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Previous results from our lab have shown that using an optical sorter to identify Fusarium head blight (FHB) resistant breeding lines was effective at reducing the toxin deoxynivalenol (DON) and FHB-associated kernel damage. In this paper we quantified the proportion of desirable genotypes at FHB resistance QTL in lines from three selection cycles of optical sorting. Breeding lines were genotyped at loci on chromosomes 3BS, 2DL, and 5A using the following DNA markers: TaHRC, CFD233, and GWM304. TaHRC is a KASP marker for Fhb1 , a major FHB resistance QTL on chromosome 3BS. CFD233 is an SSR marker for Qfhs.nau-2DL on chromosome 2DL. GWM304 is an SSR marker for Qfhs.ifa-5A on chromosome 5A. Sorter selection was effective at identifying lines that had the resistant genotype at TaHRC; in other words, the sorter was able to identify lines with resistance alleles at Fhb1. The sorter was less effective at selecting for the resistant genotype at CFD233 and GWM304. However, the proportion of lines with resistant genotypes at GWM304 did increase with additional sorter selection, just not to the degree that was observed for the Fhb1 -associated marker. The proportion of lines with resistant alleles at CFD233 did not show a consistent trend. In addition to increasing the proportion of lines with Fhb1 and Qfhs.ifa-5A each selection cycle, optical sorter-based mass selection enhanced FHB resistance in different marker genotype combinations evaluated in this study. For example, there were net reductions in DON and kernel damage after two cycles of sorter selection in 15X110601S07002, a line with Fhb1 , with Qfhs.nau-2DL, and with Qfhs.ifa-5A; final C3 DON levels were 63% of the resistant check (KY02C-3005-25). Kernel damage was also reduced in 15X110601A08221 a line without Fhb1 , without Qfhs.nau-2DL, and without Qfhs.ifa-5A. Our findings suggest the increased resistance observed in different marker genotype combinations was conferred by QTL other than Fhb1 , QFhs.nau-2DL, and Qfhs.ifa-5, and validate our previous results that the optical sorter is effective at selecting FHB-resistant breeding material. [ABSTRACT FROM AUTHOR]

Grain yield is a trait of paramount importance in the breeding of all cereals. In wheat (Triticum aestivum L.), yield has steadily increased since the Green Revolution, though the current rate of increase is not forecasted to keep pace with demand due to growing world population and increasing affluence. While several genome-wide association studies (GWAS) on yield and related component traits have been performed in wheat, the previous lack of a reference genome has made comparisons between studies difficult. In this study, a GWAS for yield and yield-related traits was carried out on a population of 322 soft red winter wheat lines across a total of four rain-fed environments in the state of Virginia using single-nucleotide polymorphism (SNP) marker data generated by a genotyping-by-sequencing (GBS) protocol. Two separate mixed linear models were used to identify significant marker-trait associations (MTAs). The first was a single-locus model utilizing a leave-one-chromosome-out approach to estimating kinship. The second was a sub-setting kinship estimation multi-locus method (FarmCPU). The single-locus model identified nine significant MTAs for various yield-related traits, while the FarmCPU model identified 74 significant MTAs. The availability of the wheat reference genome allowed for the description of MTAs in terms of both genetic and physical positions, and enabled more extensive post-GWAS characterization of significant MTAs. The results indicate a number of promising candidate genes contributing to grain yield, including an ortholog of the rice aberrant panicle organization (APO1) protein and a gibberellin oxidase protein (GA2ox-A1) affecting the trait grains per square meter, an ortholog of the Arabidopsis thaliana mother of flowering time and terminal flowering 1 (MFT) gene affecting the trait seeds per square meter, and a B2 heat stress response protein affecting the trait seeds per head. [ABSTRACT FROM AUTHOR]

Breeding for resilience to climate change is a daunting prospect. Crop and climate models tell us that global wheat yields are likely to decline as the climate warms, causing a significant risk to global food security. High temperatures are known to affect crop development yet breeding for tolerance to heat stress is difficult to achieve in field environments. We conducted an active warming study over two years to quantify the effects of heat stress on genetic variation of soft red winter (SRW) wheat (Triticum aestivum L.). Forty SRW cultivars and breeding lines were chosen based on marker genotypes at photoperiod sensitivity and reduced height loci. These genotypes were planted in a randomized complete block design replicated twice across two environments, ambient and artificially warmed. Average heading date occurred 5 days earlier in the warmed environment than in the ambient environment over both years (p ≤ 0.05). On average, grain yield was significantly reduced in the warmed environment by 211.41 kg/ha (p ≤ 0.05) or 4.84%, though we identified 13 genotypes with increased yield in response to warming in both years. Of these genotypes, eight had significantly increased N uptake while six showed significantly increased N utilization efficiency under warming. Under warming, genotypes with wild‐type alleles at the Rht‐D1 locus display significantly greater yields (p ≤ 0.01) and biomass (p ≤ 0.001) than genotypes with reduced height alleles. Of the 13 genotypes with higher (p ≤ 0.01) yields under warming, nine have the wild‐type allele at the Rht‐D1 locus in addition to being photoperiod insensitive. The next steps will be to validate these findings in other populations and to develop an efficient breeding/phenotyping scheme that will lead to more resilient cultivars. Increasing global temperatures will reduce wheat yield and productivity. To identify genetic variation for resilience to warming, we screened a set of diverse wheat genotypes in a warmed and a control environment. On average, grain yield was significantly (p < 0.05) reduced in the warmed environment though we identified genotypes which had higher yields in response to warming in both years. [ABSTRACT FROM AUTHOR]

