Study Of “Walnut Black” Pathogens And Selection Of Its Antagonism

Walnut(Juglans regia L.),is an important nut tree which is rich in nutritions,and plays an important role as a “woody oil plant” involved with edible,pharmaceutical and timber use.It is widely distributed around the world,yield 4,000,000 tons nut per year.Walnut industry in China has developed recent years,and both plantational area and fruit output are the number one in the world.However,“Walunt black”,one disaster damage,occurred anunelly in industrial farm and led a big lost in yield and frutit quality in Shaanxi Province,Sichuan Province and Shandong Province,China.Nerverthless,the causing of walnut black is still under discovery.The anthorcnose,the dark spot disease,Atrijuglans hetaohei Yang,Conogethes punctiferalis(Guenée)and so on,occurred on the fresh fruit are believed related to this disaster damage.In this paper,pathogens of anthorcnose,dark spot and kernal rot were isolated and identified through culture charerctersizes,physiological tests and phylogenic methods.Two kinds of chitosan,one bacteria isolate and one fungus were applied in the study for indoor antagnosim tests and field checking,and the results reported as follow:1.In this study,one pathogenic strain was isolated from infected plants,anthracnose fruits in Qianxian county,named HTTJ.One pathogenic strain was isolated from dark spot plant in Shanyang county,named HB and one pathogenic strain was isolated from kernel rot in Shanyang County,named XF.All isolates strains showed the corresponding pathogenicity.The strain HTTJ was identified as Colletotrichum gloeosporioides,strain HB was identified as Pantoea agglomerans and strain XF was identified as pituitosum Ochrobactrum.2.The fungal strain S21 and bacterial strain B1(Bacillus subtilis),which had significant antagonistic effects on the pathogens of anthracnose walnut,were screened by plate confrontation test,and the inhibition rate of mycelial growth of strain HTTJ reached 72.39% and 49.96% respectively.When the strain S21 was incubated with strain HB and strain XF,the inhibition zone width was 7.97 mm and 7.67 mm,respectively.The strain S21 was identified by molecular biology as Epicoccum nigrum.3.The minimum concentrations of CH and CL have inhibited the strain HB and strain XF was determined and their inhibitory effects on strain HTTJ were also determined.The minimum inhibitory concentrations of CH on strains HB and strain XF were 3.5 g/L and 0.3 g/L,respectively,and the minimum inhibitory concentrations of CL to strain HB and strain XF were 0.5 g/L and 0.2 g/L,respectively.When the concentration of CH was 0.8 g/L,the inhibition rate of strain HTTJ reached 60% and remained stable;when the concentration of CL was 1.0 g/L,the inhibition rate was 40% and its effects was not significant;the inhibition effect of strain CH on strain HTTJ was significant and stable than strain CL in same concentration.4.The results of both laboratory and field experiments showed that the mixed preparations B1GA(a mixture of B1,CH,GA,deltamethrin and sterile water)and XLCH(a mixture of CH,deltamethrin,streptpmycin sulphate and sterile water)had certain inhibitory effects on strain HTTJ,and the effect of B1 GA was more significant,reached 80%.