The Disease Progression and Molecular Defense Response in Chenopodium Quinoa Infected with Peronospora Variabilis, the Causal Agent of Quinoa Downy Mildew

Abstract

Downy mildew disease, caused by the biotrophic oomycete <i>Peronospora variabilis</i>, is the largest threat to the cultivation of quinoa (<i>Chenopodium quinoa</i> Willd.) in the Andean highlands, and occurs worldwide. However, so far, no molecular study of the quinoa-<i>Peronospora</i> interaction has been reported. Here, we developed tools to study downy mildew disease in quinoa at the gene expression level. <i>P. variabilis</i> was isolated and maintained, allowing the study of downy mildew disease progression in two quinoa cultivars under controlled conditions. Quinoa gene expression changes induced by <i>P. variabilis</i> were analyzed by qRT-PCR, for quinoa homologues of <i>A. thaliana</i> pathogen-associated genes. Overall, we observed a slower disease progression and higher tolerance in the quinoa cultivar Kurmi than in the cultivar Maniqueña Real. The quinoa orthologs of putative defense genes such as the catalase <i>CqCAT2</i> and the endochitinase <i>CqEP3</i> showed no changes in gene expression. In contrast, quinoa orthologs of other defense response genes such as the transcription factor <i>CqWRKY33</i> and the chaperone <i>CqHSP90</i> were significantly induced in plants infected with <i>P. variabilis</i>. These genes could be used as defense response markers to select quinoa cultivars that are more tolerant to <i>P. variabilis</i> infection.