[in Japanese]

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To make clear the inter-varietal and inter-strain difference of crown rust resistance of genus Lolium grasses, the disease which being the most noxious to the grass, and its relation to forage yield, a study was made using varieties and strains of mainly perennial ryegrass collected from foreign countries in 1965-66. The results obtained were as follows : 1. The difference of inter-varietal and inter-strain resistance to crown rust was clearly observed irrespective of the cultivating seasons. From this, a classification was made to divide degrees of resistance of varieties and strains cultivated in summer and autumn basing on disease susceptibility index. High correlations were shown between resistance differences of varieties and strains of various periods of disease outbreak, cultivation methods and crop years. 2. Concerning the relation between resistance and the country where the variety was originated, highly resistant ones were found among those bred in Netherlands and particularly tetraploid were highly resistant. On the other hand, those bred in Canada, USA and Sweden, and Japanese native varieties and commercial varieties in Japan had lower medium resistances, particularly Canadian varieties being highly susceptible. Those bred in Ireland, New Zealand and Australia were mixed groups of high and low resistances. 3. The outbreak of crown rust disease had grave effect on forage yield. High positive correlation existed between varietal susceptibility index and forage yield and particularly the correlation was higher in autumn, resistant varieties being positively recognized as high producing varieties.

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The experiments were carried out from November, 1966, to September, 1967, to investigate the influences of environmental conditions affecting reproductive growth of red clover plants, using Kenland as early-flowering and Altaswede as late-flowering variety of red clover in greenhouse and field. Red clover varieties were seeded at November 4, 1966, in the greenhouse, and the treatments with day-length, temperature and plant hormone were set to all seedlings from November 9, when they germinated, to March 6, 1967. After investigations in greenhouse were ended, Altaswede red clover plants were transplanted from greenhouse onto field at May 9, 1967, and were investigated on their stem-elongation and flowering in that growing season. And also, influenecs of prolongation of growing period to flowering induction of late-flowering type of red clover plants were investigated, by seeding at January, February and March, respectively. The results were summarized as follows : 1. Growth and flowering of early-flowering type of red clover plants was accelerated by long day, not by low temperature-short day conditions. Growth was rather suppressed by the latter conditions. 2. It was observed that long day was basic inducing and accelerating conditions to flowering of late-flowering type of red clover plants, while low temperature-short day was additive accelerating conditions. 3. Tendency was found that plant-height was taller and stem-number was less in red clover plants under conditions accelerating flowering. 4. Flowering of late-flowering type of red clover plants was induced within a seeding season, by prolonging more than three months of growing period in spring. In this case, opportune low temperature treatment at young stage of plants could be additive accelerating conditions. 5. There was considerable variation, which was observed as continuous, in reaction of plants, expressed as stem-elongation, budding and flowering, to environmental conditions among late-flowering type of red clover plants. 6. Effectiveness of plant hormone to flowering induction was scarcely found in these experiments, but it should be further tested on treating methods in connection with other conditions.

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Productivity was studied at western localities of Kanto for the 2-year period of 1964-66 to investigate on the practicality of artificial rutabaga obtained from interspecific crosses between B. campestris ssp. rapifera and B. oleracea var. gongyloides. The artificial rutabaga was tolerably high in yield compared with natural rutabaga especially in top than in root, and difference in yield between artificial and natural rutabaga was significant at 5% level at most of the localities. No great difference in yield was observed among the artificial rutabaga, but at some localities the difference was significant at 5% level. In the second year, difference in yield between artificial and natural rutabaga became smaller than that in the first year. Great decresse appeared in yield of top in the second year compared with that in the first year. It seems to be based upon reduction of heterosis. From the results, the artificial rutabaga named SR lines may be possible to practical use as hybrid varieties or as fix varieties after stabilized the characters.

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Studies were made of feeding value of artificial rutabaga named SR lines which were bred from interspecific crosses between B. campestris ssp. rapifera and B. oleracea var. gongyloides, in comparison with natural rutabaga varieties and forage turnip. The results were summarized as follows : 1. The content of water was higher in forage turnip than in rutabaga and no difference in water content was observed between natural and artificial rutabaga. 2. Compared with natural rutabaga, the content of crude protein in artificial rutabaga increased in root in December and in top in March. 3. In December, the content of total carbohydrate in artificial rutabaga was higher than natural rutabaga in both part, but no significant difference was seen between both rutabaga in March. 4. The content of crude ash in artificial rutabaga was almost the same as natural rutabaga or slightly lower. 5. No great difference of the content of crude fiber was appeared in natural and artificial rutabaga. 6. Fresh weight of turnip in December was the highest of all materials, but artificial rutabaga as SR-1 and SR-3 was slightly abundant than turnip in total yield of nutriment. All the artificial rutabaga except root of SR-3 were better than turnip and natural rutabaga in yield of nutriment in March, too. 7. From the results as mentioned above, it is proved that we can increase the total yield of nutriment (feeding value) in rutabaga by means of interspecific crosses among genus Brassica, but increse of the yield in green weight are more easily made from this method.

