Productive tiller number (PTN), defined as the number of tillers that produce spikes and seeds, is a key component of grain yield in wheat. Spring wheat cultivars in the northern Great Plains of ...North America differ in PTN. The objectives of this study were (1) to determine the relationship of PTN to agronomic traits using recombinant inbred line (RIL) populations derived from crosses Reeder/Conan, McNeal/Thatcher and Reeder/McNeal grown under a range of environments, and (2) to identify and validate quantitative trait loci (QTL) associated with high PTN. Correlation between PTN and plot weight ranged from
r
= 0.4–0.6 among the populations based on combined means over years, and was positive in every environment for all crosses (
P
< 0.05). A genetic map generated for the Reeder/Conan RIL allowed identification of a QTL for PTN consistent over environments, located on chromosome 6B. The QTL on chromosome 6B (
QTn.mst
-
6B
) explained 9–17% of the variation of PTN and co-segregated with a QTL for yield in the Reeder/Conan RIL.
QTn.mst
-
6B
was validated by single marker analysis in the McNeal/Thatcher RIL, McNeal/Reeder RIL, and a set of near isogenic line (NIL) developed for
QTn.mst
-
6B
. The allele for high PTN significantly increased PTN by 8.7, 4, and 13% in the McNeal/Reeder RIL, McNeal/Thatcher RIL and Choteau/Reeder NIL, respectively. The allele for high PTN also had a significant positive effect on plot weight in the McNeal/Reeder RIL. Our results suggest that high PTN, controlled to a significant extent by
QTn.mst
-
6B
, contributed to increased yield potential over a range of environmental conditions.
QTn.mst
-
6B
may be useful for improving spring wheat in the northern Great Plains of North America and similar environments.
Single-nucleotide polymorphism was used in the construction of an expressed sequence tag map of Aegilops tauschii, the diploid source of the wheat D genome. Comparisons of the map with the rice and ...sorghum genome sequences revealed 50 inversions and translocations; 2, 8, and 40 were assigned respectively to the rice, sorghum, and Ae. tauschii lineages, showing greatly accelerated genome evolution in the large Triticeae genomes. The reduction of the basic chromosome number from 12 to 7 in the Triticeae has taken place by a process during which an entire chromosome is inserted by its telomeres into a break in the centromeric region of another chromosome. The original centromere-telomere polarity of the chromosome arms is maintained in the new chromosome. An intrachromosomal telomere-telomere fusion resulting in a pericentric translocation of a chromosome segment or an entire arm accompanied or preceded the chromosome insertion in some instances. Insertional dysploidy has been recorded in three grass subfamilies and appears to be the dominant mechanism of basic chromosome number reduction in grasses. A total of 64% and 66% of Ae. tauschii genes were syntenic with sorghum and rice genes, respectively. Synteny was reduced in the vicinity of the termini of modern Ae. tauschii chromosomes but not in the vicinity of the ancient termini embedded in the Ae. tauschii chromosomes, suggesting that the dependence of synteny erosion on gene location along the centromere-telomere axis either evolved recently in the Triticeae phylogenetic lineage or its evolution was recently accelerated.
Key message
The impact of the D genome and QTL in the A and B genomes on agronomic performance of hexaploid wheat and tetraploid durum was determined using novel recombinant inbred line populations ...derived from interploid crosses.
Genetic differences between common hexaploid (6X) bread wheat (
Triticum aestivum
, 2
n
= 6
x
= 42, genome, AABBDD) and tetraploid (4X) durum wheat (
T. turgidum
subsp. durum, 2
n
= 4
x
= 28, genome, AABB) may exist due to effects of the D genome and allelic differences at loci in the A and B genomes. Previous work allowed identification of a 6X by 4X cross combination that resulted in a large number of fertile recombinant progeny at both ploidy levels. In this study, interspecific recombinant inbred line populations at both 4X and 6X ploidy with 88 and 117 individuals, respectively, were developed from a cross between Choteau spring wheat (6X) and Mountrail durum wheat (4X). The presence of the D genome in the 6X population resulted in increased yield, tiller number, kernel weight, and kernel size, as well as a decrease in stem solidness, test weight and seed per spike. Similar results were found with a second RIL population containing 152 lines from 18 additional 6X by 4X crosses. Several QTL for agronomic and quality traits were identified in both the 4X and 6X populations. Although negatively impacted by the lack of the D genome, kernel weight in Mountrail (4X) was higher than Choteau (6X) due to positive alleles from Mountrail on chromosomes 3B and 7A. These and other favorable alleles may be useful for introgression between ploidy levels.
