Screening of Biocontrol Bacillus Isolate against Potato Fusarium Wilt and Its Biocontrol Effect

Fusarium wilt of potato is one of the main soil-borne fungal diseases, which has become one of the important factors limiting the healthy development of potato production in China. A biocontrol bacterium strain ZF128 isolated from the rhizosphere soil of potatoes had significant inhibitory effect against F. oxysporum of potato. The strain ZF128 was identified as Bacillus velezensis based on biochemical and physiological characterizations, BIOLOG GENIII, and DNA phylogenetic tree analysis. The results of antimicrobial activity assay showed that strain ZF128 exhibited significant inhibitory activities against five plant pathogenic fungi and five plant pathogenic bacteria. Microscopic observation showed that strain ZF128 could cause mycelium malformation and form elliptic expansion. Fermentation tests showed that ZF128 had the significant inhibitory effect against F. oxysporum in mannitol medium. The control effect of strain ZF128 against potato Fusarium wilt was examined by pot test in greenhouse. The results indicated that the disease incidence of potato Fusarium wilt treated with strain ZF128 was significantly reduced and the control efficacy was 82.46%. Meanwhile, strain ZF128 could effectively colonize in potato rhizosphere and on root for more than 30 days. Pot tests demonstrated that the height, root length, fresh weight of aboveground and underground, and chlorophyll content of potatoes treated with ZF128 fermentation broth were significantly higher than those of the control groups. In summary, the Bacillus strain ZF128 has excellent 762 中 国 生 物 防 治 学 报 第 36 卷 biocontrol characteristics and high potential application value.