Crops emit a variety of volatile organic compounds (VOCs) that serve as attractants or repellents for pests and their natural enemies. Crop rotations, off-farm chemical inputs, and mechanical and cultural tactics – collectively called cropping systems – alter soil nutrients, moisture content, and microbial communities, all of which have the potential to alter crop VOC emissions. Soil legacy effects of diversified cropping systems have been shown to enhance crop VOC emissions in greenhouse studies, but how they influence emissions under field conditions remains virtually unknown. To determine the effect of cropping systems on plant VOC emissions in the field, air samples were collected from the headspace of wheat (Triticum aestivum L. Judee) grown in simplified wheat-fallow rotations or diversified wheat-cover crop rotations where cover crops were terminated by grazing cattle. Across two growing seasons, wheat grown in rotation with fallow emitted greater amounts of Z-3-hexenyl acetate and β-ocimene, key attractants for wheat stem sawfly (Cephus cinctus Norton), a major pest of wheat. While overall VOC blends were relatively similar among cropping system during the first growing season, emissions varied substantially in the second year of this study where wheat grown in rotation with cover crops emitted substantially greater quantities of volatile compounds characteristic of abiotic stress. Below-average precipitation in the second growing season, in addition to reduced soil water content in cover crop rotations, suggests that cropping system effects on wheat VOCs may have been driven primarily by water availability, a major factor limiting crop growth in dryland agriculture. While the specific mechanisms driving changes in VOC emissions were not explicitly tested, this work shows that agricultural practices applied in one growing season can differentially influence crop VOC emissions in the next through soil legacy effects, illustrating additional avenues through which cropping systems may be leveraged to enhance pest management.

Drought is a major concern among abiotic stresses in wheat (Triticum aestivum L.) production. Breeding resistant cultivars are the most effective means to manage drought stress. F6 recombinant inbred lines (RIL) derived from the cross of Berkut/Worrakatta were used to identify quantitative trait loci (QTL) for drought tolerance at germination stage under treatment of PEG6000 using the wheat 50 K single nucleotide polymorphism (SNP) array. Twenty-eight linkage groups were constructed, covering a length of 2220.26 cM. Eighteen QTL were detected based on the drought tolerance coefficients and D-value, explaining 2.7–6.5% of the phenotypic variances, in which 15 were likely to be novel. Three QTL, QGR.xjau-5AS, QCL.xjau-5AS and QD.xjau-5AS for GR, CL and D-value, respectively, at physical positions of 11.70–20.61 Mb between markers AX-111258240 and AX-94458300 on chromosome 5AS accounted for 3.4–4.8% of the phenotypic variances. Three QTL, QGP.xjau-5DL, QSH.xjau-5DL and QD.xjau-5DL for GP, SH and D-value, respectively, were flanked by markers AX-94524442 and AX-110998507 at 560.42–567.39 Mb on chromosome 5DL, accounting for 4.4–6.5% of the phenotypic variances. In addition, the candidate genes TraesCS5A02G022100, TraesCS5B02G014200 and TraesCS5D02G563900 were predicted. Based on transcriptional expression data, the results showed that the expression level of TaGATAs-5A, TaUbox-5B and TaGSTP-5D changed with the increase of treatment time under drought stress in tolerant and sensitive varieties. These are interesting targets in mining drought tolerance genes and the improvement of drought tolerance in wheat.

Three herbicide premixes have recently been introduced for weed control in wheat: halauxifen + florasulam, thifensulfuron + fluroxypyr, and bromoxynil + bicyclopyrone. The objective of this study was to evaluate these herbicides along with older products for their control of small-seeded false flax in winter wheat in Oklahoma. Studies took place during the 2017, 2018, and 2020 winter wheat growing seasons. Weed control was visually estimated every 2 wk throughout the growing season, and wheat yield was collected in all 3 yr. Small-seeded false flax diameter was approximately 6 cm at the time of application in all years. Control ranged from 96% to 99% following all treatments with the exception of bicyclopyrone + bromoxynil and dicamba alone, which controlled false flax 90%. All treatments containing an acetolactate synthase (ALS)–inhibiting herbicide achieved adequate control; therefore, resistance is not suspected in this population. Halauxifen + florasulam and thifensulfuron + fluroxypyr effectively controlled small-seeded false flax similarly to other standards recommended for broadleaf weed control in wheat in Oklahoma. Rotational use of these products allows producers flexibility in controlling small-seeded false flax and reduces the potential for development of herbicide resistance in this species.

