Abstract
To evaluate orchardgrass individuals, digestibility-estimating equations were introduced from the results of analysis of multiple regression between digestibility and some plant characters (Table 2). The effectiveness of these equations in the breeding program was studied. In 1977, 159 plants from 1488 orchardgrass plants in blocks I and III where plant characters were investigated were selected for high and low digestibilities of first cutting and aftermath, basing on the estimated digestibility calculated from the equations. In 1978, digestibilities of the selected plants were evaluated by the one-step cellulase method (OSDMD) (J. Japan. Grassl. Sci., 23, 177-182). Ranges of OSDMD's of both high and low groups of first cutting were similar to each other (52-76%). Means of OSDMD were 57.9% and 66.4% for groups selected for high and low digestibilities respectively, resulting in selection opposite to the expected (Fig.1). Results of selection based on OSDMD in block II was similar to those in selection by the estimated digestibility. There was observed a negative correlation for digestibility of varieties between in 1977 and in 1978 (Fig.3), which was presumed to be caused by meteorological factors, temperature and percipitation, affecting heading dates of late-maturing varieties, but not affecting that of early-maturing varieties (Figs.4 and 5). Digestibility of late-maturing varieties was higher than that of early-maturing varieties in 1977 when growth and heading of late-maturing varieties was accelerated, and vice versa in 1978. In aftermath, means of OSDMD of high and low groups selected by estimated digestibility were 60.2% and 57.0% in 1978 respectively (Fig.6). Digestibility of aftermath was not seriously affected by the meteorological factors, and estimated digestibility from some plant characters is applicable to individual selection of orchardgrass.
