1 State Key Laboratory of Conservation and Utilization of Subtropical Agro-bioresources, Guangdong Province Key Laboratory of Microbial Signals and Disease Control, College of Agriculture, South China Agricultural University, Guangzhou 510642, China.
2 Guangzhou Institute of Forestry and Landscape Architecture, Guangzhou, Guangdong 510405, China.
Phytopathology. 2019 Jun;109(6):1029-1042. doi: 10.1094/PHYTO-10-18-0384-R. Epub 2019 May 8.
f. sp. , the causative agent of Panama disease, is classified into three races: 1, 2, and 4. However, the histological characteristics, the accumulation of fusaric acid (FA), and resistant gene expression in banana infected with different races remain unclear. In this study, we compared the infection processes, FA contents, and gene expression levels in a Cavendish banana cultivar ( AAA Brazilian) inoculated with 1 and 4. Results showed that 4 can rapidly extend from the roots to the leaves, whereas 1 expands slowly from the roots to the rhizomes but cannot expand further upward. In addition, the colonization of plants by 4 was significantly higher compared with 1, as was the content of FA in those infected plant tissues. We observed that a large amount of starch granules was produced in the rhizomes and the number of starch granules was significantly higher after infection with 1 than after infection with 4. We further found that starch has an important inhibitory effect on the phytotoxicity induced by FA, thus leading to more resistance to the pathogens in the plants with high amounts of starch accumulation than in those with a low amount of starch accumulation. Moreover, the expression levels of 10 defense-related genes were analyzed and the results showed that the induction levels of those genes were higher after infection with 1 than after infection with 4. These results suggest that the observed differences in the invasion of host tissues and FA accumulation, and the number of starch granules and expression of defense-related genes, may contribute to a difference in virulence between the two races and the resulting difference in host resistance response, respectively.
f. sp. 是巴拿马病的病原体，分为 1、2 和 4 三个小种。然而，不同小种感染香蕉后的组织学特征、镰刀菌酸（FA）积累和抗性基因表达尚不清楚。本研究比较了接种 1 和 4 时，感病的卡文迪什香蕉（AAA 巴西）品种的侵染过程、FA 含量和基因表达水平。结果表明，4 可从根部迅速扩展到叶片，而 1 则从根部缓慢扩展到根茎，但不能进一步向上扩展。此外，与 1 相比，4 对植物的定殖明显更高，感染组织中的 FA 含量也更高。我们观察到，4 感染后大量淀粉粒在根茎中产生，且淀粉粒数量明显高于 1 感染。我们进一步发现，淀粉对 FA 诱导的植物毒性有重要的抑制作用，因此，与淀粉积累量低的植物相比，淀粉积累量高的植物对病原体的抗性更强。此外，分析了 10 个防御相关基因的表达水平，结果表明，1 感染后的诱导水平高于 4 感染。这些结果表明，观察到的宿主组织侵染和 FA 积累、淀粉粒数量和防御相关基因表达的差异，可能分别导致两个小种之间毒力的差异以及宿主抗性反应的差异。