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Clipping winter crop in autumn promotes the snow damage in snowy district. In this report investigations were made on definition of snow damage and regrowth in spring in relation to the prosperity and decay of TAC (total avilable carbohydrate) and total nitrogen after clipping Italian ryegrass in autumn. Tottorizairai variety was seeded Septmber 2. Whole plots were clipped October 25 for the first time, and plot II, III and IV were clipped November 10, November 26 and December 10 respectively for the second time to differentiate the days from clipping to continuous snow cover. In spring whole plots were clipped two times. Duration of continuous snow cover were 84 days. The results obtained are shown below. 1. Snow damages were different clearly among plots. There were little snow damages (area rate) on plot I, 40-60% on plot II and IV, and the most heavy snow damage on plot III, above 80%. 2. Snow damage has a direct influence on yields of each plot and both fresh and dry yields were I>II≒IV>III. 3. TAC in stubble has reduced after clipping and reached minimum about 5-10 days after clipping on plot I, II and III. Two or three weeks elapsed before TAC recovered on the level with that of clipping time, but on plot III clipped at the lower temperature, recover of TAC was insufficient in about a month after clipping. TAC in stubble just before continuous snow cover were I>IV>II>III and this order was the same as that of yields. 4. Total nitrogen in leaf was higher than in stubble. Total nitrogen in stubble tended generally to decrease after clipping and its order among each plot just before continuous snow cover was I<IV<II<III and symmetrical with that of TAC. 5. There was high negative correlation between TAC and total nitrogen, especially in stubble. There was more TAC and less total nitrogen on plot I with light snow damage. On the contrary, there was less TAC and more total nitrogen on plot III with heavy snow damage. Plot II and IV were in the middle of them. 6. According to the above mentioned, clipping in autumn must be done about a month and a half before continuous snow cover or just before continuous snow cover, but it is in danger to put the latter to practical use because it is difficult to estimate the first day of continuous snow cover correctly. 7. As there is high positive correlation between dry weight rate and TAC, dry weight rate must be index of snow resistance.

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Treatments of fertilizing, soil temperature and day length were applied to alfafa seedlings in order to clear how these environments affected the growth of lateral roots which were considered to contribute towards the top growth of this plant. Fertilizing with N+P_2O_5+K_2O favoured the growth of lateral roots which correlated closely with the increase of the top growth. Correlation coefficients of the lateral root weight to the top weight in fertilized and non-fertilized plants were 0.939 and 0.932, while those of the tap root weight were 0.675 and 0.230, respectively. Among the treatments of soil temperature ranged 10 to 25℃, the root growth treated with 20℃ of soil temperature was best in respect to allometric relations between top- and root-growth. Thickening of tap root increased with higher temperature, but the growth of laterals was improved by lower temperature. In comparing day lengths, long (16 hrs) and short (8 hrs), the long day treatment accelerated the thickening of tap root and maturity of root system as a whole. On the contrary, root system under short day still remained so young that even tap root looked like a lateral root in feature and had a higher regression coefficient in allometric relations between top and root growth than that under long day. These results seemed to be interpreted that the top growth was affected principally by the growth of lateral roots, that is the increase of surface area contacted with soil media.

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In September of 1965, the authers surveyed soil insects and some other arthropods in the three swards of Ladino clover, orchardgrass and their mixture which were sown before two years, as soil pests attacking forage crops had been little known in Japan. Fourty-one species of soil arthropods were found. The number of species of each order were recorded as follows. Insecta; Coleoptera 29 species, Diptera 7 species, Lepidoptera 2 species, Dermaptera 1 species. Curstacea; Isoptera 1 species, Deplopoda; Polydesmoidea 1 species. Main soil arthropods considered to be important forage pests were Melanotus fortnumi CANDEZE, M. senilis CANDEZE, Scepticus griseus ROELOFS, Sitona hispidula FABRICIUS, Lachnosterna kiotoensis BRENSKE, Agrotis fucosa BUTLER, Pales virgata COQUILLETT and Armandiridium vulgare (LATREILLE). A. vurgare belonging to Curstaces was a peculiar pest of the pasture fields. This pest caused serious damage for Ladino clover. The fauna of soil arthropods was the most abundant in Ladino clover sward, i.e., 30 species were found in total and 120.1 heads per 50 cm square were counted. While, in orchardgrass sward there were found only 18 species and 39.4 heads per 50 cm square. Mixture sward showed intermediate, giving 28 species and 82.5 heads per 50cm square. As to vertical inhabiting distribution of soil insects, their population was much more concentrated in the upper soil layer than the lower layer. This trend was the most intensive in case of orchardgrass sward, and in Ladino clover sward it was not so sharp. From these result, between the swards of clover and grass the fauna of soil insects is somewhat distinct, particularly the population density (number of heads per area) is remarkably different. Therefore, mixture or rotation of grass and clover may be useful to control soil pests.

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