紫花苜蓿霜霉病病株空间分布型研究

Study on spatial distribution patterns of the infected plants for alfalfa Peronospora aestivalis

为了明确内蒙古地区紫花苜蓿霜霉病的危害情况及发生规律,试验利用棋盘式取样法对随机选取的5个田块紫花苜蓿霜霉病发病情况进行调查,通过方差分析、分布频次检验、聚集度指标测定、Iwao m^(*)-m回归分析法和Taylor指数法等模型检验,探讨紫花苜蓿霜霉病田间病株的空间分布型和抽样技术。结果表明:田块4的病株率最高,为46.27%;在每个样方所调查的50株植株中,田块4的苜蓿感病株数集中在31~35株,剩余田块感病株数大多集中在11~15株;各项聚集度指标均表现出紫花苜蓿霜霉病呈聚集分布的趋势,均满足扩散系数(C)>1、water’s的负二项分布参数(K)>0、久野指数(C_(4))>0、x的比值(m^(*)/x)>1、丛生指数(I)>0;Iwao回归分析法m^(*)-m回归方程和Taylor指数法结果也显示该病呈聚集分布趋势,且随着聚集度程度的加深,逐渐由聚集分布向均匀分布过渡;分析确定了在不同病株率下的理论抽样数为n=(1.96/D)^(2)(2.698/x-0.167),式中D为允许误差值,x为平均密度。说明紫花苜蓿霜霉病的发生呈聚集分布,明确紫花苜蓿霜霉病的分布规律有助于病害的科学防控。

To clarify the harm situation and occurrence regularity of alfalfa downy mildew in Inner Mongolia,five plots were randomly selected using the checkerboard sampling method,and the incidence of alfalfa downy mildew was investigated.The spatial distribution patterns and sampling techniques of alfalfa plants with downy mildew were analyzed by using,frequency distribution test,aggregation index determination,Iwao m^(*)-m and Taylor index method.The results showed that the incidence rate of downy mildew in plot 4 was the highest(46.27%).Among the 50 plants investigated in each quadrat,the number of infected alfalfa in plot 4 was focused on 31-35 plants,and the number of infected alfalfa in the remaining plots was 11-15 plants.All the aggregation indicators showed that alfalfa downy mildew had a tendency of aggregated distribution,which met Coefficient of dispersion(C)>1,water's negative binomial distribution parameter(K)>0,Kuno index(C_(A))>0,the ratio of x(m^(*)/x)>1,clumping index(I)>0.Iwao m^(*)-m and Taylor index method also showed a trend of aggregated distribution,and with the deepening of aggregation degree,the trend gradually transforms from aggregated distribution to even distribution.On this basis,the theoretical sampling numbers under different diseased plant rates were analyzed and determined:n=(1.96/D)^(2)(2.698/x-0.167),in the formula,D represented the allowable error,x represented mean density.It indicated that the occurrence of alfalfa downy mildew was clustered,and it was helpful for scientific prevention and control of the disease to clarify the distribution law of alfalfa downy mildew.