Global temperature increases will affect Fusarium head blight (FHB) levels in wheat (Triticum aestivum L.). A pressing question is whether current sources of resistance will be effective in a warmer environment. We evaluated phenotypic response to disease in 238 soft winter wheat breeding lines and cultivars grown in 2015-2016 and 2016-2017 under control and warmed (+3 °C) conditions. Warming was achieved with heating cables buried 3 cm in the rhizosphere. We measured heading date, plant height, yield, FHB rating, Fusarium damaged kernels (FDK), deoxynivalenol (DON), leaf blotch rating, powdery mildew rating and leaf rust rating. There were significant (p < 0.01) differences among genotypes for all traits measured. Genome-wide association study (GWAS) identified 19 and 10 significant SNPs in the control and warmed treatments, respectively. FDK and DON levels were often significantly (p < 0.05) higher in warmed than in control when we contrasted alleles at important quantitative trait locus (QTL) such as Fhb1, Rht-B1 and D1 and all vernalization and photoperiod loci. Increased rhizosphere temperature resulted in a significantly (p < 0.01) earlier heading date (~3.5 days) both years of the study. Rank correlation between warmed and control treatments was moderate (r = 0.56). Though encouraging, it indicates that selection for performance under warming should be carried out in a warmed environment. [ABSTRACT FROM AUTHOR]

The complex interaction of genetics, environment, and management in determination of crop yields can interfere with selection progress in breeding programs. Specifically, the impact on selection for nitrogen use efficiency (NUE) in soft red winter (SRW) wheat (Triticum aestivum L.) can be confounded by these interactions. We utilized a multi-environment trial in Lexington and Princeton, KY, from 2013 to 2015 to assess variation in traits associated with NUE based on interactions of genotype × environment × management (G×E×M). The NUE traits were measured on 10 genotypes under three management levels and four levels of N fertility. Genotype and genotype × environment interactions were significant for NUE traits (p < 0.001) but no genotype × N rate interactions were significant. Reduced N rates had no negative effect on grain yield for any genotype. Incremental application of N rates increased yield and postanthesis N uptake significantly. The utility of incorporating management treatments into breeding programs, specifically geared to low-input systems, could help drive progress for development of increased NUE in wheat cultivars. [ABSTRACT FROM AUTHOR]

Fusarium head blight (FHB) mainly caused by Fusarium graminearum Schwabe causes devastating losses in wheat globally. 'Truman' winter wheat, developed and released by the University of Missouri has excellent broad-based FHB resistance in a superior soft red winter wheat background. This research identified QTL associated with greenhouse type II resistance and field resistance for incidence, severity, Fusarium damaged kernels (FDK), and deoxynivalenol (DON) based on phenotypic data collected in Missouri, Kentucky and Indiana. Two years of replicated phenotypic data were collected on a set of 167 recombinant inbred lines. Genetic linkage maps were constructed using 160 SSR and 530 DArT polymorphic markers. Across years, QTL for type II resistance were identified on chromosomes 1BSc, 2BL, 2DS and 3BSc, for incidence on 2ASc, 2DS, and 3DS and for severity on 2DS and 3BSc. QTL were also detected for incidence on 1DLc and 2DS and for severity on 1BL, 3AL and 3BLC from data collected in Indiana and Kentucky, respectively. Common QTL for FDK on chromosomes 2ASc and 3BLc and for DON on chromosomes 2ASc and 2DS were identified from data from both Missouri and Kentucky, respectively with additional individual QTL for FDK and DON identified from tests at each independent location. All alleles were from Truman and associated with significant reductions in the respective traits. QTL on 2ASC, 2DS and 3DS may be novel and once further validated, should diversify the FHB gene pool globally and be useful for enhancing FHB resistance through marker assisted selection. [ABSTRACT FROM AUTHOR]

