Study On The Situation And Damage Of Sainfoin Diseases In Gansu Province

Disease is the one of limiting factor of forage production. The object is this thesis is to investigate how many sainfoin diseases and the occurrence situation and damaging in recent years in Gansu Province, China. The study was carried out in Tongwei County as the hometown of, Weiyuan County, Yuzhong County and Maqu County, Gansu Province. The survey results would determine which diseases should be control in the practice of sainfoin planting. The main results are as follows.1. There are totally13diseases in Tongwei, Weiyuan, Yuzhong and Maqun from2011to2013, in which black spot caused by Macrophoma sp. and leaf spot caused by Polystigma sp. were the new diseases in the world, and mold spot caused byCercospora onobrychis and leaf spot caused by Septoria onobrychis were new records from Gansu Province2. The most common and serious disease is black stem disease in Yuzhong, Tongwei and Weiyuan County. The disease is one of syndrome that mainly caused by Ascochyta onobrychis, followed by Colletotrichum circinans and Alternaria alternate. The resulted had been conformed by pathogen isolation, identification with morphological and molecular methods, and inoculation. The disease in Yuzhong was more severe than in other sites. In one growing season of sainfoin, it appeared in April when one month after regreening, and reached disease peak in August when90%plants were infected. The disease would decreases seed and forage product as it induces stem turned black and shoot dead. The second important disease was Phoma leaf spot. In Tongwei and Weiyuan County, the disease initially exhibited symptoms in branching stage and caused most leaves defoliated. In the fields,50%leave of94%plants were infected. Loss of dry weight was823.12kg/ha after diseased leaves defoliated. However, its leaves turned thicker, the ratio of leaf weight and stem weight increased0.46, and plant weight increased4.4g during the period of diseased leaves were not defoliated. Ramularia leaf spot and Cercospora leaf spot were commonly found in fields, the incidence was up to94%and88%. Their damage less than the two diseases mentioned before. Rust, powdery mildew, Stemphylium leaf spot, Alternaria black spot mostly occurred in the late growth of sainfoin, resulting in less influence on forage production and quality.3. Anthracnose on leaves caused by Colletotrichum dematium was determined according to its molecular morphological and biological. A hyperparasite fungus on powdery mildew was identificated as Ampelommyces sp.4. Some fungi studied in this thesis were registered in NCBI such as Septoria onobrychis, Alternaria alternate, Ascochyta onobrychis, Colletotrichum dematium.5. For studying the effects of the Phoma leaf spot on plant growth and physiology, infected leaves (abbreviated as D-D leaves) and uninfected (healthy)(D-H leaves) leaves were collected from the diseased plants, and the leaves were collected from the healthy plants (abbreviated as H-H leaves). Photosynthetic physiology, conventional nutrition (crude fat, crude ash, crude protein and Ca) and18kinds of amino acid in these leaves were assayed and tested. The photosynthetic physiology results showed, on one hand, that the soluble protein and intracellular concentrations of CO2of D-D leaves were significantly higher than D-H leaves, and MDA, soluble sugar, chlorophyll, net photosynthetic rate, stomatal limitation, transpiration rate, carboxylation efficiency, water use efficiency were lower. On the other hand, the soluble protein, proline and intracellular concentrations of CO2of D-D leaves were significantly lower than H-H leaves, and MDA, chlorophyll, net photosynthetic rate, transpiration rate, stomatal limitation, carboxylation efficiency and water use efficiency were significantly lower. Except for acid detergent fiber, all conventional nutrition decreased significantly. The16of18amino acid decreased significantly except proline and methionine. The whole plant nutrition kept stable except crude protein and crude fat decreased significantly after all leaves’falling, and only glycine, alanine and leucine decreased significanly of all the18amino acids. A conclusion could be drawn that significant influences had been brought on the photosynthetic physiology and water using efficiency after infection, which draw indirect impact on series of enzymes and antipathogenetic compounds, causing a decrease of whole plant nutrition.Therefore, the disease of black stem is the key sainfoin disease followed by Phoma leaf spot. It is necessary to mange the two diseases as the key object in the course of sainfoin planting practice.