| Summary: | 碩士 === 國立中興大學 === 植物病理學系所 === 104 === Fusarium oxysporum f. sp. conglutinans, the causal agent of mustard Fusarium wilt. The pathogen causes losses in the yield and quality of many economically cruciferous crops during warm growing seasons in the world. Current strategies for controlling mustard Fusarium wilt include resistant cultivars, crop rotation, soil fungicides or soil fumigants and use of biological agents. Due to safety and environmental concerns, developing a friendly control measure is needed. In past decade, several microorganisms including Trichoderma harzianum, Pseudomonas fluoresens and Bacillus subtilis have been reported to be effective in reducing crop disease severity caused by Fusarium wilt. In general, soil amendment could change soil physical and chemical properties and increase microbial activity, and control crop diseases. The purpose of this study is to use microbial agents and soil amendments for controlling Fusarium wilt of mustard. In this study, F. oxysporum f. sp. conglutinans isolates Focn-05 and Focn-38 grew well at 28℃ and caused 49-85% disease severity in infested soil (2×104 cfu/g soil). In total, 68 isolates of antagonistic bacteria were isolated from mustard seeds and soils where mustard plants were planted. Ten bacterial isolates (BG06, BG09, BG16, GL9-1, TKM01, TKM02, TKM03, YBJ13, YBJ15 and YBJ19) significantly inhibited mycelial growth of both Fusarium isolates tested. Two bacterial isolates, designated TKM03 and YBJ13 promoted plant growth while coated on mustard seeds, and isolate GL9-1displayed strong inhibitory effects on spore germination of the pathogen. According to the result of the sequences of partial 16S rDNA and 16S-23S internal transcribed spacer, TKM03 and YBJ13 were identified as Bacillus amyloliquefaciens and GL9-1was identified as Brevibacillus brevis. Mustard seeds were individually treated with TKM03, YBJ13 or GL9-1cell suspensions (108 cfu/ml) and sown in Fusarium infested soil. Results indicated that YBJ13 and GL9-1 could significantly reduce disease severity of mustard seedlings. Six soil amendments were evaluated for the efficacy on promoting mustard plant growth and controlling the disease, the result showed shrimp and crab shell powder was more effective in promoting the shoot length and plant weight of mustard plants. Moreover, shrimp and crab shell powder, fish meal or blood meal were effective in reducing the disease severity of mustard Fusarium wilt caused by F. oxysporum f. sp. conglutinans isolates Focn-05 and Focn-38. Furthermore, combination of shrimp and crab shell powder and Brevibacillus brevis GL9-1 could obviously reduce the survival of the pathogen in the soil. The combination was amended into the infested soil, and able to reduce 26.7-30.0 % of disease severity. In addition, the combination of shrimp and crab shell powder and B. brevis GL9-1 fermented liquid cultured in soybean meal broth was added into the infested soil. The results indicated that GL9-1 fermented liquid could markedly improve the efficacy of shrimp and crab shell powder for controlling mustard Fusarium wilt.
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