A novel strategy to develop powdery mildew resistant phenotypes and diagnose reaction to Golovinomyces latisporus in sunflower (Helianthus annuus L.)

Abstract

Among the various biotic stresses limiting sunflower productivity, powdery mildew incited by Golovinomyces latisporus has become a serious problem in the tropical regions. Reliable source of resistance has been identified in the diploid annual wild species Helianthus praecox (PRA-1823). Interspecific cross of cultivated sunflower (Acc. PS-2023) with PRA-1823 was advanced to develop interspecific recombinant inbred lines (IRILs) with distinct phenotypic reaction to the pathogen. The IRILs with similar morphology were subjected to molecular analysis by adopting the bulk pooling analysis (BPA) wherein DNA of eight each of susceptible and resistant IRILs were pooled to constitute the respective bulks. Fourteen sunflower specific SSR markers that showed polymorphism between the susceptible and resistant bulk IRILs, discriminated the powdery mildew resistant and susceptible samples as well. The primer ORS 485 was dominant and showed amplification only in the susceptible bulks and accessions and hence, it was converted to a multiplex reaction with actin to overrule the possibility of PCR failure. These 14 primers were successfully validated on IRIL populations and individual plants, a set of 40 breeding lines and 205 germplasm accessions with high susceptibility to the pathogen, 11 Helianthus species and three previously reported sources of resistance to powdery mildew (PM-81, IR-6, TX-16 R). This constitutes the first successful attempt at development of a diagnostic molecular marker set for distinguishing the powdery mildew resistant and susceptible genotypes in sunflower.