Pollen Pistil Interaction in Inter-Specific Crosses of Vigna sp.

Abstract

Inter-specific hybridization is mainly used to introgress pest and disease resistant genes. Vigna radiata and Vigna mungo are widely cultivated and consumed in India. These crops are highly affected by Mungbean Yellow Mosaic Virus (MYMV) disease and bruchid (Callasobruchus spp.) pest, leading to heavy yield loss. Vigna umbellata, a divergent Vigna species is found to be resistant to both MYMV and bruchids. Utilization of this species to introgress the resistance gene is marginal because of their inherent low crossability with the cultivated Vigna species. In the present study, V. umbellata was used as pollen donors in hybridization with V. radiata and V. mungo. Low percentage of pod set observed in the cross V. radiata×V. umbellata (12.89%) and V. mungo×V. umbellata (5.56%) indicated the presence of reproductive barriers that render introgression difficult. Aim of this study was to observe pre-fertilization barriers operating in V. radiata×V. umbellata and V. mungo×V. umbellata crosses. In vivo pollen germination and growth of pollen tubes were studied in inter-specific crosses using fluorescence microscope. The pollen grain germination on stigmatic surface was normal. A very common pre-fertilization barrier of slow rate of pollen growth, in addition to structural abnormalities in stigmatic and stylar regions was observed in both the crosses. However, the level of incompatibility was high in V. mungo×V. umbellata cross than V. radiata×V. umbellata. Measures to overcome incompatibility barriers before fertilization in these crosses to produce inter-specific hybrids are discussed.