玉米田中禾本科植物叶斑病原真菌的多样性和寄主专一性研究

It was reported that 20-30 fungal genera could cause spot diseases on the maize in foreign countries, while there were 9 fungal genera often reported as spot diseases on the maize in China. It appears fungal diversity in the maize spot diseases. Several species of plants in Gramineae are the main weeds in the maize field, and the fungi causing the spot diseases on the weeds in Gramineae were often reported as the potential microbial herbicide. The weeds in Gramineae are closely related to the maize and similar plant pathogenic fungal species were reported as causing spot diseases on both of them. In this study, in the same maize field, samples of the spot diseases of plants in Gramineae are collected and fungal strains are isolated from them during three years. Morphological characteristics and phylogenetic analysis are applied to identify the fungal species, to study the fungal diversity, dormant species, populations and complex infection. The laws of current maize field development of major plant pathogenic fungal species causing spot diseases during the three years, and their relation to the factors of cultivated varieties, climate and the crop system will be studied. According to the pathogenicity tests, the host specificity of the dormant pathogenic fungal species causing spot diseases from the weeds in Gramineae will be studied. The results will show the plant pathogenic fungal species and the complex species infected the maize in the current fields, applying for the basis of scientific research of the disease resistance and disease control of maize fungal diseases. The safety, environmental adaptability and evaluation of the application of fungal strains causing spot diseases from weeds in Gramineae as the potential microbial herbicide in the maize fields will be studied.

据国外报道引起玉米叶斑病的真菌有20-30个属，我国常见的也有9个属，因此玉米叶斑病原真菌具有丰富的多样性。禾本科杂草是玉米田中主要的杂草种类，禾本科杂草的叶斑病原真菌也常被作为微生物源除草剂的候选菌株进行研究。由于玉米和禾本科杂草的亲缘关系较近，本研究选择当前玉米生产上同一地块这一特殊生境，拟采用一定的采样策略、菌种分离、分子系统学和形态学相结合的真菌鉴定方法，探明其中包括玉米在内的禾本科植物上发生的叶斑病原真菌的多样性，连续三年病原真菌的发生规律，与品种、气候和耕作等条件的关系。通过致病性测定，研究禾本科杂草叶斑病原真菌的优势种群对包括玉米在内的禾本科植物的寄主专一性。研究结果将明确当前玉米生产实际发生的玉米叶斑病原真菌的多样性和发生规律，为玉米抗病育种和病害防控等研究提供理论依据；同时为禾本科杂草叶斑病原真菌作为微生物源除草剂候选菌株在玉米田中应用的安全性和可行性提供数据支持。

在2018-2020年连续3年在我国北方玉米主产区选择3个代表性地点吉林公主岭、山东德州和北京顺义设置了不喷除草剂的玉米田，其发生的杂草种类相对单一，其丰富度与以往报道的多样的杂草种类有一定差异；共采集不喷除草剂玉米田杂草叶斑样品，喷与不喷除草剂的玉米叶斑样品1000余份，目前从700余份样品上分离到真菌1800余株，2份以上玉米叶斑样品分离到的真菌有40多个属，多样性丰富，其中有部分玉米上潜在的新病害。杂草和玉米叶斑样品分离到的真菌共同属有30多个，2份以上样品且仅分离自杂草和玉米的真菌分别有7个和6个属，仅1份样品分离自杂草或玉米的真菌属分别有19个和17个。玉米与杂草上分离到真菌多样性的关系，与地点、是否喷除草剂、生育期的联系，以及主要玉米病害的发生规律进行了总结，同一玉米样品上分离到多种病原的现象比较普遍。通过对700余株、400余株和100余株分离自玉米、稗草和马唐的真菌进行离体叶片法致病性测定，有500余株、300余株和90余株真菌分别对玉米、稗草和马唐有致病性；选择100余株真菌涂抹法接种，对稗草、马唐致病性较强的真菌分别有30余株和20余株，其中有些菌株马唐和稗草有较强致病性同时对玉米致病性弱或没有致病性，具有作为生物除草剂防除杂草的应用潜力，其致病性和安全性还需要进一步确认。通过本项目研究，了解了我国玉米主产区生产上玉米叶斑病害的发生情况，发现玉米和杂草上叶斑上分离到同属真菌的比例较高，希望通过后续的研究，选用仅分离自杂草且对玉米安全的真菌或用其活性代谢物更适合用于玉米田除草，使目前玉米生产上过量施用除草剂的情况有所改善。