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Cleistogamy or closed flowering is a widely used trait in barley (Hordeum vulgare) breeding because it reduces the risk of fungal infection in florets at anthesis. Cleistogamy in barley is caused by a point mutation within the microRNA172 (miR172) target site of the Cly1 gene, which encodes the Apetala2 (AP2) transcription factor. Because cleistogamy is not apparent in cultivars of hexaploid wheat (Triticum aestivum), a strategy to develop cleistogamous wheat was proposed by inducing point mutations in all three AP2 homoeologs, which are the wheat orthologs of barley Cly1. In this study, we investigated the effects of miR172 target site mutations on wheat cleistogamy using double mutants by combining three previously obtained mutant alleles (AP2-A1, D1 and D2) in a near-isogenic background. The AP2-D2 allele had the greatest effect on reducing the anther extrusion rate and lodicule size compared with the other two mutant alleles. The double mutant containing the AP2-A1 and AP2-D2 alleles had a much greater suppression of anther extrusion by reducing the lodicule size than the single AP2-D2 mutant, suggesting cumulative effects of the two mutant alleles. In addition, both single and double mutants exhibited compact spikes and shorter plant heights due to reduced rachis and culm internodes in the upper parts. The presence or absence of the wild-type AP2-B homoeolog had no significant effect on phenotype. This study provides insights into the cumulative effects of mutant AP2 alleles in suppressing open flowering and provides a basis for further research on the development of complete cleistogamy in hexaploid wheat. [ABSTRACT FROM AUTHOR]

Anther extrusion (AE) is the most important male floral trait for hybrid wheat seed production. AE is a complex quantitative trait that is difficult to phenotype reliably in field experiments not only due to high genotype-by-environment effects but also due to the short expression window in the field condition. In this study, we conducted a genome-wide association scan (GWAS) and explored the possibility of applying genomic prediction (GP) for AE in the CIMMYT hybrid wheat breeding program. An elite set of male lines (n = 603) were phenotype for anther count (AC) and anther visual score (VS) across three field experiments in 2017–2019 and genotyped with the 20K Infinitum is elect SNP array. GWAS produced five marker trait associations with small effects. For GP, the main effects of lines (L), environment (E), genomic (G) and pedigree relationships (A), and their interaction effects with environments were used to develop seven statistical models of incremental complexity. The base model used only L and E, whereas the most complex model included L, E, G, A, and G × E and A × E. These models were evaluated in three cross-validation scenarios (CV0, CV1, and CV2). In cross-validation CV0, data from two environments were used to predict an untested environment; in random cross-validation CV1, the test set was never evaluated in any environment; and in CV2, the genotypes in the test set were evaluated in only a subset of environments. The prediction accuracies ranged from −0.03 to 0.74 for AC and −0.01 to 0.54 for VS across different models and CV schemes. For both traits, the highest prediction accuracies with low variance were observed in CV2, and inclusion of the interaction effects increased prediction accuracy for AC only. In CV0, the prediction accuracy was 0.73 and 0.45 for AC and VS, respectively, indicating the high reliability of across environment prediction. Genomic prediction appears to be a very reliable tool for AE in hybrid wheat breeding. Moreover, high prediction accuracy in CV0 demonstrates the possibility of implementing genomic selection across breeding cycles in related germplasm, aiding the rapid breeding cycle.

