A Genetic Study of Yield Components in Three Populations of Winter Wheat (Triticum Aestivum L. Em Thell) PDF Download

Author: William Larry Alexander
Publisher:
ISBN:
Category :
Languages : en
Pages : 86

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Author: Michel Abi-Antoun
Publisher:
ISBN:
Category : Wheat
Languages : en
Pages : 228

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Five winter wheat cultivars and their diallel crosses were evaluated for plant height, harvest index, deading-maturity duration, the components of yield, (spikes per plant, spikelets per spike, kernel weight and kernels per spikelet)and total plant yield. Two diverse locations, Moro, a dryland site (250 mm annually) located in central Oregon and the Hyslop Agronomy Farm, a high rainfall site (over 1000 mm annually) located in the Willamette Valley, were utilized for one and two cropping seasons, respectively. Three rates of seeding were used as main plots in a split-plot design that was replicated four times. A modified blend method of seeding was used to simulate solid seeding conditions. Experimental seeds were planted 30.5 centimeters apart within the row over a filler cultivar in equally spaced (30.5 centimeters) rows. The data were analyzed by analysis of variance, Griffing's diallel analysis (Method 4, Model 1), correlation, path-coefficient analysis and by parent progeny regression. The correlation between grain yield, its components, harvest index, maturity-duration and plant height was dependent on the particula. r environment of the test. The re waspoorcorrelationbetween yield, tiller number and seed size under all the conditions of these studies. Negative associations between the components of yield indicated the sequential compensatory behavior of these characters under all environments. It would be very hard to select for large grain and short stature wheat because of the positive correlation between plant height and seed size within this population. The low correlations of yield with tiller number and seed size were mainly caused by indirect negative effects through one or more of the other yield components. Harvest index, maturity-duration and plant height had very small direct or indirect influences on grain yield. It was concluded that maximum yield would be obtained from a plant type which produces enough tillers to cover a particular unit of field area with large, fertile spikes, having medium to large kernels and semi-dwarf stature. No significant differences existed between parents and single crosses in the expression of the yield components. Nevertheless, hybrids outyielded their parents in grain yield and demonstrated that heterosis for complex traits was a consequence of multiplicative relationships among the components of these traits. Significant interactions between the genotypes and locations, seeding rates and years were observed in the expression of all characters studied. These interactions indicated that using data from non-competitive conditions to assess performance under competitive conditions could not be justified. Also, limiting the number of testing sites may lead to unsound generalizations and erroneous recommendations regarding gene action estimates of yield and the components of grain yield and three associated characters. Under non-competitive conditions, estimates of the additive type of gene action were more significant and contributed larger effects than the non-additive type for all traits. As competition increased at higher seeding rates, the effects of specific combining ability became more important in the expression of yield, number of spikes, spikelets per spike, and plant height. Heritability estimates confirmed these results except for yield. Of the agronomic characters, harvest index, maturity-duration and plant height, only harvest index showed some promise as a selection criterion under noncompetitive conditions. A breeding procedure utilizing the component approach consisted of selecting early generations under spaced planting with emphasis on avoiding extreme values in any of the components of yield. The balanced combinations of the components of yield should be tested under solid seeding conditions.

Author: P. Brajcich
Publisher:
ISBN:
Category : Wheat
Languages : en
Pages : 300

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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: Ruben P. Verges
Publisher:
ISBN:
Category : Winter wheat
Languages : en
Pages : 170

