Density and spatial arrangement (rectangularity) effects on the competitive relationships, yield performance, and dynamics in canopy dominance of winter wheat and Italian ryegrass were evaluated using two addition series experiments. In experiment 1, combinations of six densities of each species formed the treatment matrix of addition series. In experiment 2, each species was tested at four densities and three rectangularities (RE) of winter wheat. In monocultures, crop density (plants per square meter) explained 82 to 85% of the total variation in the per-plant biomass of winter wheat in experiment 1. In mixtures of crop and weed, initial wheat density (N1) and initial ryegrass density (N2) and interaction of N1 and N2 explained 74 to 80% of the total variation in the per-plant biomass of winter wheat and 68 to 79% of Italian ryegrass in experiment 1. Intraspecific competition was apparent between 15 and 90 days after emergence (DAE) in winter wheat and between 90 and 170 DAE in Italian ryegrass. In mixtures, RE influenced plant size of Italian ryegrass up to 50 DAE only. Maximum winter wheat intraspecific competition occurred at 170 DAE, but maximum interspecific competition occurred during reproductive stages in mixtures. High RE increased seed yield, and harvest index of winter wheat and reduced biomass of Italian ryegrass. Grain yield of winter wheat was reduced up to 92% by competition from ryegrass. Even nine ryegrass plants in 100 winter wheat plants m(-2) reduced winter wheat grain yield by 33%. However, the extent of loss in winter wheat grain yield was less in RE 16 (wider spacing) than in RE 1 (square planting) or 4 (close row spacing). Winter wheat was the stronger competitor during vegetative stages, but Italian ryegrass became the stronger competitor during the reproductive stages of development. Winter wheat leaves dominated at the top canopy during the reproductive stage, but ryegrass dominated at the top canopy during the reproductive stages. In the top canopy of mixtures at 200 DAE, the leaf area indices (LAI) of ryegrass was 6.6 times greater than winter wheat at RE 1 compared to only 1.6 times at RE 16. Greater LAI of Italian ryegrass in the top canopy reduced photosynthetically active radiation available to winter wheat by 68% at booting stage.

Cultivation for early winter seeding of spring wheat is tested to extend growing periods and to make the wheat mature earlier in central Hokkaido, where soils \are covered by snow but don't freeze in winter. In varietal trials using winter and spring wheat varieties at Naganuma, when the plants emerged and grew 1-2 leaves before continuous snow covering, two winter wheat varieties could survive 61.0-100% if seeding plants until spring, and three spring wheat varieties showed a large annual variation (0.4-54.9%) for their winter survivals. On the other hand, when the emergence did not occur before continuous snow covering, all five varieties survived at a relatively high rate. In seeding date trials using spring wheat cv. "Haruyutaka" at 3 locations (Naganuma, Shibetsu, and Pippu), the mean values for accumulated soil temperature and accumulated air temperature from seeding to emergence in early winter seeding was 140 degrees C and 115 degrees C, respectively. On a basis of the past climate trend at some points in central Hokkaido, we considered that an earliest limit of a seeding date for early winter seeding of sprig wheat if plants were to survive safely in winter was about 20-25 days before the average date of continuous snow covering

In the year 1997 distinct injures on winter wheat cv. Kobra were stated strongly resembling symptoms of infection caused by Fusarium. On prematurely ripening plants a partial or total yellowing of ears was observed, and lower parts of internodes showed brown discoloration. It was stated after cereful examination that culms and ears were infested with numerous mites, Tyrophaguslongior (Gerv.), not by species of Fusarium. The mites probably contributed to decrease in grain yield. Kernels were small and underdeveloped which influenced the decrease of quality of seeding material

We investigated the feasibility of cold hardiness manipulation in wheat, Triticum aestivum L., with the Vrn1-Fr1 interval on chromosome 5AL. The interval contains a gene(s) that has influenced vernalization requirements and cold hardiness levels. We conducted LT₅₀ tests (lethal temperature of 50% of plants) on wheat NILs (near-isogenic lines) that differed for alleles at the Vrn1-Fr1 interval, to determine the effects of the interval on cold hardiness levels between hardy and nonhardy wheat. The NILs were derived from five backcrosses between a spring wheat recurrent parent, ‘Marfed’, and two winter wheat donor parents, ‘Suweon 185’ and ’Chugoku 81’, hardy and nonhardy, respectively. The developed populations were Suweon 185/6*Marfed and Chugoku 81/6*Marfed spring and winter NILs. Results showed that the winter NILs could tolerate a 4.3 °C colder LT₅₀ score than the spring NILs, and that the Suweon 185/6*Marfed winter NILs could tolerate a 0.5 °C colder LT₅₀ than Chngoku 81/6*Marled winter NILs. Results indicate that the Vrn1-Fr1 interval explained between 71 and 91% of the variation for LT₅₀ scores between these genotypes. The NILs were analyzed with the probe Xwg644 to confirm linkage with the Vrn1-Fr1 interval and to determine its utility as a marker for vernalization requirement and cold hardiness. EcoRI-digested DNA of the winter and spring NIL wheat, probed with Xwg644, showed that a 9.7-kb band co-segregated with the winter growth habit. Results indicate that differences in cold hardiness levels between winter wheat cultivars may be explained by this interval and that the interval may be manipulated through plant breeding to improve the cold hardiness of cultivars.

