Pyricularia pennisetigena and Pyricularia urashimae can also cause wheat head blast

Abstract

Pyricularia oryzae pathotype Triticum (PoT) causes wheat blast and is associated with other poaceous hosts. In addition, there are four pathogens of the genus Pyricularia found in or near wheat fields, P. oryzae patotype Lolium (PoL), P. grisea (Pg), P. pennisetigena (Pp), and P. urashimae (Pu). The pathogenicity and virulence levels of Pp and Pu on wheat heads are still unknown. The highest yield losses happen when blast pathogens infect wheat heads. In this study, 25 isolates of Pyricularia spp. were recovered from poaceous hosts invasive of commercial wheat fields previously treated with fungicides. Multilocus phylogenetic analyses (ACT-RPB1-CAL) was used for species delimitation. Nine isolates were identified as PoT, seven as Pp, three as Pg, three as PoL, and three as Pu. Isolates' ability to cause blast disease on the wheat head cv. Anahuac 75 was also evaluated. Wheat heads artificially inoculated with PoT, Pu and Pp showed higher severity values (8.84 to 17.60% of injured area) and differed significantly from Pg, which did not cause lesions on heads. Lesions caused by isolates of Pp and Pu were indistinguishable from those caused by PoT in the inoculation tests. We are reporting for the first time that Pp and Pu cause blast lesions on the head of adult wheat plants that are indistinguishable from those caused by PoT. Our findings show that multiple Pyricularia species can cause blast disease on heads of wheat adult plants under greenhouse conditions with indistinguishable symptoms.