Author: Clarence James Peterson Publisher: ISBN: Category : Wheat Languages : en Pages : 222
Book Description
Seven winter wheats were evaluated for plant height, the components of yield and yield in a diallel cross at Pendleton, Oregon and Lind, Washington. An additional parent was added to the diallel cross at Pullman, Washington. Two levels of nitrogen and five replications were utilized at each of the locations. Ten seeds of each F1 or parent were blended with 200 seeds of WA 4303 and seeded in a ten foot row. This was done in order to simulate a solid seeding with the limited amount of F1 seed. The data were analyzed by using Griffing's diallel analysis, Method 4, Model 1. The morphological traits measured were: heading date, kernels per spike, spikelets per spike, kernels per spikelet, weight per 1000 kernels, kernels per plant, spikes per plant and yield per plant. In an effort to obtain an unbiased combining ability estimate, a blend method of seeding (F1's mixed with a short semidwarf WA 4303) was used in order to simulate solid seedings. A comparison between the solid and blend seedings indicated, however, that WA 4303 did not exert the same influence on all hybrids. The estimate obtained should be less bias than those results obtained from other investigations where space or hill plantings were utilized. Significant general combining ability estimates were associated with all measured traits within the six environments, except for kernels per plant (high fertility) at one location. Specific combining ability estimates were significant for all traits at one location. Only part of the measured traits exhibited significant specific combining ability effects at the other two locations. Under the environments where specific combining ability estimates were significant they were larger than those for general combining ability for most traits. The lines utilized in this study were previously selected on the basis of their yielding ability. Therefore, the additive portion of the total genetic variance had already been maximized. The high specific combining ability estimates were attributed to this previous selection for additive gene action in addition to the nonadditive gene action which resulted from crossing of the selected lines. Heterosis and heterobeltiosis were exhibited by some hybrids for all measured traits and within all six environments. Heterosis and specific combining ability estimates were not always in close agreement which could result in some confusion in determining which crosses would perform best in a specific environment. These data would indicate that specific combining ability is a valid estimate of the total amount of nonadditive genetic variance present but in addition the additive genetic variance and the multiplicative action of the components are important and contribute to heterosis. The influence of the environmental-genotypic interaction as measured across locations was greater for specific combining ability estimates than that for the estimates of general combining ability for all traits measured. This suggests that the nonadditive genetic variance is more susceptible to changes in environmental conditions than is the additive portion of the total genetic variance.
Author: Surinder Kumar Saini Publisher: ISBN: Category : Wheat Languages : en Pages : 138
Book Description
The F2 progeny from a diallel cross involving seven winter wheat parents along with the parents were grown at the Hyslop Agronomy Farm near Corvallis, Oregon to determine the influence of three plant densities on gene action estimates for yield and its primary components. The plant densities were designed to provide different levels of competitions involving solid, six and 12 inch spacing within the rows with one foot spacing between the rows. Gene action estimates were obtained by the combining ability analysis as well as narrow sense heritability estimates. In addition, path-coefficient analysis was utilized to investigate the direct and indirect associations of the primary components of yield under different stresses of competition resulting from the changes in population densities. The morphological characters measured were 1) total yield per plant, 2) kernel weight 3) number of kernels per spikelet, 4) number of spikelets per spike, 5) tiller number and 6) plant height. A small additive gene action for yield was noted in the six inch spacing while additive gene action effects could not be detected in the 12 inch and solid plantings. Yield being a complex trait seems to be affected by the environmental changes resulting from different plant densities. Consistent general combining ability estimates were observed for kernel weight and plant height in all the plant densities, indicating a small genotype-environment interaction. In the spaced plantings additive gene action estimates were obtained for tiller number and spikelets per spike while there was no evidence of additive gene effects in the solid planting. No additive gene action was noted for kernels per spikelet in the 12 inch planting while six inch and solid plantings revealed considerable genetic variability. These results would suggest that the genotypes are susceptible to environmental fluctuations for the traits tiller number, spikelets per spike and kernels per spikelet. The correlation coefficients reveal that in spaced plantings tiller number, spikelets per spike and kernels per spikelet are significantly and positively related to yield. In the solid seeding only spikelets per spike was significantly associated to yield. When the four variables were considered in terms of their associations with yield it was observed in the F2 that in spaced plantings all the four components of yield have direct positive influence on yield. In the solid seedings however, spikelets per spike and kernels per spikelet had high positive direct effects on yield while tiller number and kernel weight showed a negative direct influence on yield. The data revealed that spikelets per spike and kernels per spikelet are the most important traits contributing towards yield. However, the results obtained with correlation coefficients indicate that a negative association existed between these two traits as well as between kernels per spikelet and tiller number suggesting the possible existence of a biological limitation between these components of yield. The results indicate that a breeding program with emphasis on the selection of plants in competitive conditions in the early generations may make the selection work more efficient. Moreover, increases in yield which considers each of the components separately or in combination of two or more would offer the most promise. By this procedure the breeder would take advantage of the large amount of additive genetic variances associated with each of the components and at the same time take into consideration any biological limitations which may exist.
