Promiscuous breeding behaviour in relation to reproductive success in Grewia asiatica L. (Malvaceae)

Abstract

Grewia asiatica L., an Asian shrub, is indigenous to India. Despite its immense importance in the Ayurvedic and traditional systems of medicine scientific and commercial exploration has been neglected. In this direction, we undertook systematic studies to understand the sexual system, breeding behaviour and reproductive phenology deployed by the species. Our results suggest that the species practices mixed mating as a consequence of temporal dichogamy of protandrous type and herkogamy with stigma slightly above stamens. Sequential floral evocation in acropetal order and profuse visitation by pollinators predispose G. asiatica to receive cross pollen. In a situation of non-receipt of pollen through insect pollinators, self-fertilization is prevalent by recurvation of receptive stigma towards dehiscent anthers. Seed set efficiency and fruit maturation are independent of pollen genotype (self/cross). Pre-emergent reproductive success (PERS), a measure of number of viable seeds that enter the ambient environment, was around 21%, which is indicative of moderate reproductive success. A self-compatibility index (SCI) and self-fertility index (SFI) showed values of 0.66 and 0.55, respectively, indicating the self-fertile and self-compatible nature of G. asiatica. The present study provides a detailed exposition of various reproductive features and breeding system prevalent in G. asiatica. These aspects are fundamental to understand the efficiency or failure of a species for genetic variation, crop improvement and evolutionary success.