Characterization of Fusarium root rot disease in grafted watermelon

Abstract

Root rot is an emerging disease of grafted watermelon in China that causes severe yield losses. The causal agents associated with this disease were characterized in this study. A total of 70 fungal isolates were recovered from infected roots, and the most prevalent isolates were identified as Fusarium oxysporum (31% of isolates recovered). F. oxysporum isolates induced typical root rot disease symptoms in pathogenicity tests, whereas the other isolates were nonpathogenic. On the basis of combined DNA sequence analyses, specific pathogenicity tests and root rot symptoms, the F. oxysporum was identified as F. oxysporum f. sp. radicis-lagenariae. We evaluated 37 bottle gourd rootstocks for resistance to F. oxysporum f. sp. radicis-lagenariae. The mean disease rating scores (DRSs) ranged from 1.1 to 4.0 at 20 days after inoculation. The rootstock 16S-71 was most resistant to infection. These findings provide useful information for the development of bottle gourd rootstocks with resistance to fusarium root rot and to manage this disease.