Comparative Studies On Isolates Of Citrus Tristeza Virus Collected From Chongqing Municipality

Tristeza caused by Citrus tristeza virus (CTV) is an economically important citrus virus disease, which is widely spread in most citrus-growing areas by grafting and aphid. Various CTV isolates and brown citrus aphid which as the most efficient CTV vector are widely distributed in China, and it will pose the latent threat to the citrus industry of our country. Because of the better natural resource and ecological condition, Chongqing is always one of the best citrus production areas in the world, and citrus has more competitive ability than other crops. Citrus has been cultured in 31 counties (cities) of the whole 40 counties (cities) in Chongqing, and Jiangjin, Kaixian, Fengjie, Changshou as well as Wanzhou are major citrus production areas in Chongqing municipality. In this research the CTV restriction fragment length polymorphism (RFLP) groups of the field samples in Chongqing were analyzed; the characteristics of different CPG/Hinf I RFLP groups by single aphid transmission (SAT) of three CTV isolates were inspected, and some sequences of isolates before and after SAT were sequenced and analyzed. The conclusions are as follows:1. The composing of CTV CPG/Hinf I RFLP groups in field samples in citrus major production areas in Chongqing municipality.(1) Identification of samples infected CTV by direct tissue blot immuno-assay (DTBIA): Two hundred forty-three samples of sweet orange or pomelo from 9 citrus major production areas in Chongqing municipality were tested by DTBIA. One hundred ninety-three samples of them were CTV-positive, and the infected incidence was 79.4%. All of the tested 185 samples of sweet orange were infected with CTV, while the infected incidence of pomelo was 13.8%. Therefore the results indicated that CTV had been widely distributed in sweet orange in Chongqing.(2) The analysis of composing of CTV CPG/Hinf I RFLP groups in citrus major production areas in Chongqing: The composing of CTV CPG/Hinf I RFLP groups of all samples were as follows: ?the incidence of single CTV infection was about 42.0%, while the incidence of mixed CTV infection was about 58.0%, in which CTV isolates infected sweet orange were infected with CPG/Hinf I RFLP group 3 and those infected pomelo were infected with group 6. ?The CPG/Hinf...