Quantifying Airborne Dispersal Route of Corynespora cassiicola in Greenhouses.

Qian Zhao,Yanxia Shi,Lei Li,Lei Li,Yuhong Wang,Baoju Li,Baoju Li,Ali Chai,Ali Chai,Liyun Guo,Xuewen Xie,Xuewen Xie

doi:10.3389/fmicb.2021.716758

Abstract

Target leaf spot (TLS), caused by Corynespora 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 of C. cassiicola aerospores, 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 of C. cassiicola aerospores were detected in 27 air samples from nine naturally infested greenhouses, ranging from 198 to 5,969 spores/m3. The C. cassiicola strains isolated from air samples were infective to healthy cucumber plants. Exposure chambers were constructed to study the characteristics of C. cassiicola aerospores released by artificially infested cucumber plants. The particle size of C. cassiicola ranged predominately from 2.1 to 4.7 μm, accounting for 71.97% of the total amount. In addition, the transmission dynamics of C. cassiicola aerospores from donor cucumber plants to recipient cucumber plants were confirmed in exposure chambers and greenhouses. The concentration of C. cassiicola aerospores 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.

Highlights

Cucumber (Cucumis sativus L.) is an important vegetable crop widely cultivated worldwide
When the sampling volume was 500 L, the C. cassiicola aerospore concentration collected by the high-volume sampler increased 59.27% compared with that collected by the Andersen six-stage sampler, which increased to 144.28% for a sampling volume of 2,000 L
Higher concentrations of C. cassiicola aerospores were observed from the high-volume sampler when sampling for 1 and 2 min, which increased 106.59 and 54.68%, respectively; when the sampling time increased to 5 min, a decrease of 31.69% was observed

Summary

Introduction

Cucumber (Cucumis sativus L.) is an important vegetable crop widely cultivated worldwide. China is the largest cucumber producer in the world, with a cultivation area of 1.26 Mha and a production of 70.34 million tons (Food and Agriculture Organization of the United Nations, 2019).. An increase in the prevalence of cucumber target leaf spot (TLS) disease has been noted in China. The majority of commercially grown cucumber cultivars worldwide are susceptible to C. cassiicola (Liu et al, 2017b; Wang et al, 2018), which poses a risk to cucumber production. In the past ten years, outbreaks of TLS disease around the Bohai Sea of China resulted in 40–70% yield loss (Li et al, 2012; Liu et al, 2017b)

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