Segregation at major genes controlling plant height, photoperiod response, and vernalization response in wheat (Triticum aestivum L. em. Thell.) may have pleiotropic effects on several traits. ...Allelic variation at these loci can be monitored using polymerase chain reaction (PCR) markers. The effect of segregation at these loci on maturity and agronomic traits was measured for sets of recombinant inbred lines (RIL) developed from five crosses between spring wheat lines adapted to Montana and the Northern Great Plains. Results from field trials grown in multiple years in Bozeman, MT, showed that variation at Rht-B1 and Rht-D1 had large effects on most agronomic traits in two populations, including grain yield, grain protein concentration, and test weight. Variation at photoperiod response loci Ppd-B1 and Ppd-D1 influenced both heading date and date of flag leaf senescence under field conditions for two of three populations in which they were segregating. The insensitive allele at Ppd-B1 was associated with higher grain yield in one population. Variation at Vrn-B1 had a significant effect on heading date in the field for both populations in which it was segregating, with spring allele lines being earlier. Our results suggest that variation at Rht loci impacting plant height had large pleiotropic effects. Variation at photoperiod and vernalization loci impacted maturity characteristics but had less consistent effects on economic characteristics such as grain yield, test weight, and grain protein concentration.
ABSTRACT
The wheat stem sawfly (WSS) (Cephus cinctus Nort.) is an important pest of wheat (Triticum aestivum L. em. Thell.) in the Northern Great Plains. This paper reports the genetic analysis of ...antixenosis for egg‐laying WSS females in recombinant inbred lines (RIL) of hard red spring wheat. Female WSS preferentially choose certain wheat genotypes for egg‐laying, with the cultivar Reeder being preferred and Conan being less preferred. We measured percent stem infestation and percent stem cutting for 91 RIL from a Reeder–Conan cross in four sawfly‐infested locations in Montana. Heritability based on means over environments was h2 = 0.86 for infestation and h2 = 0.75 for cutting. Percent infestation was negatively correlated with heading date (r = −0.57, P < 0.001) and degree of stem solidness (r = −0.31, P < 0.01). A molecular map was created with 431 markers. Quantitative trait loci (QTL) for infestation and cutting were identified as cosegregating with QTL for heading date (controlled by Ppd‐D1 on chromosome 2D) and stem solidness (controlled by Qss.msub.3BL). Additionally, significant QTL for infestation and cutting on chromosomes 2D and 4A were present in several environments, and did not cosegregate with heading date, plant height, or solid stems. These QTL may complement the use of solid stems for host plant resistance by developing wheat lines that vary for attractiveness to the wheat stem sawfly.
ABSTRACT
Genetic approaches to lengthening green leaf duration are becoming more important in spring wheat (Triticum aestivum L. em. Thell.) as increasing temperatures hasten leaf senescence. Green ...leaf duration after heading (GLDAH) has been reported to provide drought and heat tolerance in several crops. This study was conducted in Montana under a range of temperature and moisture conditions to evaluate the relationship of GLDAH to agronomic traits and to identify quantitative trait loci (QTL) for GLDAH using a recombinant inbred line (RIL) population derived from Reeder (longer GLDAH) and Conan (intermediate GLDAH). Correlation analysis showed a positive relationship between GLDAH and test weight, seed weight, and seed diameter under late‐season heat and drought stress conditions but not under cool, well‐watered conditions. Green leaf duration after heading was negatively correlated with grain yield under cool, well‐watered conditions. Earlier heading was consistently associated with longer GLDAH in a wide range of environments. The QTL QGfd.mst‐4A had an effect on GLDAH under stress conditions in the Conan/Reeder population and an RIL population derived from McNeal/Reeder. The Reeder allele of QGfd.mst‐4A resulted in longer GLDAH and also increased the amount of xylem exudate from de‐topped plants, indicating higher root mass and/or activity. Our results suggest that the impact of alleles at QGfd.mst‐4A may vary depending on the degree of heat and drought stress.
Increasing temperatures are a threat to hard red spring wheat (Triticum aestivum L.) production in the northern Great Plains and may impact objectives for breeding programs. Weather data and ...agronomic performance of experimental lines and a check cultivar ‘Thatcher’ were compiled for six sites in Montana for 1950 to 2007. Mean annual temperature increased significantly at five sites. March temperature increased significantly at all sites, and planting date has become significantly earlier at a rate of 0.24 d yr–1. Grain yield of Thatcher increased significantly at a rate of 23.5 kg ha–1 yr–1. July temperatures increased significantly at two sites. July temperatures showed a significant negative correlation with grain yield at three sites and with grain volume weight at three sites. Nursery means over years as adjusted for Thatcher was used as a measure of genetic change and showed significantly increased grain yield and significantly earlier heading date. Our results suggest that earlier planting due to warmer spring temperatures has helped to alleviate negative effects of high temperatures during grain filling periods. Genetic changes in breeding materials have also contributed to increased yield potential, partially due to earlier heading and avoidance of July heat. Projection of increasing temperatures suggests the need for management and breeding strategies to insure productivity of hard red spring wheat in the northern Great Plains.