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The objective of this study was to compare three genetically different groups of winter wheat for their grain yield. Experimental material consisted of parental lines grown in pure stands, hybrids, and 1:1 mixtures of the parental combinations. Three sites were employed to evaluate possible interactions between the different groups across locations. Phenotypic correlations among selected agronomic traits and grain yield within each group along with the expression of heterosis and heterobeltiosis in the hybrids were studied. Results of this investigation support the general conclusion reached by other investigators that hybrids and composites are not consistently superior to the best conventional cultivars of wheat for grain yield. However, at the Moro site, with the greater environmental stresses, some hybrids and composites appeared to yield more than the parental lines grown in pure stands. At Pendleton, the best environment for yield expression, the hybrids and conventional cultivars did not differ for grain yield. At this location, the best hybrids and one composite did significantly outyield the commercial cultivars Stephens, Malcolm and Hill, but not four advanced parental selections when grown in pure stands. Low to moderate values of heterosis and heterobeltiosis for grain yield were found. The degree of expression being affected by the specific growing site. Plant height and the number of kernels per spike showed relatively higher values for heterosis and heterobeltiosis over locations when compared to the other traits. Phenotypic correlations suggested that a breeding program to develop hybrid wheat should combine high number of kernels per spike with high kernel weight. The positive correlation between grain yield and plant height indicated that increases in grain yield could be obtained by increasing plant height if lodging did not present a problem.

Author: Satender Yadav
Publisher:
ISBN:
Category :
Languages : en
Pages : 197

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Author:
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Category : Agriculture
Languages : en
Pages : 388

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Includes abstracts of the annual meetings of the American Society of Agronomy; Soil Science Society of America; Crop Science Society of America ( - of its Agronomic Education Division).

Author: Jose Juan Salmeron-Zamora
Publisher:
ISBN:
Category : Wheat
Languages : en
Pages : 210

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This study was undertaken to see if a method of handling segregating populations could be employed which combined the positive attributes of the traditional pedigree and-bulk methods. Derived F5 lines from the pedigree, bulk, and what is identified as a modified bulk method, were obtained from three winter wheat crosses. The effectiveness of the methods, representing different cycles of phenotypic selection, were evaluated in terms of plant height, plant ideotype and indirectly kernel weight and grain yield. To assess differences in levels of heterogeneity in relation to possible line x environment interactions, the material was grown at three diverse experimental sites. The modified bulk method was as effective as the pedigree method in establishing the desired semi-dwarf height level. Due to the competitive advantage of taller plants, dwarf and semi-dwarf height levels were eliminated in the unselected populations resulting from the bulk method. Although differences were observed for kernel weight between methods, no consistent trends for this trait were established when crosses and locations were considered. Based on the combined mean values of the F5 lines for each method across and within locations, the modified bulk method was superior for grain yield in only one cross. However, when individual F5 lines were compared, a higher percentage of lines obtained from the modified bulk method were superior across and within locations in two of the crosses. Data from this study suggests that to reduce the variety x environment interaction it is important to maintain a level of genetic heterogeneity within varieties. The modified bulk method does appear to be an efficient compromise in handling segregating populations when compared to the traditional pedigree and bulk methods. It is also more efficient in terms of maximizing limited resources which can be important in developing countries where funds and trained scientist are limited.

Author: F. H. McNeal
Publisher: Forgotten Books
ISBN: 9780260389077
Category : Business & Economics
Languages : en
Pages : 20

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Excerpt from Thirty Years of Testing Winter Wheats, Triticum Aestivum L. Em Thell., In the Western Wheat Region: Interstation Correlations of Grain Yield With Varietal Comparisons The State experiment stations of Idaho, Oregon, Utah, and Washington cooperated in growing the first regional winter wheat nurs ery in 1931, and workers in California and Montana have also contributed information to this program at various times. The Western Regional wheat-testing Program has been continued since 1931. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.

Author: Terd Charoenwatana
Publisher:
ISBN:
Category : Wheat
Languages : en
Pages : 152

