几丁质裂解微生物防治棉苗立枯病

研究了几丁质裂解微生物对立枯丝核菌引起的棉花立枯病的防治作用。用几丁质改良的Hutchinson培养基对几丁质裂解微生物进行分离,在42株几丁质裂解微生物中,有2株放线菌在培养基和土壤中都对立枯丝核菌有较强的抑制作用。选择上述两个菌株和几丁质配成10％生物拌种素,并用5％几丁质粉及20％几丁质酸溶物(20％拌种素),进行对棉花出苗的影响和对立枯丝核菌(立枯病)防效的田间试验。结果表明,10％生物拌种素对棉花出苗有明显促进作用,提高出苗率8.9％,出苗期提前5d以上。20％拌种素和5％几丁质对棉花出苗无明显不利影响;10％生物拌种素、5％几丁质和20％拌种素对棉花立枯病均有较好的防效,分别达68.2％、64.8％和51.9％。

Application of chitin-degrading microorganisms to biocontrol of Rhizoctonia solani

The biocontrol activity of chitin-degrading microbial strains against cotton damping-off caused by Rhizoctonia solani was studied. Chitin-degrading microbial strains were isolated and counted in an improved Hutchinson's agar medium. The results showed that the population of chitin-degrading microorganism obviously increased in the soil added with 5% chitin. Among 42 chitin-degrading microorganisms isolated, two actinomycetes strains were found to be able to strongly inhibit the mycelial growth of R. solani both in plates and in soils. These two strains were selected and mixed with chitin to obtain the 10% biological seed dressing liquor. The effects of seed treatments with 10% bio-mixed-seed, 5% chitin and 20% acid soluble chitin on seed germination and cotton damping-off caused by R. solani were investigated in field experiments. The results showed that 10% biological seed dressing liquor had growth-promoting activity on cotton seedling. Compared with the control, the rate of seed germination increased by 8.9% and the seedlings appeared 5 days in advance. No side effect was found on the seedings treated with 20% acid soluble chitin and 5% chitin. All of these treatments were effective in suppressing cotton seedling damping-off. The biocontrol efficacy of 10% biological seed dressing liquor, 20% chitin acid hydrolyzed and 5% chitin was 68.2% , 64.8% and 51.9% , respectively.