A New Source of Resistance to Cucumber Green Mottle Mosaic Virus in Melon

Abstract

Cucumber green mottle mosaic virus (CGMMV), which is easily transmitted via foliage contact, soil contamination, and seeds, is one of the major diseases affecting melon (Cucumis melo L.). However, no commercial cultivars resistant to CGMMV are available. In melon, only the symptomless carrier-type accessions ‘Phoot’ and ‘Kachri’ (var. momordica Duthle and Fueler) have been reported to be resistant to CGMMV. Therefore, to identify CGMMV-resistant accessions, 152 melon accessions were screened for resistance to CGMMV by mechanical inoculation. Only plants of the Korean accession ‘Chang Bougi’ (var. makuwa Makino) were resistant to the SH isolate (CGMMV-SH). The influences of temperature on symptom development and CGMMV accumulation in ‘Chang Bougi’ plants were studied. At 24°C, no symptoms were observed in the upper leaves of ‘Chang Bougi’ plants at 25 days after inoculation. In contrast, at 30°C, chlorotic spots were observed in the upper leaves from 15 to 20 days after inoculation. Under greenhouse conditions at an average temperature of 27.3°C, mosaic and chlorotic spots were observed in the upper leaves of ‘Chang Bougi’ plants from 30 days after inoculation. The accumulation patterns of CGMMV in the inoculated portions of ‘Chang Bougi’ and ‘Perlita’ (susceptible control) cotyledons were almost identical. CGMMV was detected in the uninoculated portions of ‘Perlita’ cotyledons from 4 days after inoculation, but was not detected in the uninoculated portions of ‘Chang Bougi’ cotyledons until 10 days after inoculation. Symptoms were observed, and the virus was detected in the upper leaves of ‘Chang Bougi’ plants inoculated with the watermelon isolate (CGMMV-W) or Kyuri green mottle mosaic virus (KGMMV). These results indicate that virus movement was restricted and that growth at 30°C enhances symptoms in this accession. Moreover, the resistance to CGMMV in this accession was specific to the SH isolate.