SCREENING OF EARLY MATURING DARK RED ONION {Allium cepi. L.) GENOTYPES FOR RANGDA (LATE KHARIF) SEASON
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Date
2000-10-09
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Mahatma Phule Krishi Vidyapeeth, Rahuri-413 722 (M.S.), India.
Abstract
Although onion is an important cash crop and cultivated throughout the year, rangda is a typical off-season for onion cultivation particularly in Maharashtra. The distinct features of rangda onion cultivation are prolong vegetative growth, late maturing^lack of natural top fall, bigger bulb size, thicker bulb neck, higher incidences of premature bolting, doubles or twins, lower marketable bulb yield and poor keeping quality. Being off-season cultivation, yet no separate variety was developed for rangda season. The use of dark red kharif cultivars was the common practice among the farmers. However, the use of light red rabi cultivars (e.g. N-2-4-1) was recommended by the MPKV, Rahuri on the basis of good keeping quality but could not be accepted on mass level because of late maturity and dull bulb colour at the time of harvesting. In this context, present investigation was undertaken to identify the suitable onion cultivar, especially for rangda season. Accordingly, the eight dark red onion genotypes along with three checks; Baswant-780 (dark red, kharif cultivar), N-2-4-1 (light red, rabi cultivar) and Phule Suvarna (Yellow onion, rabi cultivar) were screened for rangda season and horticultural traits like natural top fall, premature bolting, marketable bulb yield and keeping quality were extensively studied. While studying the occurrence of natural top fall, only three genotypes viz., Sangamner-1, Sangamner-3 and M-9 showed more than 50 per cent top fall at 120 DAT (i.e. days after transplanting) and recorded early maturity; while genotype, M-ll showed 50 per cent top fall at 128 DAT and recorded moderate maturity. Rest of genotypes were late maturing without or with limited top fall at 128 DAT such as N-2-4-1 (0%), RHR-87050 DR (1.83%), RHR 87006 DR (5%), Phule Suvarna (14%) and Baswant-780 (17%). More importantly, early maturing genotypes were found to be resistant to premature bolting and recorded less than 5 per cent values; which were at par with N-2-4-1 (5.43%) while other genotypes found susceptible to premature bolting and recorded maximum incidence e.g. 39 per cent in RHR 87050 DR, 25 per cent in Phule Suvarna, 24 per cent in RHR 154 and 23 per cent in RHR 87006 DR. The other desirable characteristics recorded ;n early maturing genotypes were limited vegetative growth (upto 57 cm plant height, 27-30 cm leaf length and 9-10 leaves), lower percentage of twin or double bulbs (0.46-1.66%), bigger bulb size (5.8 x 4 8 cm bulb diameter and 77-88 g bulb weight), thin neck (less than 1 cm), higher total yield (more than 300 q/ha), higher marketable bulb yield (more than 80%) and excellent keeping quality (11% total losses within 3 months). While studying extent of premature bolting and natural topfall for the period of 100-128 DAT, crop stage at 120 DAT was found crucial for rangda onion cultivation. The three months storage studies of rangda onion revealed that 11-23 per cent total losses including 11-17 per cent PLW, 1.13-3.61 per cent rotting and 0 78-6.06 per cent sprouting losses were observed No sprouting losses were observed within first two months of storage More importantly, early maturing dark red genotypes, Sangamner-3 and M-9 recorded least storage losses (11%) equivalent to cv. N-2-4-1 In these three cultivars, no sprouting and rotting losses were observed but only PLW (11 %) losses contributed for total loss. The higher estimates of heritability (86-99%) along with high values of genetic advance (22-177 %) were observed for important traits like day to maturity, natural top fall, bulb neck thickness, premature bolting, bulb weight and marketable bulb yield indicating additive gene action and therefore can easily be improved through simple selection methods However, characters like polar bulb diameter and bulb shape showed non-additive gene action as of high heritability (85-91%) coupled with low genetic advance (10 25 to 14 45 %) and therefore. could be improved through hybridization The correlation studies revealed that natural top fall was negatively correlated with plant height, foliage growth, neck thickness, premature bolting and doubles; while it was positively correlated with bulb diameter, bulb weight and marketable yield Whereas, the premature bolting showed positive association with number of leaves, leaf length and neck thickness; while it was negatively correlated with topfall, polar diameter and bulb weight Based on results obtained, it is concluded that Sangamner-3 and M-9 are the most promising onion genotypes suitable for rangda season; considering their early maturity (120 DAT) with more than 50 per cent natural top fall, resistant to premature bolting, production of quality bulbs, higher total and marketable yield potential, and excellent keeping quality
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