| The whitefly Bemisia tabaci is a species complex consisting of at least 35 cryptic species, and it is able to transmit geminivirus specially. It is a pest of cotton, vegetable and flowers, causing extensive damage to agriculture worldwide. Cotton leaf curl disease is an important cotton disease in Africa and south-Asia and it is caused by at least 8 species of begomovirus that are all transmitted by whitefly. In China, Multan cotton leaf curl virus, one of the viruses that cause cotton leaf curl disease was reported for the first time in 2006. After the spread for nearly 10 years, this virus is now found to cuase markable damage to Hibiscus rosa-sinensis, Abelmoschus esculentus and Malvaviscus arboreus, and even cotton. Previous reseach indicates that disease epidemic is related to cotton variety used and whitefly cryptic species. Until now, the report about Multan cotton leaf curl virus acquisition, retention and transmission is scarce, and there is no report on the comparasion transmission of this virus to different cotton varieties by different whitelfy cryptic species. So it is necessary to compare the capacity of virus transmission to different cotton varieties by different whitelfy cryptic species, in order to help establish effective control strategies. To assess the potential threat of this virus to th ecotton industry in China, we compared the acquisition, retention and transmission of CLCuMV by four whitefly cryptic species, namely MEAM1, MED, Asia Ⅱ 1 and Asia I;in addition, we compared CLCuMV transmission rate to six different cotton varieties.(1) CLCuMV transmission by four whitefly cryptic species.We tested four whitefly cryptic species, namely MEAM1, MED, Asia Ⅰ and Asia Ⅱ 1 for their efficiency of CLCuMV to Tabaco (var.NC89) and cotton (var.Zhongzhimian 2 and var. Guangxi 112-2). The rate of CLCuMV transimission by Asia Ⅱ 1 to either tabaco or cotton was significantly higher than the other three cryptic species of whiteflies. Besides, the virus transmission was also affected by the varities of cotton.(2) CLCuMV transimission to different cotton varieties by Asia Ⅱ 1To examine the impact of cotton variety on virus transmission, we chose six cotton varieties, namely Guangxi 112-2, Zhongmiansuo 72, Zhongzhimian 2, Xingluzhong 45, Xingluzhong 46 and Lumianyan 28 as the test plants for virus transmission by Asia Ⅱ 1. When the number of whitelfy individuals per test plant was set at 10, the whiteflywas able to transmit CLCuMV to only two cotton varieties, Guangxi 112-2 and Lumianyan 28 with the efficiency of 52.2% and 3.4%.(3) Virus acquisition by four whitefly cryptic speciesWe compared the relative amount of CLCuMV in four whitefly cryptic species after they were allowed to acquire the virus for 1d,2d,3d,4d,5d,6d and 7d. At the same time, we compared the relative viral amount in females and males of four whitefly cryptic species after they were allowed to acquire the virus for 48h. Our data indicate that all four whitefly cryptic species have the capacity to acquire CLCuMV, and the viral amount in Asia Ⅱ 1 increases as the acquisition period was increased;in contrast, in the other three whitefly species the viral amount stayed almost unchanged at a relatvie low level. Besides, no significant difference of viral amount between females and males was found.To sum up, our results suggest that Asia Ⅱ 1 is the most efficient vector of CLCuMV, and the virus transmission capacity is parallel positively correlated with virus acquisition capacity. In addition, Guangxi 112-2 is the most susceptive cotton variety as compared to the other cotton varieties we tested. |
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