Introgression of Cajanus platycarpus genome into cultivated pigeonpea, C. cajan

Summary

Cajanus platycarpus, an incompatible wild species from the tertiary gene pool of pigeonpea (C. cajan (L.) Millspaugh), has many desirable characteristics for the improvement of cultivated varieties. To necessitate such transfers, embryo rescue techniques were used to obtain F₁ hybrids. The F₁ hybrids were treated with colchicine to obtain tetraploid hybrids, that were selfed to obtain F₂, F₃ and F₄ progenies. All of the hybrids and subsequent progenies had an intermediate morphology between the two parents. Backcrossing of the tetraploid hybrids with cultivated pigeonpea was not possible given embryo abortion, with smaller aborted embryos than those obtained in the F₀ parental cross.

As a route of introgression, diploid F₁ hybrids were backcrossed with cultivated pigeonpea and BC₁ progeny obtained by in vitro culture of aborting embryos. BC₂ plants were obtained by normal, mature seed germination. Although embryo rescue techniques had to be used to obtain F₁ and BC₁ plants, it was possible to produce BC₂ and subsequent generations through direct mature seed. Every backcross to cultivated pigeonpea increased pollen fertility and the formation of mature seeds.