Downy mildew, caused by Peronospora variabilis Gäum, is the most important quinoa disease worldwide. In Spain this disease severely affects quinoa crop, infecting up to 90% of plant area and causing defoliation in susceptible cultivars under favourable con ditions for the development of the disease. Despite the relevance of this trait for quinoa breeding, little is known about the genetics of resistance to downy mildew in quinoa (1). Quinoa accession PI614911 has shown high level of resistance to this disease under field conditions in Córdoba (Spain) during several seasons. The objective of this study was to unravel the inheritance of resistance to downy mildew in this accession. Towards this objective, accession PI614911 was crossed with a susceptible line a nd segregation of resistance analysed in the F2 generation under field conditions in Córdoba, Spain. Differences between resistant and susceptible plants were evident. The segregation ratio in the F2 population gave a good fit to the 3:1 ratio expected for a single gene inheritance (ꭕ2 = 0.01; p= 0.92). These results demonstrate that resistance to downy mildew in quinoa accession PI614911 is controlled by a single dominant gene. Knowledge of the genetic control of resistance to downy mildew in this accession will be relevant to design the best strategy to introduce this character into new cultivars.

Trabajo presentado en el XLII Congreso de la Sociedad Española de Genética (SEG2021), celebrado online del 14 al 18 de junio de 2021.

This study was supported by project P18-TP-592, co-financed by FEDER.