Genetic evidence for gametophytic selection of wilt resistant alleles in chickpea

Gametophytic selection can drastically reduce the number of selection cycles during crop improvement programs. The objective of the present investigation was to test whether the nature of inheritance of two unlinked disease-resistant loci, h(1) and h(2), against Fusarium wilt in chickpea (Cicer arietinum L.) under gametophytic (pollen) selection was similar to that already observed at sporophytic level. A homozygous dominant (H(1)H(1)H(2)H(2)) susceptible genotype JG-62 was crossed to a recessive (h(1)h(1)h(2)h(2)) resistant genotype WR-315 to produce 20 F(1) hybrid seeds. In the following generation, flower buds of 10 F(1) hybrid plants were subjected to toxin stress before anthesis and the remaining ten control F(1) plants' flowers were sprayed with water. Thirty-four selected BC(1) plants were generated by test crossing resistant WR-315 individuals with pollen from toxin-stressed F(1) individuals. Both control and treated F(1) plants were selfed to produce respective F(2) generations. Two DNA markers, CS-27(700bp) and A07C(430bp), linked to susceptible alleles H(1) and H(2), respectively, were used to study the inheritance patterns of h(1) and h(2) loci in the F(2) and BC(1) generations. One hundred and forty-four selected F(2), 129 control F(2), and 34 selected backcross individuals were tested for the presence or absence of DNA markers. Except for the control F(2), observed ratios of selected F(2) and BC(1) populations exhibited significant chi-square deviations from expected monogenic and digenic ratios. Our results suggest that gametophytic selection is as effective as that realized at the sporophytic level, and that the gametophytic selection can be an effective breeding tool for plant breeding programs.