A Quantitative Trait Response Evaluation to Selection in the BS13(S) Maize (Zea Mays L.) Population PDF Download
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Author: Clinton J. Turnbull
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Category :
Languages : en
Pages : 246
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Seven cycles of half-sib recurrent selection were conducted in the BSSS maize population followed by ten cycles of S2 progeny recurrent selection. The population under S2 progeny recurrent selection is formally known as BS13(S). The selection criteria have always placed importance on high grain yield, low grain moisture, and reduced plant lodging. Two evaluations estimating the response of multiple agronomic traits in multiple response units including the population sampled at F[subscript IS] = 0, F[subscript IS] = 0.5, and F[subscript IS] = 0.75 levels of inbreeding, and multiple testcrosses of the population were conducted. The average response of grain yield in the F[subscript IS] = 0.5 and F[subscript IS] = 0.75 response units (i.e. inbred response units) of the population are significantly greater than the average responses in both the panmictic population and multiple testcrosses of panmictic population. There is no statistical grain yield response to selection in the F[subscript IS] = 0 response unit (panmictic population). A testcross of the panmictic population to BS13(S)C0 has an average response greater than the panmictic population indicating that the limited response in the F[subscript IS] = 0 response unit is not likely due to random genetic drift, however, the allelic frequencies are diverging from the progenitor population. Favorable responses have been observed for root lodging in all of the response units however, a limited response for stalk lodging exist. The response of grain moisture is inconsistent between the two evaluations likely as a result of inconsistent selection practices and the difficulty to select for this trait. We hypothesize that the most important reason for the realized lack of response in the panmictic population is due to a low inbred-outbred correlation and may be caused by an overdominant-like gene action within this population. To avoid the necessity for assumptions about gene action controlling the traits in maize and importance of additive and non-additive effects, the genetic gain equation must be developed in relation to the selection unit and target response unit (i.e. S1s, S2S, half-sibs, or full-sibs). This dissertation supports both the genetic gain equations reported by Wardyn (2006) and the hypothesis of overdominant-like gene action in this population reported by Edwards and Lamkey (2002).
Author: Clinton J. Turnbull
Publisher:
ISBN:
Category :
Languages : en
Pages : 246
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Book Description
Seven cycles of half-sib recurrent selection were conducted in the BSSS maize population followed by ten cycles of S2 progeny recurrent selection. The population under S2 progeny recurrent selection is formally known as BS13(S). The selection criteria have always placed importance on high grain yield, low grain moisture, and reduced plant lodging. Two evaluations estimating the response of multiple agronomic traits in multiple response units including the population sampled at F[subscript IS] = 0, F[subscript IS] = 0.5, and F[subscript IS] = 0.75 levels of inbreeding, and multiple testcrosses of the population were conducted. The average response of grain yield in the F[subscript IS] = 0.5 and F[subscript IS] = 0.75 response units (i.e. inbred response units) of the population are significantly greater than the average responses in both the panmictic population and multiple testcrosses of panmictic population. There is no statistical grain yield response to selection in the F[subscript IS] = 0 response unit (panmictic population). A testcross of the panmictic population to BS13(S)C0 has an average response greater than the panmictic population indicating that the limited response in the F[subscript IS] = 0 response unit is not likely due to random genetic drift, however, the allelic frequencies are diverging from the progenitor population. Favorable responses have been observed for root lodging in all of the response units however, a limited response for stalk lodging exist. The response of grain moisture is inconsistent between the two evaluations likely as a result of inconsistent selection practices and the difficulty to select for this trait. We hypothesize that the most important reason for the realized lack of response in the panmictic population is due to a low inbred-outbred correlation and may be caused by an overdominant-like gene action within this population. To avoid the necessity for assumptions about gene action controlling the traits in maize and importance of additive and non-additive effects, the genetic gain equation must be developed in relation to the selection unit and target response unit (i.e. S1s, S2S, half-sibs, or full-sibs). This dissertation supports both the genetic gain equations reported by Wardyn (2006) and the hypothesis of overdominant-like gene action in this population reported by Edwards and Lamkey (2002).
