The Relationship Between Soil Factors And Bacterial Wilt Root Of Ginger In Qianwei Sichuan

Ginger (Zingiber ofieinale Rosco) is one of the world’s most important spices; it also can be used as vegetable and herbal medicine. Qianwei County is one of the main producing areas of ginger in Sichuan province, but because of long planting age, and high cropping index, a serious bacterial wilt disease often occurred in the ginger planting area, which affected the development of ginger cultivation. Though many studies focus on the soil environment factor, included soil temperature, physical and chemical properties and microbial community, affected the bacterial wilt have been performed, these researches were not systematic, and the relationship between the soil microbiology diversity and disease hasn’t been disclosed.In this paper, the treatments of the greenhouse and conventional (control) cultivation were performed in field experiment in Qianwei County in 2012 and 2013; the correlation between the bacterial wilt incidence and soil environmental factors was analyzed. Microbial community of the surrounding and rhizospheric soil samples of healthy and diseased ginger were investigated by 454 pyrosequencing method. Furthermore, strain SCAU611 isolated from the disease ginger rhizosphere soil was classfied.1. The analysis of data collected in 2012, and 2013 showed that soil water content was positive correlated to the ginger wilt incidence significantly, and the correlation curve was y=1.3223x+28.717 (R2= 0.523, P<0.05) (2012); y= 2.0726x+27.269; (R2= 0.685, P<0.01) (2013), respectively; The soil temperature was positively correlated to the ginger wilt incidence, and the correlation curve was y=0.6275x+ 24.756, (R2=0.789, P<0.01), (2012), y=0.0652x+27.661, (R2=0.06), (2013). Also, the soil available phosphorus content was positive correlated to the ginger wilt incidence, while soil available nitrogen content was negative correlated to the ginger wilt incidence significantly. Multiple linear regression and PCA analysis showed that the interpretation degree of both soil temperature and water content to the incidence ratio was 53 to 65% in the regression model, both were the main factors; the interpretation degree of soil available phosphorus and available nitrogen to the incidence ratio was 34% to 46%, they were the secondary factors. The results of preliminary study confirmed that the threshold of soil water content which the ginger wilt occurred was 25%.2. The result of 454 pyrosequencing analysis showed that microbial community structure is different between healthy ginger soil samples and disease at the classification of phylum, class, order, family, and genus level. The characteristic of microbial community changed in phylum and genus as follows:At the phylum level, the proportion of Proteobacteria, Actinobacteria and Chloroflexi were decreased by 2.1-7.2%,0.6-3.5%, and 1.1-2.4% in disease ginger soil samples than healthy, respectively. While the proportion of Acidobacteria increased by 2.1%-8.4%.At the genus level, the abundance of Ralstonia in the disease and healthy ginger rhizospheric soil is 0.44% and 0.47%, respectively. But the abundance of the bio-control and beneficial bacterial, such as Pseudomonas, Sphingomonas, Burkholderia, Bacillus, Rhizobium, and Arthrobacter, have an decreased signally in the disease ginger rhizospheric soil. These bacteria can control pathogen by follow aspects:first, established a stable microbial community structure; two, inhibited pathogen by produce antibiotic; three, inhibited pathogen by competed nutrient and colonization sites and induced resistance. All above result show that the abundance of bio-control and beneficial bacterial decreased in the rhizospheric soil is a inducement of bacterial wilt.CCA analysis showed that pH, Available phosphorus, and water content have significant effect on soil bacterial communities, pH is the most important factor variable. Decreased of pH and increased of the content of Available phosphorus and water in rhizospheric soil can change the structure of bacterial communities, and caused disease.3. Identification of a new strain SCAU611 isolated from the bacterial wilt ginger rhizosphere soil was done. The result showed that the strain is gram-stain negative, aerobic, rod-shaped,0.7-0.9 μm in diameter and 1.5-3.0 μm in length, and motile by means of multitrichous polar flagella. Colonies on LB agar are circular, translucent, primrose yellow, with a smooth and wet surface. Green fluorescent pigment produced on King’s medium B. The optimum growth temperature is 30℃, with growth observed at-1-37℃. Able to grow in LB medium at pH 4.5-9.5 and containing 0-6% NaCl. The oxidase, catalase and arginine dihydrolase test is positive, while the nitrate reduction test is negative. Positive for hydrolysis of Tween-80, gelatin and esculin. Acid was produced when using D-glucose, D-maltose, and inositol. The DNA G+C content is 65.2%. The major fatty acids are C10:0(3-OH), C12:0 (2-OH), C12:0(3-OH); C16:0, C17:0 cyc, Summed feature 3 (C16:1 w7c/C16:1 w6c), and Summed feature 8 (C18:1 w7c). Based mainly on the Bergey’s Manual of Systematic Bacteriology, Volume Ⅱ (1984), the possesses characters common of strain SCAU611 to Pseudomona, But some others are different from Pseudomonas chlororaphis DSM 21509T and Pseudomonas psychrophila JCM 10889T, which are reference strains. The binding degree of DNA between strain SCAU611 and P.chlororaphis DSM 21509T and P.psychrophila JCM 10889T is 42.85% and 43.92%, respectively. In addition SCAU611 can growth in 37℃, hydrolysis of Tween-80 and esculin, it can utilize D-sorbierite, acid was produced when using inositol, but the reference strain didn’t. So, strain SCAU611 is identified as a new species of Pseudomonas and named Pseudomonas leshanense sp. Nov. strain SCAU611 is considered as a type strain.