Flower Sex Expression in Cucurbit Crops of Kerala: Implications for Pollination and Fruitset

Cucurbits are monoecious in general; the female flowers occur lower than the male flowers in fields. Often farmers are not aware of this type of sex expression, and are concerned about the low fruit set despite 'profuse' flowering and abundant pollinators in the crop fields. We assessed flower sex expression during the peak (female) flowering and fruiting period in three widely grown cucurbit crops, Cucurbita maxima, Benincasa hispida and Momordica charantia in a village ecosystem of northern Kerala. Sex expression was male-biased in two species. In M. charantia, 97.65% of the flowers produced were staminate. In this condition, the farmers should ensure that effective pollinators are available in plenty to achieve maximum fruit set from the low number of pistillate flowers. C. maxima produced an average of 75.39% of staminate flowers, which varied across the fields; three fields consistently produced 100% pistillate flowers in all the 14 days of observations. The fruit set in fields with only pistillate flowers is likely to be affected by pollen limitation, rather than pollinator limitation. These fields may require supplementary manual pollination to enhance the fruit set. B. hispida produced more or less equal proportion of staminate and pistillate flowers across the fields and days studied. This kind of information may help the farmers to manage pollination services in their fields as well as to predict a realistic yield.