Search

The relationships of grain yield to plant height and yield components in spring wheat (Triticum aestivumL.) were studied in two yield nurseries in 1971 and 1972 at Bozeman, Montana, in order to determine if selection should be directed at yield, or at yield components. Genetic and environmental effects were separated by correlation analysis and analysis of variance. Correlation coefficients computed with various combinations of replications, years, and cultivars or selections (genotypes) showed that cultivars account for most of the variation among both plant height and yield component comparisons. Simple correlation coefficients showed that grain yield was more closely related to heads/4.9 m than with kernels/head or kernel weight. A multiple correlation analysis between grain yield and yield components was found to be significant for only one of the two nurseries. Simple correlations among the three yield components were either negative or of a nonsignificantly positive value. We were unable to determine whether selection should be based on grain yield or on one or more of the yield components. However, the r values among yield components provided very small R2values, suggesting that compensating effects among yield components were small in this study.

Dry weight and nitrogen content of leaves, stems, kernels, and roots were determined for five spring wheat varieties on seven dates. Maximum leaf development occurred by July 19 (flowering), and maximum stem development ocurred by July 29 (filling). By August 19 (maturity) the top weights were similar for all varieties except ‘Mindum’, which was significantly higher. The average ratio of root (to 5‐ft depth) to top growth on August 19 was 1:14.9. Uptake of nitrogen continued until harvest, although the rate was much slower after July 19. Nitrogen content in the roots was low at all sampling dates, indicating rapid translocation to aboveground parts. If all root nitrogen had been translocated to the kernels, the effect on kernel nitrogen would have been insignificant. The average ratio of root to top nitrogen on August 19 was 1:23.4. The rvalue of 0.95 between pounds of kernel nitrogen and pounds of top dry weight indicates that 90.2% of the variation in kernel nitrogen in this experiment is due to differences in plant dry weight. This leaves only 9.8% of the variation in kernel nitrogen which the plant breeder might be able to manipulate. We suggest that if wheat varieties which will translocate as much as 70% or more of leaf and stem nitrogen to the kernels can be found, they might be useful in breeding programs.

We have investigated the relative pollen‐shedding abilities of 11 hard red spring and 3 durum wheat varieties and the relationships between pollen‐shedding and other varietal characteristics. The varieties differed in amount of pollen shed, number of pollen grains/anther, percent anthers extruded, tillers/plot, fertile florets/plot, fertile florets/tiller, yield, and kernel weight. Anther extrusion varied from 72% for ‘Thatcher’ spring wheat to 22% for ‘Lakota’ durum wheat. Number of pollen grains/anther varied from 3,867 for ‘Rescue’ to 2,687 for ‘Fortuna’ spring wheat. The amount of pollen shed was positively correlated with percent anthers extruded and tillers/plot but negatively correlated with fertile florets/tiller. Path coefficient analysis indicated that percent anther extrusion had the largest direct effect on pollen shedding. Pollen shedding ability of a variety was predicted on the basis of percent anther extrusion, pollen grains/anther and fertile florets/plot.

UV-mikrospektrophotometrische Messungen der Nucleinsäuren- und Eiweißkörper-Konzentration sowie der Kern- und Nukleolengröße nach Virusinfektion und unspezifischer Reizung der Chorion-Allantoismembran zeigen, daß es in beiden Fällen zu einer gleich starken Stimulierung des nucleinsäuren- und eiweißkörperbildenden Systems der Zelle kommt. Bei der Infektion mit Vaccinevirus auf das Ektoderm setzt die Reaktion der Membranzellen in der Eklipse ein, nach Infektion mit Newcastle-Disease-Virus fällt der Titeranstieg mit der Zellreaktion zeitlich zusammen.

Samples of high and low grain protein content (%) were compared from each of eight spring wheat crosses. The high protein samples were obtained by compositing 14 F3progeny rows from the high end of the F3distribution curve; the low protein samples were obtained similarly from the low end of the F3distribution curve. These composites were seeded at three Montana locations and evaluated for agronomicharacteristics and for grain and plant nitrogen to help determine the nature of the expression of grain nitrogen content in spring wheat. Grain nitrogen content was negatively related to grain yield and to the graln‐straw ratio. High and low protein composites at Bozeman produced the same amount of above ground plant nitrogen, and each translocated the same percent of nitrogen to grain. However, grain nitrogen content of the high protein composite was significantly higher because of the distribution of a similar amount of nitrogen to a smaller amount of grain. Differences in plant growth characteristics among the eight crosses seem to account for the differences in grain nitrogen content.