Screening quinoa (Chenopodium quinoa) germplasm for resistance to downy mildew (Peronospora variabilis) in Turkey

Abstract

Downy mildew caused by Peronospora variabilis is a major fungal disease limiting yield of quinoa (Chenopodium quinoa) around the world. Existing quinoa cultivars do not have adequate levels of resistance to the disease. In the present study, 165 quinoa accessions were screened for resistance to the disease in two consecutive years. Disease ratings were performed by using a three-leaf scoring technique. In 2018, of 70 quinoa accessions, 47.14% were moderately resistant and 18.57% were highly resistant. However, in 2019, of 95 accessions, 44.21% showed moderately resistant reaction and 26.31% highly resistant reaction to the disease. The average of AUDPC (area under disease progress curve) of all the accessions was 1293.42 in 2018, and 931.68 in 2019. The disease caused significant (P < 0.01) cumulative defoliations in susceptible accessions. AUDPC was positively correlated (r = 0.796 in 2018, r = 0.896 in 2019) with defoliation rate and negatively correlated (r = –0.834 in 2018, r = –0.599 in 2019) with plant height. There were also negative correlations (r = –0.755 in 2018, r = –0.580 in 2019) between defoliation rate and plant height. The study not only revealed resistant germplasm but also showed the importance of screening downy mildew resistance by comparing disease-related agronomic characteristics.