Japanese Journal of Grassland Science
Online ISSN : 2188-6555
Print ISSN : 0447-5933
ISSN-L : 0447-5933
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Research Paper
  • Kazunori Ashikaga, Kenzaburo Deguchi
    2019 Volume 65 Issue 3 Pages 167-172
    Published: October 15, 2019
    Released: December 03, 2019
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    Improvement of the competitive ability of timothy (Phleum pratense L.) against quackgrass (Agropyron repens (L.) Beauv.) and reed canarygrass (Phalaris arundinacea L.) through breeding should lead to long-term maintenance of high-quality vegetation in timothy-based grasslands. In this study, we investigated differences in the competitive ability of 20 clonal lines of timothy against quackgrass and reed canarygrass. These evaluations were conducted from 2012 to 2014 in Shintoku, Japan. The dry weight differed significantly among the clonal lines of timothy, and showed moderate to high broad-sense heritability in most harvests. The total dry matter weight (an index of competitive ability), showed a strong genetic correlation between the two weedy conditions. There were also strong genetic correlations between the visual rating of plant vigor in all harvest or regrowth periods and the total dry matter weight. Quackgrass had a lower suppressing effect and lower plant height than reed canarygrass, suggesting that evaluations of competitive ability against quackgrass would be easier than those against reed canarygrass. These results suggested that selection based on growth in quackgrass weedy conditions is potentially useful to improve the competitive ability of timothy, and that the visual rating of plant vigor is an alternative easy method for evaluating yield.

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  • Kazunori Ashikaga, Kenzaburo Deguchi
    2019 Volume 65 Issue 3 Pages 173-183
    Published: October 15, 2019
    Released: December 03, 2019
    JOURNALS RESTRICTED ACCESS

    Breeding improvement of the competitive ability of timothy (Phleum pratense L.) against quackgrass (Agropyron repens (L.) Beauv.) and reed canarygrass (Phalaris arundinacea L.) could help to sustain high-quality vegetation in timothy-based grasslands. In this study, we investigated the potential of indirect selection under weed-free conditions and the effectiveness of selection under white clover (Trifolium repens L.) competitive conditions, a selection method against forage legumes, to improve the competitive ability of timothy. Two tests were conducted using 20 and 25 clonal lines of timothy from 2012 to 2017 in Kunneppu and Shintoku, Japan. The total dry matter weight of timothy under weedy conditions served as an index of competitive ability. Early spring, first- and second-crop plant vigor, and second-crop plant height showed comparatively strong genetic correlations and high indirect selection efficiency. Multiple regression and canonical discriminant analyses significantly selected first-crop stem density and the second-crop internode elongation stem ratio as factors associated with competitiveness. Therefore, selection for these traits under weed-free conditions is likely to be useful. By contrast, the results obtained under white clover competitive conditions suggested that the indirect selection is likely not to be useful. Therefore, some types of the selection are not effective for improving competitive ability.

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  • Kazunori Ashikaga, Kenzaburo Deguchi
    2019 Volume 65 Issue 3 Pages 184-194
    Published: October 15, 2019
    Released: December 03, 2019
    JOURNALS RESTRICTED ACCESS

    Breeding cultivars of timothy (Phleum pratense L.) that are competitive against quackgrass (Agropyron repens (L.) Beauv.) and reed canarygrass (Phalaris arundinacea L.) would offer many benefits for farmers. In this study, we investigated the effectiveness of selection under weedy conditions and indirect selection under weed-free conditions. We also investigated the potential simultaneous improvement of competitive ability with other major traits. These trials were conducted using five strains or cultivars under sward conditions and 20 and 25 clonal lines under spaced-plant conditions from 2012 to 2017 in Kunneppu and Shintoku, Japan. In a yield trial under weedy conditions, the total dry matter yield was significantly higher for the progeny of a strongly competitive group than for the progeny of a weakly competitive group. This suggested that the selection of clonal lines under spaced-plant conditions is potentially effective for improving progeny under sward conditions. The mean total dry matter yield was significantly higher for an indirectly selected group than for a non-selected group under weedy conditions, suggesting that indirect selection is a useful screening method. A genetic correlation analysis suggested that continuous crosses among desirable genotypes for lodging resistance, nutritive traits, and competitive ability would be necessary for simultaneous improvement.

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  • Yuri Kobashi, Makoto Seki, Yuichi Miyakoshi
    2019 Volume 65 Issue 3 Pages 195-203
    Published: October 15, 2019
    Released: December 03, 2019
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    We conducted an experiment to investigate the maximum feed amount of unhulled rice grain silage for lactating dairy cows in separate feeding system. We first evaluated the ruminal disappearance rate using an in situ technique with unhulled rice grain silage prepared by different methods. Further, a 3×3Latin square experiment was performed with nine Holstein dairy cows in the early to latter lactation period. The three diets were 0% unhulled rice grain silage (control), 20% unhulled rice grain silage in all feed twice a day, and 20% unhulled rice grain silage in all feed four times a day. Ruminal in situ disappearance of ensiled unhulled rice grain was faster than when it was not ensiled. Furthermore, ruminal in situ disappearance of unhulled rice grain and those silage that crushed finely were faster than crushed coarsely. No significant effects were observed on dry matter intake, lactation performance, rumen fermentation, and blood constituents. However, on days when two cows did not finish eating, unhulled rice silage was observed. The results indicate that the maximum feed amount of unhulled rice silage for lactating dairy cows in separate feeding system is approximately 20% in all feed.

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Mission to Overcome and Promising Potential of Plant Genetic Resources
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