Quantifying Airborne Dispersal Route of Corynespora cassiicola in Greenhouses

Abstract

Target leaf spot (TLS), caused byCorynespora cassiicola, is an emerging and high-incidence disease that has spread rapidly on the global scale. Aerospores released by infected plants play a significant role in the epidemiology of cucumber TLS disease; however, no data exist concerning the infectiousness and particle size ofC. cassiicolaaerospores, and the experimental evidence for the aerospores transmission was lacking. In the present study, highly effective approaches to collect and quantify aerospores were developed for exposure chamber and greenhouse studies. Quantifiable levels ofC.cassiicolaaerospores were detected in 27 air samples from nine naturally infested greenhouses, ranging from 198 to 5,969 spores/m³. TheC. cassiicolastrains isolated from air samples were infective to healthy cucumber plants. Exposure chambers were constructed to study the characteristics ofC. cassiicolaaerospores released by artificially infested cucumber plants. The particle size ofC. cassiicolaranged predominately from 2.1 to 4.7 μm, accounting for 71.97% of the total amount. In addition, the transmission dynamics ofC. cassiicolaaerospores from donor cucumber plants to recipient cucumber plants were confirmed in exposure chambers and greenhouses. The concentration ofC. cassiicolaaerospores was positively associated with cucumber TLS disease severity. This study suggested that aerospore dispersal is an important route for the epidemiology of plant fungal disease, and these data will contribute to the development of new strategies for the effective alleviation and control of plant diseases.