枸橼种质对柑橘溃疡病的抗性鉴定

柑橘溃疡病(Xanthomonas citri subsp. citri,Xcc)是严重阻碍柑橘产业发展的世界性检疫病害,防控困难,选育抗病品种为防治溃疡病的唯一有效办法。枸橼C-05是柑橘属独特的抗溃疡病种质,为抗性机理和抗病育种提供了种质基础。为了进一步评价枸橼C-05的抗性,另外收集了13份枸橼种质,对其进行溃疡病的离体和活体抗性评价。叶片形态学观察表明,14份枸橼种质存在较大的形态学差异。采用离体与活体注射接种不同浓度的柑橘溃疡病菌,根据叶片的感病症状、病斑周围黄色晕圈大小等典型溃疡病症状,综合评价枸橼类种质的抗病性。结果表明:枸橼种质之间对溃疡病的抗性存在极大差异,溃疡病的抗性评价综合病情指数显示枸橼C-05、园香橼、矮果香橼、美国枸橼、普通枸橼和印度大果综合病情指数较小,表现为极抗病或抗病,其他枸橼种质表现不同程度的感病性;枸橼种质的抗病或感病性与其叶片形态特征无关。枸橼C-05和5个抗病枸橼种质对柑橘溃疡病具有针对性的抗性,这对进一步研究抗病机理和抗病育种具有重要意义。

Evaluation of citron genotypes for the resistance to citrus canker

Citrus canker(Xanthomonas citri subsp. citri, Xcc) is a worldwide quarantine disease that seriously hinders the development of citrus industry, and it is difficult to prevent and control. Breeding for resistant cultivars is the only way to effectively control the disease. Citron C-05 is the unique disease resistant genotype within Citrus identified previously. To fully evaluate the resistance of Citron C-05, in this study, other 13 citron genotypes were collected and investigated for their behaviors in reaction to the inoculation with Xcc by in vitro and in vivo assays. Leaf morphological characteristics were quite different among all the 14 citron genotypes. The reaction to the inoculation with Xcc was evaluated according to the symptoms on leaf surface and the size of yellow halo around disease spots. The results showed that the susceptibility and resistance were different among the tested citron genotypes. Citron C-05, Round citron, Aiguo citron, American citron, Common citron and Inerdonato had the lowest comprehensive disease index demonstrating resistance or high resistance to the canker disease, while the other citron genotypes were susceptible with different degrees to the disease. The behaviors to the canker disease of the citrons were not related to their leaf morphological differences. It is suggested that Citron C-05 and five resistant citron genotypes had specific innate resistant to canker disease. These results should be important for further study on the mechanism of resistance and the breeding for resistant citrus cultivars.