Concerns about the genetic control and environmental influence of various stages of development including the grain filling period, and the relationship between early maturity and grain yield prompted this study. The experimental material consisted of two facultative and two winter wheat cultivars. A dial!el cross, excluding reciprocals, was also developed to provide an Fl generation. Information was collected for 14 traits and subjected to statistical analyses. Genetic differences among varieties were found for time of heading, flowering and physiological maturity, duration and rate of the grain filling period, grain yield and yield components. The facultative types, AI Feng 2 and Selection CB 83-52, showed earlier heading, flowering and physiological maturity, longer lag period (period between heading and flowering), and longer duration and lower rate of grain filling, resulting in lower grain yield. The winter cultivars, Stephens and Yamhill Dwarf, in contrast had later heading, flowering and maturity, shorter lag period, and shorter duration and higher rate of grain filling, giving higher grain yield. For the developmental stages after heading, larger differences were observed in the lag period while differences in duration of grain filling period were relatively small among the cultivars. Depending on the specific Fl population, there was a tendency toward dominance for early heading, a range from no to complete dominance for early flowering and no dominance for physiological maturity. Long duration and fast rate of grain filling were generally dominant. Grain yield was positively associated with the number of days to heading, flowering and physiological maturity. Also positive associations of grain yield were obtained with tiller number, kernel weight, grain weight per spike, biological yield and rate of grain filling. Negative associations of grain yield were noted with lag period and duration of grain filling period. No clear associations between physiological maturity and the yield components were found. Grain filling duration showed no association with yield components while grain filling rate exhibited positive association with tiller number and kernel weight. There was negative association between duration and rate of grain filling period. According to heading responses from different planting dates, Stephens and Yamhill Dwarf had high sensitivity while Selection CB 83- 52 and AI Feng 2 showed low sensitivity to vernalization. Genotype X environment interaction was observed with each cultivar responding differently for several traits depending on the planting dates.

The need to develop a shorter life cycle wheat cultivar which would be more adapted to multiple cropping systems prompted this study. Thus the following information was obtained. Greatest variations in developmental patterns were found in the stem elongation, booting, inflorescence emergence and anthesis for five winter and five spring cultivars when planted at different dates. Differences among the ten winter wheat cultivars in time, duration and rate of grain filling was also observed. Generally later flowering cultivars had a more rapid rate of grain filling than early flowering cultivars with the net result being that physiological maturity was similar between the two groups. Actual grain filling period from flowering to physiological maturity varied among the cultivars, but larger differences were observed in lag period from heading to flowering. The duration of lag period contributed to the largest difference in total grain filling period from heading to physiological maturity. Changes in visual spike color of the glumes and main axis of a spike was satisfactory in identifying physiological maturity without destruction of the spike; however changes in kernel color was a more direct and precise method. Physiological maturity is a better measure of the optimum harvesting time to provide for maximum grain yield for planting sequential crops. Grain yield was positively associated with time of heading, flowering, physiological maturity, rate of grain filling and components of grain yield, but negatively associated with duration of grain filling period, lag period and harvest index. There was little association with the duration of the actual grain filling period and grain yield. However, a large association was observed between grain yield and the rate of grain filling. The direct effects of tiller number and rate of grain filling on grain yield were consistently positive and high. The indirect effects of rate of grain filling on grain yield were positive and high via time of heading, flowering and physiological maturity, components of yield and whole plant dry weight, but negative and high via duration of grain filling period, lag period and harvest index.

Sept.-Oct. issue includes list of theses and dissertations for U.S. and Canadian graduate degrees granted in crop science, soil science, and agronomic science during the previous academic year.

The lack of information regarding the inheritance of the duration and rate of grain filling, and the possible relationship between grain fill and grain protein content in wheat prompted this study. Early maturing Chinese cultivars, 'AI Feng 2' and 'CB 83-52', and late maturing cultivars adapted to Oregon, 'Stephens' and 'Yamhill Dwarf', were examined for vernalization and photoperiod responses. Progeny from a diallel cross of the genotypes was evaluated for grain filling parameters, grain protein content and other agronomic traits for two years. 'Yamhill Dwarf' required six weeks of vernalization, while other cultivars needed only four weeks. The two Oregon developed genotypes were more sensitive to photoperiod than Chinese genotypes. Variation in developmental patterns among genotypes was related to differences in leaf number, spikelet number, rate of spikelet initiation, and rate of grain fill. Compared to solid planting, space-planting reduced the grain filling period. Significant genotypic variation for grain filling rate, duration, and kernel weight was observed in both seasons. Genotype X year interaction was not significant for any of the grain filling traits. General combining ability effects for grain filling rate, duration, and kernel weight were much larger than specific combining ability effects. Additive gene action made the major contribution to the inheritance of the grain filling traits. However, dominance effects appeared also to be involved in the genetic control of grain filling duration and kernel weight. Narrow sense heritability estimates were high for all three grain filling traits. Results indicated that early generation selection for both duration and rate of grain fill should be effective in these populations. Rate, but not duration of grain fill was closely associated with kernel weight. There was an inverse relationship between duration and rate of grain filling. Kernel protein percentage was positively associated with duration, but negatively related to rate of the grain filling. Results suggest that starch and protein accumulations in the kernel are two highly independent processes and may not necessarily compete for assimilates or energy. It may be necessary under the environments of this study to increase the duration of the grain fill to obtain high protein content with acceptable grain yield.