This research was conducted near North Platte, NE, over an 18-yr period to determine the feasibility of using herbicides to replace tillage as the weed control method in a winter wheat (Triticum aestivum L.)-sorghum [Sorghum bicolor (L.) Moench.]-fallow rotation. Five tillage treatments [two tillage and three reduced or no-till treatments] were used on the same plots during the duration of this experiment on a Holdrege silt loam (Typic Argiustolls). Herbicides effectively replaced tillage for weed control. The no-till plots treated with atrazine [6-chloro-N-ethyl-N′-(1-methylethyl)-1,3,5-triazine-2,4-diamine] after wheat harvest had higher sorghum and winter wheat yields, higher crop residue remaining on the soil surface, and lower weed yields than tilled plots. The most difficult weeds to control were volunteer wheat and barnyardgrass [Echinochloa crus-galli (L.) Beauv. # ECHCG]. Soil surface pH decreased over time because of increased use of nitrogen. The pH in nontilled plots was significantly lower than in tilled plots due to lack of soil mixing. Exchangeable calcium was the predominant cation leached from the top 5 cm but showed accumulation between the 5- to 12.5-cm depth. Organic matter content showed little change over time.

Stripe rust, caused by Puccinia striiformis f.sp. tritici (Pst), is an important disease of winter wheat in Central Asia. Stripe rust races contain diverse virulence/avirulence patterns and change rapidly. Therefore the objectives of this research were to: (i) examine current pathotype variability of Pst races collected from Kazakhstan and Uzbekistan and (ii) evaluate stripe rust resistance in leading cultivars and advanced breeding lines targeted to those regions. Analyses of 152 Pst samples showed diverse virulence patterns with avirulence to Yr5, Yr10 and Yr15 being common. Most of identified races are among the rare. Analysis of a mixed Pst population showed 10 distinct pathotypes with frequencies ranged from 1.2 to 8.7%. The virulence patterns ranged from least ‘31–1.5’ and X-1.5 to highly virulent ‘86 + E16’. Seedling evaluation of 62 genotypes using the 10 pathotypes showed variations for resistance. Bunyodkor and Barhayot showed resistance to all pathotypes. Five Yr genes were postulated. Yr1 in KR12-5075, and Yr6 in KR11-03 and KR12-5003 were postulated. Yr5 combined with Yr10 and Yr15 genes were determined in Bunyodkor. The wheat genotypes also showed different levels of resistance in adult plant stage under field conditions. Twenty genotypes showed <20% severity in both Kazakhstan and Uzbekistan. The disease severity on several genotypes differed in this countries, suggesting different Pst populations in the two countries. Several resistant genotypes were identified, which should be further evaluated for release as new varieties or used in breeding programmes. Two resistant lines from this study were identified as new varieties in Georgia and Uzbekistan.

Maintaining crop residues on the soil surface has changed cropping practices in the Central Great Plains. Where previously winter wheat–fallow was the prevalent rotation, producers now grow warm-season crops in sequence with winter wheat and fallow. Controlling weeds during fallow with herbicides eliminates the need for tillage, thus conserving more crop residues. However, producers are considering subsurface tillage as an option to manage herbicide-resistant weeds. We reviewed the impact of subsurface tillage with the sweep plow on weed dynamics and crop growth compared with no-till systems. Cropping systems studies show that rotations can be designed to reduce weed community density severalfold; tillage lessens this rotational effect by burying weed seeds and prolonging their survival in soil. Crop residues on the soil surface reduce weed seedling establishment in no-till systems, but tillage eliminates this effect. Crops also yield less after tillage compared with no-till in this semiarid climate. Tillage may help in managing herbicide resistance, but it also may increase weed density as well as reduce crop yield.