In the soft red winter wheat ( Triticum aestivum L.) regions of the US, Fusarium head blight (FHB, caused by Fusarium spp.) resistance derived from locally adapted germplasm has been used predominantly. Two soft red winter wheat cultivars, Massey and Ernie, have moderate resistance to FHB. Mapping populations derived from Becker/Massey (B/M) and Ernie/MO 94-317 (E/MO) were evaluated for FHB resistance and other traits in multiple environments. Eight QTL in B/M and five QTL in E/MO were associated with FHB variables including incidence, severity (SEV), index (IND), Fusarium damaged kernels (FDK), deoxynivalenol (DON), and morphological traits flowering time and plant height. Four QTL were common to both populations. Three of them were located at or near known genes: Ppd- D1 on chromosome 2DS, Rht- B1 on 4BS, and Rht- D1 on 4DS. Alleles for dwarf plant height ( Rht- B1b and Rht- D1b) and photoperiod insensitivity ( Ppd- D1a) had pleiotropic effects in reducing height and increasing FHB susceptibility. The other QTL detected for FHB variables were on 3BL in both populations, 1AS, 1DS, 2BL, and 4DL in B/M, and 5AL ( B1) and 6AL in E/MO. The additive effects of FHB variables ranged from 0.4 mg kg of DON to 6.2 % for greenhouse (GH) SEV in B/M and ranged from 0.3 mg kg of DON to 8.3 % for GH SEV in E/MO. The 4DS QTL had epistasis with Ppd- D1, Qdon.umc- 6AL, and Qht.umc- 4BS, and additive × additive × environment interactions with the 4BS QTL for SEV, IND, and FDK in E/MO. Marker-assisted selection might be used to enhance FHB resistance through selection of favorable alleles of significant QTL, taking into account genotypes at Rht- B1b, Rht- D1a and Ppd- D1a. [ABSTRACT FROM AUTHOR]

Exotic resistance quantitative trait loci (QTL) such as Fhb1 and QFhs.nau-2DL provide one strategy for breeding wheat (Triticum aestivum L.) cultivars resistant to Fusarium head blight (FHB). The first objective of this study was to evaluate the effectiveness of these QTL in reducing FHB in diverse genetic backgrounds and to measure their impact on agronomic and quality traits. Lines from five susceptible × resistant crosses were evaluated in the FHB nursery at Lexington, KY, in 2010 and 2011. The populations were also grown in yield trials at Lexington (2010 and 2011) and Princeton (2011), KY, to measure agronomic and quality traits. Fhb1 reduced Fusarium damaged kernels (FDK) by 32% and deoxynivalenol (DON) concentration by 20%. QFhs.nau-2DL reduced FDK by 29% in two of five populations and DON by 24% in four of five populations. Significant QTL effects (P < 0.05) on agronomic and quality traits were observed although impact was small. One cycle of direct or indirect simulated phenotypic selection was effective at reducing DON levels. The frequency of Fhb1-homozygous resistant lines among the phenotypically selected lines was higher than the frequency of QFhs.nau-2DLhomozygous resistant lines. The second objective was to assess the effectiveness of nearinfrared reflectance (NIR) to estimate damage from FHB. Near-infrared reflectance-based predictions of FDK and DON showed that FDK measured by NIR was at least as good as FDK measured by air separation in predicting DON in four of five populations. [ABSTRACT FROM AUTHOR]

Fusarium head blight (FHB), caused by Fusarium graminearum, of wheat (Triticum aestivum L.) is a disease that periodically strikes the mid-Atlantic region of the United States. Breeding for resistant wheat varieties is an effective method of disease control. The objective of this study was to evaluate the effects of exotic FHB resistance quantitative trait loci (QTL), singly and in combination, on FHB resistance in soft red winter wheat (SRWW). Three FHB resistance QTL on chromosomes 3BS (Fhbl), 2D, and 5A were introgressed from nonadapted Chinese cultivar Ning7840 into the adapted SRWW cultivar McCormick. Eight near-isogenic lines (NIL) were developed by marker-assisted backcrossing. The NIL that combined 3BS and 2DL expressed the highest resistance and lowest deoxynivalenol (DON) content in four environments that included three field and one greenhouse studies. These results indicate that the combination of just two QTL (3BS and 2DL) would be useful to breed for improved FHB resistance in SRWW in the mid-Atlantic region. [ABSTRACT FROM AUTHOR]

