Screening Of Antagonistic Trichoderma Strains Against Pathogens Of Fusarium Dry Rot And Black Scurf In Potato In Gansu And Its Analysis Of Genetic Diversity

1. Rhizosphere soil samples of potato plants were collected in4different treatments with various continuous cropping years and8different potato varieties by using five-sited sampling method in Tiaoshan Farm, Jingtai County in Gansu province. Trichoderma strains were isolated using serial dilution plat method. The results showed that a total of227isolates of Trichoderma were collected from96soil samples. With the extension of year of continuous cropping of potato, the total amount of Trichoderma strains tended to decline; The distributions of Trichoderma spp. strains collected from different soil samples of potato varieties were different, the largest amount of Trichoderma spp. strains were isolated from soil sample of potato variety Dingshu No.1.2.4Trichoderma strains were obtained by using competitive growing method on PDA media with the dominant pathogen isolates Fusarium solam、F. sambucinum which cause Potato Dry Rot disease and Rhizoctoniasolaniisolates RSI、RS2causing Potato Black Scurf disease, according to inhibition ratios,4isolates which showed higher inhibition ratio (>70) to the target pathogen isolates were screened from227Trichoderma strains.3. The pathogenicity of the4dominant Trichoderma strains were tested, the results showed that the isolate1-X-2was nonpathogenic to the potato tubers. Based on the morphological identification and analysis of ITS sequencing, strain1-X-2was identified as T. rossicum. The bio-control research of T. rossicum is the first report in China.4. Based on inhibition ratio of Trichoderma strains to4target pathogen isolates,10Trichoderma strains with the highest and the lowest ratio to each of the target pathogenic isolates were selected respectively,40Trichoderma strains were got in total. AFLP techniques were used in this research to analyze genetic diversity of these Trichoderma strains. DNA was extracted via SDS method, the genomic DNA was doubled digested with enzymes EcoR I and Mse I,2primer pairs E-T/M-G、E-A/M-C were screened for selective amplification in this AFLP techniques based on their lighter, stable, and high polymorphic bands, rate of polymorphic bands were highest under E-T/M-G (91.84%).5. For each plant pathogenic isolate, clustering analysis under primer pairs E-T/M-G was used for10strains with the highest ratios and10strains with the lowest ratio. The results showed that AFLP band types of these Trichoderma strains were very different, the strains population showed very high genetic diversity; Trichoderma strains with good antagonistic ability were clustered into one group, Trichoderma strains with poor antagonistic ability were also clustered into one group. The result preliminarily reported that there was correlation between cluster groups of Trichoderma strains and their inhibition.