in average performance and variability. Similarly, all bulb characters of selected population showed improvement over parental population by displaying different performance and variability between two populations. More importantly export oriented bulb production of yellow onion was noticed in selected population with mean of equatorial bulb diameter 6.34 cm and mean bulb weight of 206.18 g. Nevertheless, lower premature bolting was noticed in selected population than parental population at various crop stages and eventually 14.58% premature bolting was noticed in selected population at 110 DAT stage as compared to 20.45% in parental population. At last the most significant result was recorded in selected population where more than fifty per cent natural topfall was recorded as a sign of physiological maturity which otherwise meager in parental population i.e. 16.43%. Thus, with exclusive selection pressure applied on seed bulbs and by open pollinated synthetic line selection system promising yellow onion genotypes suitable for late kharif cultivation were initially identified.
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