Workneh F, Allen T W, Nash G H, Narasimhan B, Srinivasan R, Rush C M
Texas Agricultural Experiment Station, Bushland 79012, USA.
Phytopathology. 2008 Jan;98(1):95-100. doi: 10.1094/PHYTO-98-1-0095.
Karnal bunt of wheat, caused by the fungus Tilletia indica, is an internationally regulated disease. Since its first detection in central Texas in 1997, regions in which the disease was detected have been under strict federal quarantine regulations resulting in significant economic losses. A study was conducted to determine the effect of weather factors on incidence of the disease since its first detection in Texas. Weather variables (temperature and rainfall amount and frequency) were collected and used as predictors in discriminant analysis for classifying bunt-positive and -negative fields using incidence data for 1997 and 2000 to 2003 in San Saba County. Rainfall amount and frequency were obtained from radar (Doppler radar) measurements. The three weather variables correctly classified 100% of the cases into bunt-positive or -negative fields during the specific period overlapping the stage of wheat susceptibility (boot to soft dough) in the region. A linear discriminant-function model then was developed for use in classification of new weather variables into the bunt occurrence groups (+ or -). The model was evaluated using weather data for 2004 to 2006 for San Saba area (central Texas), and data for 2001 and 2002 for Olney area (north-central Texas). The model correctly predicted bunt occurrence in all cases except for the year 2004. The model was also evaluated for site-specific prediction of the disease using radar rainfall data and in most cases provided similar results as the regional level evaluation. The humid thermal index (HTI) model (widely used for assessing risk of Karnal bunt) agreed with our model in all cases in the regional level evaluation, including the year 2004 for the San Saba area, except for the Olney area where it incorrectly predicted weather conditions in 2001 as unfavorable. The current model has a potential to be used in a spray advisory program in regulated wheat fields.
由印度腥黑粉菌引起的小麦卡纳尔腥黑穗病是一种国际管制病害。自1997年在得克萨斯州中部首次发现该病以来，发现该病的地区一直处于严格的联邦检疫规定之下，导致了重大经济损失。开展了一项研究，以确定自该病在得克萨斯州首次发现以来天气因素对其发病率的影响。收集了天气变量（温度、降雨量和降雨频率），并将其用作判别分析中的预测因子，利用1997年以及2000年至2003年圣萨巴县的发病率数据对腥黑穗病阳性和阴性田块进行分类。降雨量和降雨频率是通过雷达（多普勒雷达）测量获得的。在该地区小麦易感阶段（孕穗期至软面团期）重叠的特定时期，这三个天气变量将100%的病例正确分类为腥黑穗病阳性或阴性田块。随后建立了一个线性判别函数模型，用于将新的天气变量分类到腥黑穗病发生组（阳性或阴性）。使用得克萨斯州中部圣萨巴地区2004年至2006年的天气数据以及得克萨斯州中北部奥尔尼地区2001年和2002年的数据对该模型进行了评估。该模型除了2004年外，在所有情况下都正确预测了腥黑穗病的发生。还利用雷达降雨数据对该模型进行了该病特定地点预测的评估，在大多数情况下，其结果与区域水平评估相似。在区域水平评估中，包括圣萨巴地区2004年的情况，湿度热指数（HTI）模型（广泛用于评估卡纳尔腥黑穗病风险）在所有情况下都与我们的模型一致，除了奥尔尼地区，在该地区它错误地将2001年的天气状况预测为不利。当前模型有潜力用于受管制小麦田的喷雾咨询计划。
