اتيولوژي زردي كدوييان در استان بوشهر

YELLOWS IN THE BOUSHEHR PROVINCE, IRAN

Yellows is a prevalent disease of longmelon, snakemelon, squash and other cucurbits in the Boushehr Province of Iran. The disease begins as yellow spots which may spread and cover the whole leaf surface. Yellowing is more severe in older leaves. This paper reports the results of studies on the etiology of the disease. In a preliminary serological study, extracts of diseased leaves did not react with antisera to viruses reported from the area, namely, Watermelon mosaic virus, Cucumber mosaic virus and Squash mosaic virus . Electron microscopy showed presence of filamentous viruslike particles in concentrated extracts of diseased plants. The disease agent was not transmitted to cucurbit seedlings by mechanical inoculation (rubbings on leaves or stem injection) of diseased extracts. Typical disease symptoms, however, were produced under greenhouse conditions when cucurbit seedlings were inoculated with two (a local and a non-local) populations of whitefly(Bemisia tabaci) previously fed on diseased plants. Reverse transcription - polymerise chain reaction with a pair of primers corresponding to the coat protein region of Cucurbit yellow stunting disorder virus (CYSDV) resulted in the expected product. The type of symptoms, morphology of the associated particles, failure to be transmitted by mechanical inoculation, successful transmission with B. tabaci and RT-PCR results indicate that cucurbit yellows in Boushehr Province is caused by CYSDV, a member of the genus Crinivirus (Family Clastenwiridae).