Anther extrusion (AE) is the most important male floral trait for hybrid wheat seed production. AE is a complex quantitative trait that is difficult to phenotype reliably in field experiments not only due to high genotype-by-environment effects but also due to the short expression window in the field condition. In this study, we conducted a genome-wide association scan (GWAS) and explored the possibility of applying genomic prediction (GP) for AE in the CIMMYT hybrid wheat breeding program. An elite set of male lines (n = 603) were phenotype for anther count (AC) and anther visual score (VS) across three field experiments in 2017–2019 and genotyped with the 20K Infinitum is elect SNP array. GWAS produced five marker trait associations with small effects. For GP, the main effects of lines (L), environment (E), genomic (G) and pedigree relationships (A), and their interaction effects with environments were used to develop seven statistical models of incremental complexity. The base model used only L and E, whereas the most complex model included L, E, G, A, and G × E and A × E. These models were evaluated in three cross-validation scenarios (CV0, CV1, and CV2). In cross-validation CV0, data from two environments were used to predict an untested environment; in random cross-validation CV1, the test set was never evaluated in any environment; and in CV2, the genotypes in the test set were evaluated in only a subset of environments. The prediction accuracies ranged from −0.03 to 0.74 for AC and −0.01 to 0.54 for VS across different models and CV schemes. For both traits, the highest prediction accuracies with low variance were observed in CV2, and inclusion of the interaction effects increased prediction accuracy for AC only. In CV0, the prediction accuracy was 0.73 and 0.45 for AC and VS, respectively, indicating the high reliability of across environment prediction. Genomic prediction appears to be a very reliable tool for AE in hybrid wheat breeding. Moreover, high prediction accuracy in CV0 demonstrates the possibility of implementing genomic selection across breeding cycles in related germplasm, aiding the rapid breeding cycle. [ABSTRACT FROM AUTHOR]

Phenotyping wheat (Triticum aestivum L.) is time-consuming and new methods are necessary to decrease labor. To develop a heterotic pool of male wheat lines for hybrid breeding, there must be an efficient way to measure both anther extrusion and the size of anthers. Five hundred and ninety-four soft red winter wheat lines in two replications of randomized complete block design were phenotyped for anther extrusion, a key trait for hybrid wheat production. A device was constructed to capture images using a mobile device. Four heads were sampled per line when anthesis was evident for half the heads in the plot. The extruded anthers were scraped onto a surface, their image was captured, and the area of the anthers was taken via ImageJ. The number of anthers extruded was estimated by counting the number of anthers per image and dividing by the number of heads sampled. The area per anther was taken by dividing the area of anthers per spike by the number of anthers per spike. A significant correlation (R=0.9, p<0.0001) was observed between the area of anthers per spike and the number of anthers per spike. This method is proposed as a substitute for field ratings of anther extrusion and to quantitatively measure the size of anthers.

Variation and inheritance of anther extrusion and its effects on Fusarium head blight were studied. On a 0 to 9 scale, variation ranged from 1 to 6 in a North American oat panel and from 0 to 8 in a Nordic population. The inheritance was studied in two recombinant inbred line populations (Fiia × Stormogul and Svea × Stormogul). Fiia and Svea are recent white-seeded cultivars with low to medium anther extrusion, while Stormogul is an old black-seeded cultivar with high anther extrusion. Highly significant transgressive segregations and high heritabilities were observed (h2 = 0.91 in Fiia × Stormogul and h2 = 0.83 in Svea × Stormogul). Another extrusion was negatively correlated with Fusarium head blight and deoxynivalenol in spawn-inoculated field experiments, but significantly only in Fiia × Stormogul where the range in resistance was widest. Correlations were reversed in spray-inoculated greenhouse experiments, apparently spraying open florets defeated the avoidance mechanism. Anther extrusion may help oat avoid Fusarium infection in the field, but the genetic variance is inadequate and high anther extrusion is rare in modern genepools.

Pronounced anther extrusion (AE) is associated with field resistance to Fusarium head blight (FHB), one of the most devastating diseases of wheat globally. In this study, two recombinant inbred line (RIL) populations were used to map quantitative trait loci (QTL) for AE and field FHB resistance and to investigate the association of both traits at the genetic level. Furthermore, two panels of International Maize and Wheat Improvement Center (CIMMYT) wheat breeding lines were evaluated to describe the phenotypic association between the two traits in detail. Highly significant negative correlation was identified between AE and FHB severity in the two populations and the two panels, with r-values ranging from 0.55 to 0.74. QTL analysis in the two RIL populations identified 12 QTL for AE and nine for FHB resistance, of which five QTL located on chromosomes 3BL, 4BS, 4DS, 5AL, and 5BL were associated with both AE and FHB, collectively explaining over 50% of phenotypic variation for FHB. The QTL on chromosomes 4BS, 4DS, 5AL, and 5BL were closely linked to Rht-B1, Rht-D1, Vrn-A1, and Vrn-B1 genes, respectively. In conclusion, AE is closely related to field FHB resistance and could be used as a morphological marker in wheat breeding for field FHB resistance.

