2019 Volume 65 Issue 3 Pages 173-183
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.
