Pyricularia oryzae incites gray leaf spot disease on hard fescue (Festuca brevipila)

Abstract

AbstractGray leaf spot, caused by the fungal pathogen Pyricularia oryzae, is a widespread and destructive foliar disease of turfgrasses in the United States. Characteristic gray leaf spot disease symptoms were observed on hard fescue (Festuca brevipila Tracey) turf in New Jersey during October 2018. Prior to this observation, P. oryzae had not been documented as a pathogen of F. brevipila. Therefore, this study was conducted to determine if P. oryzae was the cause of the observed gray leaf spot disease symptoms. Morphological assessments and molecular analyses identified fungal isolates as the potential incitant from symptomatic F. brevipila turf as P. oryzae. Two isolates of P. oryzae (D300452 and 181001P12) and two F. brevipila cultivars (‘Beacon’ and ‘Reliant IV’) were used in growth chamber studies to fulfill Koch's postulates for pathogenicity. Inoculations were carried out using conidial suspensions at 4 × 104 conidia ml−1 concentration. Disease symptoms were observed 7 d post‐inoculation for both isolates on both cultivars. Koch's postulates were fulfilled by morphological evaluations and DNA sequencing of the reisolated fungi. This study confirms that P. oryzae is the causal agent of gray leaf spot disease on F. brevipila. Given the historical significance of gray leaf spot disease in other turf species, this study suggests that gray leaf spot could be a major concern for managing F. brevipila turf in the future.