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Abstract Full Text

Physiological characteristics of melon plants showing leaf yellowing symptoms caused by CABYV infection.

Abstract

Melon leaves showing yellowing symptoms were analyzed using electron microscopy and RT-PCR for major cucurbit-infecting-viruses (CMV, MNSV, CGMMV, SqMV, WMV, KGMMV, PRSV and ZYMV) reported in Korea, but these viruses were not detected. As the result of further analysis by next-generation sequencing (NGS), the virus was identified as Cucurbit aphid-borne yellows virus (CABYV), and then confirmed by RT-PCR using CABYV-specific primers. When photosynthetic capacity was measured based on chlorophyll fluorescence yield (ChlFY), the leaves of the diseased plants showed 4.09 µmol.m-2.s-1, which was one-third of the readings observed for unaffected normal plants (12.36 µmol.m-2.s-1). The root functions of plants affected by leaf yellowing symptoms (LYS) was 0.28 mg.g-1, about half that measured for the normal unaffected plants (0.48 mg.g-1). Cytological observations revealed that there were no morphological differences in the palisade parenchyma and mesophyll spongy cells of the leaves between the diseased and the normal plants. However, the same leaf cells of the affected plants contained more starch granules compared to those of the normal, unaffected plants. We conclude that the LYS of muskmelon is not merely a physiological disorder but a viral disease caused by CABYV and spread by aphids.