INCIDENCE OF SOME SWEET POTATO VIRUSES, THEIR INTERACTION AND FREQUENCY UNDER FIELD CONDITIONS

Abstract

During 2005-2006 a field survey of sweet potato viruses was carried out and 19216 plants growing in 42 feddans were examined. Symptoms suspected to be due to virus infection reached about 4.5%, 10% and 22% in Menoufiea, Damietta and Kalyoubia Governorates respectively. Symptomatic plants showed mosaic, yellowing or leaf curl accompanied with mosaic. Percentage of each pattern was varied according to the tested cultivar and location. One hundred and forty six symptomatic and sixty nine asymptomatic plants were collected and serologically analyzed by ELISA against the most wide spread sweet potato viruses (i.e. SPFMV, SPMMV, SwPLV, SPCFV, SPCaLV, SPMSV and SPCSV). Data revealed that 13 % of asymptomatic and 68% of symptomatic plants was virus(s)-infected. SPFMV were detected in most infected plants either exhibiting symptoms or not. The virus existed either alone or in combination with the other viruses in double and mixed infections. Plants singly infected with this virus showed mild or no symptoms. Variable data were obtained with the other viruses. In contrast, SPMMV was found to be the lowest detectable virus. It was not detected in any single infection but tended to combine with SPFMV in double and mixed infections. Only three samples were infected with all tested viruses. Due to its wide spread, incidence in high frequency and problems facing its detection and diagnosis, some additional studies were carried out on the most predominant virus, SPFMV. It was identified by NCM-ELISA, immunosorbent electron microscopy and specific primers were used to ensure the identity.