苜蓿褐斑病对牧草质量光合速率的影响及田间抗病性

研究了田间自然发病条件下褐斑病 (Pseudopeziza medicaginis)对紫花苜蓿 (Medicagosativa)叶片营养成分含量和光合速率的影响 ,并评价了 85个紫花苜蓿 ,5个杂花苜蓿 (M.varia)和 4个黄花苜蓿 (M.falcata)品种或群体对褐斑病的抗性。结果表明 ,褐斑病使苜蓿病叶中粗蛋白质含量显著下降 ,与健叶相比 ,其含量可减少 2 5% ,减少的幅度与病害严重度极显著负相关 ,r=0 .96 5(P<0 .0 1)。叶片光合速率随病害严重度的增加而降低 ,当病斑平均面积为叶面积的 13%时 ,光合速率仅为健叶的 52 % ,而当病斑平均面积为叶面积的 85%时 ,其光合速率仅为健叶的 15.9%。在参试的 94个品种或群体中 ,仅润布勒杂花苜蓿的一个群体表现为免疫。抗病性较强的有来自加拿大的巴瑞尔、阿毕卡 ,来自美国的威斯康星和我国的兴平、武功、肇东等 10个紫花苜蓿品种和润布勒杂花苜蓿的另一个群体。其余 83个品种均表现出较高的感病性 ,包括美国的 78- 15,加拿大的大西洋 ,我国的和田、咸阳等紫花苜蓿品种和内蒙黄花等黄花苜蓿品种

Lucerne common leaf spot: forage quality, photosynthesis rate and field resistance

Effects of lucerne ( Medicago sativa ) common leaf spot caused by Pseudopeziza medicaginis on contents of the major nutrient components and leaf photosynthesis rate were studied. Disease resistance of 85 lucerne varieties (populations), 5 Medicago varia varieties (populations) and 4 M. falcata varieties (populations) was evaluated under alpine grassland conditions. Compared to the healthy leaves the crude protein content in the diseased leaves were reduced by 25%. A significant negative correlation between the crude protein content and the disease severity was found ( r =0.965, P <0.01). Leaf photosynthesis rate decreased as the disease severity increased. The photosynthesis rate was reduced by 48% when 13% of the leaf area was infected by the pathogen, whereas 84.1% of reduction was found when 85% of the leaf area was infected. Among 94 varieties (populations) evaluated for disease resistance only one of Rambler populations was immune. Ten lucerne varieties (populations) and another Rambler population were found highly resistant to common leaf spot, which included Baron and Apex from Canada, Wiscosin from the USA, and Xingping, Wugong, Zhaodong from China. The remaining 83 varieties (populations) were susceptible to the disease, which included 78 15 from the USA, Atlantic from Canada, Hetian and Xianyang from China, and M. falcata from Inner Mongolia, China.