Hybrid wheat breeding is gaining prominence worldwide because it ensures higher and more static yield than conventionally bred varieties. The cleistogamous floral architecture of wheat (Triticum aestivum L.) impedes anthers inside the floret, making it largely an inbreeder. For hybrid seed production, high anther extrusion is needed to promote cross pollination and to ensure a high level of pollen availability for the seed plant. This study, therefore, aimed at the genetic dissection of anther extrusion (AE) in panels of spring (SP), and winter wheat (WP) accessions by genome wide association studies (GWAS). We performed GWAS to identify the SNP markers potentially linked with AE in each panel separately. Phenotypic data were collected for 3 years for each panel. The average levels of Pearson's correlation (r) among all years and their best linear unbiased estimates (BLUEs) within both panels were high (r(SP) = 0.75, P < 0.0001;r(WP) = 0.72, P < 0.0001). Genotypic data (with minimum of 0.05 minor allele frequency applied) included 12,066 and 12,191 SNP markers for SP and WP, respectively. Both genotypes and environment influenced the magnitude of AE. In total, 23 significant (|log10(P)| > 3.0) marker trait associations (MTAs) were detected (SP = 11; WP = 12). Anther extrusion behaved as a complex trait with significant markers having either favorable or unfavorable additive effects and imparting minor to moderate levels of phenotypic variance (R2(SP) = 9.75−14.24%; R2 (WP) = 9.44−16.98%). All mapped significant markers as well as the markers within their significant linkage disequilibrium (r2 ≥ 0.30) regions were blasted against wheat genome assembly (IWGSC1+popseq) to find the corresponding genes and their high confidence descriptions were retrieved. These genes and their orthologs in Hordeum vulgare, Brachypodium distachyon, Oryza sativa, and Sorghum bicolor revealed syntenic genomic regions potentially involved in flowering-related traits. Moreover, the expression data of these genes suggested potential candidates for AE. Our results suggest that the use of significant markers can help to introduce AE in high yielding varieties to increase cross fertilization rates and improve hybrid-seed production in wheat.

Hybrid breeding facilitates the exploitation of heterosis and it can result in significant genetic gains and increased crop yields. Inefficient cross-pollination is a major limiting factor that hampers hybrid wheat seed production. In this study, we examined the genetic basis of anther extrusion (AE), which is an important trait in increasing cross-pollination, and thus improving seed set on the female lines and hybrid wheat seed production. We studied 300 segregating F2 plants and F2:3 families that result from a cross of two elite spring wheat lines. We observed that F2 and F2:3 populations hold significant and continuous genetic variation for AE, which suggests its reliable phenotypic selection. Composite interval mapping detected three quantitative trait loci (QTL) on chromosomes 3A, 5A, and 5D. The QTL on chromosome 5A (i.e., QAe.cimmyt-5A) was of large-effect, being consistently identified across generations, and spanned over 25 cM. Our study shows that (1) AE possesses strong genetic control (heritability), and (2) the QTL QAe.cimmyt-5A that imparted on an average of 20% of phenotypic variation can be used for marker-assisted selection (MAS) in breeding programs. In addition, pyramiding the large-effect QTL for MAS could efficiently complement the phenotypic selection since it is relatively easy and cheap to visually phenotype AE. This study reports the first large-effect QTL for AE in spring wheat, endorsing the use of this analysis in current hybrid wheat breeding and future Mendelization for the detection of underlying gene(s).

