Influence of plant growth retardants on growth, seed yield and quality in onion (Allium cepa) cv. Pusa Riddhi

A field experiment was conducted at New Delhi during rabi 2013-14 and 2014-15 to evaluate the effect of growth retardants on seed scape height, seed yield and quality attributes in onion (Allium cepa L.) cv. Pusa Riddhi.The experiment consisted of 15 treatments in combinations of three growth retardants, viz. paclobutrazol, ethephon and triadimefon. The results revealed that among different growth retardants, 100 ppm paclobutrazol significantly reduced the seed scape height (69.9 cm) and increased the seed scape diameter (3.71 cm). The paclobutrazol application also significantly improved the umbel diameter, umbellates/umbel, productive umbellates/umbel, seed setting (%), 1 000 seed weight and seed yield/umbel but it reduced the leaves/plant and seed scapes/plant. The triadimefon treatment significantly reduced the disease severity and disease incidence which affects the seed yield and quality. Seed quality attributes were not much influenced by growth retardant applications but higher seed vigour index-I (952.14) and II (186.13) were recorded under triadimefon and paclobutrazol treatments respectively. Paclobutrazol application also influenced the total leaf chlorophyll content and seed antioxidant enzymes, viz. SOD, catalase and glutathione reductase over the control treatment.