Occurrence of Cladosporium herbarum causing leaf spot on Avena sativa in China

Abstract

Oat (Avena sativa) is a quality feed crop for livestock with an expanding growth area of cultivation in China. Leaves of oat plants with necrotic spots were widely observed in the summer of 2019 in Tongwei county, China, with a rate of diseased leaves of 94.32% and a disease index of 69.96. Pathogenicity was tested by inoculating of oat plants with a conidia suspension of the isolate YMZZ2. Colony characteristics and conidial morphology of the isolates were determined on potato dextrose agar (PDA) and molecular identification of the isolate was conducted using phylogenetic analysis of the ITS, ACT, and HIS3 genes. The results showed that the morphological characteristics of the conidia were consistent with those described for species in the genus Cladosporium. Leaf spot symptoms appeared on all inoculated leaves within 5 days post-inoculation. At 10 days post-inoculation, all symptomatic leaves developed necrotic spots, each consisting of a brown or light brown border with a yellow halo. All control plants were asymptomatic. The morphological characteristics of the colony reisolated from the pathogenicity test lesions were morphologically similar to those of the isolate from the naturally infected leaves. Phylogenetic analysis of the gene sequences grouped them into a clade belonging to Cladosporium herbarum. To our knowledge, this is the first report of C. herbarum causing lesions on oat in China.