Study On The Biological Control Of Potato Black Scurf And Its Prevention Mechanism

Potato black scurf is a kind of soil-borne diseases caused by Rhizoctonia solani.I t has severely affected the yield and quality of potatoes,and has greatly restricted the development of potato industry in China.In order to reduce the occurrence of potato black scurf and provide a basis method for its biological control,Rhizoctonia solani i solates,witch was isolated from the high incidence of potato black scurf in Gansu Pr ovince has been served as targrt pathogens in this study.Then Chaetomium globosum strain ND35,Trichoderma asperellum strain MX,Penicillium purpurogenum strain Q2 and their combinations have been selected for the prevention and control of potato bla ck scurf.In the same time,mechanism of disease prevention has been investigated.Th e research contents mainly include the isolation and identification of pathogen;antagon ism and growth factors of biocontrol agent;compatibility testing of biocontrol strains;antagonism of biocontrol strains aganst pathogen;experiments of control disease in the greenhouse and in the field;effect of biocontrol strains and their combinations on de fense enzyme activities,malondialdehyde,chlorophyll content,root activity of potato plants in potting.The results show as follows:1?According to morphological characteristics and pathogenicity of the isolated and purified pathogen,result of identification of strain HZ1 showed that it was Rhizoctoni a solani..2?The antagonism of Chaetomium globosum strain ND35,Trichoderma asperellu m strain MX,Penicillium purpurogenum strain Q2 aganst pathogenic Rhizoctonia solan i HZ1 showed that each biocontrol strain had a significant inhibitory effect on myceli a gfrowth of fungal pathogen Among them,the inhibition percentage of plate antagoni sm were 66.46%,84.25% and 57.83%,respectively;the fermentation filtrate of biocont rol strains against fungal pathogen were 41.62%,9.76% and 76.07%,respectively;Res ults of antagonism between the biocontrol strains showed there were no inhibitory zon e.3?The results of antagonism of biocontrol strains and growth factors showed that strain ND35 can produce cellulase,glucanase and auxin;strain MX can produce cellul ase,auxin,and has the ability to dissolve phosphorus;strain Q2 can produce cellulase,protease,glucanase and auxin,and has the ability to dissolve phosphorus.At the sam e time,the mycelium at the junction of the three fungal biocontrol agent and the HZ1 strain was examined under microscope.It was found that each of the biocontrol strai ns had mycoparasitic effects such as entanglement,invasion,and parasitism.Another o ne,the metabolites of the biocontrol strains could cause mycelium of pathogen to brea k and deform,dissolved.4?Inspection of plant physiological indicators found that the strain Q2 and the bi ocontrol combination A in each treatment had significant growth-promoting effects on the plant height,stem diameter,fresh weight,and dry weight of the potato plant.The strain MX had a obvious growth-promoting effects on the stem diameter.The combin ation of biocontrol agent C has significant growth-promoting effects on the stem diam eter and dry weight of potato plants.Other biocontrol strains and their combinations d id not affect the growth of potato plants.It was found control test that each biocontro l strain and its combination significantly reduced the incidence and disease index of p otato black scurf disease in the potting.Among them,the most significant reduction i n the incidence of potato black scurf disease was the strain ND35 and biocontrol com bination A,which reduced by 12.7% and 14.28%,respectively.The best control effect s were the strain Q2?biocontrol combination A and combination C.The control effica cy were 42.79%,43.9%,and 41.74%,respectively.5?Tests of control disease found that treatments with various biocontrol strains a nd their combinations significantly reduced the incidence and disease index of potato mole nevus in the field.Among them,Penicillium purpurogenum Q2 and combination C were the most significant in reducing the incidence of black scurf,which reduced by 28.33% and 23.33%,respectively.The best control efficacy were the strain Q2,bio control combination A and combination C.The control efficacy were 41.16%,37.52%,and 37.57%,respectively.6?The detection results of plant defense enzyme activity,root activity and chloro phyll content showed that the detection values of different biocontrol agents and their combinations were significantly higher than the control(CK)treatment group without any biocontrol strains On the 30 th day,the peroxidase(POD)activity of the strain Q2 was the highest,reaching 5814.67 U/g,which was more than three times that of the control(CK)treatment group;The activity of superoxide dismutase(SOD)of the stra in ND35 was the highest,reaching 746.85 U/g,which was more than three times that of the control treatment group;The catalase(CAT)activity of the biocontrol combina tion A was the highest,reaching 186.66 U/g,which was more than 6 times that of th e control treatment group.The root viability of the strain ND35 was the highest,reac hing 69.23 mg/(g·h),which was 91.67% higher than that of the control group;The ch lorophyll content of the biocontrol combination A was the highest,reaching 2.69 mg/g,which was an increase of 29.84% compared with the control treatment group.The test results of plant MDA content showed that the accumulation of MDA in different biocontrol agents and their combinations did not increase significantly during the test period,while the MDA content of the control(CK)treatment group increased with ti me.It prolonged and accumulated more and more.At the 30 th day,the content reach ed 48.47 nmol / g fresh weight.To sum up,the biological control of strain ND35,strain MX,strain Q2 and their combinations A,B,and C all have different degrees of control effect on potato blac k scurf,and improve plant system resistance.The study of biocontrol strains ND35,MX,Q2 and their combinations on the control efficacy of black scurf and its mechani sm of action has laid the foundation for the research and development of excellent bi ocontrol agents and antagonistic antimicrobial agents for potato black scurf.