Abstract
Variabilities and relationships of lodging resistance and relating characteristics were investigated. In order to get information for the selection of lodging resistant characteristics in Italian ryegrass under the seed production cultivation, two cultivars, Waseaoba and Wasehikari were used in this experiment. Waseaoba is a lodging resistant, upright plant type and early cultivar, while Wasehikari is a poor-lodging resistant, intermediate plant type and early cultivar. One hundred plants of Waseaoba and 54 plants of Wasehikari were investigated on the lodging resistance and the relating 36 characteristics. The characteristics and the observation criteria are shown in Table 1. The results were as follows; 1) Lodging was observed in Waseaoba and Wasehikari at the beginning of heading and its degree increased with the progress of maturity. The degrees of lodging of Waseaoba were always lower than those of Wasehikari. On the other hand, seed yield of Wasehikari was 42.5 per cent higher than that of Waseaoba. 2) Lodging resistance in Waseaoba correlated significantly with heading date, days for flowering from heading, plant type, upper most internode length, thickest internode diameter, stem number, secondary tiller number, ear number, floret number per spikelet and bending resistance. Lodging resistance in Wasehikari correlated significantly with seed weight per ear, droop of leaf, thickest internode diameter, stem number, secondary tiller number, ear weight/culm weight ratio and bending resistance. On the other hand, seed yield in Waseaoba correlated significantly with the lodging resistance on May 26, seed weight per ear, vigor, plant type, plant height at heading, natural height, plant height at the harvesting time, stem number, ear number, spikelet number per ear and ear weight. Seed yield in Wasehikari correlated significantly with the secondary tiller number, ear number and ear weight/culm weight ratio. 3) According to the stepwise multiple regression analysis, upper most internode length, plant height at heading, heading date, plant type and bending resistance were selected as highly correlated characteristics to the lodging resistance in Waseaoba. Similarly, bending resistance, plant height at heading, upper most internode length, secondary tiller number, thickest internode diameter, ear weight/culm weight ratio and leaf length were selected as highly correlated characteristics to the lodging resistance in Wasehikari. On the other hand, seed weight per ear and ear number were selected as highly correlated characteristics to the seed yield in Waseaoba. Seed weight per ear, ear number, plant height at heading, branch number, upper most internode length and internode number were selected as highly correlated characteristics to the seed yield in Wasehikari. Furthermore, in Waseaoba, the lodging resistance and the seed yield per se, in addition to these, spikelet number per ear, upper most internode length, leaf type, heading date and second internode length were selected as highly correlated characteristics to the lodging resistance with high seed yield. Similarly, in Wasehikari, the lodging resistance and the seed yield per se, secondary tiller number were selected as highly correlated characteristics to the lodging resistance with high seed yield. According to above results, it is important to improve the lodging resistance and the seed yield simultaneously, by the selection of higher seed weight per ear and thick bottom part of stem to increase bending resistance to bear increased ear weight.