Hybrid wheat breeding is gaining prominence worldwide because it ensures higher and more static yield than conventionally bred varieties. The cleistogamous floral architecture of wheat (Triticum aestivum L.) impedes anthers inside the floret, making it largely an inbreeder. For hybrid seed production, high anther extrusion is needed to promote cross pollination and to ensure a high level of pollen availability for the seed plant. This study, therefore, aimed at the genetic dissection of anther extrusion (AE) in panels of spring (SP), and winter wheat (WP) accessions by genome wide association studies (GWAS). We performed GWAS to identify the SNP markers potentially linked with AE in each panel separately. Phenotypic data were collected for 3 years for each panel. The average levels of Pearson's correlation (r) among all years and their best linear unbiased estimates (BLUEs) within both panels were high (r(SP) = 0.75, P < 0.0001; r(WP) = 0.72, P < 0.0001). Genotypic data (with minimum of 0.05 minor allele frequency applied) included 12,066 and 12,191 SNP markers for SP and WP, respectively. Both genotypes and environment influenced the magnitude of AE. In total, 23 significant (|log10(P)| > 3.0) marker trait associations (MTAs) were detected (SP = 11; WP = 12). Anther extrusion behaved as a complex trait with significant markers having either favorable or unfavorable additive effects and imparting minor to moderate levels of phenotypic variance (R² (SP) = 9.75 - 14.24%; R² (WP) = 9.44 - 16.98%). All mapped significant markers as well as the markers within their significant linkage disequilibrium (r² = 0.30) regions were blasted against wheat genome assembly (IWGSC1+popseq) to find the corresponding genes and their high confidence descriptions were retrieved. These genes and their orthologs in Hordeum vulgare, Brachypodium distachyon, Oryza sativa, and Sorghum bicolor revealed syntenic genomic regions potentially involved in flowering-related traits. Moreover, the expression data of these genes suggested potential candidates for AE. Our results suggest that the use of significant markers can help to introduce AE in high yielding varieties to increase cross fertilization rates and improve hybrid-seed production in wheat. [ABSTRACT FROM AUTHOR]

Hybrid breeding is an efficient system to break the yield barriers in many crops. For an effective hybrid seed production, a pool of male parental lines with appropriate anther extrusion (AE) ensuring pollen shedding outside the florets for efficient cross fertilization is required. We investigated the genetic architecture of AE using genome-wide association studies (GWAS) and examined the potential of genome-wide prediction (GP) for AE based on a panel of 309 CIMMYT spring wheat lines evaluated in field trials and fingerprinted with genotyping-by-sequencing. The broad-sense heritability of AE was 0.64. Genotypic data consisted of 14,921 polymorphic markers. GWAS discovered no significant marker at FDR (P) B 0.20, suggesting that this trait is controlled by many small effect loci. Average accuracy of ridgeregression best linear unbiased prediction was 0.62. We conclude that GP is a suitable method to select for AE, which is otherwise challenging to phenotype. [ABSTRACT FROM AUTHOR]

