Genetic analysis of mutations at loci controlling leaf form in cowpea (Vigna unguiculata

Mutations affecting leaflet number and shape occurred at high frequencies in some cowpea crosses. Mutant plants were nonpetiolate and unifoliolate as opposed to normal plants which were petiolate and trifoliolate. Two types of unifoliolate mutants were distinguishable on the basis of leaf shape which was ovate in one mutant and orbicular in the other. The nonpetiolate and the unifoliolate traits in the two mutants are each controlled by single recessive genes, but the genes controlling the traits in the different mutants were nonallelic. The orbicular leaf shape was also under the control of a single recessive gene. In the F2 and subsequent generations of the cross IBS 2497 x IBS 2625, orbicular-shaped unifoliolate leaf mutants were regularly produced, although the two parents involved in the cross were both trifoliolate. Linkage tests showed that the genes pt-1 for nonpetiolate trait, un-2 for unifoliolate leaf, and orb for orbicular leaf shape in one of the mutants were located on the same chromosome, while the genes pt-3 and un-3 in the other were also linked on a different chromosome. The results of this study provide further evidence indicating the involvement of transposable elements in the mutations observed in the cowpea lines used in this study.