Japanese Journal of Grassland Science

To save seeds, field area and labor on the evaluation test of many selected strains in Italian ryegrass breeding program, application of micro plot method was examined. Yield date of 16 varieties of Italian ryegrass from micro plot (0.1 m^2 per plot) with 8 replications and check plot (3.5 m^2 per plot) with 4 replications were compaired. These varieties were sown on Sep. 3, 1965 and cut four times, Nov. 4, 1965, Apr. 26, May 24 and June 21, 1966 respectively. Average correlation coefficients of micro and check plot for green yield on each cutting date were 0.864, and 0.850 for total green yield respectively. These coefficients were highly significant. For plant height on each cutting date correlation coefficients between both plots were high, and average of them was 0.889, and for mean weight per stem and stem number per area were 0.841 and 0.767, respectively. Remarkable differences between micro and check plot were not recognized on the coefficients of variance of error for each character on every cutting date other than 2nd. Coefficients of variance of error for each character in micro plot on 2nd cutting date were larger than those in check plot, these were presumably affected by snow damage. Varietal differences of each character in micro plot seemed to be clearer than those in check plot, and heritability of green yield was higher in micro plot than in check plot. From these results, it may be concluded that micro plot method is adequate when large number of strains are screened in early generation of ryegrass breeding.

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The susceptibility of clones contained in the red clover cultivar (CV) to this disease was observed to distribute in a wide range. In the case of resistant CV, they contained a large number of resistant clones and a small number of susceptible ones. On the other hand, in that of susceptible CV, it was in an adverse relationship. To select resistant clones and lines, the following experiments were carried out. The plants were held for 48 hours at 19 ℃ in the moist chamber after inoculation, and removed to a green house under controlled conditions at 18 to 23 ℃ and were watered 4 to 5 times a day with an atomizer. The appropriate concentration of conidial suspension for selection of resistant clones was about 10^6 conidia per ml. The clones whose leaf petiolules only could be infected or those which showed no symptoms were selected as resistant clones. The susceptibility of the lines to this disease could easily be compared when artificially inoculated in the second trifoliate stage. The degree of susceptibility was expressed as the percentage of infected seedlings in all the inoculated seedlings. In this case, the appropriate concentration of conidial suspension in order to compare the susceptibility of the lines was 10^5 to 3×10^5 conidia per ml. In the screening test at the second trifoliate stage, the populations which showed the disease symptom earlier contained a larger number of susceptible clones and a smaller number of resistant clones than those which showed the symptom later.

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Grasses undergo seasonal change in their growth habit, i.e. upright or prostrate. This may be caused by the curvature of leaf-sheath. To clarify this point, the effects of environmental conditions and CCC or GA application on the curvature were tested by using an orchardgrass clone. Low air-and soil-temperature, short days, stronger daylight or supplemental light in the longday treatment, abundant nutrition, and CCC application all tended to increase the curvature resulting in the more prostrate growth of the plant. The inverse environments and GA application, on the contrary, made the plant to grow more upright (Table 1-5.) Since there is an inverse relation between environmental conditions favouring shoot elongation and those favouring tillering, and the conditions which promote the curvature as mentioned above are favourable for tillering, the curvature has a positive or a negative correlation with tiller number or plant height, respectively. (Fig. 2-3)

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The main purpose of this report was to know the effects of growth stage in making silage, on pH, organic acids composition, digestibility and nutrients intake by dairy cows. 1) First growth of orchard grass and Ladino clover mixture was harvested four times at two weeks interval on the same field from 4th of June 1966 in 2 tons experimental pilot silo under the same treatments without preservative. Herbage was cropped by mower bar type's forage harvester. 2) Results are summarized in the following Table 1. 3) Dry matter yield of the pasture was reached maximum at heading stage, but crude protein contents in dry matter basis decreased in the order of harvesting date. 4) Earlier harvested silages contained higher dry matter per cubic meter than later harvested ones. 5) Maximum fermentation temperature was closely related to air temperature of ensiled day. Also, even in the small pilot silo, higher fermentation temperature was observed in upper layer. 6) From the point of pH, organic acids and ratio of ammoniacal nitrogen to total one were improved in the order of growth stages until flowering, but very poor at the seed setting stage. 7) DDM content of the silage was indicated higher in earlier stage. Significant negative correlation (r : -0.969) was found between growing days of the pasturage (X) and TDN content in the silage (Y%). The regression equation was Y=101.37-0.66 X. And also, a significant correlation, (r : -0.938) was shown between the growing days (X) and DCP % in dry matter basis (Y%). The regression equation was obtained Y=18.65-0.18X. 8) TDN intake of the silage by cow was rapididly decreased after flowering stage. Significant negative correlation, (r : -0.609) was shown between growing days (X) and TDN intake of the silage (Y kg). The regression equation was Y=10.48-0.086X. 9) Silage evaluation should be decided after general consideration of pH, organic acids, digestibility and nutrients intake by cow. 10) From the view point of general silage evaluation and production of the pasture, heading stage but before flowering may be recommended as favorable growth stage in making high moistore silage.

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