Babadoost M, Pavon C
Department of Crop Sciences, University of Illinois, Urbana 61801.
Plant Dis. 2013 Nov;97(11):1478-1483. doi: 10.1094/PDIS-12-12-1123-RE.
This study assessed survival of Phytophthora capsici oospores in soil in Illinois. Soils differing in texture and other characteristics were collected from four Illinois Counties (Champaign, Gallatin, Madison, and Tazewell), equilibrated to -0.3 MPa, and infested with oospores of P. capsici at a density of 5 × 10 oospores/g of dry soil. Samples (25 g) of the infested soil were placed in 15-μm mesh polyester bags, which were sealed and placed at 2-, 10-, and 25-cm depths in 15.3-cm-diameter PVC tubes containing the same field soil as the infested bags. Tubes were buried vertically in the ground at the University of Illinois Vegetable Research Farm in Champaign in October 2004. Soil samples were assayed for recovery and germination of oospores 1 day and 3, 6, 12, 24, 30, 36, and 48 months after incorporation of oospores into the soil. Overall, the percentage of oospore recovery and the percentage of germination of oospores were not affected significantly by soil source and burial depth but both the oospore recovery and oospore germination were significantly (P = 0.001) affected by the duration of oospore burial. The rate of oospore recovery from soil samples was 61.06, 16.69, 10.28, 1.05, 0.30, 0.06, 0.05, and 0.004% after 1 day and 3, 6, 12, 24, 30, 36, and 48 months, respectively, following incorporation of oospores into the soil; and mean oospore germination was 47.17, 30.53, 21.33, 15.64, 7.42, 2.67, 2.61, and 0.00%, respectively. Survival of P. capsici oospores was compared in soil samples stored in a laboratory at 22°C versus on the soil surface or buried 2, 10, or 25 cm deep in a field. Oospores were recovered 1, 3, 6, 12, and 24 months after incorporation for both storage locations. The percentage of oospores recovered from samples stored in the laboratory was significantly (P = 0.004) greater than recovery from samples stored in the field, regardless of the depth of burial. Twenty-four months after incorporation of oospores, 26.52% of oospores were recovered from soil samples in the laboratory, whereas only 0.12% of oospores were recovered from soil samples in the field. Overall, the percentages of germination of oospores recovered from samples in the laboratory and field over 24 months were not significantly different. In both experiments, germinated oospores produced mycelia, sporangia, and zoospores, and were virulent on 'California Wonder' bell pepper. This study showed that oospores of P. capsici can survive and remain virulent in Illinois soils for more than 36 months but oospores were no longer viable after 48 months in soil in a field environment.
本研究评估了辣椒疫霉卵孢子在伊利诺伊州土壤中的存活情况。从伊利诺伊州的四个县（尚佩恩、加拉廷、麦迪逊和塔泽韦尔）采集了质地和其他特性不同的土壤，将其平衡至-0.3 MPa，并以每克干土5×10个卵孢子的密度接种辣椒疫霉卵孢子。将受侵染土壤的样本（25克）放入15微米网眼的聚酯袋中，密封后放置在直径15.3厘米的PVC管中2厘米、10厘米和25厘米的深度处，PVC管中装有与受侵染袋子相同的田间土壤。2004年10月，将管子垂直埋在伊利诺伊大学尚佩恩蔬菜研究农场的地下。在将卵孢子掺入土壤后1天、3、6、12、24、30、36和48个月，对土壤样本进行卵孢子回收和萌发检测。总体而言，卵孢子回收百分比和卵孢子萌发百分比不受土壤来源和埋藏深度的显著影响，但卵孢子回收和卵孢子萌发均受卵孢子埋藏时间的显著影响（P = 0.001）。将卵孢子掺入土壤后1天、3、6、12、24、30、36和48个月，从土壤样本中回收卵孢子的比例分别为61.06%、16.69%、10.28%、1.05%、0.30%、0.06%、0.05%和0.004%；卵孢子的平均萌发率分别为47.17%、30.53%、21.33%、15.64%、7.42%、2.67%、2.61%和0.00%。比较了保存在22°C实验室中的土壤样本与田间土壤表面或埋深2厘米、10厘米或25厘米处的土壤样本中辣椒疫霉卵孢子的存活情况。在两个保存地点，掺入卵孢子后1、3、6、12和24个月对卵孢子进行回收。无论埋藏深度如何，从保存在实验室的样本中回收的卵孢子百分比均显著高于从保存在田间的样本中回收的卵孢子百分比（P = 0.004）。掺入卵孢子24个月后，从实验室土壤样本中回收了26.52%的卵孢子，而从田间土壤样本中仅回收了0.12%的卵孢子。总体而言，24个月内从实验室和田间样本中回收的卵孢子的萌发百分比没有显著差异。在两个实验中，萌发的卵孢子产生了菌丝体、孢子囊和游动孢子，并且对‘加利福尼亚奇迹’甜椒具有毒性。本研究表明，辣椒疫霉卵孢子在伊利诺伊州土壤中可存活并保持毒性超过36个月，但在田间环境中，卵孢子在土壤中48个月后不再存活。
