Study on growth, bulbing and bolting behaviour of onion (Allium cepa L.) germplasm collected from different latitudes in India
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Date
2019
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Punjab Agricultural University, Ludhiana
Abstract
The present study was carried at Vegetable Research Farm, Punjab Agricultural University, Ludhiana in 2017-18 with thirty three onion genotypes from seven different latitudes of India to determine genetic variability, correlation and path coefficient analysis, their stability and adaptability for growth, bulbing and bolting characters under six different environments comprising of six transplanting dates viz. September 21, 2017, October 30, 2017, November 30, 2017, December 30, 2017, February 26, 2018 and March 31, 2018. In all six environments moderate to high GCV and PCV estimates, high heritability coupled with high genetic advance were observed for plant height, number of leaves plant-1, number of rings bulb-1, equatorial bulb diameter, average bulb weight, bolting per cent, bolter height, umbel diameter and marketable bulb yield indicating that these traits can be improved through selection by exploitation of additive gene effects. The phenotypic and genotypic correlation analysis in all the environments showed that marketable bulb yield was positively and significantly correlated with average bulb weight, equatorial bulb diameter, plant height, leaf length, leaf diameter and pseudo-stem diameter therefore an indirect selection for these traits can be practiced for the improvement of marketable bulb yield. However, marketable bulb yield is negatively and significantly correlated with bolting per cent, days to bolting score, bolter height and umbel diameter. Path analysis showed that in all six environments average bulb weight and equatorial bulb diameter had high positive direct effect on marketable bulb yield. Combined analysis of variance revealed that differences among genotypes were significant for all the characters except for pseudo-stem diameter indicating that the genotypes had significant differences for the studied traits; and differences among environments (linear) were significant for all the characters indicating that all the six environments were different from one another. Similarly, genotype × environment interaction was significant for all the characters indicating variable expression of these characters across environments. The genotypes Palam Lohit, DPWO-1, Bhima Shakti and PKR 126 were identified as promising for marketable bulb yield, average bulb weight and equatorial bulb diameter; whereas, the genotype ADR was found promising for average bulb weight and equatorial bulb diameter based upon the mean performance and stability. The genotypes PKR 126 and ADR were found suitable for the environment E1 (September); the genotypes Palam Lohit and DPWO-1 were found suitable for the environments E2 (October), E3 (November) and E4 (December); while, the genotype Bhima Shakti was found to be suitable for the environments E5 (February) and E6 (March) for marketable bulb yield. Whereas, the genotypes Co-On-5, Bangalore rose onion and Arka Bindu are considered most desirable for bolting per cent. The discrimination and representativeness view of the GGE biplot indicated that environment E3 (November) followed by E4 (December) as the ideal environments for bulb production; whereas, the environment E2 (October) was considered ideal for onion seed production. From this study, it can be concluded that due to premature bolting, none of the genotypes from the lower latitudes (8-12 and 12-16° N); and middle latitudes (20-24 and 24-28° N) except from 16-20° N are suitable for marketable bulb yield. However, the genotypes from the higher latitudes (28-32 and 32-36° N) except Yellow Globe and Brown Spanish can be exploited for cultivation in different seasons under sub-tropical conditions of north-western India. This indicates that more emphasis should be laid on the genotypes from higher latitudes (28-32° N) for the improvement in marketable bulb yield under Punjab conditions.
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