Sexual Compatibility Types in F(1) Progenies of Sclerospora graminicola, the Causal Agent of Pearl Millet Downy Mildew

Sclerospora graminicola is primarily heterothallic in nature with two distinct mating types (G(1) and G(2)); however, homothallism does exist in the pathogen populations. In this study, a cross was made between two self-sterile isolates (Sg 019, Mat-2, G(2) × Sg 445-1, Mat-1, G(1)) of S. graminicola and a total of 39 F(1) progenies were established. The study on sexual compatibility types in F(1) progenies was conducted by crossing each F(1) progeny with both the parents (Sg 445-1, Mat-1, G(1); and Sg 019, Mat-2, G(2)). The results revealed the presence of four sexual compatibility types, viz. G(1), G(2), G(1)G(2) and G(0) (neuter) in the progenies. The G(1)G(2) progenies that produced oospores with both the parents were found as self-fertile (homothallic) and self-sterile (heterothallic) types. Similarly, self-fertile parental type G(1) and G(2) progenies were designated as secondary homothallic, whereas self-sterile parental type G(1) and G(2) progenies were of heterothallic type. The result of the present study revealed Mendelian segregation of mating type locus in S. graminicola which indicates that sexual reproduction plays an important role in the evolution of new genetic recombinants in the pathogen. The study also helps in understanding the genetic structure of S. graminicola populations and potential for possible evolution of new virulences in the pathogen.