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Rutkoski J.,Cornell University | Benson J.,Norrolina State University | Jia Y.,Cornell University | Brown-Guedira G.,U.S. Department of Agriculture | And 2 more authors.
Plant Genome | Year: 2012

Fusarium head blight (FHB) resistance is quantitative and difficult to evaluate. Genomic selection (GS) could accelerate FHB resistance breeding. We used U.S. cooperative FHB wheat nursery data to evaluate GS models for several FHB resistance traits including deoxynivalenol (DON) levels. For all traits we compared the models: ridge regression (RR), Bayesian LASSO (BL), reproducing kernel Hilbert spaces (RKHS) regression, random forest (RF) regression, and multiple linear regression (MLR) (fixed effects). For DON, we evaluated additional prediction methods including bivariate RR models, phenotypes for correlated traits, and RF regression models combining markers and correlated phenotypes as predictors. Additionally, for all traits, we compared different marker sets including genomewide markers, FHB quantitative trait loci (QTL) targeted markers, and boThsets combined. Genomic selection accuracies were always higher than MLR accuracies, RF and RKHS regression were often the most accurate methods, and for DON, marker plus trait RF regression was more accurate than all other methods. For all traits except DON, using QTL targeted markers alone led to lower accuracies than using genomewide markers. This study indicates that cooperative FHB nursery data can be useful for GS, and prior information about correlated traits and QTL could be used to improve accuracies in some cases. © Crop Science Society of America.

Vann M.C.,North Carolina State University | Fisher L.R.,North Carolina State University | Jordan D.L.,North Carolina State University | Smith W.D.,Norrolina State University | And 2 more authors.
Agronomy Journal | Year: 2013

Research was conducted at two locations in 2009 and 2010 to evaluate the effect of various K rates and application methods on the yield and quality of flue-cured tobacco (Nicotiana tabacum L.). Treatments included five rates of K from sulfate of potash magnesia (0-0-22): 0, 84, 140, 196, and 252 kg K2O ha-1 that were applied: broadcast 1 mo before transplanting, broadcast 1 wk before transplanting, banded at transplanting, and a split application wiThone-half rate banded at transplanting followed by one-half rate banded at layby. Tissue samples were collected throughout the season at three separate growThstages: layby, topping, and aft er curing. Tissue samples were analyzed for total alkaloid and reducing sugars, N, P, K, and Mg content. Soil samples were collected the same day as K fertilizer application from plots not receiving supplemental K. Data were subjected to ANOVA using the PROC GLM procedure in SAS. Treatment means were separated using Fisher's Protected LSD test at p ≤ 0.05. Application method and timing had no effect on any measured parameters; furthermore, crop yield and quality was not affected by K rates >0 kg K2O ha-1 at three of four locations. It is likely that early broadcast applications of K2O wiThcurrent rate recommendations would only be of concern wiThcombinations of conditions that included coarse soil textures, low K indices, and/or excessive leaching rainfall. © 2013 by the American Society of Agronomy, 5585 Guilford Road, Madison, WI 53711. All rights reserved.

Benson J.,Norrolina State University | Brown-Guedira G.,U.S. Department of Agriculture | Murphy J.P.,Norrolina State University | Sneller C.,Ohio State University
Plant Genome | Year: 2012

The occurrence of epidemics of Fusarium head blight (FHB), caused by Fusarium graminearum Schwabe, in U.S. winter wheat (Triticum aestivum L.) during the past two decades led to significant emphasis on development of resistant cultivars. Understanding the genetic diversity, population structure (PS), and linkage disequilibrium (LD) in winter wheat in the eastern United States is important for marker-assisted breeding and association analysis in this germplasm. Lines selected from collaborative FHB screening nurseries were genotyped wiThsimple sequence repeat (SSR), sequence tagged site (STS), and Diversity Array Technology (DArT) markers to assess LD, genetic diversity, and PS. The genomewide average of LD decay to r2 < 0.2 was 9.9 cM and moderate levels of LD (r2 > 0.2) were generally constrained to markers less than 5 cM apart. Although the lines evaluated were targeted to distinct production zones of the eastern winter wheat region, cluster and principal component analyses did not detect separation of lines into subpopulations. The short, intense breeding history for scab resistance may have localized effects on LD. Lack of subgroups within our population could be due to intercrossing among common resistant parents and indicate frequent admixture and germplasm exchange among U.S. winter wheat programs focused on development of FHB resistant cultivars. © Crop Science Society of America.

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