Effect of various growth retardants and detopping techniques on Bt cotton (Gossypium hirsutum L.) for source sink manipulation

Abstract

A field experiment to study the manipulation of source sink through growth regulators was carried out during kharif, 2023 at Agricultural Research Station, Dharwad Farm. The experiment was laid out in Randomized Block Designwith ten treatments and three replications. The treatments include foliar spray of maleic hydrazide, cycocel, mepiquatchloride and detopping in isolation and control. The study revealed that the significant impacts of growth retardants anddetopping on morphological parameters such as plant height, monopodial and sympodial branch count.The study foundthat significant variations in physiological parameters such as SPAD values and dry matter production. Among differenttreatments the application of maleic hydrazide, cycocel and mepiquat chloride as growth retardants along with detopping,resulted in increased seed cotton yield, attributed to delayed senescence of leaves, leading to an extended period ofphotosynthate supply to the reproductive parts.Whereas, the treatment with maleic hydrazide at 30 ppm after 80 days ofsowing showed superior growth and productivity compared to other treatments. The study concluded that the applicationof growth retardants and detopping techniques can optimize dry matter allocation, enhance photosynthetic activity andimprove crop productivity in Bt cotton.