Isolation,Identification And Biological Control Of A Pathogen Of Heart Rot Of Pineapple In Hainan

The pineapple heart rot disease is the main reason for the declining of yields. Biocontrol has been proving safety and environmengtally friendly to such plant disease,It is urgent to screening and developing new microbial fungicides for the Pineapple heart rot diseases.In this study,the pathogen (Phytophthora nicotianae) ofpineapple heart rot disease was isolated from the infected pineapple plants in LeDong county Hainan province and then a high efficient antagonist was screened and fermented with organic fertdistrictilizer to prepare a bio-organic fertilizer.A series of experiments were conducted to investigate the disease suppressive effects of the bioorganic fertilizer on the pineapple plants/The results were as follows:The pathogen was isolated from the infected go lden pineapple plants, which is planted in Wan Zhong farm in Ledong County,Hainan province. The fungal using Koch’s Rule to identify its pathogenicity. According to the morphological and18s rDNA sequence phylogenetic analysis,the pathogen was identified as Phytophthora nicotianae. The study showed the optimum condition for pathogen mycelial growth:the temperature were25℃,the pH were greater than6,the calcium ion concentration were1-4g/L.Among them,the growth medium were V8juice agar medium and oatmeal agar medium.From the31soil samples of health golden pineapple soil and banana soil etc,224strains of bacteria were isolated by plant dilute.Taking golden pineapple heart rot pathogens as material, and screening obtain two strong antagonistic function bacteria using flat confrontation law. The strain number is HL2and HL3.The antagonistic bacteria HL2was identified as bacillus subtilis,and HL3strain was identified as Streptomyces. The antibacterial test results show that golden pineapple heart rot pathogens mycelium inbition rate respectively71.6%and53.3%,and the inhibition rate of its spore germination were respectively83.3%and61.7%,volatiled antimicrobial substances secreted from antagonistic bacteria during training can significantly inhibit the growth of mycelia.Antibacterial substance,extracted from fermentation broth of antagonistic bacterium HL2,the result shows that the antibacterial substances main is surfactin and iturin by analyzed with LC-MS.Application of bioorganic fertilizers containing the antagonists in high incidence of soils was carried out to investigate effects of two types of bio-organic fertilizers(BIO2,BIO3) made from these two antagonists on the control efficiency of the heart rot pineapple and plant growth.The result showed that the BIO2can significantly promote the growth of pineapple and reduce the pineapple heart rot incidence, the relative control incidence was73.5%.The culturable microorganisms of pineapple rhizosphere soil from BIO2treatment in pot experiments,the test result that BIO2treatment bacteria and actinomycetes was significantly higher than control treatment,but the quantity of fungi was lower control treatment The result of PCR-DGGE analysis that BIO2increased the number and types of bacteria, and the evenness index,richness index,simpson index and uniformity of fungi were relatively high, but reduces the number and types of fungi in soil.