Journal of Experimental Agriculture International

Ethylene plays a particularly important regulatory role in the control of sex determination in Cucurbita pepo, with exogenous application of ethylene-releasing compounds promoting femaleness and reducing the male-to-female flower ratio. Under high temperature and long photoperiod conditions, which are characteristic of the subtropical summer season in northern India, the crop tends to exhibit a preponderance of male flowers with a concomitant reduction in the number of female flowers, thereby adversely affecting fruit set and ultimate yield. The present investigation was carried out at the experimental field of the Department of Agriculture, Khalsa College, Amritsar, during the Rabi season of 2018–2019 (more precisely late Rabi–Zaid transition season) to evaluate the influence of foliar applications of ethephon and maleic hydrazide on the yield attributes of zucchini (Cucurbita pepo L.) cv. Dark Green. The experiment was laid out in a Randomized Complete Block Design (RCBD) comprising nine treatments — ethephon at 50, 100, 150 and 200 ppm; maleic hydrazide at 50, 100, 150 and 200 ppm; and an untreated control — replicated three times. Both plant growth regulators were applied as foliar sprays at the two- and four-leaf stages. Significant differences were recorded for all yield parameters studied, namely fruit length, fruit diameter, average fruit weight, fruit yield per plant, fruit yield per plot, and total fruit yield per hectare. Ethephon at 200 ppm (T4) recorded the maximum fruit length (28.89 cm), fruit diameter (7.53 cm), average fruit weight (514.82 g), fruit yield per plant (2.11 kg), fruit yield per plot (25.21 kg) and total fruit yield per hectare (259.27 q ha⁻¹), all of which were significantly superior to the untreated control. The beneficial effect of ethephon on yield attributes was attributed to its ability to suppress male flowers, promote female flower production, and thereby improve fruit set percentage. Maleic hydrazide at lower concentrations (50–100 ppm) also produced yields that were superior to the control, although its efficacy was inferior to that of ethephon across all parameters. The findings indicate that ethephon at 200 ppm is the most effective treatment for enhancing yield productivity in zucchini under subtropical conditions.