Bell Ashley A, Hubbard Judith C, Liu Li, Davis R Michael, Subbarao Krishna V
Department of Plant Pathology, University of California, Davis, c/o U.S. Agricultural Research Station, Salinas, CA 93905.
Department of Plant Pathology, University of California, Davis 95616.
Plant Dis. 1998 Mar;82(3):322-328. doi: 10.1094/PDIS.1998.82.3.322.
The effects of chitin and chitosan on disease incidence and severity of Fusarium yellows of celery and on populations of Fusarium oxysporum were investigated between 1994 and 1996. Field experiments were conducted at two locations with a history of severe Fusarium yellows. Disease incidence and severity were significantly reduced by pre-plant chitin amendments to soil. Chitosan applied as a root dip alone did not reduce disease incidence but significantly (P < 0.05) reduced disease severity when used with a tolerant celery cultivar. Standard soil dilution methods were used to enumerate populations of soil microflora. Chitin increased bacterial and actinomycete populations in soil in 2 of the 3 years of study. The effects of potential biocontrol agents recovered from chitin-treated plots in 1995 were studied in 1996; enriching the transplant medium with isolates of bacteria and actinomycetes 4 weeks and 1 week prior to transplanting did not alter the established equilibrium in the field, and no biocontrol effect was observed. Chitin amendments to soil or chitosan treatment of transplants did not reduce soil populations of F. oxysporum. Whether these treatments affected the F. oxysporum f. sp. apii subpopulation within the F. oxysporum population could not be determined.
1994年至1996年期间，研究了几丁质和壳聚糖对芹菜枯萎病发病率和严重程度以及尖孢镰刀菌种群数量的影响。在两个有严重枯萎病病史的地点进行了田间试验。种植前向土壤中添加几丁质可显著降低发病率和严重程度。单独用作浸根处理的壳聚糖不会降低发病率，但与一个耐病芹菜品种一起使用时，可显著（P < 0.05）降低病情严重程度。采用标准土壤稀释法对土壤微生物群落数量进行计数。在3年研究中的2年里，几丁质增加了土壤中的细菌和放线菌数量。1996年研究了1995年从用几丁质处理过的地块中分离出的潜在生物防治剂的效果；在移栽前4周和1周用细菌和放线菌分离物富集移栽培养基，并没有改变田间已建立的平衡，也未观察到生物防治效果。向土壤中添加几丁质或对移栽苗进行壳聚糖处理并没有减少尖孢镰刀菌的土壤数量。无法确定这些处理是否影响了尖孢镰刀菌种群内的尖孢镰刀菌芹菜专化型亚种群。
