为了研制高效、无毒、成本低廉的生物农药,安全有效地防治烟草黑胫病,利用自主分离的寡雄腐霉生防菌株(Pythium oligandrum CQ2010)制备发酵液(Pythium oligandrum broth,POB),通过拮抗、盆栽和田间试验研究了POB对烤烟生长和黑胫病的防治效果,以及对小鼠的急性毒性.拮抗试验表明,POB能显著抑制离体烟草黑胫病菌的菌丝生长和孢子萌发.在盆栽试验中,POB能显著提高烟草叶片叶绿素含量(质量分数),增强烟株根系活力,增加烤烟对氮、磷、钾的吸收,促进烟苗生长,生物量比对照提高58.91%,效果优于寡雄腐霉卵孢子制剂.POB还能激活烟草叶片中与抗病性相关酶如过氧化物酶和过氧化氢酶的活性,诱导烟株产生抗病性反应,有利于消除活性氧和过氧化氢,使病害减轻.烤烟幼苗接种黑胫病菌后,施用POB使烟株发病率下降42.95%~65.77%,相对防治效果达到46.99%~57.32%,并显著降低烟草叶片中丙二醛含量,减轻病原菌对细胞膜的伤害.在田间试验中,POB对烟草黑胫病的防治效果达47.91%,烟叶产量提高44.47%,产值增加36.33%.小鼠急性毒性试验表明,用POB大剂量灌胃给药对小鼠体质量无显著影响,供试小鼠外观和行为均无异常,心、肝、肾、肺等器官未见病理改变.因此,POB能有效防治烟草黑胫病,促进烟株生长,提高烟叶产量和产值,且对动物安全无毒.%In order to develop efficient, nontoxic and cost-effective bio-control agents against tobacco black shank, antagonism, pot and field experiments were carried out to study the effects of fermentation broth produced from a self-isolated Pythium oligandrum (strain CQ2010) on the growth and control of black shank for flue-cured tobacco, and its acute toxicity to mice. The results of antagonism experiment indicated that Pythium oligandrum broth (POB) significantly inhibited mycelial growth and spore germination of in vitro Phytophora nicotiana Breda de Haan. Comparing to the blank control (without POB), the biomass of tobacco seedlings grown in pots increased by 58.91% after POB application. Similarly, chlorophyll contents in the leaves, root vigor and nitrogen, phosphorus and potassium uptake were increased by POB, and the effect of POB treatment was better than that of P. oligandrum spores. POB also promoted the activities of enzymes, such as peroxidase and catalase in tobacco leaves, furthermore induced tobacco plants'biochemical reactions for disease resistance. The effects were beneficial to eliminating reactive oxygen and H2O2 and alleviating the damage caused by diseases. The incidence of tobacco plants decreased by 42.95%-65.77% via POB treatment before or after pathogen inoculation, and the relative control efficacy reached 46.99%-57.32%. The content of malondialdehyde in tobacco leaves was also significantly reduced by POB application, and the damage of pathogen to cell membrane was relieved. In field experiments, botrytis control-efficacy of POB reached 47.91% and tobacco leaf yield was increased by 44.47% and output value by 36.33%. The mice tested showed that there was no significant weight difference between mice fed with pure water (the control) and gastric lavage with high doses of POB, no abnormality in appearance and behavior was observed in tested mice, and their heart, liver, kidney, lung and other organs had no pathologic changes. In summary, the preliminary results demonstrated the potential of POB as an animal safe bio-control agent. In the tests shown, POB controls botrytis efficiently, promotes the growth of flue-cured tobacco and increases the yield and output value of tobacco leaves.
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