Screening And Identification Of The Biocontrol Strains About Cucumber Fusarium Wilt And Effects Of Its Bio-organic Fertilizer

Gansu province is the main planting area of cucumber in northern China.In recent years,with greenhouse vegetable cultivation rapidly developingand cucumber planting scale expanding,soil borne diseases of cucumber have been growing,especially fusarium wilt of cucumber caused by Fusarium oxysporum f.sp.cucumerinum.It is destructed.It is a kind of fungal soil borne diseases.The disease not only bring huge economic losses to growers,but also seriously affected the healthy development of the industry.It is imminent and great significance for the main producing areas of cucumber that taking the safe and effective method to prevent fusarium wilt of cucumber.In this study,using the pathogenic bacteria ofcucumber Fusarium wilt disease as target,screening biocontrol strains by plate confrontation method;using organic fertilizer?OF?as the carrier that together with screened biocontrol to make bio-organic fertilizer?BOF?,through pot experiment to examine the effects of preventing disease and promoting growth about bio-organic fertilizer of screened biocontrol strains.The results as follows:1.By plate confrontation test,after repeated screening,the strains of QHZ-2 and QHZ-3 were achieved that have strong inhibition effect on Fusarium oxysporum f.sp.cucumerinum.?pretest named QHZ-Yb1 and QHZ-Yb2?.The study found that the inhibition zone width of 3.37 mm and 3.42 mm,the diameter of inhibition zone was greater than2.7cm,the inhibitory rate respectively.61.9% and 62.3%.Two strains were initially identified as Bacillus atrophaeus,through the morphological and physiological and biochemical determination and the 16 S r DNA gene sequence analysis.2.Determinating the biological function of the strains QHZ-2 and QHZ-3showed that two strains had strong biological function containing a variety of antagonistic and stimulating factors.The experimental results showed that the lipopeptide extracting the strains QHZ-2 and QHZ-3?dosage: 100 L?can inhibite Fusarium oxysporum f.sp.cucumerinum and the inhibitory rate reached 57.4% and58% respectively.The secretion of growth hormone IAA were 1.56mg/L and3.69mg/L,amount of solubilizing P were 0.77mg/L and 1.19mg/L,respectively.Meanwhile,the two strains could also produce siderophore and casease.3.The determination results about growth characteristics of strains QHZ-2 and QHZ-3 showed that in the LB culture medium,28? culture,the strains QHZ-2 andQHZ-3logarithmic growth period were 2-8 h and 6-20 h.Two strains can use various carbon and nitrogen sources.They have good ability to adapt environmental temperature and p H and salt concentration.The strain of QHZ-2 like sucrose and?NH₄?₂SO₄,the best survival temperature is 30 degrees Celsius,live in the p H 5-9environment.The strain of QHZ-3 like maltose and?NH₄?₂SO₄ or NH₄NO₃,the best survival temperature of 30-37 ?,live in p H5-8 environment.Two strains can survivein salinity concentrationof 0-100 g/L and good growthin less than 50g/L.4.Seed germination test showed that QHZ-2 and QHZ-3 could promote the germination of cucumber seeds.5.Pot experiments were taked to determine the effects of bio-organic fertilizer that were made by the strains QHZ-2 and QHZ-3 together with organic fertilizer?BOF1 made by the strain of QHZ-2,BOF2 made by the strain of QHZ-3,BOF3 made by the strains QHZ-2 and QHZ-3 according to 1:1?.The results showed that BOF can reduce the incidence of cucumber wilt,in different degrees,and reduce the number of plant rhizosphere culturable fungi and Fusarium oxysporum,increase the number of bacteria,actinomycetes.BOF1 and BOF3 can significantly increase the biomass of cucumber plant.Compared with CK,the incidence rate of OF and BOF1 and BOF2 and BOF3 decreased by 22.2% and 44.4% and 50% and 58.3%.In the all treatments,control effect of OFwas 27.59%,BOF exceeded 50.00%.,BOF3 reached72.41%.Compared with CK,the plant dry weight OF and BOF1 and BOF2 and BOF3 increased 0.94 and 1.22 and 0.92 and 1.24 times,the number of Fusarium oxysporum Were reduced by 1.30 and 3.22 and 2.60 and 5.13 times.The above description: 3 kinds of biological organic fertilizer not only have good biocontrol abilityand have the ability of promoting growthexcepting BOF2.The effect of BOF3 was most significant indicating that the strains QHZ-2 and QHZ-3 have additive effect.In summary,the Bacillus atrophaeus strains QHZ-2 and QHZ-3 have the potential to against the cucumber fusarium wilt.BOF1 and BOF3 can promote plant growth.