Fusarium head blight (FHB) poses a challenge for wheat breeders worldwide; there are limited sources of resistance and the genetic basis for resistance is not well understood. In the mid-1980s, a shuttle breeding and germplasm exchange program launched between CIMMYT-Mexico and China, enabled the incorporation of FHB resistance from Chinese bread wheat germplasm into CIMMYT wheat. Most of the Chinese wheat materials conserved in the CIMMYT germplasm bank had not been fully characterized for FHB reaction under Mexican environments, until 2009, when 491 Chinese bread wheat lines were evaluated in a FHB screening nursery in Mexico, and 304 (61.9 %) showed FHB indices below 10 %. Subsequent testing occurred in 2010 for plant height (PH), days to heading (DH), and leaf rust response. In 2012, 140 elite lines with good agronomic types were further evaluated for field FHB reaction and deoxynivalenol (DON) accumulation. Most of the tested lines showed good resistance: 116 (82.9 %) entries displayed FHB indices lower than 10 %, while 89 (63.6 %) had DON contents lower than 1.0 ppm. Significant negative correlations were observed between FHB traits (FHB index, DON content, and Fusarium damaged kernels) and PH, DH, and anther extrusion. A subset of 102 elite entries was selected for haplotyping using markers linked to 10 well known FHB quantitative trait loci (QTL). 57 % of the lines possessed the same 2DL QTL marker alleles as Wuhan 1 or CJ 9306, and 26.5 % had the same 3BS QTL allele as Sumai 3. The remaining known QTL were of low frequency. These materials, especially those with none of the above tested resistance QTL (26.5 %), could be used in breeding programs as new resistance sources possessing novel genes for FHB resistance and DON tolerance. [ABSTRACT FROM AUTHOR]

Fusarium head blight ( FHB) remains a serious problem due to yield loss and mycotoxin accumulation in wheat production worldwide. We previously reported that the closed-flowering (no anther extrusion) characteristic was effective for increasing resistance to FHB infection. In this study, we investigated the relationships between the degree of anther extrusion ( AE) and FHB damage using double haploid lines ( DHLs), derived from F1 plants from crosses between closed-flowering and opened-flowering varieties. These DHLs exhibited various degrees of AE, and the degree of AE was significantly different among DHLs, regardless of the year and environment (pot- or field-grown). FHB severity was the lowest in closed-flowering DHLs, and DHLs with partially extruded anthers showed significantly higher FHB symptoms than those with closed-flowering phenotypes. In general, DHLs with partially extruded anthers also had relatively severe FHB symptoms compared with those exhibiting full anther extrusion. FHB severity was significantly correlated with Fusarium-damaged kernels and deoxynivalenol concentration. The results of this study showed that partially extruded anthers were considered to be a source of FHB infection. The closed-flowering phenotype improved resistance to FHB infection. Meanwhile, phenotypes with rapid anther extrusion and ejection also could contribute to the avoidance of FHB infection. [ABSTRACT FROM AUTHOR]

With 6 figures and 3 tables Anther extrusion (AE) has been suggested as one of the resistance mechanisms to Fusarium head blight (FHB) in wheat, but not well investigated. The objectives of this study were to assess AE in the double haploid population ‘Arina’ × ’NK93604’, evaluate its relationship both with FHB and deoxynivalenol (DON) accumulation, and map quantitative trait loci (QTLs). AE was studied in 2005−2007 and its relationship to FHB and DON content was analysed with data from Fusarium culmorum inoculations in 2001–2003 and with Fusarium graminearum in 2007. AE showed continuous distribution, transgressive segregation, minimal genotype × year interactions and was highly heritable ( H2 = 0.91). Mean AE showed highly significant negative correlations both with FHB ( r = −0.53 to −0.69, P = 0.0001) and DON ( r = −0.39 to −0.46, P = 0.0001). Composite interval mapping identified 4 QTLs for mean AE over 2 years that explained 53.6% of the total phenotypic variation. The phenotypic variance explained by the QTLs on chromosomes 1AL, 1BL, 4DL and 6AS varied from 7.4% to 18.3%. This is the first report describing QTLs for AE and to look systematically for association of AE with FHB and DON. [ABSTRACT FROM AUTHOR]

