Genotypic response to bolting tolerance in short day onion (Allium cepa L.)

Abstract

Onion is considered as an important vegetable crop in the
world. India is the second largest producer of onion
contributing about 20% world production. At the present
times, onion is adapted to various agro-climatic conditions
of India and cultivated in all seasons (kharif, late kharif
and rabi) using advanced technology and improved
varieties. Bolting is a physiological disorder and reduces
quality and marketable yield of onion and having poor
storability. Onion plants are biennials i.e. they normally
flower in the second season of their development. However,
under favourable conditions, some sensitive varieties bolt
in the first season itself. Bolting is a result of complicated
interaction between genotype, plant age and environmental
factors. Bolting is essential for seed production, but
undesirable during bulb production. Bolting varies with
genotype susceptibility and resistance, and is clearly
influenced by temperature or cultivar or both. This problem
occurs mostly in late kharif due to variation in temperature
during vegetative growth under Indian plains. With suitable
screening method more potent lines can be screened by
critical selection for bolting resistance. Twelve advance lines/
varieties of short day onion were screened for bolting
tolerance during late kharif season with five dates of
planting at 15 days interval. On the basis of two years data,
highest marketable yield was recorded in DOGR-1168 (38.84
t/ha) followed by DOGR-595 (37.02 t/ha) with the minimum
bolting percentage (<5%). Thus, these lines can be further
exploited in breeding programme.