Rubber Research Institute of Vietnam, Ho Chi Minh City, Vietnam.
CIRAD, UMR-AGAP, F-34398 Montpellier, France.
PLoS One. 2016 Oct 13;11(10):e0162807. doi: 10.1371/journal.pone.0162807. eCollection 2016.
An indirect phenotyping method was developed in order to estimate the susceptibility of rubber tree clonal varieties to Corynespora Leaf Fall (CLF) disease caused by the ascomycete Corynespora cassiicola. This method consists in quantifying the impact of fungal exudates on detached leaves by measuring the induced electrolyte leakage (EL%). The tested exudates were either crude culture filtrates from diverse C. cassiicola isolates or the purified cassiicolin (Cas1), a small secreted effector protein produced by the aggressive isolate CCP. The test was found to be quantitative, with the EL% response proportional to toxin concentration. For eight clones tested with two aggressive isolates, the EL% response to the filtrates positively correlated to the response induced by conidial inoculation. The toxicity test applied to 18 clones using 13 toxinic treatments evidenced an important variability among clones and treatments, with a significant additional clone x treatment interaction effect. A genetic linkage map was built using 306 microsatellite markers, from the F1 population of the PB260 x RRIM600 family. Phenotyping of the population for sensitivity to the purified Cas1 effector and to culture filtrates from seven C. cassiicola isolates revealed a polygenic determinism, with six QTL detected on five chromosomes and percentages of explained phenotypic variance varying from 11 to 17%. Two common QTL were identified for the CCP filtrate and the purified cassiicolin, suggesting that Cas1 may be the main effector of CCP filtrate toxicity. The CCP filtrate clearly contrasted with all other filtrates. The toxicity test based on Electrolyte Leakage Measurement offers the opportunity to assess the sensitivity of rubber genotypes to C. cassiicola exudates or purified effectors for genetic investigations and early selection, without risk of spreading the fungus in plantations. However, the power of this test for predicting field susceptibility of rubber clones to CLF will have to be further investigated.
为了评估橡胶树无性系品种对由子囊菌 Corynespora cassiicola 引起的科雷氏叶斑病（CLF）的易感性，开发了一种间接表型测定方法。该方法通过测量诱导的电解质泄漏（EL%）来定量评估真菌分泌物对离体叶片的影响。测试的分泌物要么是来自不同 C. cassiicola 分离株的粗培养滤液，要么是纯化的 cassiicolin（Cas1），这是一种由侵袭性分离株 CCP 产生的小分泌效应蛋白。该测试被发现是定量的，EL%反应与毒素浓度成正比。对用两种侵袭性分离株测试的 8 个无性系，滤液的 EL%反应与孢子接种诱导的反应呈正相关。用 13 种毒素处理对 18 个无性系进行的毒性测试表明，无性系和处理之间存在很大的变异性，并且存在显著的无性系 x 处理互作效应。使用来自 PB260 x RRIM600 家族的 F1 群体构建了 306 个微卫星标记的遗传连锁图谱。使用纯化的 Cas1 效应物和来自 7 个 C. cassiicola 分离株的培养滤液对群体进行敏感性表型分析，揭示了多基因决定论，在 5 条染色体上检测到 6 个 QTL，解释表型方差的百分比从 11%到 17%不等。在 CCP 滤液和纯化的 cassiicolin 中鉴定到两个共同的 QTL，表明 Cas1 可能是 CCP 滤液毒性的主要效应物。CCP 滤液与所有其他滤液明显不同。基于电解质泄漏测量的毒性测试为评估橡胶基因型对 C. cassiicola 分泌物或纯化效应物的敏感性提供了机会，用于遗传研究和早期选择，而不会有在种植园中传播真菌的风险。然而，这种测试预测橡胶无性系对 CLF 的田间易感性的能力还需要进一步研究。
