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 F₁ hybrid seeds. In the following generation, flower buds of 10 F₁ hybrid plants were subjected to toxin stress before anthesis and the remaining ten control F₁ plants’ flowers were sprayed with water. Thirty-four selected BC₁ plants were generated by test crossing resistant WR-315 individuals with pollen from toxin-stressed F₁ individuals. Both control and treated F₁ plants were selfed to produce respective F₂ 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 F₂ and BC₁ generations. One hundred and forty-four selected F₂, 129 control F₂, and 34 selected backcross individuals were tested for the presence or absence of DNA markers. Except for the control F₂, observed ratios of selected F₂ and BC₁ 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.