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The effectiveness of early generation selection for yield and yield stability and the possible identification of superior parental combinations were studied in winter wheat populations representing different levels of genetic diversity. Experimental material for evaluating yield stability consisted of nine bulk and seven modified bulk populations derived from nine parental combinations which represented the F, F9, and F10 generations. The F9 and F10 generations of nine bulk, nine modified bulk and two modified pedigree populations along with the respective parental populations were studied to determine the relationship of yield to genetic diversity. Linear regression of the mean yield of individual entries on the mean yield of all entries for each year was used to describe yield stability. Grain yield differences among populations and crosses were analyzed by a functional analysis of variance. The modified bulk populations were found to be superior to their respective parents in yield and to the bulk populations in yield and yield stability. The modified pedigree populations had the highest yield of all populations measured. It was concluded that populations with high genetic diversity not only do not produce the highest yield but may not provide the greatest stability of yield. Selection for grain yield in the F4 generation was effective in identifying superior segregates. It was also possible to develop populations which had more yield stability. The highest yielding progeny were obtained from crosses between the medium yielding parents rather than between the highest yielding parents. This suggested that parental performance was of limited value in predicting the yielding ability of their resulting progeny. Therefore, selection for suitable parental combinations could not be based on their individual performance in the present study. It appeared that genetic factors for adaptability are as important as the level of genetic diversity in determining yield stability. A breeding system that allows the breeder to identify and incorporate genetic factors for adaptability and still maintain some genetic diversity in a new variety is suggested. Such a breeding system would prolong the length of time a variety could remain in commercial production and would allow such a variety to be grown over a more extensive range of environments.

Author: Ahmet Ertug Firat
Publisher:
ISBN:
Category : Wheat
Languages : en
Pages : 280

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Parental and segregating populations derived from four winter x spring wheat crosses were investigated to obtain information concerning the inheritance and association of earliness, grain yield and yieldrelated traits. Feasibility of selecting in early generations for these characteristics was also evaluated. Four winter wheat cultivars (Hyslop, Yamhill, Bezostaia 1, and Sprague) and one spring wheat cultivar (Inia 66) were chosen on the basis of their relative maturity and contrasting agronomic characteristics. Parents, F1 s, F2' s, and reciprocal backcrosses to both parents were planted in the fall in a space-planted randomized complete block design. The two environmentally diverse locations selected were the Hyslop Agronomy Farm, Corvallis, Oregon (1000 mm of rainfall) and Sherman Experimental Station, Moro, Oregon (250 mm of rainfall). The effectiveness of early generation selection for the measured characteristics was evaluated by growing F3 lines identified as the earliest 1% and the highest yielding 1% of F2 individuals in each cross. These were grown along with the parents, F1s, BC1 s, BC2 s and F2' s under space-planted conditions at Hyslop Agronomy Farm. A study with the same populations was conducted by vernalizing and planting in the spring to gain further information on earliness. Analyses of variance were conducted for all characteristics measured. Frequency distributions for days to heading of F1, F2, backcross generations and parents were examined. From the data collected, estimates of F 1 -midparent deviations, degree of dominance, heritability in the narrow sense and genetic advance under selection were determined for each cross. The data were further analyzed by parent-progeny regression, correlation and path-coefficient analyses, polynomial and multiple regressions. Partially dominant major genes, varying in number between one to five depending on the particular cross, appeared to influence heading date. Modifying factors also seemed to affect the date of heading. The gene action involved in the inheritance of earliness was primarily additive indicating that selection for earliness would be effective as early as the F2 generation under both high and low rainfall conditions. Estimates of additive and nonadditive gene action suggested both were equally important in determining the yield components. Higher heritability estimates for the components of yield indicated that there was more genetic variability associated with the yield components than yield per se. Occurrence of additive genetic variation by location interaction implied that selection should be practiced simultaneously under different environments if wide adaptability of potential lines is desired. Since pronounced additive effect by year interactions occurred for the yield components, delayed selection for these traits may not be productive. Positive correlations were obtained between yield and the number of days to heading when all generations were combined. However, in the F2 generations, it appeared possible to select for the desired earliness with high yields as indicated by the low association between these two traits. The path-coefficient analyses suggested that tiller number had the highest direct effect on grain yield. However, because of a negative association between tiller number and kernel weight, selection pressures would have to be balanced between these two components. In most cases, linear relationships existed between grain yield and seven measured traits, respectively. The result of regression analyses also showed that grain yield may be described best as a linear function of its components.