中文摘要
苜蓿根腐病是影响苜蓿生产的主要因素，国外报道的病原种类达100多种，而我国仅确定了镰刀菌属、丝核菌属等10余种，为确定我国苜蓿根腐病的病原种类作为后续研究和生产上防治的重点，本论文在室内测定了从苜蓿根部分离出的15种真菌25个菌株对苜蓿的致病性有无及大小。为保证接种结果的可靠性，在致病性测定之前通过调整培养苜蓿的营养水平，解决了接种室培养苜蓿时出现植株生长异常的问题。获得如下主要结果：
1.对苜蓿有致病性的苜蓿根部真菌有12种，分别为：毁灭刺盘孢(Coltetotrichum destructivum)、三叶草刺盘孢(C. trifolii)、北美刺盘孢(C. americae-borealis）、立枯丝核菌(Rhizoctonia solani)、苜蓿茎点霉(Phoma medicaginis)、根异茎点霉(Paraphoma radicina)、茎点霉未定种(Phoma sp.)、尖镰孢(Fusarium oxysporum)、腐皮镰孢(F. sonali)、木贼镰孢(F. equiseti )、层出镰孢(F. proliferatum)和三线镰孢(F. tricinctum)，首次确定其中的3种刺盘孢属和2种茎点霉属真菌为苜蓿根腐病的病原，已知对苜蓿有致病性的菊异茎点霉(Paraphoma chrysanthemicola)和苜蓿轮枝孢(Verticillium alfalfae)未见发病。
2.致病性由强至弱的5种真菌分别为：毁灭刺盘孢、三叶草刺盘孢、北美刺盘孢、立枯丝核菌和层出镰孢，接种8周时植株死亡率分别为68.40%、10.53%、10.00%、5.30%和5.00%，其他有致病性的真菌均
未引致植株死亡，仅主根皮层变、腐烂。与对照相比，有致病性的12种真菌对根长、根直径、根表面积和根干重分别降低8.4%～56.8%、11.4%～45.7%、30.7%～77.2%、50%～89%。
3.在22 ℃16 h光照（LED植物灯，光强6680 LUX）和18 ℃8 h黑暗的接种室内，灭菌土壤中培养苜蓿植株时浇灌施可得牌植物生长液可确保植株健康生长，而浇灌霍格兰营养液（自配）、自来水和蒸馏水均可出现叶片干枯变黄甚至脱落，与浇灌自来水相比，浇灌施可得植物生长液的株高、地上鲜重、地上干重、根鲜重、根干重、根表面积、根直径、叶片数和节间数分别增加256%、731%、655%、384%、445%、101%、27%、84%和112%，均显著(P<0.05)增加。
关键词：紫花苜蓿，根病，致病性测定，根腐病，草地衰退
Pathogenicity test on 15 fungal species isolated from alfalfa
roots
Abstract
Alfalfa root rot is one of the key factors limiting production. There are more than 100 species pathogens in abroad, while in China only found were less than 10 species such as Fusarium, Rhizoctonia. In order to determine our country‟s pathogens of alfalfa root ro in China so that late ma
nagement and further research, the pathogenicity of 15 species (25 isolates) fungi isolated from alfalfa roots were tested in greenhouse in this thesis. Prior to do this work, a problem occurred during alfalfa culture in greenhouse will be resolved by optimizing nutrition and water supply. The main results are as follows:
1. Among tested fungal species, there were 12 species pathogenic to alfalfa. There were Coltetotrichum destructivum, C.0 trifolii, C. americae-borealis, Rhizoctonia solani, Phoma medicaginis, Paraphoma radicina, Phoma sp., Fusarium oxysporum, F. Sonali, F. equiseti, F. proliferatum and F. tricinctum. In which, 3 species in Coltetotrichum genes and 2 species in Phoma genus were first report in the world.Paraphoma chrysanthemicola and Verticillium alfalfae already known were alfalfa pathogen, whereas, no symptoms presented in this test.
2 The pathogenity from high to low were as Coltetotrichum destructivum, C. trifolii, C. americae-borealis, Rhizoctonia solani and F. proliferatum. All caused plant death, the mortality in 8 wk is 68.40%, 10.53%, 10.00%, 5.30% and 5.00%. Others did induced death, only discoloration presented on root surface. Root length, root diameter, root surface area, and root dry weight of plants inoculated the 12 pathogenic fungi decreased 8.4%-56.8%,11.4%-45.7%, 30.7%-77.2%, 50%-89%.
3 The optimized condition for culturing healthy alfalfa plants in the greenhouse is irrigated Scotts plant nutrient solution, 12 h 6680 LUX light using LED plant light at 22°C, and then 12 h dark at 18°C, and soil were sterilized. Leaves were green, and no one leaf blade turned to yellow or defoliated under supplied the Scotts solution, while some leaves are not healthy under supplied with Hoagland's nutrient solution, tap water and distilled water. Compared with tap water, plant height, fresh weight, shoot dry weight, root fresh weight, root dry weight, root area, root dimeter, number of leaves, and stem node number all increased, respectively increaed 256%,
731%, 655%, 384%, 445%, 101%, 27%, 84% and 112%, significantly higher (P<0.05).
Keywords: Medicago sativa L.，root diseases，pathogenicity test，disease of root rot，grassland decline
目录
中文摘要..................................................................................................................... . I I 第一章前言 (1)
第二章文献综述 (2)
2.1 我国苜蓿草产业发展现状 (2)
2.1.1 苜蓿的营养品质及用途 (2)
2.1.2 我国苜蓿种植与生产状况 (2)
2.1.3 影响苜蓿生长的因素及栽培技术 (3)
2.2 苜蓿根腐病 (6)
2.2.1 病原种类及分布 (6)
2.2.2 致病性强弱 (7)
2.2.3 产量损失 (8)
第三章材料与方法 (10)
3.1 共用材料与方法 (10)
3.1.1 接种室光温条件 (10)
3.1.2 供试苜蓿品种与土壤 (10)
3.1.3 数据分析 (11)
3.2 接种室苜蓿叶片干枯原因研究 (11)
3.2.1 营养处理 (11)
3.2.2 幼苗的培养 (11)
3.2.3 测定与观察 (12)
3.3 苜蓿根部分离菌的致病性测定 (12)
3.3.1 培养基的种类及制备 (12)
3.3.2 供试真菌 (13)
3.3.3 接种幼苗的准备 (15)
3.3.4 孢子和菌丝悬浮液的配制 (15)
3.3.5 接种方法 (15)
3.3.6 测定与观察 (15)
3.3.7 再分离 (16)
第四章结果 (17)
4.1 接种室苜蓿叶片干枯原因研究 (17)
4.1.1 出苗率 (17)
4.1.2 叶与株型 (18)
4.1.3 株高 (25)
4.1.4 生物量 (27)
4.1.5 根系指标 (28)
4.2 苜蓿根部分离菌的致病性测定 (29)
4.2.1 出苗率 (29)
4.2.2 生长状况 (29)
4.2.3 株高 (32)
4.2.4 生物量 (33)
4.2.5 根系特征 (37)
4.2.6 再分离率 (40)
4.2.7 症状 (41)
4.2.8 发病率及发病进程 (50)
苜蓿草种植4.2.9 死亡率及死亡进程 (51)
4.2.10 根腐病情指数 (52)
第五章讨论 (54)
5.1 接种室苜蓿叶片干枯原因研究 (54)
5.2 苜蓿根部分离真菌的致病性测定 (55)
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