Gametophytic selection for wilt resistance and its impact on the segregation of wilt resistance alleles in chickpea (Cicer arietinum L.)

In the present study, the effect of gametophytic selection on the segregation of molecular markers linked and unlinked to wilt resistance loci was investigated. A homozygous resistant genotype WR315 (h₁h₁ h₂h₂) was crossed to two susceptible lines, Karikadle (H₁H₁ H₂H₂) and BG256 (h₁h₁ H₂H₂), to generate two different F₁ populations. Three F₁ plants from each cross were subjected to gametophytic selection by spraying a pathotoxin at flower bud initiation stage, while the remaining F₁ plants in each cross were treated as control by spraying them with water. Both control and treated F₁ plants were selfed to generate respective F₂ populations. The seeds of control and selected F₂ populations of both crosses were sown to raise the plants. The DNA from 60 to 70 plants in each treatment group were isolated and tested for presence of the markers linked and unlinked to wilt resistance loci. Both the linked and unlinked markers showed expected monogenic ratio of 3:1 individually in control population. In the selected F₂ population the markers CS 27₇₀₀ linked to H₁ locus, A07C₄₁₇ and H₄G₁₁ linked to H₂ locus of wilt resistance exhibited significant deviations for monogenic and digenic ratios. The unlinked markers NCPGR93 and NCPGR48 showed expected monogenic ratios in the selected F₂ population. The results demonstrated that the gametophytic selection for wilt resistance increase the frequency of resistance alleles and resistant plants in the progeny. Deviation from the expected segregation ratio of the marker closely linked to resistance loci suggests the presence of linkage drag in gametophytic selection for resistance. The significant deviation from monogenic ratio was also observed for the linked marker A07C₄₁₇ in the selected F₂ population of second cross BG256 × WR315. On the contrary, the segregation of markers in a different linkage not linked to resistance loci was not affected. Thus demonstrating the utility of gamete selection for resistance is increasing the frequency of resistant plant in the progeny independent of the parental genotype. Gametophytic selection can be applied in plant breeding programmes to develop wilt resistant genotypes in a short period.