| Phytophthora blight of pepper by soil-borne oomycete Phytophthora capsici is a common destructive disease and has resulted in serious economic losses worldwide. Effective methods for controlling the disease are needed and become a hot-spot in management of soil-borne pepper pathogens of the world. Biological control of plant diseases has proven to be safe to animal and human and friendly to environments, and therefore become an important and promising way in control of soil-borne plant pathogens. In this paper, isolation, screening and identification of two bacterial antagonists against Ph. capsici and effects of a bio-organic fertilizer enhanced with the two antagonists on control of Phytophthora blight of pepper are presented. Results were as follows:Ninety-eight isolates with antifungal activities against Ph. capsici were isolated from rhizosphere soil of healthy pepper in seriously pepper fields that infected with the disease. Based on their antifungal activities, growth rate under poor condition, and capacity of colonization of radicles, two strains named as HL-3 and LZ-8 were screened for further study. HL-3 and LZ-8 could inhibit the mycelium growth of Ph. capsici. The inhibition rates of HL-3 and LZ-8 against the pathogen were 72.4% and 68.0% respectively. The inhibition zones of their fermentation broth against Ph. capsici lawn were about 16-17 mm. Both isolates also exhibited antifungal activities toward other plant pathogen such as Verticillium dahliae, Fusarium oxysporum f. sp. cucumerinum, F. oxysporum f. sp. niveum, F. oxysporum f. sp. melonis, F. oxysporum f. sp. vasinfectum, F. oxysporum f. sp. cubense, Rhizoctonia solani, Phptophthora parasitica var. nicotiana and Ralstonia solanacearum. Under greenhouse condition, control efficiencies of HL-3 and LZ-8 against pepper Phytophthora blight reached to 71.9% and 83.1% respectively. Meanwhile, both of them demonstrated significant growth-promoting effect.HL-3 and LZ-8 were identified as Paenibacillus polymyxa and Bacillus pumilus, respectively, by their morphological and biochemical characteristics and 16S rDNA sequences. The optimum growth conditions for HL-3 were: mannose as carbon source, yeast extract as nitrogen source, initial pH value at 6, incubation temperature at 26℃loading volume at 25 ml in 250 ml flask. The optimum growth conditions for LZ-8 were: maltose as carbon source, peptone as nitrogen source, initial pH value at 6, growth temperature at 26℃, loading volume at 50 ml in 250 ml flask.Four levels, i.e.,0.5%,1.0%,1.5% and 2.0% of application rates of bio-fertilizer in nursery experiment were studied. The results showed that pepper was grown best at the level of 1.5% soil. Pot experiment showed that the yields and biomass of pepper plants treated with the bio-organic fertilizer were significantly increased and that the bio-organic fertilizer significantly reduced the incidence of Phytophthora blight of pepper and gained a control efficiency of 75%. The treatment of the bio-organic fertilizer with mixed culture of HL-3 and LZ-8 (Bm) was the best with only 6.22% of disease incidence and 92.94% of control efficiency. The treatment of the bio-organic fertilizer with HL-3 (B3) showed better bio-controlling effect but poorer growth-promoting effect than the treatment of the bio-organic fertilizer with (B8).The biological control effect of the bio-organic fertilizer (BIO) was also studied in field experiment in Funan County, Anhui Province. The results showed that BIO could promote pepper growth, retard outbreak of the disease, reduce disease incidence, and increase pepper yields. The disease incidence of BIO treatment was less than 5% and the control efficiency reach to 80%. In addition, the yields of pepper in Qiandang village and Menglao village of Funan County were increased 26% and 34%, respectively. |
PDF Full Text Request