Author: P. Brajcich Publisher: ISBN: Category : Wheat Languages : en Pages : 300
Book Description
This investigation was motivated by the apparent increase in genetic variability resulting from the systematic combining of gene pools represented by winter and spring types of wheats. It was the objective of this study to provide information regarding the nature of this genetic variability for nine agronomic characters in populations resulting from winter x spring crosses. Evaluations were made for: 1) the amount of total genetic variability; 2) the nature of the gene action making up this genetic variability using parent-progeny regression and combining ability analysis and 3) possible direct and indirect associations for traits which influence grain yield. Experimental populations which involved parents, Fl, F2 and backcross generations were grown at two locations where a spring and a winter environment could be utilized. At the winter site, the research was evaluated over a two year period. When the two experimental sites were compared, greater genetic diversity was observed at the spring site for maturity date, plant height, tillers per plant, kernel weight and grain yield. At the winter site, heading date, grain filling period, harvest index and kernels per spike were found to have more total genetic variation. From the expected mean square values, it would appear that the winter parents contributed more to the total genetic variation for most traits measured at both locations. A large genotype-location interaction was also noted suggesting that estimates of gene action and selection for adapted plant types can be done only at the specific winter or spring site. A large portion of the total genetic variation controlling the traits measured was due to additive gene action. However, at the winter site there was also a large influence of non-additive gene action associated with heading date, plant height, harvest index, tillers per plant, kernel weight, kernels per spike and grain yield. Of special interest was that at the winter site the most promising parental combinations could be predicted based on the general combining ability effects of the individual cultivars for each trait studied. Such data were not available for the spring site. Consistent and high correlations were observed between tillers per plant, kernels per spike and, to a lesser extent, kernel weight and grain yield at the winter location. Some negative associations were observed at the spring location between these traits and grain yield suggesting that yield component compensations were involved in the final expression of grain yield. The other characters measured did not reflect significant correlations with yield. When the correlation values were considered in terms of direct and indirect effects for specific traits, a large direct effect was noted for the three components and grain yield. The other traits exhibited small or no direct effects on grain yield but did have a slight influence on grain yield through tillers per plant, kernels per spike or kernel weight.
Author: Mark J. Larson Publisher: ISBN: Category : Genotype-environment interaction Languages : en Pages : 312
Book Description
Extensive research has been devoted to evaluating potential genotype-environment interactions. However, plant breeders are still in need of a simple way to describe how genotypes respond to different locations and years. In an environmentally diverse state like Oregon, significant genotype-environment interactions do occur The resulting lack of association between actual and genotypic potential yield performance makes it difficult to select genotypically superior lines. This study was prompted to evaluate the extent of such an interaction and compare various yield stability models. A significant genotype-environment interaction encompassing lines, environments, and years was discovered for each individual year analyzed and for the combined analysis of 1992, 1994 and 1995, and 1989 through 1994. Most lines evaluated during 1992, 1994 and 1995 were adapted to low yielding environments. However, two genotypes (OR880172 and OR880525) exhibited broad adaptation. Stephens and Mac Vicar were less adapted to the relatively high yielding Chambers site than the other genotypes tested during 1992, 1994 and 1995 due to Septoria tritici infections. The most stable genotypes during the combined 1992, 1994 and 1995 and 1989-1994 seasons were OR870831, Madsen and OR8500933H. Gene was the most desirable genotype based on stability and yield for both the combined 1992, 1994 and 1995 and 1989-1994 seasons. Due to an inability to adapt to higher yielding environments, the cultivar Rohde was the least stable genotype during the same combined periods. High and low temperatures and precipitation had minor yet significant effects on yield responses at all three sites during various periods identified. Advanced winter wheat selections and cultivars were grown in three diverse environments and compared over different time periods. Due to trial design and the objective of identifying superior genotypes from a set tested in target environments a combination of two methods, stability variance and a selection index, emerged as the most appropriate techniques. These approaches are considered the most appropriate because they use the mean of the trial as a gauge for measuring stability.
