Identification Of The Pathgen In Tagetes Erecta L. Seed In Yanqing And Exploration Of The Control Methods

Seedborne pathogen is one of the main source of the pathogen resulted the crop disease in field。With the the expanded planted area of Tagetes erecta, the disease of Tagetes erecta such as leaf spot disease is serious year by year. We studied the seedborne pathogen in the Tagetes erecta seed which was collected by the local farmer. The result shows that the main pathogen in Tagetes erecta seed is Alternaria sp., and they are identificated as Alternaria alternata(A)and Alternaria tagetica(B)through the identification of morphology and molecular biology. Other seedborne pathogen includes Fusarium sp.. The rate of Alternaria sp. in the seed of 2012 and 2013 were 35% and 50%, respectively. What’s more, this data of Fusarium sp. were 1% and 2%, respectively. The result shows that Alternaria sp. was the main pathogen of Tagetes erecta seed, and the main target that should be reduced through seed disinfection. The effect evaluated a seed disinfection method depend on the reduced rate of Alternaria sp. in the seed.This research compared the effect of different seed disinfection methods and different chemical. There were four different treatment conditions in the hot water treatment of seeds. They were different in the water temperature and the time of seed soaking. The result showed that the seed disinfection effect turned to be better with the higher water temperature and longer seed soaking time. However, the germination rate turned to be lower with the rise of water temperature and longer in water. Our research illustrated that the hot water treatment of seeds was not suitable for control the seedborne pathogen in Tagetes erecta seed. Different fungicides were also studied in this research through seed soaking and seed dressing. The result showed that the disinfection effect of seed soaking was absolutely better than seed dressing. The seed soaking in azoxystrobin showed the bast disinfection effect, which was 95.07% and 87.50% in azoxystrobin(1800 diluted) and azoxystrobin mix liquid(900 diluted),respectively. And the effect of total fungi reduced was 50.87% and 86.93%, respectively. Our result illustrated that azoxystrobin was a suitable fungicide to control Alternaria sp. in Tagetes erecta seed. Three different fumigants were used in this research for the seed fumigation, namely methyl bromide, propargyl bromide and carbonyl sulfide. There was few reports about the research on seed fumigation. The result showed that the effect of methyl bromide and propargyl bromide treatment was much better than carbonyl sulfide. What’s more, the effect turned to be better with the rise of concentration of the chemicals except carbonyl sulfide. The all research above showed that seed soaking in azoxystrobin(1800 diluted) after 8h、methyl bromide and propargyl bromide treatment after 48 h were the suitable treatment to reduce Alternaria sp. in Tagetes erecta seed.The special primer AaltDAlta1/ AinfIAlta1 reported by Miguel ángel Pavón in 2010 was used for the real-time PCR detection of Alternaria alternata in Tagetes erecta seed. After established the standard curve and prepared the seed sample with different carrier rate of Alternaria alternata in Tagetes erecta seed, the unknown seed samples were detected through the method of the real-time PCR. The result illustrated, this detection method could exactly detect the carrier rate of Alternaria alternata in Tagetes erecta seed above 10%, and the accuracy of the detection about lower carrier rate was not credible enough.