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

Abstract

Summary 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. radiataϫV. umbellata (12.89%) and V. mungoϫV. 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. radiataϫV. umbellata and V. mungoϫV. 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. mungoϫV. umbellata cross than V. radiataϫV. umbellata. Measures to overcome incompatibility barriers before fertilization in these crosses to produce interspecific hybrids are discussed.

Alien Introgression Studies Involving Vigna mungo x V. umbellate Hybridization

“…Plate. Plate.4 Pollen stain ability of parents and their F 1 's Thiyagu et al(2008) observed low percentage of pod set (5.56%) in V. mungo x V. umbellata indicating the presence of reproductive barriers that renders introgression. They also found normal pollen grain germination on stigmatic surface but slow pollen tube growth in addition to structural abnormalities in stigmatic and stylar regions.…”

“…Pollen sterility was also reported in V. radiata x V.umbellata crosses by Pandiyan et al, (2008) due to which viable F 2 segregants were not obtained by them as in present study. In Vigna crops, inability of pollen tube to germinate and penetrate stigma and style (Chowdhury and Chowdhury, 1977) and ovary (Gopinathan et al, 1986), slow rate of pollen growth (Thiyagu et al, 2008); are reported to be significant pre-fertilization barriers. Post-fertilization barriers of varying degrees have been reported in most of the inter-specific Vigna crosses (Gopinathan et al, 1986;Bharithi et al, 2006;Pandiyan et al, 2010;Chaisan et al, 2013;Basavaraja et al, 2018;Bhanu et al, 2018).…”

Successful Interspecific hybridization between mungbean (Vigna radiata L. Wilczek) and ricebean (V. umbellata (Thunb.) Ohwi and Ohashi)

“…The different cross ability level of Vigna species has been reported by Bharathi et al (2006) and Chen et al (1977). Some researchers have successfully crossed mungbean and ricebean but they have reported a low level of cross compatibility (Chowdhury and Chowdhury, 1978, Ahn and Hartmann 1978, Thiyagu et al, 2008. The relatively high cross compatibility that we report in Table 1 implies that the two species can be successfully hybridized, provided that the timing of anthesis and stigma receptivity is the same for both parents.…”

“…Hybridization was successful with mungbean as the female receptor but was unsuccessful if the ricebean was used as the female receptor (Table 2). The incompatibility with ricebean as the female receptor could be because it lack a compound suitable for the germination of mungbean pollen (Thiyagu et al, 2008 andSomta et al, 2006). Another possibility could be the relative length of the stylus in mungbean and ricebean, where that of mungbean is shorter, being 1.6 mm compared with 1.4 for ricebean.…”

Vigna

“…In Vigna crops, slow rate of pollen growth, in addition to abnormalities in stigmatic and stylar regions, has been reported to be the major cause for low percentage of pod set in V. radiata × V. umbellata and V. mungo × V. umbellata crosses (Thiyagu et al 2008 ). Crossability was reported to be genotype dependent by Rashid et al ( 1988 ), hence leading to cross-incompatibility in some particular combinations, while the other cross-combinations were successful.…”