Author: Muluken Bayable Tadege Publisher: LAP Lambert Academic Publishing ISBN: 9783847311546 Category : Languages : en Pages : 84
Book Description
Stable genotype would not contribute much variation to the variance in productivity over a region. In practice, however, genotypes do usually interact with their environment and show wide variations in stability. Since crop productivity is usually subject to risk, breeders have to exploit the opportunity of genotype by environment interaction which describes how well each genotype will respond to different growing conditions. To analyze such interactions, a number of parametric and nonparametric statistical methods have been developed by different researchers. However, considerable debates of opinion still exist between the leading protagonists of the different statistical methods in identifying the best and most suitable procedure to be used for a specific data set or production environment. This Thesis work, therefore, provides information about the relationship among the various statistical methods. I hope this work will help plant breeders in judging which method will explain best for a specific data set and whether a genotype is widely or specifically adapted.
Author: Amanda De Oliveira Silva Publisher: ISBN: Category : Languages : en Pages :
Book Description
Understanding factors underpinning the variation in nitrogen (N) utilization efficiency (NUtE) [i.e., grain yield per unit of N uptake at maturity] is critical to direct future breeding and agronomic management strategies in wheat. However, no study has summarized changes in wheat NUtE across a wide range of environments. Further, the conservative behavior of producers to intensify management practices may have been contributing to the yield stagnation in the US southern Great Plains. Our goals were to: (i) perform a synthesis-analysis using published data to study NUtE in wheat, and (ii) conduct field studies to investigate the influence of genotype, environment, and management on grain yield and nutrient uptake. Results from our synthesis-analysis (n=529) showed a positive and curvilinear relationship between grain yield and NupMAT, indicating that opportunities to enhance yield through improving NUtE would only be possible at greater-than-average yield and N uptake levels. By measuring the effects of other reported variables on the residuals of the relationship between NUtE and N uptake, we observed that the variability in NUtE at particular levels of N uptake was greater for fall- than for winter-sown wheat, but it was similar for all wheat classes. The negative correlation between grain protein concentration and the residuals indicated a challenge to increase yield through improving NUtE with no penalties in grain protein. We conducted two field research experiments at difference sites during the 2015-16 and 2016-17 growing seasons in Kansas. In our experiment 1, we conducted on-farm experiments across three locations and two growing seasons in Kansas using 21 modern winter wheat genotypes grown under either standard (SM) or intensified management (IM) systems. Results showed that across all sites-years and genotypes, the IM increased yield by 0.9 Mg ha−1 relative to the SM. Even in the lowest yielding background condition, the IM outyielded SM, and expectedly, the yield response to IM increased with the achievable yield of the environment. The yield response of genotypes to IM was related to the responses of biomass between the two management systems rather than harvest index, strongly driven by improvements in grain number while independent of changes in grain weight, and related to improvements in N uptake. In our experiment 2, we evaluated the partial contribution of 14 management practices on grain yield and the accumulation of N, P, K and S during the growing season using a single bread-wheat genotype grown under four site-years. Fungicide was the main treatment affecting yield and nutrient uptake. Overall, all nutrients were accumulated at a similar proportion at each growth stage relative to their respective accumulation at the end of the season. Shoot concentration for IM seemed to maintain higher concentration of nutrients as compared to the SM control during the growing season. This was emphasized by the significant increase in nutrition indices for N and S from SM to IM control, indicating possible luxury uptake under IM. Hence, crop intensification strategies may alter nutrient uptake at the end of season, but will not affect timing and rate of uptake during the growing season.
Author: Clarence James Peterson
Author: Surinder Kumar Saini
Author: P. Brajcich
Author: Mark J. Larson
Author: John Luscombe Purchase
Author: Samuel Lee Shafer
Author: Muluken Bayable Tadege
Author: Amanda De Oliveira Silva
Author: Paul Norman Fox
Author: Badri Nath Kayastha