| Rice bakanae disease is a worldwide rice disease,which mainly caused by Fusarium fujikuroi and occurs in various rice regions of China.As a result,the yield of rice was severely reduced,and the quality of rice was greatly reduced,and brought huge losses to agricultural production.At present,chemical prevention and control methods are mainly used to control rice bakanae disease in China.However,the large-scale application of chemical pesticides will certainly damage the ecological environment,and it may cause the resistance of pathogenic bacteria.In contrast,another control method-biological control is safe and reliable.It not only guarantees the healthy growth of crops,but also has less pollution to the environment.Therefore,it is of great significance to use biological control to prevent rice bakanae disease.In the development of biological control,Actinobacteria have been studied because of their many types,large bases,and their functions of preventing diseases,insecticides,weeding,and promoting growth.In this study,samples were collected from rice fields infected with rice bakanae disease.Taken the disease resistance test of rhizosphere actinobacteria isolated from healthy and infected rice.Separation and extraction of its secondary metabolites and test for rice bakanae resistance.At the same time,determining the active of rice bakanae disease prevention,the colonization and growth promotion of different crops.Find the useful ability of agriculture,such as disease resistance and growth promotion in active strains.Aim to treatment of rice bakanae disease in agriculture and provide bacteria resources for commercial microbial agents.The main results of this study are as follows:(1)Fusarium fujikuroi was isolated from the stem of diseased rice,and 135 strains of actinobacteria were isolated from the rhizosphere soil of healthy and susceptible rice plants.Among them,47 actinobacteria from healthy rice plants,63 actinobacteria from susceptible rice plants,and25 coexisting actinobacteria,the susceptible plants have certain advantages in the types of actinobacteria.(2)The activity of strain C42 against rice bakanae disease is preferably 61.27±0.02%.The strain C42 was subjected to multiphase classification and identification.The results showed that the strain was a Streptomyces strain.The 16S r RNA gene sequence of Streptomyces scabiei NRRL B-16523~T(99.59%),Streptomyces europaeiscabiei KACC 20186~T(99.52%)has the highest similarity and is always on one evolutionary branch.The strain conforms to the characteristics of the genus Streptomyces and is named Streptomyces oryzagri according to its isolation source.(3)Fusarium fujikuroi was used for rice infection testing.The results showed that the spore suspension of pathogenic bacteria 10~7CFU/m L had the strongest infectivity to rice and the incidence rate was 84.22±0.71%,the incidence time was 15-20 days and the disease index was 45.91±0.45.Strain C42(10~9CFU/m L)had the best resistance to rice bakanae disease.The incidence rate decreased from 83.75±0.81%to 22.73±0.87%and the disease index decreased from 45.57±0.75 to18.77±0.47.(4)Strain C42 can produce indole acetic acid,and also has the ability of dissolving phosphorus and producing chitinase,and has the growth promoting effect on rice,maize,wheat and lettuce.It can also improve the CAT enzyme activity,SOD enzyme activity,soluble protein content,chlorophyll content and carotenoid content of crops.This strain can stably colonize the rhizosphere of rice,maize and lettuce for a long time.The colonization amount on the 20th day after inoculation is 6.3×10~4CFU/g dry soil weight,7.9×10~4CFU/g dry soil weight and 5.7×10~4CFU/g dry soil weight,in addition,it can be colonized in the roots,and the colonization capacity at the 20th day after inoculation were 2.3×10~4CFU/g fresh root weight,1.3×10~4CFU/g fresh root weight and3.4×10~4CFU/g fresh root weight.The intra-root colonization ability is lower than that of the rhizospher(5)After tracking the activity against rice bakanae disease,two compounds were identified,namely dibutyl phthalate and phencomycin,and their activities of rice bakanae disease were verified again. |
