The Glycine max (L.) Merr. cultivar Waseshiroge is highly resistant to several races of Phytophthora sojae in Japan. In order to determine which Rps gene might be present in Waseshiroge, 15 differential cultivars were challenged with 12 P. sojae isolates. None had a reaction pattern identical to that of Waseshiroge, indicating that Waseshiroge may contain a novel Rps gene. In order to characterize the inheritance of Waseshiroge resistance to P. sojae isolates, 98 F 2 progeny and 94 F 7:8 lines were produced from crosses between the susceptible cultivar Tanbakuro and Waseshiroge. Chi-square tests indicated that segregation fit a 3:1 ratio for resistance and susceptibility in two F 2 sub-populations of 42 and 56 seedlings. This and a 46.27:1.46:46.27 (or 63:2:63) ratio for resistance: segregation: susceptibility among the 94 F 7:8 lines indicated that resistance was controlled by a single dominant gene. DNA analyses were carried out on Tanbakuro, Waseshiroge and the 94 F 7:8 lines, and a linkage map was constructed with Electronic supplementary material The online version of this article (
To identify markers for the everbearing gene in strawberries, 199 F 1 progeny plants were produced from a cross between ÔEver BerryÕ (a Japanese everbearing strawberry) and ÔToyonokaÕ (a Japanese Junebearing strawberry) as the experimental population. The results of flowering tests produced 97 everbears and 102 Junebears. The chi-square test gave a goodness of fit for the expected ratio of 1 : 1 for everbears to Junebears, suggesting the inheritance of the everbearing trait is controlled by a monogenic dominant gene. RAPD analyses on this trait were carried out using ÔEver BerryÕ and ÔToyonokaÕ. Seventy-one primers, which produced 89 polymorphic fragments between the two parents, were identified from a total of 175 primers. Five markers relating to the everbearing trait were selected from 26 of the 199 progeny plants. The remaining 173 seedlings were analysed with these five markers and a linkage map was constructed using all of the 199 F 1 progeny plants. The length of this linkage group is 39.7 cM. The closest markers found, OPE07-1 and OPB05-1, are respectively mapped at 11.8 and 15.8 cM on each side of the everbearing gene.
To identify markers for the Phytophthora resistance gene, Rps1-d, 123 F 2 : 3 families were produced from a cross between Glycine max (L.) Merr. ÔTanbakuroÕ (a Japanese traditional black soybean) and PI103091 (Rps1-d) as an experimental population. The results of virulence tests produced 33 homozygous resistant, 61 segregating and 29 homozygous susceptible F 2 : 3 families. The chi-squared test gave a goodness-of-fit for the expected ratio of 1 : 2 : 1 for resistant, segregating and susceptible traits, suggesting that the inheritance of Rps1-d is controlled by a monogenic dominant gene. Simple sequence repeat (SSR) analyses of this trait were carried out using the cultivars ÔTanbakuroÕ and PI103091. Sixteen SSR primers, which produced 19 polymorphic fragments between the two parents, were identified from 41 SSR primers in MLG N. Eight SSR markers were related to Rps1-d, based on 32 of the 123 F 2 : 3 families, consisting of 16 homozygous resistant and 16 homozygous susceptible lines. The remaining 91 families were analysed for these eight markers, and a linkage map was constructed using all 123 F 2 : 3 families. The length of this linkage group is 44.0 cM. The closest markers, Sat_186 and Satt152, are mapped at 5.7 cM and 11.5 cM, respectively, on either side of the Rps1-d gene. Three-way contingency table analysis indicates that dualmarker-assisted selection using these two flanking markers would be efficient.
This study investigated the effects of several calcium compounds on Phytophthora stem rot of soybean (Glycine max) and fungal growth and zoospore release of a Phytophthora sojae isolate in vitro. All concentrations of five formulated calcium products [Ca(COOH)2-A, Ca(COOH)2-B, Ca(COOH)2-C, CaSO4-A, and CaCl2-A] and two chemical compounds [CaCl2 and Ca(NO3)2] applied prior to inoculation significantly suppressed disease incidence. Among all the products and chemicals, Ca(COOH)2-A was the most effective in suppressing the incidence of disease. In most cases, no significant relationship was observed between inhibition of growth rate in vitro and disease reduction in growth chamber tests. Therefore, disease suppression recorded in laboratory experiments using pathogen mycelium was likely due to the responses of plant tissues rather than the direct inhibition of pathogen fungal growth by the calcium compounds. The extent of disease reduction was related to increased calcium uptake by plants, suggesting that calcium was the effective element in reducing Phytophthora stem rot. Seedling tray experiments using zoospores indicated that the application of 10 mM Ca(COOH)2-A was more effective for reducing incidence of disease under growth chamber conditions, compared to other concentrations. The presence of 4 to 20 mM of all seven calcium solutions decreased the release of zoospores, although 0.4 mM of all compounds significantly increased zoospore release. Therefore, disease reduction in the growth-chamber experiments was due to the multiple effects of direct suppression on zoospore release and fungal growth in combination with the response of the host plant tissue to Ca(COOH)2-A.
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