Fusarium head blight (FHB), caused by Fusarium graminearum (Schwabe), is an economically important disease of wheat (Triticum aestivum L.). After epidemics in the USA during the 1990s, a resistance-breeding effort was undertaken focusing initially on the transfer of Type II resistance from unadapted Chinese cultivars. The objective of this study was to determine the magnitude and heritability of resistance in populations derived from adapted parents. Three soft red winter (SRW) wheat populations of 40 families each were artificially inoculated with Fusarium graminearum under mist irrigation in 2003 and 2004 at Lexington and Princeton, KY. Traits measured included anthesis date, plant height, disease severity, Fusarium-damaged kernels (FDK) and deoxynivalenol (DON) concentration. Broad sense heritability (BSH) estimates were generated from entry means over the four environments. Heritability of severity was approximately 0.30 in all populations; heritability of FDK ranged from 0.16 to 0.20. In 2003, a selection intensity of 20% was imposed on all populations, and the eight lowest severity families were advanced and evaluated at Lexington and Princeton in 2004. Direct selection response, averaged over both locations, ranged from 1.9 to 4.1% reduction in severity. Correlated reduction in FDK ranged from 0.4 to 6.5%; there was also a correlated increase in plant height of 1.7 to 4.1 cm after one cycle of selection. Progress in FHB resistance breeding in the absence of major QTL is likely to be constrained by low heritability and genotype x environment (G × E) interaction. [ABSTRACT FROM AUTHOR]

Increases in global mean temperature since 1960 are largely attributed to the rise in minimum nighttime temperatures thereby decreasing diurnal temperature variation. Increased night temperatures are known to affect crop development. A multi-year study investigating the effects of increased night temperatures on soft red winter wheat (Triticum aestivum L.) varieties was conducted during the 2015-2016 growing seasons at the University of Kentucky Spindletop Research Farm in Lexington, KY. Thirty-six cultivars and breeding lines were chosen based on their genotypes at photoperiod and vernalization loci. This material was planted in a randomized complete block experiment with two replications and two environments, control and passively warmed. To create a passively warmed environment, thermal covers were mounted to frames in plots and connected to a datalogger programmed to cover plants from dusk to dawn based on coordinate location. Night temperature increases ranged from 0.27–0.75 °C above ambient temperature. Grain yield, averaged across genotypes, was significantly reduced in the passively warmed environment by 224 kg ha−1 (p ≤ 0.05) or 6.44%; however, yield response to environment varied among genotypes with several genotypes displaying an increased yield in the warmed environment. Yield reductions may reflect reduced nitrogen utilization (9.4%; p ≤ 0.001) under increased night temperatures. [ABSTRACT FROM AUTHOR]

Fusarium head blight (FHB) of wheat (Triticum aestivum L.) results in discolored Fusarium damaged kernels (FDK) contaminated with deoxynivalenol (DON). DON accumulation, a primary measure of FHB resistance, can be used as a basis for selection, but testing each genotype in several genetically variable populations is expensive and time-consuming. Therefore, FHB resistance breeding decisions are routinely based on in-field phenotypic evaluation. However, using an optical sorter as an alternative to in-field evaluation, mass selection (MS) for FHB resistance can be quickly performed post-harvest. The objective of this study was to utilize an optical seed sorter to select breeding lines with enhanced FHB resistance (lower DON and FDK values). Three hundred F4 derived breeding lines were grown in an inoculated disease nursery over several years in Lexington, KY. Grain from each breeding line was sorted using an optical seed sorter calibrated to reject scabby (discolored) seed. The accepted (non-scabby) seed was used to plant subsequent generations. DON and kernel damage traits were lowered each cycle of line selection with the optical sorter. Our findings suggest that optically sorting grain may be an effective breeding strategy for lowering DON accumulation and limiting kernel damage associated with FHB. [ABSTRACT FROM AUTHOR]

Nitrogen use efficiency (NUE) is of great interest to wheat ( Triticum aestivum L.) breeders because it addresses the daunting prospect of feeding the burgeoning population under the constraints of limited land resources and a warming climate. In this study, we evaluated a 56 entry panel of SRW breeding lines and cultivars from the eastern US wheat region in 2014 for NUE and related traits. The 56-entry block was grown at Lexington and Princeton, KY at two N rates (0 and 112 kg ha −1 ) in a complete factorial design. We measured normalized difference vegetative index (NDVI), biomass, harvest index, N harvest index, N uptake efficiency, N utilization efficiency, post-anthesis N uptake, N remobilization efficiency and overall NUE. Breeders usually apply high rates of N fertilizer to their plots in order to maximize genetic yield potential. Our study indicates that without screening breeding lines in low N environments concurrently, it will not be possible to identify high NUE genotypes. Post-anthesis N uptake, was highly correlated with yield (r = 0.79) under high N, but heritability of this trait was close to zero. Heritability of NUE, on the other hand was moderately high (h 2 = 0.65). Five breeding lines ranked within the top 10 for NUE in both low and high N environments. NDVI was found to be both heritable and highly correlated with yield across N environments (R 2 = 0.78). Genome wide association studies of NUE and related traits revealed QTL associated with NUE (chromosome 2B), uptake efficiency (chromosome1B) and utilization efficiency (chromosomes 1A and 3A). In accord with other studies, these QTL are of small effect and will likely only be useful in genomic selection as opposed to marker-assisted selection. [ABSTRACT FROM AUTHOR]