| Budget Amount *help |
¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 2001: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 2000: ¥2,700,000 (Direct Cost: ¥2,700,000)
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| Research Abstract |
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.
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