Transmission Efficiency of Cucumber green mottle mosaic virus via Seeds,Soil, Pruning and Irrigation Water

Cucumber green mottle mosaic virus (CGMMV; genus Tobamovirus) infects frequently the grafted watermelon and is widely distributed in China. Investigating the transmission modes and their efficiency is urgently needed to understand the factors contributing to the epidemiology of this viral disease. In the present study, we found that the occurrence of CGMMV in a bottle gourd seed production base reached 100%, while the contamination rate and transmission rate were 100 and 0.92%, respectively. The bottle gourd plants showed obvious mottle symptom on leaves starting 36 days after seed sowing. The long latent period of CGMMV in seedlings implies a potential risk to use contaminated seeds in the production of grafted watermelon. This virus could overwinter in soil with debris of infected plants, and the infection rate of CGMMV from contaminated soils was 10.30%. CGMMV could be transmitted from infected watermelon plants to healthy ones by pruning at least to the ninth plant during the whole growing season. The transmission distance was 1.87 m by drip irrigation and 2.31 m by flow irrigation. This study suggested that contaminated seeds, contaminated soil, pruning and irrigation could transmit CGMMV at different efficiency, and all contribute to the epidemiology of CGMMV.