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Seeds of common buckwheat usually mature while leaves are still green, causing problems for harvest machinery and limiting yields. We developed an early leaf-senescence line, Kyushu 1, from spontaneous mutants. To characterize this mutant line physiologically and genetically, we measured the change in leaf chlorophyll content in two regions of Japan with different environments, and performed genetic analyses with self-compatible lines. The chlorophyll content of Kyushu 1 was lower than that of the wild type at seed maturity in both regions. F1 progeny of the cross between wild-type plants and Kyushu 1 showed a wild-type phenotype. F2 progeny segregated into wild-type and early leaf-senescence phenotypes in a 3:1 or 13:3 ratio, suggesting that the early leaf senescence of Kyushu 1 is controlled by either a single recessive gene or an epistatic interaction between two loci. Discipline: Plant breeding Additional key words: chlorophyll, genetic analysis, mutant, SPAD

The firmness of buckwheat noodles plays an important role in its palatability. We investigated the effects of artificial sprouting after harvest and preharvest sprouting in the field of buckwheat grains on the firmness of cooked buckwheat noodles by measuring the force required to compress the cooked noodles. Sprouting significantly decreased the peak force and peak strain to compress cooked noodles, suggesting that sprouting lowers the palatability of cooked buckwheat noodles. Sprouting significantly decreased the force needed to compress cooked noodles largely, suggesting that the cooked noodles made from sprouting grains lead to the perception of less resistance to completely cut off by mastication.

Common buckwheat plants have heteromorphic self-incompatibility. Using two self-fertilizing lines, we revealed that there are two distinct systems of sell-compatibility, one using a self-compatible allele, S', the other using modifier genes located outside the S locus and suppressing the functions of the S-locus genes. S h appears to have been produced by recombination in the S supergene (gi s I P PA/gi S I p PA), in which each gene is functional. The modifier genes control the intensity of self-incompatibility and have three distinctive features: (1) Pollen shows cross-compatibility with styles of all flower types, although the compatibility is influenced by the genetic background of those plants. (2) Flower morphology of F 1 plants is controlled by the genotype of the S locus. (3) F 1 plants show high self-compatibility, although the level of self-compatibility is influenced by genetic background. The use of these genes for buckwheat breeding is discussed.

Rain before harvest often causes buckwheat to sprout. Preharvest sprouting reduces the processing suitability of buckwheat flour. We examined the effects of preharvest sprouting on buckwheat flour quality by rapid visco-analysis (RVA) of milled sprouting grains of six buckwheat cultivars. Both artificial and natural rainfall increased the frequency of sprouting and decreased pasting viscosity. The difference in pasting viscosity between sprouting and non-sprouting buckwheat grains was not decreased by adding wheat flour. These results suggest that the mechanical characteristics of dough and boiled noodle may be affected by flour made from sprouting grains. Differing responses of the cultivars to rainfall indicate that higher pasting viscosity could be achieved by using cultivars that are resistant to preharvest sprouting caused by rain.

Common buckwheat (Fagopyrum esculentum Moench cv. Shinano No.1) and Tartary buckwheat (F. tataricum (L.) Gaertn. cv. Nepal) were grown in pots to examine their responses to soil flooding. Flooding treatment was carried out during the early growth stage by completely submerging the pots in a nutrient solution from 12 to 36 days after sowing. The plant growth rate, relative growth rate and mean leaf area under the flooding treatment were reduced to 72, 90 and 83% of the control, respectively, in Shinano No.1, and to 29, 71 and 45% of the control, respectively, in Nepal. The excess moisture stress had no effect on the net assimilation rate (NAR) in Shinano No.1, but lowered the NAR to 68% of that in the control in Nepal. Excess moisture stress decreased the total leaf area to 76 and 34% of the control in Shinano No.1 and Nepal, respectively. Leaf growth rate, number of leaves and leaf area per leaf, which influenced the total leaf area, were reduced by the excess soil moisture. The relative water content of leaves was unchanged in Shinano No.1, but was decreased in Nepal. Reduction in bleeding from the cut end of stem due to flooding was greater in Nepal than in Shinano No.1. Excess moisture stress reduced the K+ concentration of the stem and increased the Na+ concentration of leaves, stem and roots more strongly in Nepal than in Shinano No.1. Development of adventitious roots in the surface layer of the nutrient solution was better in Shinano No.1 than in Nepal. In conclusion, Shinano No.1 (common buckwheat) had a stronger tolerance to excess soil moisture than Nepal (Tartary buckwheat). In Shinano No. 1, leaf growth and photosynthetic rate were not markedly affected and the capacity of absorbing water and nutrients was retained by developing adventitious roots in the solution above the surface of the soil keeping proper physiological activity under excess moisture conditions.