Author: Benjamin Aaron Ford
Publisher:
ISBN:
Category :
Languages : en
Pages : 374
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Increases in grain yield, the primary trait for selection, include a direct response of 2.2 percent per cycle in the population cross, and indirect responses of 3.3 and 1.2 percent per cycle in BS10 and BS11, respectively, but only the response for BS11 fits a linear model. Linear trends through the first nine selection cycles, however, indicate a 4.6 percent per cycle increase for the population cross, as well as increases of 1.6 percent in BS10 and 1.6 percent in BS11 parent populations. Evaluations of random S1 line performance for BS10CO, BS10C13, BS11CO, and BS11C13 indicate decreasing trends in genetic variability over 13 cycles of FR. Exceptions are grain yield in BS10 and BS11 and plant height in BS11. While genetic variance estimates for grain yield are nearly equal for BS11CO and BS11C13, a nearly significant increase in variability is evident from BS10CO to BS10C13. Variability estimates suggest FR for grain yield in BS10 and BS11 will be effective in future selection cycles.
Author:
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Category : Dissertations, Academic
Languages : en
Pages : 854
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Author: Brandon M. Wardyn
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Category :
Languages : en
Pages : 228
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The genetic relationship among individuals is at the core of nearly all quantitative genetic theory. Dominant gene action has long been either ignored or disregarded as insignificant in many previous genetic models. For grain yield in maize (Zea mays L.), dominance has consistently accounted for a large proportion of genetic variance. We have used previously developed genetic theory that accounts for dominance variance during inbreeding and applied it to a unique breeding design. Our breeding design allowed us to estimate five genetic covariance parameters for six traits. In addition, we developed genetic gain equations that accounted for both dominance and inbreeding. We found that the genetic covariance parameters introduced via inbreeding were significant for five traits. Our estimates of the genetic covariance parameters allowed us to predict genetic gain over a range of selection units and response units. Half-sib selection proved superior to inbred progeny selection when the response was measured in the outbred progeny. In addition, the relative proportions of additive and dominance variance influenced the effectiveness of inbred progeny selection. We also showed that even when dominance constitutes a larger proportion of the total genetic variance than additive variance, the loss of additive effects has a greater influence on the decline associated with inbreeding than the addition of homozygous dominance deviations. Our results also indicated that the reason realized gain often falls short of predicted gain is due to the negative covariance between additive effects and homozygous dominance effects. The effect of a negative covariance is that positive gain via additive effects is offset by negative gain via homozygous dominance deviations.
Author: Rkia Moutiq
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ISBN:
Category :
Languages : en
Pages : 280
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In general, maize, especially germplasm from the tropics and subtropics, is sensitive to photoperiod. This sensitivity hindered the exchange of germplasm between latitudes. To identify quantitative trait loci (QTL) associated with the response to photoperiod, a population of 236 F3 lines produced from a cross between a photoperiod-sensitive line CML9 and insensitive inbred A632Ht was used. These F3 lines were evaluated in three long and three short-day environments, in adjacent fields using artificial light, and in fields located in different latitudes, Mexico and Iowa. Days from sowing to anthesis (DTA), final leaf number (FLN) and plant height (PH) were measured. For each of these traits, photoperiod response (PPR) was estimated as the difference between the trait in long- and short-days divided by the trait in short-days. Composite interval mapping was used to detect QTL for each trait and comparison of locations of QTL detected in different daylengths for the same trait and for different traits were examined. A unique set of QTL was detected for each photoperiod and for each trait. One QTL for DTA, three QTL for FLN and four QTL for PH were detected in the same genetic regions in both daylengths. Five QTL for DTA, four QTL for FLN and three QTL for PH were detected only in long-day environments. Nine QTL for DTA, five QTL for FLN and three QTL for PH were detected only in short-day environments. QTL for photoperiod response were detected on four chromosomes for PPR[Subscript DTA], on three chromosomes for PPR[Subscript FLN] and on three chromosomes for PPR[Subscript PH]. Chromosomes 2, 3, 4, 5, 6, 8, 9, and 10 had a cluster of QTL for different traits. This might suggest a common initial mechanism with subsequent specific pathways that regulate different traits.
