Assessment of downy mildew resistance (peronospora farinosa) in a quinoa (chenopodium quinoa willd) germplasm.

Abstract

In the present study, seventy-nine accessions, including two local wild species (Chenopodium album and C. murale) and several cultivated quinoa lines developed through recurrent selection in Morocco were screened for their resistance against Peronospora farinosa that is the causal agent of downy mildew disease. The method of artificial inoculation on detached leaves taken from the middle stage of the plant before the natural infection was used. Screened accessions showed different levels of resistances to downy mildew as they were scored through the calculation of their area under diseases progress curve and their two resistance components, the incubation period and the latent period. Significant differences were found between accessions regarding the three criteria (Incubation Period, Latent Period and area under diseases progress curve). Accessions M2a and S938/1 were ranked resistant as they showed the longest Incubation Period (7 days) and Latent Period (12 days) and the lowest area under diseases progress curve (4). Therefore, M24 is the most susceptible accessions as it has presented the highest area under diseases progress curve (34.5) and the shortest Incubation Period (1 day) and Latent Period (3 days). In parallel to this evaluation approach, the accession resistance was confirmed under the field conditions through natural infection by using the tree-leaf method. The high correlation found between detached leaf inoculation method and field screening under natural infection allows us to use this laboratory technique with sureness in further selection works.