Effect of pollen morphology on hybridization and seed setting in hibiscus (Hibiscus rosa sinensis)

Abstract

Pollen studies are vital for selecting suitable pollen donor and enabling successful cross-breeding in Hibiscus rosa sinensis. A crucial pollen morphometry and viability experiment involving 10 hibiscus varieties was conducted at BCKV, West Bengal, in 2021-22. Pollen viability of the germplasm was determined by using an acetocarmine solution. The highest pollen viability was found in Versicolour Pinwheel (95.12%), followed by Cherry Glow (92.28%). Following a thorough screening, the three most promising pollen parent varieties, i.e., Brilliant, Versicolour Pinwheel, and Cherry Glow, were selected. Hybridization (line x tester) was performed to understand the effects of pollination on seed set and to confirm cross-compatibility. Among all possible combinations in the one-line cross, Cinnamon Girl displayed high-degree compatibility with all 3 pollen donors. Double Peach exhibited compatibility with Versicolour Pinwheel, while Agni showed compatibility with Cherry Glow for a desirable seed set. The percentage of capsule set varied widely from 0 - 45.67%. These variations in capsule set percentages could be attributed to differences in compatibility between various genotypes, pollen viability percentages, pollen tube growth rates, and potentially fluctuating climatic conditions during the blooming period. This report is beneficial for the breeders to identify potential pollen donors for successful hybridization programs.