Study Of Bacillus Subtilis BS-2 On Relieving The Replant Disease In Apple

In order to found the method of preventing the replant disease of apple,we studied the characteristics of Bacillus subtilis new strain BS-2 and it effected the soil microbial diversity,microbial community structure,soil enzyme activity and nitrogen uptake and utilization in 0g,15 g,30g,60 g and 120 g.Our test provided biological control theory and practice basis for the production of apple.The main results are as follows:?1?The new strain BS-2 was induced by UV lamp could resist grey speck disease,fusarium,gray mold,brown blotch,ring spot and alternaria leaf spot of apple.Fusarium is the main pathogen causing replant disease.The alternaria leaf spot is caused by the Alternaria.From the in vivo antagonism experiment,we found that the BS-2 could significantly decrease the grow of the Alternaria.?2?The secretion of Bacillus subtilis BS-2 contained auxin?IAA?and salicylic acid?SA?,the concentration was 0.4ng/ml and 1.39ng/ml,when the OD was 600.The 30 g concentration of Bacillus subtilis BS-2 could obviously promote the leaf specific weight and the diameter of the main stem.It could increase 8.5% thickness of palisade tissue.Bacillus subtilis BS-2 had no effect on the high growth of apple plant.?3?Bacillus subtilis BS-2 had a certain role in enhancing the resistance enzyme activity and soil enzyme activity.BS-2 could improve the POD enzyme activity of 70u/g · FW,SOD 56u/g · FW enzyme activity in apple leaves and increase catalase activity in soil.BS-2 could also increase the soil enzymes related to nitrogen metabolism and phosphorus metabolism.Such as urease,nitrate reductase,nitrite reductase and acid phosphatase.BS-2 reduced denitrification enzyme,related to nitrogen volatilization.?4?Bacillus subtilis BS-2 increased the diversity of bacteria and fungi in soil,and changed the structure of soil microbial community.BS-2 decreased the abundance of Proteobacteria in the bacteria,and increased the richness of Bacteroidetes and Acidobacteria,with the increased of BS-2 amount,the richness of Proteobacteria was declined at first,then it was rised.Proteobacteria richness was the highest in the 120 gtreatment,reached 55.91%.0g treatment was followed,15 g treatment was the lowest.Bacteroidetes was the second dominant bacteria.The abundance of Bacteroidetes was higher than control group,after applying BS-2.The richness of Acidobacteria was the smallest in the control group,and the 30 g treatment was the maximum,30 g treatment was 5.45 percentage points more than the control group.BS-2 increased the abundance of Blastocatella and Pseudomonas,and it reduced the richness of Sphingomonas in genus.The total abundance of three bacteria were 19.02%,21.67%,24.75%,23.65% and 43.26% in0 g,15g,30 g,60g and120 g treatment.BS-2 had a great influence on the community structure of fungi.The dominant species in the control group were Ascomycota,Basidiomycota and Chytridiomycota three kinds,but BS-2 changed the dominant species in the fungal community.It reduced the richness of Basidiomycota and Chytridiomycota.In addition to the three kinds of fungi,soil sample added three dominant species after the application of BS-2.This change was more significant in genus.Stephanospora that it was the dominant species in control group weakened and disappeared in the treatment group,and the treatment group even could produce new dominant species.When the concentration of BS-2 increased to 120 g,there were no dominant species in soil samples,the abundance of fungus below 10%.?5?Bacillus subtilis BS-2 promoted the absorption and utilization of nitrogen on Apple.After ¹⁵N urea was applied,we found that BS-2 was able to increase the dry weight of apple root and Xylem.Dry weight accumulation increase230 g.BS-2 improved the Leaves,xylem and phloem of the Ndff value.BS-2 increased the total nitrogen from 3.44 mg to7.29 mg,and increase the absorption amount of ¹⁵N 0.64 m.Bacillus subtilis BS-2 was able to improve the nitrogen use efficiency.The effect of 60 g treatment was the best,it was 30.76%.The effect of 120 g treatment was reduced,it was just 15.93%.The distributed of nitrogen in leaves was the highest,reached 40.37%.The second was xylem,the lowest was 25.27%.BS-2 significantly improved the distribution of nitrogen in the phloem and root.