Coefficients of parentage values of 200 Czech and Slovak winter wheat cultivars released from 1919 to 1997 were used to estimate the latent diversity within winter wheat gene pool. Cluster analysis, based on the coefficient of parentage matrix, resulted in 18 major clusters of related cultivars. Changes in genetic diversity through the time were estimated by averaging coefficient of parentage for all possible combinations of cultivars released within a 10 year period. Since 1950s the genetic similarity of Czech and Slovak winter wheat cultivars varied around the level of quarter sibs similarity. The most commonly used parents of cultivars released in different time periods were determined on the basis of direct contribution to the parentage of current winter wheat cultivars.

An experiment to investigate the influence of sowing time on the yield formation of winter triticale was performed at the Dept. of Field Crop Husbandry in 1996/97. Triticale cv. 'Modus', 'Dato', 'Presto' and Sv 92280' were compared to winter wheat 'Sirvinta' and rye 'Vambo'. Depending on the share of yield components, grain yields were highest in triticale cv. 'Modus' (7273-8101 kg ha sup(-1) depending on sowing time). Both rye cv. 'Vambo' and winter wheat 'Sirvinta' yielded less, 5279-6466 and 2524-4551 kg ha sup(-1), respectively. Lower grain yield of winter wheat was associated with smaller grain number per ear, and in case of rye, lower 1000 kernel weight compared to those of triticale

Preliminary investigations on weed control with the use of mechanized weeding techniques were presented. Tests were carried out in winter wheat and spring triticale fields using a weeder type harrow. Twofold harrowing of the fields reduced weeds by 60% in winter wheat and by 49% in spring triticale. However, the yield decrease by 10% in winter crop and by 18% in spring crop were observed

Research was conducted in 4 states (Colorado, Montana, Texas, and Washington) to determine the economic injury level for the Russian wheat aphid, Diuraphis noxia (Kurdjumov), as affected by climate zone and wheat growth stage. Fall infestations were established on winter wheat at the 2-leaf and 2-tiller growth stages. Russian wheat aphid infestations did not develop well on the 2-tiller stage wheat because late fall temperatures became too cold before the infestation period was complete. In the coldest climate zones, where winter kill of wheat becomes a factor, the loss value for 2-leaf wheat will be 1% per percentage infested or damaged tillers and 1.1% per infestation or damage day. This was 3 times greater than the loss in the southern climate of Texas and 1.6 times greater than the loss in the Pacific Northwest (Washington). Therefore, different fall infestation economic injury levels will be used in different climate zones in the United States. Russian wheat aphid infestations on winter wheat were initiated in the spring at spring regrowth, one node, and boot growth stages. Losses from Russian wheat aphid infestations in Colorado in the spring were similar to those reported in earlier research in Texas, 0.5% loss in bulk seed weight per percentage of infested or damaged tillers.

The AACC Approved Method for near-infrared reflectance (NIR) spectroscopy to produce a wheat hardness score for wheat market classification can be corrected for variation in wheat moisture content. The cause of the variation in NIR spectra resulting from variation in wheat moisture was investigated. Ten samples each of soft red winter, soft white winter, hard red winter, and hard red spring wheats were stored at 20, 40, 60, and 80 equilibrium relative humidity. Wheats were then ground on a cyclone grinder as required by the standard method. Variation in unground wheat kernel moisture content resulted in variation in NIR data. NIR log l/reflectance values increased at all wavelengths as wheat moisture content increased. Spectral changes were related to changes in the apparent particle size of ground wheat meal as it was influenced by moisture content. Higher moisture contents produced slightly higher apparent particle size in meal, suggesting larger particles of pericarp that became more pliable at higher moisture (temper) levels. The apparent particle size of meal of high moisture wheats resulted in greater NIR radiation scattering and decreased reflectance. Meal moisture content itself had no effect on the two NIR wavelengths used to evaluate wheat hardness.