VIRULENCE OF SEPTORIA TRISETI AND FUNGICIDE CONTROL OF LEAF MOTTLE AND FUSARIUM SEED INFECTION OF CANARY SEED (PHALARIS CANARIENSIS)

Abstract

Leaf mottle, caused by Septoria triseti, is the most important disease of canary seed (Phalaris canariensis L.) in western Canada and when severe it may cause reduction of canary seed yield. Understanding the host-pathogen interaction and the variation in virulence of the pathogen population is important for the development of durable resistance in canary seed cultivars. Recently, canary seed was approved as food for human consumption and identification of pathogenic fungal species on canary seed panicles is necessary to monitor seed quality. The objectives of this project were: 1) to evaluate variation for virulence among 27 isolates of S. triseti on Phalaris spp., 2) to identify the fungal species present on canary seed, and 3) to evaluate the effect of fungicides, application timings and canary seed genotypes on leaf mottle and fusarium seed infection of canary seed. Under controlled conditions, 24 Phalaris genotypes were evaluated for leaf mottle severity after inoculation with 27 isolates of S. triseti collected during 2005, 2013 or 2014. Differential interactions were detected in this study, which suggest that this patho-system follows the gene-for-gene model. Accession PI 189547 from Mexico was identified as resistant to 25 of the 27 isolates, which should be a valuable parent in a canary seed breeding program. Survey reports from 2014 and 2015 indicated the presence of Alternaria spp. and Fusarium spp. related to the FHB complex (Fusarium graminearum Schwabe, F. culmorum (W. G. Smith) Sacc., F. avenaceum (Corda ex Fr.) Sacc. and F. poae (Peck) Wollenw). A field study at Saskatoon and Indian Head during 2014 and 2015, using moderately resistant (PI 251274-3) and susceptible (Keet) canary seed genotypes, and three fungicides (propiconazole, prothioconazole + tebuconazole and pyraclostrobin + metconazole) applied at flag leaf and heading stages indicated that fungicide application reduced disease severity in years of high humidity, but application timing had little to no effect. Canary seed genotypes did not differ for leaf mottle severity or fusarium seed infection. Although these studies increased our knowledge of the interaction between S. triseti and canary seed, the benefit of fungicide applications were more difficult to measure. Thus, more research is needed to integrate this information into effective strategies to control leaf mottle and FHB in this crop.