Reproductive biology in monoecious and gynoecious cucumber cultivars as a result of IBA application

Abstract

The understanding of both the reproductive biology and the regulation of the sexual expression of cucumber flowers (Cucumis sativus) makes crop management easier and can improve fruit yield and quality. The objective of this study was to evaluate the physiological answer of cucumber floral verticils to the application of IBA. The experiment was carried out in a greenhouse, in completely randomized blocks, with four replications of 4-plant plots, and treatments applied to a 5 x 2 factorial (0, 50, 100, 200, and 500 µmol of IBA, and two cultivars: Wisconsin MR28, gynoecious, and Caipira, monoecious). Cultivar Wisconsin MR28 produced in average 7,636 pollen grains (PG) per flower, with a positive linear response to the increase in IBA concentration. Instead, in cultivar Caipira (5,160 PG) all IBA concentrations reduced PG production. Cultivars did not differ from each other in relation to PG viability (average in vitrogermination of 75.4 and 79.9% to cultivars Wisconsin MR28 and Caipira, respectively) and in both PG viability increased linearly with the increase in AIB concentration. Cultivars Wisconsin MR28 and Caipira presented in average 71.6 and 70.6 seeds per fruit respectively, and responded with an increase in seed number and improvement in fruit general aspect to the rise in IBA concentration. The ratio male:female flowers was significantly different between cultivars (4.2:1 and 3.5:1, respectively to cultivars Wisconsin MR28 and Caipira) and responded in a distinct way to IBA concentrations. While in cultivar Caipira, IBA concentrations near to 100 µmol increased the number of male flowers; in cultivar Wisconsin MR28 the same IBA concentration reduced it. The two cultivars had a similar number of female flowers. However, whereas it remained relatively stable in cultivar Caipira in spite of the increase in IBA concentration, there was an increase in the number of female flowers in cultivar Wisconsin MR28, as a result of the rise in IBA concentration.