TRANSMISSION CHARACTERISTICS OF SPIROPLASMA-CITRI AND ITS EFFECT ON LEAFHOPPER VECTORS FROM THE CIRCULIFER TENELLUS COMPLEX

Several leafhopper variants of the Circulifer tenellus complex were co llected in ''citrus stubborn'' affected areas in Israel. Two of these variants transmitted the Spiroplasma citri to Matthiola incana after b eing injected with the disease agent. The variant from Atriplex halimu s was designated Circulifer tenellus-A (CTA) and the variant from Port ulaca oleracea was designated Circulifer tenellus-P (CTP). Transmissio n characteristics were determined for both leafhoppers. A high rate of transmission (43.3%) was obtained by single CTA leafhoppers that were injected with the Amiad S. citri isolate from the Upper Galilee, comp ared with 7% transmission obtained with the CTP leafhoppers. The Gilga l S. citri isolate from the Jordan Valley, was not transmitted by eith er. Injection was more effective than acquisition access feeding to re nder the leafhopper infective for both CTA and CTP. The minimum acquis ition access period needed for the CTA variant to transmit the Amiad i solate was 1 h. Longer AAPs did not necessarily result in a higher rat e of transmission. The minimum incubation period was 6 days and the ma ximum was 32 days. The LP50 calculated from the logarithmic curve y = 45.74Ln(x)-53.68 was 9.64 days. The minimum inoculation access period (IAP) was Ih. The same transmission parameters for the CTP variant cou ld not be determined, as no transmission was obtained even when groups of five-six insects were placed on a single plant.