Genetics and Molecular Mapping of a Gene Conferring Resistance to a New Pathotype of Bipolaris sorokiniana in Barley

Spot blotch is an economically important disease of barley in North Dakota and many other regions of the world. The disease is caused by the fungus Bipolaris sorokiniana (teleomorph: Cochliobolus sativus). Three pathotypes (0, 1 and 2) of the pathogen have been described based on virulence patterns on three barley differential lines (ND5883, Bowman and NDB112). The spot blotch resistance derived from the barley line NDB112 has been effective against these pathotypes for more than 50 years. However, a new pathotype of the fungus has recently been identified in North Dakota and Canada, which can overcome the resistance in NDB112. To identify sources of resistance to the new pathogen, a total of 2,062 barley accessions from the national small grains collection were inoculated at the seedling stage in the greenhouse using isolate ND4008. Among the 2,062 barley accessions tested, only 44 (2.1%) were rated as resistant. To understand the genetics of resistance, we conducted a genetic analysis of the cross between the resistant line PI235186 and the susceptible parent PI356741. The results showed that F₁ plants were resistant and the 212 F₂ individuals segregated into a 3 (resistant) to 1 (susceptible) ratio (χ² =0.23, p=0.63), suggesting a dominant monogenic inheritance of the resistance. To map the resistance gene, we are genotyping-by-sequencing the F₂ population using a 384 single nucleotide polymorphism (SNP) marker panel specific to the population that are evenly distributed across the barley genome. The information on chromosome location of the gene will be presented in the conference.