In connection with crop improvement strategies for marginal regions it has been proposed to increase the outcrossing rate in barley which would presuppose high and persistent pollen viability to ensure successful cross fertilisation. The present study was designed to investigate the viability of mature pollen from extruded and non-extruded anthers of cultivated and wild barley ( Hordeum vulgare ssp vulgare and ssp spontaneum, respectively) in comparison with the closely related but obligatory outcrossing species H. bulbosum. Pollen viability (PV) was assessed employing the p-phenylenediamine-peroxidase-test on pollen derived from spikes or anthers immediately after collection and after treatment at 20, 30 and 40 ∘C for 1, 2, 4, 8 and 16 h. The latter treatment was interposed after 8 h by a 10 h period of darkness at 12 ∘C and thus called 26 h treatment, consecutively. Initial PV was high with 98% across all genotypes and even at 40 ∘C did not fall below 80% after 8 h. After the 26 h treatment, PV of two H. vulgare genotypes originating from semi-arid regions and of H. bulbosum fell below 60% while the other genotypes retained a PV of > 80%. Viability of pollen of extruded anthers in H. vulgare ssp. spontaneum was on average slightly but significantly lower than PV of non-extruded anthers but still remained above 90%, even after the 26 h treatment at 40 ∘C. Pollen viability of the outcrossing species H. bulbosum ranged on a very similar level as PV of H. vulgare. Results indicate that pollen of H. vulgare retains a sufficiently high level of viability to ensure successful cross-fertilisation over a period of at least 26 h even at high temperatures of up to 40 ∘C. [ABSTRACT FROM AUTHOR]

Phenotyping wheat (Triticum aestivum L.) is time-consuming and new methods are necessary to decrease labor. To develop a heterotic pool of male wheat lines for hybrid breeding, there must be an efficient way to measure both anther extrusion and the size of anthers. Five hundred and ninety-four soft red winter wheat lines in two replications of randomized complete block design were phenotyped for anther extrusion, a key trait for hybrid wheat production. A device was constructed to capture images using a mobile device. Four heads were sampled per line when anthesis was evident for half the heads in the plot. The extruded anthers were scraped onto a surface, their image was captured, and the area of the anthers was taken via ImageJ. The number of anthers extruded was estimated by counting the number of anthers per image and dividing by the number of heads sampled. The area per anther was taken by dividing the area of anthers per spike by the number of anthers per spike. A significant correlation ( R = 0.9 ,   p < 0.0001 ) was observed between the area of anthers per spike and the number of anthers per spike. This method is proposed as a substitute for field ratings of anther extrusion and to quantitatively measure the size of anthers. [ABSTRACT FROM AUTHOR]

The flowering characteristics of a highly inbreeding species such as barley might influence the extent of outcrossing that can be expected. Increased outcrossing is a prerequisite to exploit heterosis in inbreeding species, which can lead to considerable yield increase as has been demonstrated for barley grown under marginal conditions. Anther extrusion (AE) in barley has been demonstrated to be a genetically controlled, quantitative trait with intermediate to high heritability. Some authors consider AE and open flowering in barley as identical. The present study was conducted to investigate whether barley genotypes with increased AE exhibit increased outcrossing rates under field conditions in comparison with genotypes showing no AE. Field experiments were conducted in three contrasting environments in Jordan in the 2001/02 growing season using six adapted barley genotypes, three with high AE and three with no AE. Outcrossing rates were investigated employing codominant DNA markers (microsatellites). No significant difference in outcrossing rates was detected between anther-extruding and non-extruding barley genotypes. Results indicate that high AE is not a sufficient condition to cause increased outcrossing rates and thus cannot be termed open flowering. [ABSTRACT FROM AUTHOR]

Variation and inheritance of anther extrusion and its effects on Fusarium head blight were studied. On a 0 to 9 scale, variation ranged from 1 to 6 in a North American oat panel and from 0 to 8 in a Nordic population. The inheritance was studied in two recombinant inbred line populations (Fiia × Stormogul and Svea × Stormogul). Fiia and Svea are recent white-seeded cultivars with low to medium anther extrusion, while Stormogul is an old black-seeded cultivar with high anther extrusion. Highly significant transgressive segregations and high heritabilities were observed (h2 = 0.91 in Fiia × Stormogul and h2 = 0.83 in Svea × Stormogul). Another extrusion was negatively correlated with Fusarium head blight and deoxynivalenol in spawn-inoculated field experiments, but significantly only in Fiia × Stormogul where the range in resistance was widest. Correlations were reversed in spray-inoculated greenhouse experiments, apparently spraying open florets defeated the avoidance mechanism. Anther extrusion may help oat avoid Fusarium infection in the field, but the genetic variance is inadequate and high anther extrusion is rare in modern genepools. [ABSTRACT FROM AUTHOR]

