| Tobacco black shank disease is an important disease in tobacco production.When it is serious,it will greatly affect the yield and quality of tobacco leaves and bring huge economic losses to the tobacco industry.Chemical control is still an important means to control the harm of tobacco black shank in the heavy occurrence area of tobacco black shank.Chemical control has the advantages of good control effect and quick effect,but frequent and overuse of fungicides is easy to cause sequelae such as fungcide residues,pathogen fungcide resistance,and ecological pollution.Biological control is gradually applied to the field of tobacco black shank control because of its advantages of low toxicity,no fungcide resistance and no pollution in plant disease control.Antagonistic actinomycete H-3 has a good inhibitory effect on Phytophthora nicotianae,which can be applied to the control of tobacco black shank.In this paper,the fermentation conditions of H-3 were optimized;The compound composition of H-3 fermentation broth was detected;To investigate the colonization ability of strain H-3 in tobacco plants and microbial fertilizer;To explore the control effect of H-3 on tobacco black shank in pot and field。The main results are as follows:1.Optimization of H-3 fermentation conditions.In millet medium,When the carbon source was replaced with 25.75 g / L corn starch,the nitrogen source was replaced with2.13 g / L yeast extract and the inorganic salt was replaced with 1.88 g / L ammonium sulfate.It was found that the cell concentration of H-3 in the optimized medium and the inhibition rate of sterile metabolic solution on P.nicotianae were significantly better than that in the initial millet medium.At the same time,when the culture time was 84-96 h,the temperature was 28℃,the p H value was 7.0,and the number of revolutions was 180-200 rmp,the fermentation broth concentration of actinomycetes in H-3 fermentation broth was higher than that in other conditions.2.LC-MS / MS detection of H-3 fermentation broth.The results showed that 856 compounds were measured in positive ion mode and 260 compounds were measured in negative ion mode;Some compounds were identified to have certain antibiotic effects.The identified compounds were classified according to their antibiotic functions.The results showed that most compounds had the function of accelerating cell metabolism.3.Effect of H-3 on enzyme activity of tobacco leaves.The results showed that the activities of SOD and POD in tobacco leaves increased compared with the control group within 12 days after root irrigation with H-3 suspension,and the concentration of MDA decreased compared with the control group.4.Determination of colonization ability of H-3.The colonization ability of H-3 on tobacco was discussed.It was found that H-3 could colonize in tobacco roots and stems within 35 days after root irrigation;H-3 could also colonize in organic fertilizer,organic fertilizer containing 15% or 20% inorganic fertilizer.5.Pot control effect of H-3 on tobacco black shank.When H-3 suspension was used to irrigate tobacco plants,the disease plant rate and disease index of tobacco black shank disease were lower than those in the control group,and the control effect of high-dose suspension was significantly better than that of low-dose suspension.6.Field control effect of H-3 actinomycete fertilizer on tobacco black shank.The results of field control showed that there were significant differences in the control effects of different fertilization treatments on tobacco black shank,and the control effect of microbial fertilizer was better than that of compound fertilizer;In the treatment of microbial fertilizer,the control effect of H-3 actinomycete fertilizer on tobacco black shank was better than that without H-3,and the control effect of H-3 actinomycete fertilizer with high H-3content on tobacco black shank was better than that with low H-3 content. |
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