Abstract
1. Mature hybrids were raised from P. aureus×P. trilobus cross. Reciprocal combination failed to produce mature pods.
2. The F1 plants resembled one or other parent in some characters and were intermediate between the two parents in others. The plants had on average 30.7 per cent pollen fertility and produced few pods with viable seeds.
3. Structural heterozygosity with regard to duplication, inversion and translocation was noted during analysis of pachytene and later stages of meiosis in F1.
4. Colchicine induced amphidiploid plants had on average 83 per cent pollen fertility and produced many pods with viable seeds. Preferential pairing of chromosomes was observed in meiosis of these plants.
5. The genomic notation AA has been proposed for the two parental species.
6. The role of hybrid inviability, weakness and sterility in isolation has been discussed. The hybrid sterility is haplontic and chromosomal in nature. The significance of structural alterations in speciation has been pointed out.