Pronounced anther extrusion (AE) is associated with field resistance to Fusarium head blight (FHB), one of the most devastating diseases of wheat globally. In this study, two recombinant inbred line (RIL) populations were used to map quantitative trait loci (QTL) for AE and field FHB resistance and to investigate the association of both traits at the genetic level. Furthermore, two panels of International Maize and Wheat Improvement Center (CIMMYT) wheat breeding lines were evaluated to describe the phenotypic association between the two traits in detail. Highly significant negative correlation was identified between AE and FHB severity in the two populations and the two panels, with r-values ranging from 0.55 to 0.74. QTL analysis in the two RIL populations identified 12 QTL for AE and nine for FHB resistance, of which five QTL located on chromosomes 3BL, 4BS, 4DS, 5AL, and 5BL were associated with both AE and FHB, collectively explaining over 50% of phenotypic variation for FHB. The QTL on chromosomes 4BS, 4DS, 5AL, and 5BL were closely linked to Rht-B1, Rht-D1, Vrn-A1, and Vrn-B1 genes, respectively. In conclusion, AE is closely related to field FHB resistance and could be used as a morphological marker in wheat breeding for field FHB resistance. [ABSTRACT FROM AUTHOR]

Abstract Previous studies have revealed that, in areas affected by severe drought, yielding ability and stability of barley (Hordeum vulgare L.) could be improved by increasing the level of heterozygosity. One possible approach to increase the heterozygosity level is to improve the outcrossing rate. In view of that, the genetic variability and phenotypic correlation coefficients involving four floral traits related to outcrossing behaviour were investigated in 274 drought adapted barley lines from the International Center for Agricultural Research in the Dry Areas (ICARDA's) current breeding programme. A significant quantitative variation existed in anther length and width, stigma length, and anther extrusion, which indicate that selection for these traits may be effective. Anther extrusion showed weak but highly significant positive correlations with anther and stigma length. Somewhat higher positive correlations were found between anther and stigma length. The results indicate that selection for high anther extrusion and longer anthers and stigmata may increase outcrossing in cultivated barley and consequently improve yielding ability through enhanced heterozygosity. [ABSTRACT FROM AUTHOR]

Hybrid breeding facilitates the exploitation of heterosis and it can result in significant genetic gains and increased crop yields. Inefficient cross-pollination is a major limiting factor that hampers hybrid wheat seed production. In this study, we examined the genetic basis of anther extrusion (AE), which is an important trait in increasing cross-pollination, and thus improving seed set on the female lines and hybrid wheat seed production. We studied 300 segregating F2 plants and F2:3 families that result from a cross of two elite spring wheat lines. We observed that F2 and F2:3 populations hold significant and continuous genetic variation for AE, which suggests its reliable phenotypic selection. Composite interval mapping detected three quantitative trait loci (QTL) on chromosomes 3A, 5A, and 5D. The QTL on chromosome 5A (i.e., QAe.cimmyt-5A) was of large-effect, being consistently identified across generations, and spanned over 25 cM. Our study shows that (1) AE possesses strong genetic control (heritability), and (2) the QTL QAe.cimmyt-5A that imparted on an average of 20% of phenotypic variation can be used for marker-assisted selection (MAS) in breeding programs. In addition, pyramiding the large-effect QTL for MAS could efficiently complement the phenotypic selection since it is relatively easy and cheap to visually phenotype AE. This study reports the first large-effect QTL for AE in spring wheat, endorsing the use of this analysis in current hybrid wheat breeding and future Mendelization for the detection of underlying gene(s). [ABSTRACT FROM AUTHOR]