| Gansu Province has the largest alfalfa aear in China. It was 66.33 thousant hectare in 2016. Disease is one of the main limiting factors for high yield as the area increasing, in which leaf and stem diseases commonly occur across whole growing seasons. Planting resistant varieties to these diseases is the most econimic and effective strategy for managing. However, it is extremely insufficient in our country. The object is this thesis is to screen out resistant varieties so that recommend to use in practice, or to use in resistan breeding to diseases. Resistance level of 40 varieties to leaf and stem diseases were evaluated based on incidence and grading standard that popular and international used in alfalfa resistance evaluation to diseases. Based on that results, integrated performances including survial and yield of all tested varieties were compared. The main results are as follows:1. There were 5 leaf and stem diseases occurred in Shuangchuan town, Yongdeng county since tested varieties were seeded in 2014 to the end of 2015, in which alfalfa downy mildew(DM)(Peronospora aestivalis), common spot(CS)(Pseudopeziza medicaginis), and phoma leaf spot and black stem(PS)(Phoma medicaginis) were occurred commonly and caused more damage than stemphylium leaf spot disease(SS)(Stemphylium botryosum) and and powdery mildew(PM)(Leveillula leguminosarum). Only alfalfa phoma leaf spot and black stem disease mainly infected stems, and other diseases mainly infected leaves and blades.2. DM initially occurred soon after regreening in April, and its incidence reached peaks is May and August. CS and SS initially occurred in June, and the former one reached peak in September, and the later one has no peak. PS occurred until August. PM was only occurred in the late growth stage.3. Once the disease happened(incidence more than 0%), incidence of DM was 0.13%-98.66%, CS was 0.47%-100.00%, PS was 3.47%-34.23%, SS was 0.63%-40.00%, and PM was 6.67%-73.33%.4. All the tested varieties were high resistance(HR) to PS and SS. Longdong, Zhongmu No. 3 and Jungar were susceptable(S) to DM, Gannong No. 3 and Xinjiang Daye were resistant(R), and other 35 varieties were HR to the disease. There were no low resistance(LR) and moderal resistance(MR) varieties. Percentage of HR or R varieties were 92.5%. Nevertherless, the 3 S varieties were all breed domestically. For resistance to CS, Zhongmu No. 3 and Jungar were HR, 15 varieties(Algonquin, Debo, Giant No. 6 and No. 7) were R, 10 varieties(Sanditi, MF3010, Salt resistant star) were MR, 9 varieties(WL319HQ, Gannong No. 3, MF4010, Zhongmu No. 2) were LR, 4 varieties(MF4020, MF4030, Surprise,WL354HQ) were S. Among the tested varieties, 30.00% was domestic, in which 41.18% were HR or R level to the disease.5. The mortality during the first winter was 41.73-92.10%, in which Gannong No. 6, Gannong No. 4, Gannong No. 1 and Zhongmu No. 2 were the lower than others. The hay yield was 3.07-5.77 ton/ha in 2015 July, in which SK3010, Giant No. 2, Suntory, MF4010, MF3010 were higher than others. The best varieties were Xinjiangdaye, Rambler, MF3010, WL319 HQ, Zhongmu, No. 2, Gannong No. 1, Gannong No. 4 and Gannong No.6, which not only resistance to leaf and stem diseases, but also had strong survival characteristic and high yield. |
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