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Substantial difference of selenium tolerance was found between the tall fescue (Festuca arundinacea Schreb.) and white clover (Trifolium rapens L.) An inverse relationship between Se accumulation and Se tolerance suggests an exclusion mechanism that restricts Se uptake by the plant with greater Se tolerance. A positive relationship between the increase of protein Se concentration and growth inhibition in the plants suggests that assimilation of Se into protein is responsible for the reducing Se toxicity at the protein level. No evidence of a Se exclusion mechanism which exclude Se from incorporating into protein plays any major role of Se tolerance in this two species.

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Crape myrtle (Lagerstroemia indica L. ‘Near East’) explants of 2 nodes were cultured on woody plant medium (WPM) supplemented with PBA, BA, or kinetin. PBA was most effective in promoting axillary shoot proliferation. Maximum number of axillary budbreaks occurred on modified WPM containing 3-9 μm PBA. Subcultured shoots ≥2 cm in length rooted in medium without auxin, and ex vitro rooting and acclimization was also obtained. Chemical names used: 1H-indole-3-butanoic acid (IBA); N-(phenylmethyl)-9-(tetrahydro-2H-pyran-2-yl)-9H-purin-6-amine (PBA), N- (phenylmethyl)-1H-purin-6-amine (BA); N-(2-furanylmethyl)-1H-purin-6-amine (kinetin).

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Chokecherry (Prunus virginiana L.) germplasm collected from North Dakota, South Dakota, and Minnesota and established in Bismarck, N.Dak. was screened for infection by the X-disease phytoplasma and for putative X-disease-resistant plants. A total of 1792 chokecherry trees were first screened by observation of characteristic disease symptoms and were given a visual disease rating. In 1996, 97% of the trees were severely diseased, or rated 3 or lower on a 5-point scale. The remaining 3% (55 trees) showed vigorous growth and had few or no X-disease symptoms, and were rated 4 or 5. Of these trees, 44 (80%) were found to contain the X-disease phytoplasma as indicated by reactions with a monoclonal antibody that is specific for this phytoplasma. The other 11 trees (20%) were then found to contain the X-disease phytoplasma using the highly sensitive, but more expensive and time-consuming, nested-polymerase chain reaction (PCR). Employment of a combination of visual screening, monoclonal antibody assay, and nested-PCR provided an effective and efficient means for examining a large number of plant materials for infection by the phytoplasma. The chokecherry trees that were infected but had few or no X-disease symptoms were considered to be resistant/tolerant to X-disease.

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We used amplified fragment length polymorphism (AFLP) markers to analyze 14 fruiting mei cultivars from China and Japan. The levels of polymorphism and genetic relationship among cultivars were studied using two types of AFLP primer combinations [EcoR I + Mse I (E+M) and EcoR I + Taq I (E+T)] and the combined data from both types of primer combinations (E+M+T). The polymorphism among the cultivars was 57.92% based on E+M primers and 63.04% based on E+T primers. All three dendrograms generated by the three sets of data showed similar relationships among the fruiting mei cultivars. The corresponding main clusters contained the same cultivars and the subgroups correlated closely with the known geographic origins of the cultivars.

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