VIEW ARTICLE

Effects of Strain, Source Plant, and Temperature on the Transmissibility of Citrus Tristeza Virus by the Melon Aphid. M. Bar- Joseph, Virus Laboratory, Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel; G. Loebenstein, Virus Laboratory, Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel. Phytopathology 63:716-720. Accepted for publication 19 December 1972. DOI: 10.1094/Phyto-63-716.

Three citrus tristeza virus isolates, which were considered to be related strains in cross protection tests, differed markedly in their transmissibility by Aphis gossypii. High transmission rates, averaging 40%, were obtained with the VT isolate, compared with less than 5% with the CT and ST isolates; all three were acquired from ‘M^me Vinous’ sweet orange. The source of the aphid population had no significant effect on transmission rates. M^me Vinous was a much better host for virus acquisition than ‘Palestinian’ sweet lime, although no differences in the concentration of threadlike particles (TLP) were observed. The differences in transmissibility of the tristeza isolates were not correlated with TLP content. Significantly higher transmission rates were obtained when source plants were kept at 22 C, compared with those from plants held at 31 C. This was correlated with a decrease in TLP content. The high transmissibility of the VT strain by A. gossypii, compared with the low rates of the two other strains, may explain the natural spread observed recently in Israel, as well as the lack of spread from previously located tristeza sources.