The variation in seed shape and husk color was investigated in 56 Japanese native cultivars of common buckwheat. Analysis of variance revealed highly significant differences among the cultivars in seed shape characteristics and husk colors. The 1000-seed weight (1000-SW) ranged widely, from 20.4 to 39.0 g, among the cultivars. The cultivars collected from the Kanto region of the mainland had a large length and width of seed and heavy 1000-SW. On the other hand, the cultivars from the Chugoku and Shikoku regions of Japan had a small length and width of seed. The length and width of seeds showed a high positive correlation. The cultivars with a high 1000-SW showed a slight difference between length and width of seed and were typically the triangular type in seed shape. The length/width ratio (L/W) depended on the width rather than the length of seed, though both were negatively correlated with the L/W. Highly positive correlations were found among the L*, a* and b* husk color value. The L* showed a highly positive correlation with growth duration, and the husk color of the cultivars became more deep black as growth duration decreased. The husk color of the cultivars from the Kyushu region (long growth duration) was grayish brown, but that of the cultivars from Nagano Pref. (the shortest growth duration) was characterized as typically deep black. The cultivars collected at lower latitude regions tended to have a lighter color of husk than those from higher latitude regions. The cultivars from the Tohoku region showed a smaller variation for seed size characteristics and 1000-SW, and the cultivars from the Kyushu region showed a smaller variation for husk color.

The shattering habit in buckwheat occurs because of brittle or weak pedicels. Brittle pedicels are observed in wild buckwheat but not in cultivated buckwheat. Using 2 self-compatible lines, 01AMU2 with brittle pedicels and Kyukei SC2 (KSC2) with non-brittle pedicels, produced by an interspecific cross between Fagopyrum esculentum cv Botansoba (non-brittle) andF. homotropicum (brittle), we investigated the inheritance of brittle pedicels. F1 plants derived from crosses between Botansoba × 01AMU2 and Botansoba × KSC2 had brittle pedicels. The F2 population derived from the cross between Botansoba × 01AMU2 showed segregation of brittle and non-brittle pedicels that fit the expected 3:1 ratio, suggesting that non-brittle pedicel in Botansoba is controlled by a single recessive gene (sht1). Another F2 population, derived from the cross between Botansoba × KSC2, showed segregation of brittle and non-brittle pedicels that fit an expected ratio of 9:7,suggesting that non-brittle pedicel in KSC2is controlled by a different single recessive gene (sht2). Thus, brittle pedicel is achieved by 2 complementary genes Sht1 and Sht2. The sht1 locus is linked to the S locus with a recombination frequency of5.46±1.18 (%). We investigated whether common buckwheat has the allele sht2by crossing 6 common buckwheat lines withKSC2. An analysis of the preliminary data showed that some of the F1 had brittle pedicels and others had non-brittle pedicels, suggesting that some common buckwheat lines possess both the allelesSht2 and sht2.

The plant-type variation in 56 Japanese native cultivars of common buckwheat (Fagopyrum esculentum Moench) was investigated. Eleven quantitative characteristics, such as main stem length, the lengths of the 1st order branches at the 2nd, 3rd, and 4th nodes, the number of nodes, the numbers of the 1st, 2nd and 3rd order branches, total number of branches, the number of flower dusters and the node position of the lowest flower, positively correlated with each other, and these characteristics positively correlated with the growth duration. The ratio of branch length to main stem length positively correlated with the angle between the main stem and the 1st order branch. In the principal component analysis based on 15 quantitative characteristics, the first component mainly related with plant size and the scores correlated with the growth duration. The second component related with the plant shape became more variable as the score of the first component increased. There was a significant variation in the plant types of native cultivars collected in western Japan. Thus, it is suggested that the native cultivars from western Japan have various plant types.

