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  • Author or Editor: Hiromichi Yamazaki x
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The relationship between Ca nutrition and bacterial wilt development was studied on three tomato (Lycopersicon esculentum Mill.) cultivar seedlings with various degrees of resistance to the disease. Seedlings were transplanted into nutrient solutions with Ca at 0.4, 4.4, or 20.4 mm. One week after initiating the Ca treatment, tomato seedlings were inoculated by wounding the stem with scissors dipped in a suspension of the pathogen (Pseudomonas solanacearum E.F. Smith). Disease development was rapid in `Ponderosa' (a susceptible cultivar) at all Ca concentrations. Increased Ca concentration in the nutrient solution reduced disease severity in `Zuiei' (a moderately resistant cultivar). Resistance was negated at the low Ca concentration in `Hawaii 7998' (a highly resistant cultivar). Pathogen populations in stems decreased with increased Ca concentrations and degrees of resistance.

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We analyzed sequence variation in chloroplast DNA (cpDNA) to investigate the origin of the cultivated strawberry, Fragaria ×ananassa. From analysis of two noncoding regions, trnLtrnF and trnRrrn5, we found three haplotypes (V, C, and X) in F. ×ananassa. Haplotype V corresponded to the haplotype of F. virginiana and was possessed by cultivars bred over a wide geographic range, including North America, Europe, and Japan. Almost all the North American cultivars analyzed in this study possessed haplotype V, suggesting a founder effect. Haplotype C corresponded to the haplotype of F. chiloensis and was detected mainly in Japanese cultivars. Haplotype X was found in only two English cultivars. This haplotype was positioned as intermediate between haplotypes V and C in a median-joining network and was considered to be representative of the process of differentiation between F. virginiana and F. chiloensis. Results of controlled crosses indicate that cpDNA haplotypes of F. ×ananassa are maternally inherited. These results verify that F. ×ananassa is an interspecific hybrid between F. virginiana and F. chiloensis and indicate that traditional cultivars of F. ×ananassa have been derived from at least three maternal lineages. We demonstrate that the cpDNA variation detected in this study can be used to verify parentage and for extending hypotheses about June yellows, a leaf variegation disorder in strawberry.

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