Effects of timothy Cladosporium eyespot on photosynthesis and biomass.

Timothy is a forage mainly grown in Min County, Gansu Province, China. In 2021, a leaf spot disease outbreak on timothy grass occurred in Min County, adversely affecting its growth and productivity. Therefore, this study investigated the leaf spot disease incidence in Min County, morphologically and molecularly characterized the disease-causing pathogen, and assessed its effects on the growth, photosynthesis, and biomass of timothy seedlings re-inoculated with the isolated pathogen. In the field, the disease incidence on plants and leaves was 100 and 85%, respectively. Morphologically, young lesions were ellipsoidal-fusiform with dark purple margins and an off-white center, while the mature lesions were eye-shaped spots with a light brown center and dark purple edges. Molecular characterization identified the pathogen as Cladosporium phlei causing Cladosporium eyespot disease. The net photosynthetic rate, transpiration rate, fresh shoot weight, and dry shoot weight of timothy seedlings 14 days after inoculation with the pathogen were decreased by 29.77, 56, 45.45, and 46.42%, respectively, implying that Cladosporium eyespot disease is an important timothy grass disease in Min County. Therefore, developing an integrated control strategy is urgent to lessen the economic loss.