Yamamoto Pedro T, Bassanezi Renato B, Wulff Nelson A, Santos Mateus A, Sanches André L, Toloy Rodrigo S, Gimenes-Fernandes Nelson, Ayres Antonio J, Jesus Junior Waldir C, Nagata Tatsuya, Tanaka Francisco A O, Kitajima Elliot W, Bové Joseph M
Departamento Científico, Fundo de Defesa da Citricultura, Fundecitrus, Av. Dr. Adhemar Pereira de Barros, 201, CEP 14807-040, Araraquara - SP, Brazil.
Laboratório de Fitopatologia, Departamento de Fitotecnia, Universidade Federal do Espírito Santo, Alto Universitário, S/N, CEP 29500-000, Alegre - ES, Brazil.
Plant Dis. 2011 Feb;95(2):104-112. doi: 10.1094/PDIS-04-10-0307.
Citrus sudden death (CSD) transmission was studied by graft-inoculation and under natural conditions. Young sweet orange trees on Rangpur rootstock were used as indicator plants. They were examined regularly for one or two characteristic markers of CSD: (i) presence of a yellow-stained layer of thickened bark on the Rangpur rootstock, and (ii) infection with the CSD-associated marafivirus. Based on these two markers, transmission of CSD was obtained, not only when budwood for graft-inoculation was taken from symptomatic, sweet orange trees on Rangpur, but also when the budwood sources were asymptomatic sweet orange trees on Cleopatra mandarin, indicating that the latter trees are symptomless carriers of the CSD agent. For natural transmission, 80 young indicator plants were planted within a citrus plot severely affected by CSD. Individual insect-proof cages were built around 40 indicator plants, and the other 40 indicator plants remained uncaged. Only two of the 40 caged indicator plants were affected by CSD, whereas 17 uncaged indicator plants showed CSD symptoms and were infected with the marafivirus. An additional 12 uncaged indicator plants became severely affected with citrus variegated chlorosis and were removed. These results strongly suggest that under natural conditions, CSD is transmitted by an aerial vector, such as an insect, and that the cages protected the trees against infection by the vector.
通过嫁接接种和自然条件下的实验对柑橘猝死病（CSD）的传播进行了研究。以兰普柚砧木上的幼龄甜橙树作为指示植物。定期检查这些指示植物是否出现CSD的一两个特征标记：（i）兰普柚砧木上增厚树皮的黄色染色层，以及（ii）与CSD相关的马拉病毒感染。基于这两个标记，不仅当用于嫁接接种的接穗取自兰普柚上有症状的甜橙树时能实现CSD的传播，而且当接穗来源是埃及酸橙上无症状的甜橙树时也能实现传播，这表明后一种树是CSD病原体的无症状携带者。对于自然传播，在一个受CSD严重影响的柑橘园内种植了80株幼龄指示植物。在40株指示植物周围建造了单独的防虫网罩，另外40株指示植物不设网罩。40株设网罩的指示植物中只有两株受到CSD影响，而17株未设网罩的指示植物表现出CSD症状并感染了马拉病毒。另外12株未设网罩的指示植物受到柑橘杂色黄化病的严重影响并被移除。这些结果有力地表明，在自然条件下，CSD是通过诸如昆虫之类的空气传播媒介传播的，并且网罩保护树木免受该媒介的感染。
