Molecular detection of watermelon virus disease in Liaoning Province, China, and resistance evaluation of nine rootstocks to cucumber green mottle mosaic virus

Watermelon diseases have become increasingly severe in Liaoning Province, which is a major watermelon-growing region in China. To investigate the occurrence of watermelon virus diseases and identify the predominant virus types, 330 symptomatic samples from three major producing areas in Liaoning Province (Yingkou City, Xinmin City, Chaoyang City) were tested by seven specific primer pairs using reverse transcription-polymerase chain reaction (RT-PCR). The detection results indicated that the incidence of cucumber green mottle mosaic virus (CGMMV) was 54.85% (181/330), followed by watermelon mosaic virus (WMV) with an incidence of 15.76% (52/330). Considering CGMMV’s predominance and the extensive application of grafting in watermelon production, the disease resistance of nine commercially available rootstocks with diverse Cucurbitaceae backgrounds was evaluated. The results showed that all three pumpkin-type rootstocks uniformly exhibited robust resistance to CGMMV, with significantly lower viral accumulation. The bottle gourd rootstock also demonstrated strong resistance to CGMMV. However, wild watermelon rootstocks, due to intraspecific variation and genetic diversity within their germplasm, display a bimodal distribution of high resistance and high susceptibility. These results confirm that CGMMV is the primary watermelon virus in Liaoning Province and highlight the use of pumpkin-type rootstocks as an effective grafting strategy to enhance CGMMV resistance.