‘Enrei’ is the second leading variety of soybean (Glycine max (L.) Merr.) in Japan. Its cultivation area is mainly restricted to the Hokuriku region. In order to expand the adaptability of ‘Enrei’, we developed two near-isogenic lines (NILs) of ‘Enrei’ for the dominant alleles controlling late flowering at the maturity loci, E2 and E3, by backcrossing with marker-assisted selection. The resultant NILs and the original variety were evaluated for flowering, maturity, seed productivity and other agronomic traits in five different locations. Expectedly, NILs with E2 or E3 alleles flowered later than the original variety in most locations. These NILs produced comparatively larger plants in all locations. Seed yields were improved by E2 and E3 in the southern location or in late-sowing conditions, whereas the NIL for E2 exhibited almost the same or lower productivity in the northern locations due to higher degrees of lodging. Seed quality-related traits, such as 100-seed weight and protein content, were not significantly different between the original variety and its NILs. These results suggest that the modification of genotypes at maturity loci provides new varieties that are adaptive to environments of different latitudes while retaining almost the same seed quality as that of the original.

Coat protein sequences of two isolates in strain A 2 and five isolates in strain D of Soybean mosaic virus (SMV), which caused a recent mosaic outbreak in soybeans (cv. Sachiyutaka) in Chugoku and Shikoku in Japan, were compared to published data on 15 other Asian-origin isolates. Sequence comparison and cluster analysis showed that SMV isolates of strain A 2 from these districts were closely related, as were those of strain D, but strains A 2 and D were not. Thus, the two strains may have different origins and be carried through seed transmission.

Although seed priming is well known to be an effective method for enhancing seed vigor and seed performance, the efficacy of priming (soaking in water and re-drying) on the physiological performance of iron-coated rice (Oryza sativa L.) seeds under submerged conditions, and the physiological mechanisms of coleoptile elongation of the primed rice seeds under anoxia, have not been well elucidated. In the present study, primed and unprimed rice seeds with or without iron-coating were produced. We examined the physiological performance of these rice seeds and the physiological efficacy of priming on coleoptile elongation under anoxia. For the primed rice seeds, seed germination, coleoptile elongation, seedling emergence and the establishment of iron-coated rice seeds all improved considerably, which resulted in an increase of plant height and dry weight for the iron-coated primed rice seeds. Increases in -amylase activity and glucose concentration over time were significantly higher in the primed rice seeds than in the unprimed rice seeds. Under anoxia, the -amylase activity and soluble sugar concentration were significantly higher in the primed rice seeds than in the unprimed rice seeds. The glucose and fructose concentrations in the coleoptiles were significantly higher in the primed rice seeds than in the unprimed rice seeds, suggesting that the stimulated coleoptile elongation is partly related to the increased availability of soluble sugar from the seed to the coleoptiles. The increased availability of soluble sugar from the rice seeds to the coleoptiles can be assumed to help maintain glycolytic flux and alcoholic fermentation under the submerged conditions. These results clearly indicate the efficacy of priming on iron-coated rice seeds, and that the coleoptile elongation of the primed rice seeds can be partly ascribed to the sugar availability from the rice seeds to the coleoptiles. Therefore, the use of primed rice seeds for iron coating is highly effective to induce the emergence and establishment of stable seedlings in direct rice sowing systems.

The peanut stunt virus (PSV) causes yield losses in soybean and reduced seed quality due to seed mottling. The objectives of this study were to determine the phenotypic reactions of soybean germplasms to inoculation with two PSV isolates (PSV-K, PSV-T), the inheritance of PSV resistance in soybean cultivars, and the locus of the PSV resistance gene. We investigated the PSV resistance of 132 soybean cultivars to both PSV isolates; of these, 73 cultivars exhibited resistance to both PSV isolates. Three resistant cultivars (Harosoy, Tsurunotamago 1 and Hyuga) were crossed with the susceptible cultivar Enrei. The crosses were evaluated in the F1, F2 and F2:3 generations for their reactions to inoculation with the two PSV isolates. In an allelism test, we crossed Harosoy and Tsurunotamago 1 with the resistant cultivar Hyuga. The results revealed that PSV resistance in these cultivars is controlled by a single dominant gene at the same locus. We have proposed Rpsv1, as the name of the resistance gene in Hyuga. We also constructed a linkage map using recombinant inbred lines between Hyuga × Enrei using 176 SSR markers. We mapped Rpsv1 near the Satt435 locus on soybean chromosome 7.

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