Summary
Extensive herbicide usage has led to the evolution of resistant weed populations that cause substantial crop yield losses and increase production costs. The multiple herbicide‐resistant (MHR) ...Avena fatua populations utilised in this study are resistant to members of all selective herbicide families, across five modes of action, available for A. fatua control in US small grain production, and thus pose significant agronomic and economic threats. Resistance to acetolactate synthase and acetyl‐CoA carboxylase inhibitors is not conferred by known target site mutations, indicating that non‐target site resistance (NTSR) mechanisms are involved. Understanding the inheritance of NTS MHR is of upmost importance for continued agricultural productivity in the face of the rapid increase in resistant weed populations worldwide. As few studies have examined the inheritance of NTSR in autogamous weeds, we investigated the inheritance and genetic control of NTSR in the highly autogamous, allohexaploid species A. fatua. We found that NTSR in MHRA. fatua is controlled by three separate, closely‐linked nuclear genes for flucarbazone‐sodium, imazamethabenz‐methyl and pinoxaden. The single‐gene NTSR inheritance patterns reported here contrast with other examples in allogamous species and illustrate the diversity of evolutionary responses to strong selection.
Bread baking is the primary end-use criterion used to select hard spring wheat (Triticum aestivum L.) genotypes for the northwestern USA, yet the use of hard wheats has expanded beyond traditional ...pan breads to include Asian noodles. We assessed the relative influence of genotype, N management, and location on quality characteristics of a set of spring wheat cultivars that provided a range in gluten strength and acceptability for bread and Asian noodle quality, and determined whether grain characteristics could predict bread and/or noodle market suitability. Seven spring cultivars were grown at four locations across 3 yr with two levels of N fertilizer in irrigated and moisture-limited conditions. Bread quality, alkaline noodle color, and Chinese noodle color and texture were assessed on grain samples. Cultivar was the most important determinant of bread and noodle quality traits in both the irrigated and moisture-limited environments. Nitrogen level influenced only Chinese noodle color in irrigated environments, but impacted test weight, flour ash, loaf volume, and bake absorption in moisture-limited environments. Responses to N management and location were usually not cultivar specific, as interactions were not important relative to main effects of cultivar and location. Grain protein had more value than test weight or grain hardness in predicting bread and noodle quality, and was most useful in predicting loaf volume and Chinese noodle color characteristics. Cultivar selection is critical for achieving a desired end use, with location effects being of secondary importance. Nitrogen management for a particular end use will be difficult, with N level being much less important than cultivar selection and location. Grain protein may be the best predictor of the suitability of a particular cultivar produced in a specific year for alternative end-use possibilities, with high-protein grain most suitable for bread production and low-protein, high-quality grain more suitable for noodle production.
Conversion of amplified fragment length polymorphisms (AFLPs) to sequence-specific PCR primers would be useful for many genetic-linkage applications. We examined 21 wheat nullitetrasomic stocks and ...five wheat-barley addition lines using 12 and 14 AFLP primer combinations, respectively. On average, 36.8% of the scored AFLP fragments in the wheat nullitetrasomic stocks and 22.3% in the wheat-barley addition lines could be mapped to specific chromosomes, providing approximately 461 chromosome-specific AFLP markers in the wheat nullitetrasomic stocks and 174 in the wheat-barley addition lines. Ten AFLP fragments specific to barley chromosomes and 16 AFLP fragments specific to wheat 3BS and 4BS chromosome arms were isolated from the polyacrylamide gels, re-amplified, cloned and sequenced. Primer sets were designed from these sequences. Amplification of wheat and barley genomic DNA using the barley derived primers revealed that three primer sets amplified DNA from the expected chromosome, five amplified fragments from all barley chromosomes but not from wheat, one amplified a similar-sized fragment from multiple barley chromosomes and from wheat, and one gave no amplification. Amplification of wheat genomic DNA using the wheat-derived primer sets revealed that three primer sets amplified a fragment from the expected chromosome, 11 primer sets amplified a similar-sized fragment from multiple chromosomes, and two gave no amplification. These experiments indicate that polymorphisms identified by AFLP are often not transferable to more sequence-specific PCR applications.
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