Studies on pollen storage and utilization in sunflower (Helianthus annuus L.) hybrid seed production

Abstract

Hybrid seed production in sunflower is a challenging task. Pollen theft by pollinators is a problem in sunflower hybrid seed production. The male parent block is always covered with a net to avoid pollinator visits. Hence, manual pollination method was recommended for good seed set and higher seed yield in sunflower. During hand pollination, a shortage of pollen due to lack of synchronization between male and female parents and unfavourable weather conditions leads to poor seed set and low yield. The utilization of stored pollen grains is a viable option to ensure pollen availability during pollen scarcity periods. In this study, sunflower pollen grains were stored at room temperature (RT), earthen pot under the pit in the open field, refrigerator (5℃) and non-polar solvents (both in RT and 5℃) for up to seven days. The viability of stored pollen was tested every day both in the laboratory (staining method) and in field conditions (hand pollination method). The staining method used for testing pollen viability was modified and standardized in laboratory conditions because of non-satisfactory results observed in existing methods. The highest pollen viability was observed in dry pollen stored at 5℃ for up to 7 days. Pollen grains stored in hexane at 5℃ recorded viability and seed set up to 4 days. Dry pollen grain at room temperature and in an earthen pot remains viable for two days. Though the pollen grains stored in acetone (both RT and 5℃) was showing viability in staining methods for three days, it failed to set seeds in field conditions. Therefore, the dry pollen grains can be effectively stored at 5℃ and utilized for up to seven days in hybrid seed production of sunflower.