Evaluation of pollen storage strategies in Cucurbita pepo L.

Abstract

Male flower shortage is a major reason of insufficient pollination in zucchini (Cucurbita pepo L.), leading to pointy fruits that rot quickly in the post-harvest phase. Harvesting pollen grains early in the season, when male flowers are abundant, followed by storage and subsequent manual pollination, could be a solution, provided that high pollen viability is maintained. Therefore, insight in parameters affecting pollen viability during anthesis and under storage are needed to advice growers on the most successful pollination strategy. Pollen viability was determined using Fluorescein Diacetate (FDA) and digital image analysis performed with Image J. Under practice conditions, viability started to diminish three hours after anthesis. At flower closing, only 60% of pollen grains remained viable and the next morning no more than 10%. In order to assess the impact of storage on pollen viability, pollen grains were subjected to different relative humidities and storage times. Stored at 20°C and 80% RH or lower for four hours, at least 90% of the pollen turned out to be non-viable. At 20°C and 90%, RH pollen viability remained above 50% for eight hours. When female flowers were pollinated with stored pollen (five days or longer), none of the fruits set sufficiently to be marketable, while fresh harvested pollen resulted in 90% marketable fruits. Therefore, pollen should be harvested and applied on the stigma within three hours after anthesis in order to ensure good fruit setting. Pollen could not be stored longer than eight hours without severe loss of viability or pollinating capacity.