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In a clonally propagated crop, such as potato (Solanum tuberosum L.), an estimate of genetic variance as a proportion of the total phenotypic variance (broad-sense heritability) is desirable. Because of its importance to the processing industry, tuber specific gravity has been widely studied. Earlier estimates of narrow-sense heritability for specific gravity in a diploid hybrid population of Solanum phureja × Solanum stenotomum (PHU-STN) were moderate. The purpose of this study was to identify stable, high specific gravity clones for future population improvement efforts and to estimate broad-sense heritability based on cloual means in this PHU-STN population. From 1990 to 1992, 72 diploid hybrid PHU-STN clones were grown in replicated field plots in Presque Isle, ME, and evaluated for specific gravity. There were significant differences among clones. There was also a significant replication (year) effect and clone × year interaction. From the analysis of variance on specific gravity, broad-sense heritability based on clonal means was estimated as 0.66, with a 95% confidence interval of 0.50 to 0.78. Stability-variance statistics calculated for each clone were used to identify stable high specific gravity clones. There was no correlation between average specific gravity during 3 yr and the stability-variance statistic, indicating that selecting for high specific gravity should not result in clones that are less stable for specific

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The functional role of the Nicotiana plumbaginifolia cytochrome P450 gene CYP72A2 was investigated in transgenic plants. N. tabacum plants transformed with a sense or antisense CYP72A2 construct exhibited diminished heights, branched stems, smaller leaves and deformed flowers. Western blot analysis revealed reduced levels of a 58 kDa protein corresponding to CYP72A2, suggesting that the CYP72A2 homolog was suppressed in the sense and antisense plants. Transgenic plants had increased resistance to Manduca sexta larvae that consumed about 35 to 90 less of transgenic versus control leaves. A virulent strain of Pseudomonas syringae pv. tabaci induced a disease-limiting response followed by a delayed and decreased development of disease symptoms in the transgenics. CYP72A2 gene mediated resistance suggests that the plant-pest or -pathogen interactions may have been modified by changes in bioactive metabolite pools.