INHERITANCE OF GROWTH HABIT IN PIGEONPEA

Determinate (DT) pigeonpea [Cajanus cajan (L.) Millsp.] has a production advantage but the genetics of this trait and indeterminate (IDT) and semideterminate (SDT) growth habits are not well defined. Inheritance of DT, SDT, and IDT growth habits in short-duration pigeonpea was studied in F1, F2, and BC1F1 generations of 15 crosses involving six parents (two of each growth habit) grown in the field in 1986. The segregation pattern in the crosses involving IDT and DT parents indicates that IDT growth habit is governed by a single dominant allele. Similarly, crosses between SDT and DT parents showed that the SDT trait also is controlled by a single dominant allele. The F2 population of the crosses between IDT and SDT parents segregated in the ratio of 12 IDT to 3 SDT to 1 DT, suggesting that the expression of the SDT allele (Dt2s) was masked by the presence of the IDT allele (Dt1) and that the homozygous recessive genotype for both genes (dt1dt1dt(2s)dt2s) has the DT phenotype. The results obtained in BC1F1 with both parents also supported the F2 data. The desirable determinate phenotype can be obtained from crosses of different phenotypes, including IDT X SDT, provided the IDT parent has the Dt1-dt(2s)dt2s genotype.