The overexpression of wheat Bx7 subunit (Bx7OE) encoded by the Glu-B1al allele is originated from a duplication event of the Bx7 gene, and has a positive effect on gluten strength. Thus, it is an important genetic resource for wheat quality improvement. In this study, the Bx7OE subunit from a large number of bread wheat and related species was characterized by sodium dodecyl sulphate–polyacrylamide gel electrophoresis, reversed-phase high-performance liquid chromatography (RP-HPLC) and Sequence-Tagged sites (STS) markers. Only 31 bread wheat varieties were found to carry Bx7OE. RP-HPLC quantification analysis revealed that the mean proportion of the Bx7OE subunit to the total amount of high-molecular-weight glutenin subunits among the 31 bread wheat varieties was 41.8%, which is much higher than that of varieties with the normal Bx7 subunit (generally at 30%). Flour quality analysis of seven representative varieties with Bx7OE and three with the normal Bx7 subunit showed that the varieties with Bx7OE generally displayed better gluten strength than those with the normal Bx7 subunit. STS markers demonstrated that, in addition to the 31 bread wheat varieties with Bx7OE, no PCR products were obtained from the related Triticum and Aegilops species. This suggests that the retroelement-mediated recombination event at the Glu-B1 locus could have occurred more recently, later than the formation of hexaploid wheat. The Bx7OE subunit is mainly distributed in some bread wheat varieties from American countries with a low frequency, which is of particular importance for the quality improvement of wheat gluten.

Drought is one of the major factors limiting wheat yield in many developing countries worldwide. Parameters of chlorophyll a fluorescence kinetics under drought stress conditions have been used to characterize dehydration tolerance in wheat. In the present study, a set of 94 doubled haploid lines obtained from Chinese Spring × SQ1 (CSDH), mapped with 450 markers, was evaluated for yield (grain dry weight/main stem ear), number of grains/main stem ear (NG) and chlorophyll a fluorescence parameters (FC) under moderate and severe drought stress, and compared with results for well-watered plants. quantitative trait loci (QTLs) were identified using Windows QTLCartographer version 2.5 software and the results were analysed using single-marker analysis (SMA) and composite interval mapping (CIM). Analysis using SMA and CIM showed mostly similar QTLs for all traits, though more QTLs were identified by SMA than by CIM. The genetic control of yield, NG and FC varied considerably between drought-stressed and non-stressed plants. Although no major QTL co-locations were found for yield and FC using CIM, the co-location of QTLs for NG, yield and Fv/Fm in drought-stressed plants was observed on chromosome 5A using SMA.

The objective of our study was to determine the composition of high-molecular weight-glutenin subunits (HMW-GS) in 120 cultivars of common wheat (Triticum aestivum L.). Fourteen alleles and 34 allelic compositions were detected using sodium dodecyl sulphate-polyacrylamide gel electrophoresis. The most frequent HMW-GS alleles at the Glu-A1, Glu-B1 and Glu-D1 loci were null (57.1%), 7+9 (43.3%) and 5+10 (61.9%), respectively. However, low-frequency HMW-GS alleles were also observed, such as 13+16, 20, 21, 7 and 18, encoded by the Glu-B1 locus, and 4+12, encoded by the Glu-D1 locus. The wheat–rye 1BL.1RS translocation was identified in 25 cultivars, using acid polyacrylamide gel electrophoresis. The Glu-score varied greatly, and some lines reached the maximum value of 10.

Kernel texture (grain hardness) in common wheat (Triticum aestivum L.) is of primary technological importance and is largely determined by puroindoline gene sequence and expression. We investigated the puroindoline haplotypes of 246 Asian common wheat varieties. All but three were conclusively characterized for puroindoline a and b haplotypes. Of the total, 174 possessed the soft Pina-D1a/Pinb-D1a ‘wild-type’ gene sequences with SKCS hardness indexes (HI) ranging from 13.5 to 61.8. Among the remaining 72 varieties with HIs of 56.1–97.8, nearly half (30) were Pina-D1a/Pinb-D1b, 4 were Pina-D1a/Pinb-D1c, 19 were Pina-D1a/Pinb-D1p, 10 were Pina-D1b/Pinb-D1a (‘a-null’), 3 were Pina-D1l/Pinb-D1a, 2 possessed a new C-to-T SNP mutation at position 382, which is tentatively designated Pinb-D1ab, 1 was a ‘double null’ with neither puroindoline a nor b expressed and no PCR-detectable gene sequence, and 3 had undetermined/ambiguous puroindoline a sequence but possessed Pinb-D1a. The double null was the hardest of all varieties tested with an HI of 97.8. The frequency of soft and hard varieties and puroindoline hardness haplotype varied depending on the origin of the varieties. The lowest frequency of hard varieties occurred in Korea and south-western Japan. Tibet and Pakistan also had low frequencies of hard varieties. The highest frequency of hard varieties appeared in north-east China followed by north-west China and Nepal. Within Asia, the Pinb-D1p allele appears in a region extending from north-eastern China through Inner Mongolia, north-western China, Xinjiang and Tibet, with the greatest frequency in north-western China. This allele was also present in Pakistan and Afghanistan, but not found in Japan, and may have been dispersed along the ‘Silk Road’. All three Pina-D1l varieties came from China. The newly discovered SNP originated in Afghanistan and the ‘double null’ in Xinjiang.

