Effects of sainfoin Phoma leaf spot on the yield and nutrition

Sainfoin disease with leaf chlorosis and thickened occurred in Yuzhong County,Gansu Province which severely affect sainfoin yield since most leaves defoliated pre-harvest.The pathogen and effects of this disease on yield and nutrient were evaluated in the present study.Pycnidia and conidiospores which identified as Phoma were easily observed on diseased leaves with reddish brown spots under microscope.However,this pathogen cannot be isolated and cultured on artificial media such as potato dextrose agar (PDA).Disease incidence was 94% in the field and 50% leave of the whole plants were infected.Leaf weight of 100 leaves increased by 0.5 g after infected.Crude protein,calcium,phosphorus and crude ash of diseased leaves decreased significantly (P0.05) by 28.54%,10.26%,13.64% and 6.05%,respectively,compared with healthy leaves.Sixteen amino acids including 7 essential amino acids for the livestock decreased significantly.Crude fat increased by 160.95% and neutral detergent fiber (NDF) increased by 97.27%.Compared with healthy plants,most tested indices of diseased plant increased significantly such as weight increased by 4.4 g,ratio of stems to leaves increased by 0.46,NDF increased by 7.27% ,acid detergent fiber (ADF) increased by 5.08% and forage yield increased by 579.87 kg·ha-1.Some tested indices of diseased plant decreased significantly such as crude ash (decreased by 12.19%),total amino acids,essential amino acids and tyrosine,isoleucine and leucine.However,if compared with diseased plants before disease development,crude fat,crude ash,crude protein and Ca decreased by 48.54%,4.30%,0.34% and 3.70%,and forage loss was 823.12 kg·ha-1.Results of amino acids content were similar to that compared with healthy plants.The method of compare diseased plants before and after disease development was more reliable than the method of compare diseased plants and healthy plants because the disease occurred on most field plants which make it difficult to find healthy plants.The explored method of loss evaluation should be applied for other similar diseases