| Wuzhi mountain is located at 18°45′20″～18°58′54″N, 109°39′38″～109°47′50″E, and in the central part of Hainan island. Its main peaks are located at the Wuzhi mountain city and the highest altitude is 1867 m. It is the largest nature reserve in Hainan and the area belonging to national nature reserve are 134.4 km2. Wuzhi mountain is also one of the highest existing virgin tropical rain forests in the world. Wuzhi moutain contains extremely plentiful microorganism resources but so far not be exploited. In order to find new genus or species of actinomycetes and obtain the isolates that have good biocontrol potentialities against the main tropical plant pathogens and novel high-efficient antibiotic-producing isolates, for the first time, we have carried out soil sample collection from different altitudes and vegetation habitats of Wuzhi mountain virgin forest, preliminary isolation and identification of actinomycetes, and preliminary evaluating their biocontrol potentiality of parts isolates against three important tropical plant pathogens, such as Fusarium oxysporum f.sp. cubense race 4(Focr4), Phytophthora capsici and Alternaria cucumerina, The preliminary results were as follows:1. A total of 1261 actinomycetes isolates were isolated from 110 soil samples collected from Wuzhi mountain by mainly use glucose asparagine agar and soil extract agar and soil dilution plate methods. Among these actinomycetes, there are 750 isolates belonging to streptomycetes and 511 isolates belonging to rare actinomycetes.2. 750 streptomycete strains were divided into 12 groups according to its aerial mycelium exist or not on culture plate. Off them, there are 77 strains of Flavicant group, 7 strains of Albosporus group, 64 strains of Aureus group, 306 strains of Griseofuscus group, 8 strains of Globisporus group, 5 strains of Glaucus group, 11 strains of Hygroscopicus group, 29 strains of Roseosporus group, 5 strains of Viridis group, 225 strains of Cinerogriseus group, 10 strains of Griseorubroviolaceus group, 3 strains of Cyancus group. The Cinerogriseus and the Griseofuscus were dominant groups.3. The results of statistical analysis on the quantity of isolates from different altitude soil samples indicate that the quantity of soil actinomycetes decreased along with the altitude of sampling site increased.4. The antifungal activity assay of 223 isolates of 1261 isolates were carried out by pairing culture on PDA plate against Focr 4, P. capsici and A. cucumerina. The results showed that most of isolates had more or less inhibitive activity against above pathogens. But only small isolates have strong inhibitive effects. Off them WZ45, WZ60, WZ196 and WZ179 have stronger inhibitive effects against Focr4, their inhibitive distance are 11,12,12,10mm,respectively; WZ45 and WZ60 have stronger inhibitive effects against P. capsici, their inhibitive distance all are 10mm; WZ160 have very strong inhibitive effects against P. capsici and its inhibitive distance is 17mm; WZ160,WZ32 and WZ260 have very strong inhibitive effects against A. cucumerina, and their inhibitive distance are 18,15,16,1respectively.5. Strain WZ60 , which has stronger antifungal activity against Phytophthora capsici, together with two strains LA5 and BM10 early isolated with strong antifungal activity were carried out biocontrol test against pepper Phytophthora blight in the field. The results showed that WZ60 strain fermentation has 90% control effect, and significant higher the control effects of LA5 and BM10 strain fermentation.6. Strain WZ60 was also chosen to carry out biocontrol test against banana fusarium wilt caused by Focr4 in the field. The result shows that strain WZ60 preparation have 81.5% better control effect after banana seedlings were plant 185 days and the most of control were died after plant 90 days.7. 18 actinomycetes isolates were assigned to the genus Streptomyces on the basis of morphological observation and 16S rDNA sequences analysis. |
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