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首页> 外文期刊>Plant Pathology >Relationship between disease severity and escape of Pseudoperonospora cubensis sporangia from a cucumber canopy during downy mildew epidemics
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Relationship between disease severity and escape of Pseudoperonospora cubensis sporangia from a cucumber canopy during downy mildew epidemics

机译：霜霉病流行期间黄瓜盖层假单胞菌孢子囊孢子囊的疾病严重程度与逃逸的关系

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Fundamental to the development of models to predict the spread of cucurbit downy mildew is the ability to determine the escape of Pseudoperonospora cubensis sporangia from infected fields. Aerial concentrations of sporangia, C (sporangia m~(-3) ), were monitored using Rotorod samplers deployed at 0·5 to 30 m above a naturally infected cucumber canopy in two sites in central and eastern North Carolina in 2011, where disease severity ranged from 1 to 40%. Standing crop of sporangia was assessed each morning at 0700 h EDT and ranged from 320 to 16 170 sporangia m~(-2). Disease severity and height above the canopy significantly (P < 00001) affected C with mean concentration (C_m) being high at moderate disease. Values of C_m decreased rapidly with canopy height and at a height of 2-0 m, C_m was only 7% of values measured at 0·5 m when disease was moderate. Daily total flux (F_D) was dependent on disease severity and ranged from 5·9 to 2242·3 sporangia m~(-2). The fraction of available sporangia that escaped the canopy increased from 0028 to 0171 as average wind speed above the canopy for periods of high C increased from 1·7 to 3·6 m s~(-1). Variations of C_m and F_D with increasing disease were well described (P < 00001) by a log-normal model with 15% as the threshold above which C_m and F_D decreased as disease severity increased. These results indicate that disease severity should be used to adjust sporangia escape in spore transport simulation models that are used to predict the risk of spread of cucurbit downy mildew.
机译：预测葫芦丝霜霉病扩散的模型开发的基础，是确定假单孢菌孢子孢子囊孢子从感染田中逃逸的能力。使用2011年在北卡罗来纳州中部和东部两个地点的自然感染黄瓜冠层上方0·5至30 m部署的Rotorod采样器，监测孢子囊的空气浓度C（sporangia m〜（-3））范围从1％到40％。每天早晨美国东部时间0700 h评估孢子囊的常熟作物，其范围为320至16170孢子囊m〜（-2）。疾病的严重程度和冠层上方的高度显着（P <00001）影响了C，中度疾病的平均浓度（C_m）高。 C_m值随冠层高度的增加而迅速降低，在2-0 m的高度处，C_m仅为中等程度疾病时在0·5 m处测得的值的7％。每日总通量（F_D）取决于疾病的严重程度，范围为5·9至2242·3孢子囊m〜（-2）。随着高C时段冠层上方的平均风速从1·7增至3·6 m s〜（-1），逸出冠层的可用孢子囊比例从0028增加到0171。对数正态模型很好地描述了C_m和F_D随疾病增加的变化（P <00001），以15％为阈值，超过此阈值，C_m和F_D随着疾病严重程度的增加而降低。这些结果表明，应在孢子运输模拟模型中使用疾病的严重程度来调整孢子囊逃逸，该模型可用于预测葫芦丝霜霉菌扩散的风险。

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