Effect Of Bio-Organic Fertilizer On Microbial Flora In Rhizosphere Soils Of Continuous Cropping Tomato And Pepper

The bacterial wilt, one of worldwide soilborne plant diseases, is caused by Ralstonia solanacearum. The disease has heavily attacted many Solanaceae crops and intimidated the production of vegetables in China. Continuously cropping Solanaceae crops is the main factor that induces the disease. The disorder caused by continuous cropping is related to the interactions among rhizosphere soil, roots and microbes of crops. This paper was aimed to study effects of application of the bio-organic fertilizer (BOF), common organic fertilizer (OF) and chemical fertilizers (CK) on plant growth, control of bacterial wilt and microbial flora in the rhizosphere soils of continuous cropping tomato and pepper grown in greenhouse and in field. The main results was listed as follows.BOF had significant biocontrol effect on the bacterial wilt of tomato and pepper. The greenhouse pot experiment showed that the control efficiencies for the disease in tomato and pepper with application of BOF reached to56.2%and56.1%, respectively. The field experiment showed that the incidence rates of the disease in tomato and pepper with application of BOF decreased by41.5%and44.7%, respectively, as compared with the conventional chemical treatment (CK).BOF significantly promoted the growth of tomato and pepper. The greenhouse pot experiment showed that the BOF treatment increased the dry weights of above-ground and underground parts of tomato by138.7%and148.5%, respectively, while increased those of pepper by157.2%and109.4%, respectively, as compared with CK. When compared with the OF treatment in the pot expriment, the BOF treatment increased the dry weights of above-ground and underground parts of tomato by61.1%and31.2%, respectively, while increased those of pepper by66.8%and79.6%, respectively. In field, BOF increased the yields of tomato and pepper by26.0%and19.9%, respectively, as compared with CK.BOF significantly improved microbial flora in rhizosphere soils of tomato and pepper. For non-diseased plants, plate counts showed that the BOF treatment increased the numbers of bacteria and actinomycetes by62.7%and32.8%, respectively, in rhizosphere soils of tomato and by142.4%and39.6%, respectively, in rhizosphere soils of pepper, and decreased the numbers of fungi by43.9%and53.1%in rhizosphere soils of tomato and pepper, respectively, as compared with CK. For diseased plants, no significant difference between the BOF treatment and CK existed in the numbers of bacteria and actinomycetes in rhizosphere soils of both tomato and pepper, but the BOF treatment significantly decreased the numbers of fungi in rhizosphere soils of both tomato and pepper as compared with CK. PCR-DGGE analysis showed that application of BOF enhanced the diversity, richness and stability indices of microbial community in the rhizosphere soils of tomato and pepper. Analysis from454squencing techniques showed that the healthy plants of tomato and pepper maintained more diversy bacterial flora than the diseased plants in case of application of BOF. The bacterial phyla Acidobacteria, Actinobacteria, Chloroflexi, Firmicutes and Proteobacteria contained rich species as compared with other phyla.BOF significantly improved that the factional microbial groups in rhizosphere soils of tomato and pepper in field. For non-diseased plants, the BOF treatment increased the numbers of Azotobacter and Pseudomonas flurosecens by23.5%and29.5%, respectively, in rhizosphere soils of tomato and by25.8%and20.2%, respectively, in rhizosphere soils of pepper, and decreased the numbers of R. solanacearum by73.2%in rhizosphere soils of tomato and by90.1%in rhizosphere soils of pepper.In conclusion, the bio-organic fertilizer plays a regulatory role on microbial community structure in the rhizosphere soil of continuously cropping tomato and pepper. The improvement of microbial flora in rhizosphere soils may account for the high efficiency of control of bacterial wilt and promotion of crop growth with application of the bio-organic fertilizer.