Research was conducted to define the characteristics of rutin, protein, and oil contents of common buckwheat in the Kyushu area with the use of local and breeding varieties containing various origins and ecotypes. The analysis of variance showed that the differences among varieties and years were significant at the 1% level for the rutin, protein, and oil contents. The range of the varietal differences of rutin content was larger than protein and oil content. Except for protein content, environmental variation was bigger than the genetic one. There were many high rutin content varieties in Nepal, but varietal characteristics depending on origin were not found in other origins. It was indicated that a high temperature was advantageous for rutin accumulation during maturing. There was an inverse significant correlation between grain yield and rutin content and a significant correlation between protein content and oil content. But it was unclear that a relationship existed between flour to grain ratio, 1, 000 grain weight, and these contents.

Research was conducted to define the characteristics of common buckwheat in the Kyushu area by using local and breeding varieties containing various origins and ecotypes. In 1995, summer cultivation was researched, and the results showed the need to develop a new variety that has a short growing period and resistance to pre harvest germination for summer cultivation in the Kyushu area. As a result of autumn cultivation, by the use of 3 years data from 1995 to 1997, the differences in years and variety were indicated to be statistically significant for all agronomic characters. It seemed that the characters of productivity, however, such as total weight and grain yield, were influenced easily by environmental effects. On the other hand, there were high year-to-year correlations of morphological characters, such as plant heights, number of nodes, and 1, 000-grain weights, showing that these characters were indicators of varietal characteristics. It was indicated that big growing characters are advantageous for obtaining high grain yield. These genetic resources showed varietal differences, depending on their origins. Especially, the native varieties of the Kyushu area had a long growing period and high grain yield, showing that they were suitable ecotypes for growing in that area.

We examined the feasibility of near-infrared (NIR) reflectance spectroscopy to estimate the contents of moisture, fat, and protein in the flours of common and tartary buckwheat harvested in 1996 and 1997. Multiple linear -regression analysis for NIR spectral and chemical data was carried out. The standard error of the prediction (SEP) for the samples harvested in 1996 was 0.22% for moisture, 0.06% for fat, and 0.21% for protein, when the calibration equations obtained from the analysis of common and tartary buckwheat were used. When the same calibration equations for the buckwheat flour harvested in 1997 were used, the correlation graphs between the reference values and the calculated values were skewed and biased. However, the relative values were sufficient for the selection based on the contents of the constituents, and the bias-corrected SEPs were 0.15% for moisture, 0.10% for fat, and 0.44% for protein. We also examined the feasibility of NIR spectroscopy to estimate the total polyphenol content and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging activity in the flours of common buckwheat harvested in 1998. The estimation error was acceptable for use in the selection of varieties with a higher activity. Using the NIR method, the contents of moisture, fat and protein, and physiological activity (total polyphenol content and DPPH radical-scavenging activity) in the buckwheat flours could be successfully estimated for a simple and rapid-breeding selection.

The feasibility of near-infrared (NIR) spectroscopy for the nondestructive determination of fatty acid composition in rapeseed was examined. NIR spectra were measured on extracted oil, intact rapeseed kernels, and an intact signle rapeseed with an InfraAlyzer 500 in a syrup cup or a single-grain cup. NIR spectra were scanned from 1100 to 2500 nm at 2-nm intervals. As the percentage of linoleic acid increased, the spectral values in the region 1696–1724 nm, where linoleic acid has its absorption band, became always stronger downward in second-derivative NIR spectra. As the percentage of erucic acid increased the spectral value at 1728 nm, where erucic acid has its absorption band, became always a little bit stronger downward in the second-derivative NIR spectra. On the basis of their NIR spectral patterns, linoleic acid and erucic acid could be successfully determined in both intact seed kernels and in a single seed of rape without damaging them.