大豆作为陷阱植物防治十字花科植物根肿病的机理研究

Clubroot, caused by the obligate parasite Plasmodiophora brassicae Woronin, is an economically important disease on plants belonging to the family Brassicaceae.In recent years, rapid expansion of the disease in Western China resulted in contamination of soils no longer being suitable for growing any cruciferous crops.Main dependence on the use of highly toxic chemical fungicides, prevention and control of the clubroot disease becomes a serious challenge for safe production of cruciferous crops. Therefore, there is an urgent need to exploit novel control strategies to control the clubroot disease. The dormant spore germination and infection of plant roots are the main factors affecting clubroot disease severity. Our previous studies showed that plantation of soybean could effectively reduce the incidence of clubroot on oilseed rape or cabbage.Thus, soybean may act as the trap plants of P. brassicae.In this point of view, this project is initiated and will focus on clubroot resting spores germination and infection of the plants, on screening trap plant with only infection in the root hair epidermal tissues, on analysis of the composition of the root exudates from trap plant, on screening of the chemical components promoting germination of spores of the clubroot pathogen,on the mechanisms invoving the plant disease prevention and finally on verification of control efficacy of the trap plant against the clubroot disease under field conditions.Completion of the project can not only enrich and develop knowledge about the infection mechanisms for the clubroot pathogen, but also open new avenues for prevention and control of the clubroot disease.

根肿病是由芸薹根肿菌（Plasmodiophora brassicae）引起的世界性土传病害。近年来该病在我国中西部地区迅速蔓延，致使发病土壤不再适宜种植十字花科作物。目前缺乏抗根肿病的作物品种及经济有效的杀菌剂，如何防治根肿病是一个急需解决的问题。根肿菌休眠孢子萌发和侵染是其发生流行的主导因子。为此，我们开展了利用"陷阱植物"（侵染但不能完成生活史）防治根肿病的研究，筛选出非十字花科"陷阱植物"大豆，证实种植大豆能够有效减轻后作种植油菜或白菜根肿病的发生。在这些前期研究的基础上，本项目提出研究前作种植大豆防治根肿病的机理。具体研究内容报括：根肿菌对大豆侵染过程观察，大豆根系分泌物成分分析及促进根肿菌休眠孢子萌发的活性物质筛选，最终验证利用大豆根系分泌物中活性物质防治十字花科根肿病的效果。项目的完成将为发展防治根肿病新策略奠定理论基础。

本项目研究了大豆等不同前作植物对后茬作物根肿病的发生和危害的影响以及大豆作为前作植物防治后茬作物根肿病的机理。取得了如下研究结果：.1 明确了对大豆作为陷阱植物防治根肿病的机理。机制之一是大豆根系分泌物刺激根肿菌休眠孢子萌发。非寄主植物（大豆、豌豆和三叶草）和寄主植物（白菜和油菜）均可以刺激根肿菌休眠孢子萌发。大豆根系分泌物处理过的休眠孢子萌发率最高，达到40.13%。显著高于其他非寄主植物豌豆（26.97%）和三叶草（30.25%），寄主植物白菜（28.68%）和油菜（26.80%）及对照处理无菌水（14.48%）和营养液（18.12%）。研究还表明根系分泌物和土壤中的N、Ca、B和Mg等元素可以抑制根肿菌休眠孢子萌发。.2 明确了不同轮作方式对土壤根肿菌含量的影响。血球计数板法测定结果表明：大豆处理后土壤根肿菌含量为1.5 × 106个孢子/g土壤，显著低于白菜处理（6.6 × 106个孢子/g土壤）、油菜处理（4.2 × 106个孢子/g土壤）、豌豆处理（5.5 × 106个孢子/g土壤）、三叶草处理（3.7 × 106个孢子/g土壤）和休耕处理（9.3 × 106个孢子/g土壤）。实时荧光定量PCR法检测结果表明：大豆处理后土壤根肿菌含量为7.4 × 105个孢子/g土壤，显著低于白菜处理（2.3 × 106个孢子/g土壤）、油菜处理（2.5 × 106个孢子/g土壤）、豌豆处理（1.3 × 106个孢子/g土壤）、三叶草处理（1.2 × 106个孢子/g土壤）和休耕处理（2.5 × 106个孢子/g土壤）。.3 明确了大豆作为前作植物防治后茬作物根肿病的效果。在温室试验中，大豆对后茬白菜根肿病的防治效果达到44.82%。后茬白菜株高和干重明显高于对照和其他处理。在田间轮作试验中，大豆作为前作植物对后茬白菜根肿病防治效果分别达到66.40%。.