Canadian Western Hard Red Spring (CWRS) wheat is recognized as premium quality wheat, ideal for breadmaking due to its superior milling qualities, baking characteristics and protein content. Organic wheat production is becoming more prevalent in Canada, due to increasing consumer demand for organic wheat products. Differences may exist in the baking and milling quality of wheat grown under conventional and organic management, a result of the dissimilarity between organic and conventional soil and crop management practices. Five CWRS cultivars released from 1885 to 1997 were grown under conventional and organic management and were assessed for their breadmaking potential. Several traits were investigated, including test weight, protein content, flour yield, kernel hardness and several mixograph parameters. Test weight was higher under conventional management, while no differences in protein content were observed between organic and conventionally grown wheat. Higher sodium dodecyl sulfate sedimentation (SDSS) volume, a reflection of gluten strength, was observed under conventional management, while there was a trend towards higher dough strength under organic management. Cultivars differed in grain protein, flour yield, kernel hardness and mixograph parameters, with Park and McKenzie superior to the others, particularly Red Fife, a much older cultivar. Management×cultivar interaction effects suggest that cultivars exhibit somewhat different baking characteristics when grown in the two management systems. There was no evidence that older cultivars (developed prior to the widespread use of pesticides and fertilizers) are better suited, in terms of breadmaking quality, for organic production.

Wheat grain dormancy is a multigenic trait controlled both by R genes conferring red testa pigmentation and by other genes, at least one of which has a major effect in the embryo. Enhanced grain dormancy and red test colour are inherited as pleiotropic effects of dominant R alleles at triplicate loci in hexaploid wheat. However, polymorphism for R genes cannot account for the wide variation in dormancy observed among different redgrained varieties. A variety of different dominant R alleles all have equivalent effects on dormancy when introgressed into white-grained wheats, although the latter vary in dormancy both in the absence and in the presence of dominant R alleles. As a result, certain redgrained genotypes can exhibit intermediate dormancy, similar to that of some white-grained genotypes with different genetic backgrounds. A new major gene (Phs) was identified as controlling the difference between two red-grained cultivars with widely different dormancies. The Phs gene appeared to exert its effect in the embryo of the grain, in contrast to R gene expression in maternal testa tissue. Discrete genetic functions thus underlie physiologically distinct mechanisms of coatimposed dormancy and embryo-imposed dormancy in wheat

Information is needed on the role of cover crops as a weed control alternative due to the high adoption of conservation tillage in soybean [Glycine max (L.) Merr.] production. Field experiments were conducted from fall 1994 through fall 1997 in Alabama to evaluate three winter cereal cover crops in a high-residue conservation-tillage, soybean production system. Black oat (Avena strigosa Schreb.), rye (Secale cereale L.), and wheat (Triticum aestivum L.) were evaluated for their weed-suppressive characteristics compared to a winter fallow system. Three herbicide systems were utilized: no herbicide, a mixture of two pre-emergence (PRE) herbicides, or PRE plus post-emergence (POST) herbicides. The PRE system contained pendimethalin plus metribuzin. The PRE plus POST system contained pendimethalin plus a prepackage of metribuzin and chlorimuron ethyl applied PRE, followed by an additional chlorimuron ethyl POST application. No cover crop was effective in controlling weeds without a herbicide. However, when black oat or rye was utilized with only PRE herbicides, weed control was similar to the PRE plus POST input system. Thus, herbicide reductions may be attained by utilizing cover crops that provide weed suppression. Rye and black oat provided more effective weed control in the PRE only herbicide input system than wheat in conservation-tillage soybean. The winter fallow, PRE plus POST herbicide input system yielded significantly less soybean one out of three years when compared to systems that included a winter cover crop.