Author: Todd Eugene Frank
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ISBN:
Category :
Languages : en
Pages : 418
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Author: Mulamba Ngandu-Nyindu
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ISBN:
Category :
Languages : en
Pages : 282
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Author: Pedro Justino Jasa-Vega
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ISBN:
Category : Corn
Languages : en
Pages : 206
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The objective of this study was to determine the correlated and direct responses to divergent mass selection for days-to-antheis (DTA) in a Mecican land-variety belonging to the race Chalqueno. Ten cycles of selection and evaluations were conducted at Chapingo. The tenth (final cycle) also was evaluated at College Station. Also, a combined general analysis involving all data collected over the six evaluation in Chapingo, was done. The response of DTA to selection was significant in both directions in all evaluations from 1976 to 1982. However, there was asymmetry in response, the later direction being about three times that of the earlier. The total response in DTA over six evaluation in Chapingo, was: 42.5% at a rate of 4.04% +- 0.21 per cycle in the later direction and, -11.7% at a rate of -1.38% +- 0.21 per cycle in the earlier direction. In addition, response of F1 crosses (between later by earlier selection) to DTA was found to be exactly intermediate between parents. The high linear response to selection in both directions and the intermediate F1 value, suggested and average additive effect of the genes controlling DTA. Realized heretability for DTA was calculated as the coefficient of linear regression between the cumulative response on DTA against cumulative calculated differential selection, which were 0.25 +- 0.03 in the later direction, 0.19 +- 0.02 in the earlier direction, and 0.24 +- 0.02 for divergence (later - earlier) values. All b1 coefficient were different from zero at P=0.01 level. (...).
Author: Kathryn Michel
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ISBN:
Category :
Languages : en
Pages : 0
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Maize (Zea mays L.) yield is a highly quantitative trait controlled by many loci of small effect, the environment, and genotype by environment interactions, which make it a difficult trait to study at the gene level. However, yield may be broken into components such as ear and kernel size and shape, which are more heritable than yield measured in small plots. Multiparent advanced generation intercross (MAGIC) populations and diversity panels are two types of populations that are useful for identifying quantitative trait loci (QTL) that influence phenotypes. This dissertation contains three research projects designed to investigate the control of quantitative traits impacting maize yield. First, we present the genomes of five founders of a Stiff Stalk MAGIC population. Between the reference inbred B73 and the other five inbreds, we found substantial genetic and genomic variation in addition to conservation of haplotypes from the base population from which the inbreds were selected. Second, we describe the Wisconsin-Stiff Stalk-MAGIC population, its associated resources, and demonstrate QTL mapping and genomic prediction for flowering time and plant height. Flowering time and plant height are important characteristics in hybrid maize breeding, so we measured them in both the per se population and two test-crossed hybrid populations. We found that QTL detection depended on the tester used, which was consistent with lower genomic predictive ability when training models with per se data to predict hybrid phenotypes. Third, we used a high throughput image analysis pipeline to measure yield components on four MAGIC populations and a diversity panel. We performed genetic mapping to identify candidate genes underlying ear and kernel size and shape. We found substantial overlap of our results across traits within and between populations and overlap with known metaQTL identified through previous studies. The results from these projects provide new insight into the genetic control of traits including flowering time, plant height, and the size and shape of ears and kernels, all of which impact overall maize yield.
Author:
Publisher:
ISBN:
Category : Corn
Languages : en
Pages : 982
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