INHERITANCE OF ISOZYME VARIATION IN ASCOCHYTA BLIGHT-RESISTANT CHICKPEA LINES

Isozymic variation in chickpea (Cicer arietinum L.) crosses involving ascochyta blight [incited by Ascochyta rabiei (Pass.) Lab.] resistant germplasm was studied with the objective of identifying linkages of allozyme variation with ascochyta resistance genes. Such linkages, if found, could allow indirect selection of genes for ascochyta resistance. Eight F2 populations were scored for allozymes of four polymorphic isozyme loci. Five isozymes encoded by the loci Est-1, Est-2, Est-4, Est-5, Gal-1, and one previously identified isozyme locus, Pgd-c, were inherited codominantly. Linkage relationships among isozyme loci and genes for ascochyta resistance, growth habit (hg), and leaf type (slv) were also investigated. No linkage was found among isozyme loci, or between isozyme loci and ascochyta resistance; however, a loose linkage was observed between the gene controlling growth habit (hg) and the gene encoding for the cytosolic form of 6-phosphogluconate dehydrogenase (Pgd-c). Linkage of ascochyta resistance with the available isozymic variation was not found in this study. This was not unexpected, due to the limited number of loci segregating in the F2 populations we used. The inheritance of several isozyme loci was determined, however, and a previous report of a gene duplication in the Est-4/Est-5 region was confirmed. Hybridization of cultivated chickpea with closely related C. reticulatum Lad., the presumed wild progenitor, might increase the number of polymorphisms that can be used to locate ascochyta resistance genes.