The grain yield of winter wheat (Triticum aestivum L.) increased over time through plant breeding, and preliminary research suggested that yield response to fertilizer differs in modern versus historical genotypes. However, this response is not universal. We hypothesize selection for yield may have unintentionally modified the dynamics of nutrient uptake and partitioning in the plant. Thus, our objectives were to identify the key shifts in crop phenotype, in above-ground biomass and in dynamics of nutrient uptake and partitioning during vegetative and reproductive phases in response to selection for yield and to in-furrow fertilizer. Field experiments were conducted in four Kansas environments in a factorial trial combining eight winter wheat varieties released between 1920 and 2016, and two fertilizer practices (control versus 112 kg ha−1 in-furrow 12-40-0-10-1). Grain yield and grain N-removal increased non-linearly with year of release (YOR), with greater increases between 1966 and 2000. In-furrow fertilizer increased yield in ~300 kg ha−1 with no variety x fertility interactions. Grain protein concentration (GNC) related negatively to yield, and the residuals of this relationship were unaffected by YOR. Yield increase in semi-dwarf varieties were associated with shorter vegetative period and longer grain filling period, and more kernels m−2 derived from more kernels head−1. Historical varieties were taller, had thinner stems, and allocated more biomass to the stem than semi-dwarf varieties. At grain filling and maturity, shoot biomass was similar among varieties but semi-dwarf varieties allocated more dry matter to the kernels, suggesting that increases in yield derived from greater harvest index (HI) rather than greater biomass. Whole plant nutrient concentration negatively related to whole plant biomass and increased over decades for N, P, and S and decreased for K. In-furrow fertilizer increased the concentration of all nutrients. Grain-N, P, K, and S uptake increased from historical to semi-dwarf varieties; thus, nutrient HI increased with YOR, with greater increases between 1966 and 2000. Nutrient HI decreased with in-furrow fertilizer as the fertilizer increased biomass allocation to the vegetative tissues more than to the grain. Nutrient allocation rate to the head related positively to whole plant uptake rate, and YOR increased the head allocation rate for N, K, and S. There were positive and significant relationships between NHI and the HI of P, K, and S. Whole plant N uptake and P, K, and S uptake were also positively related, with ratios of 9.2, 1.1, and 15.4 for N:P, N:K, and N:S. Direct selection for grain yield modified the dynamics of nutrient uptake and partitioning over time, with semi-dwarf varieties allocating more N, P, K, and S to the grain. The ability of modern varieties to allocate more biomass and nutrients to the grain, coupled to an early maturity and longer grain filling period, increased grain yield and grain N-removal over time. However, increases in yield were greater than those in N-removal, reducing GNC. In-furrow fertilizer increased grain yield, biomass, and grain N, P, K, S uptake; nonetheless, the lack of variety x fertility interaction suggested variety response to fertility was similar.

Four winter wheat cultivars, Bezostaya, Maris-Hobbit, Roussalka and Stephens, selected on the basis of the diversity of their pedigree and phenotype, were planted at Hyslop Experiment Station near Corvallis in Western Oregon to study their performance at three different row spacings (10, 16 and 24 cm), three seeding rates (100, 160, and 240 Kg/ha) and at two seeding dates (October 13 and November 12). A similar experiment was conducted at the Sherman Experiment Station, Moro in Eastern Oregon, using only two winter wheat cultivars, Stephens and Jackmar. Data were obtained on grain yield, tillers and spikes per square meter, heading and anthesis date, plant height, kernels per spike, 1000 kernel weight, test weight and harvest index. At Hyslop Experiment Station, Stephens, Bezostaya and Roussalka produced maximum grain yield at 10 cm row spacing and 160 Kg/ha seeding rate, and Maris-Hobbit at 24 cm row spacing and 160 Kg/ha seeding rate. At Sherman Experiment Station, 30 cm row spacing and 90 Kg/ha seeding rate constitutes the best combination for Stephens, and 30 cm row spacing and 120 Kg/ha seeding rate for the club wheat Jackmar. The interaction between row spacings x cultivars and seeding rates x cultivars indicated that all the cultivars produced high numbers of tillers and spikes per m2 at narrow (10 cm) row spacing and high (240 Kg/ha) seeding rate. There were no significant differences between row spacings for heading and anthesis date. Lower seeding rate resulted in later heading date. The cultivar Roussalka was the earliest and Maris-Hobbit the latest in average heading date, Plant height decreased with increased row spacing and increased with increased seeding rate. The plants of the four cultivars were shorter at the second date than at the first. More kernels per spike were produced at the second than at the first date. An increase in seeding rates was accompanied by a decrease in the number of kernels per spike. There were no significant differences between the three row spacings, the three seeding rates and the four cultivars for test weight. The different row spacings and seeding rates did not affect the TOGO kernel weight. Considering the cultivars, Stephens produced a higher 1000 kernel weight at the two seeding dates than Maris- Hobbit, Bezostaya and Roussalka.

The objective of this study was to determine interrelationships among agronomic traits in early and late maturing populations. Two populations were obtained from the crosses, Roussalka/Tesopaco 76 and Yamhill/Aspen. Seeds were space planted with split plot design and nine agronomic traits were observed. In comparative studies between early and late populations, the early population was earlier in heading date, maturity date, longer maturity duration, heavier kernel weight, and higher harvest index. However, it was shorter in plant height, had fewer tillers, kernels and lower grain yield than the late population. Grain filling duration expressed positive relationships with grain yield in both crosses, although the correlation coefficient with grain yield was very low compared to other agronomic traits. Grain filling duration showed consistent positive relationships with kernel weight in both populations and with kernel number in the late population. No relationship was found between grain filling duration and tiller number. Grain filling duration influenced grain yield mainly by the indirect effects of kernel weight and kernel number. Yield components generally showed high positive relationships with grain yield; tiller number being the most important, followed by kernel number, and kernel weight. Competition among yield components was minimal in this space planted study. Heading date showed a negative association while plant height and harvest index expressed high positive relationships with grain yield.