Ecological and Genetical Studies on Multi-herbicide Resistance of of Echinochloa oryzicola Vasing.

对15个多重除草剂抗性菌株的形态特征和AFLP指纹图谱的相似性进行了研究。来源于在加利福尼亚州萨克拉门托山谷的不同稻田收集的材料，并参照敏感(S)品系。在田间试验中测定了植株和小穗的形态特征。R品系植株体型细小，表现为株高、旗叶长宽、茎粗均较小。他们的小穗也更小、更细。R品系间的平均变异系数远小于S品系间的变异系数，表明15个R品系在植株形态和小穗形态上具有较大的相似性。用Ward方法进行的聚类分析表明，R株在早期聚类，在形态上与S株有较大差异。R菌株的AFLP图谱也显示出很大的相似性。在基于UPGMA的系统聚类图中，R株与S 8株的聚类不同，但聚为6个群，Nei和Li‘s系数不同，表明R株之间非常相似，但在遗传成分上略有不同。结果表明，R菌株起源于加州萨克拉门托河谷种群中的一个预先存在的和预先适应的突变体。在连续的世代过程中，由于罕见的近交和杂合性状的分离而导致形态和AFLP指纹性状变异增加的后代，通过鸟类和水道等方式分散，并长期暴露在除草剂的自然选择中，导致R生物型成为水稻种植者的有形生物型。

Similarities in morphological characters and AFLP fingerprints were studied between 15 multiple-herbicide resistant strains of Echinochloa oryzicola Vasing. derived from accessions collected in various rice fields of Sacramento Valley in California, with a reference to susceptible (S) strains. Morphological characters of the plant and spikelet were determined in a field experiment. All R strain plants were small and slender, being reflected by small size in plant height, flag leaf length and width and in culm diameter. Their spikelets were also smaller and slender. The mean coefficients of variation among R strains values were much small than those among S strains, indicating large similarities in plant and spikelet morphology among 15 R strains. Cluster analysis with the Ward's method exhibited that R strains clustered at early clustering stages and morphologically apart from S strains that largely varied. AFLP electropherograms of R strains also showed a large similarity between them. In the cluster dendrogram based on the UPGMA, R strains grouped differently form the group of eight S strains, but were clustered in six groups different in Nei and Li's coefficients, suggesting that R strains very resembles each other but a little differed between them in genetic constituents. It was concluded that R strains originated from a preexisting and preadapted variant E. phyllopogon in population in Sacramento Valley of California. During period of successive generations, descendents of the variant increasing variation in morphological and AFLP fingerprinting traits by rare outbreeding and segregation of heterozygous traits were dispersed by means such as birds and water channels, and exposed to the natural selection by herbicides for extended period, that led for R biotypes to become tangible by rice growers.