香蕉枯萎病田间分布型及病原菌在植株上的分布

Spatial distribution pattern for the Fusarium wilt disease in banana field and the Fusarium oxyporum f.sp.cubense in different parts of banana plants

为探讨香蕉枯萎病大田病株及其体内尖孢镰刀菌(Fusarium oxyporum f.sp.cubense)的分布情况,首先对大田病株的发病情况进行调查,通过分布频次检验、聚集指标测定、Taylor幂法则、Iwao m*-m模型等对田间病株的空间分布型进行研究,在此基础上,检验聚集均数λ,分析其聚集原因。同时,在香蕉植株不同部位取样,检测病原菌在植株体内的分布情况。结果表明:香蕉枯萎病大田病株的理论分布符合聚集类型,各项聚集度指标均满足C>1、I>0、m*/m>1、CA>0、K>0。大田病株的空间图式也趋于聚集分布,聚集程度随着种群密度升高而升高,病株间互相吸引,以病株群为单元在蕉地分布均匀,其相对聚集度随种群密度变化的速率为(11.0962+0.1752)m,密度越高,相对聚集度随密度变化速率越大。这种聚集分布是环境作用导致。建立最适理论抽样数模型后,根据一定置信水平下的允许误差值可估测相应发病情况时所配套的最适理论抽样数,且随着病情加重,配套抽样数随之减少。在进行序贯抽样时,假如累计病情等级高于判据上限即可视为防治蕉地,若累计病情等级低于判据下限可视为安全蕉地,如果累计病情等级在判据上限和下限之间,需增加抽样量,但可以理论抽样模型中的最大抽样量终止抽样。最适宜的抽样方法为棋盘式取样法和单、双对角线取样法。此外,枯萎病菌在香蕉植株体内的分布因样地发病程度和植株部位不同而有显著差异,植株球茎的平均含菌量显著高于其它部位。

The objectives of this work were to clarify the spatial distribution pattern for the Fusarium wilt disease in the banana field and the amounts of Fusarium oxyporum f. sp. cubense population inside the banana plants. An investigation was conducted on the diseased plants in banana field. The spatial distribution pattern of the Fusarium wilt disease in banana field was studied by determination of frequency distribution, aggregated indices, the Taylor＇s power law and Iwao＇s regression equation. The reasons for the aggregation of the Fusarium wilt disease in banana field was analyzed according to estimation by aggregation mean λ. Meanwhile, comparative investigation was conducted on the amounts of the pathogen inside the healthy plants and diseased plants. Results indicated that the diseased plants in banana field belong to negativebinomial distribution and neyman distribution, and the aggregated indices of diseased plants met C〉 1, I〉0, m^＊/m〉 1, CA 〉0, K〉0, so they presented pattern of aggregation distribution, and the fundamental component was the individual that was mutually attractive, and the individual colonies characterized with uniform distribution. The degree of aggregation increased with the population density of diseased plants. The rate of relative aggregation change of fundamental component was （11.0962＋0.1752） m, which changed with the population density of Fusarium wilt disease in banana field. The greater the population density of diseased plants, the greater the change rate of relative aggregation degree. Aggregation mean A value indicated that the aggregation might be due to the combined actions of the environmental factors. The optimal sampling formula was built up. The sample number （n） negatively decreased with the pathogen indeces increasing, and it could be estimated with the parameters of t = 1.96, deviation D = 0.1-0.4. The sequency sampling procedure was based on the equation. It was necessary to take actions to control Fusarium wilt disease when the plant numbers were higher than the upper limit numbers according the index list for sequential sampling of infected plants in banana field. Chessboard type and diagonal type sampling were the best method for sampling technique. The application of spatial pattern to data transfer was discussed. In addition, the amounts of the pathogen in the bulbs were more than those in roots and leaves. The pathogens in different parts of banana plants were significantly different due to the disease severity of the fields and sampling parts of banana plants.