Efeito do ethephon (ácido 2-cloro etilfosfônico) na expressão do sexo e produção de semente híbrida de moranga (Cucurbita maxima Duch.)

Abstract

This investigation aimed to study the effect of the application of ethephon on the sex expression and squash hybrid seed production. The trial was carried out at the Horticulture Experimental Field of Escola Superior de Agricultura de Lavras, State of Minas Gerais, Brazil. Test plots were arranged ín a randomized completely block design in a 4x4 factorial scheme with two additional treatments and four replications. The main plot was made up of by dosages of ethephon (100, 200, 300 e 400 ppm), the subplots of number of applications (1, 2, 3 e .4) and the additional treatments of spray with water and water plus wetting agent. Data were subjected to analysis of variartce and means compared by the Tukey's test, at the 5% levei of probability. According to the observations and results obtained we concluded that the use of ethephon promoted the temporary ginoecious character and enabled the squash hybrid seed production. Ali treatments receiving ethephon had more pistillate flowers and lower staminate to pistillate flowers ratio than the control. There was a trend for treatments with higher dosages and multiple applications of ethephon to decrease the plant growth, the average fruit weight, total fruit yield and total seed yield. The treatment that received three applications of ethephon in the dosage of 200 ppm had higher number of pistillate flowers per plant and a reduction of •• staminate to pistillate flowers ratio which were almos the same as those ratios obtained with the dosages of 300 and 400 ppm of ethephon. The average number of fruit was increased, the plant growth and seed yield were not affected by the treatment. Thus, three applications of 200 ppm of ethephon showed to be the best treatment to squash plants aiming the hybrid seed production.