Phookan, Deepa BorboraBaruah,Rimjim2024-07-102024-07-102023https://krishikosh.egranth.ac.in/handle/1/5810211772An experiment was carried out under a naturally ventilated polyhouse at the experimental farm, Department of Horticultural, Assam Agricultural University, Jorhat, during 2022-23 on the topic ‘Effect of Plant growth substances on Growth, Sex expression and Yield of Zucchini (Cucurbita pepo L.) under protected condition’. For the experiment the variety of zucchini used was Joy F1 Hybrid. The experiment was laid out in a randomized block design with three replications. There were total of ten treatments namely, T1(Control),T2 (150ppm Ethrel),T3(250ppm Ethrel),T4 (350ppm Ethrel),T5 (50ppm NAA),T6 (75ppm NAA),T7(100ppm NAA),T8(100ppm MH),T9 (150ppm MH), T10 (200ppm MH). The treatments were applied to various growth stages i.e. two leaf, three leaf and four leaf stages. Treatments significantly affected most of the growth and yield attributing parameters, but not the quality parameters except ash content. The best treatment was found to be T3 (250ppm Ethrel), which improved plant height (121.16 cm), plant spread (1.57 m), petiole length (140.95 cm), days to emergence of the first female flower (41.93 days), nodal position of first female flower (2.53), number of female flowers (20.27), fruits per plant (20.13), yield per plant (6.65 kg), yield per plot (86.44 kg), and yield per 500m 2 (33.71 q) . The highest female to male sex ratio of 1.47 was also found in 250 ppm Ethrel (T3) followed by 1.38 in 350 ppm Ethrel (T4). Ethrel treatments performed better than NAA and MH treatments, and NAA was better than MH. The highest benefit-cost ratio of 2.74 was obtained from T3, followed by T4 with 2.64. Therefore, T3 can be recommended to the farmers for zucchini cultivation under protected conditions.EnglishThesis