Decline in soil organic carbon (SOC) due to intensive tillage and removal or burning of crop residues is considered a major threat to maintaining soil quality and meeting future challenges of food production at national and global scales. Adoption of conservation-agriculture practices (no till and residue retention) is necessary to promote soil structural stability and increases in SOC content and enzyme activities. We evaluated the impact of tillage and residue-management practices on yield, soil labile-C pools, aggregate stability and soil enzyme activities after seven cycles of a rice (Oryza sativa L.)–wheat (Triticum aestivum L.) system on the Indo-Gangetic Plain of India. Treatments included four combinations of tillage and crop establishment in rice (main plots), and three combinations of tillage and residue management in wheat (subplots). Irrespective of rice-establishment method, mean grain yield of no-till wheat with rice-residue mulch (NTW+RR) was 9% and 22% higher, respectively, than of conventional-till (CTW) or no-till wheat with no rice-residue mulch. Soil C pools (very labile, labile, less-labile and non-labile) were significantly higher under a no-till dry-seeded rice (NTDSR)–NTW+RR cycle than conventional-till puddled transplanted rice–CTW. Macro-aggregates (>0.25 mm) had higher labile C pools, glomalin content and enzyme activities than micro-aggregates. NTW+RR significantly increased soil C pools within both macro- and micro-aggregates. Compared with CTW, NTW+RR increased soil dehydrogenase, cellulase and alkaline phosphatase activities by 23%, 34% and 14%, and water-soluble organic C by 31%, and increased water-stable aggregates and mean-weight-diameter. NTDSR–NTW+RR increased SOC, enzyme activity, aggregate stability and wheat grain yield. Results indicated that soil labile-C pools across aggregate fractions were the most sensitive indicators of soil quality when determining the effects of changes in management practices. Furthermore, adoption of no till and residue retention may improve sustainability in rice–wheat systems of the Indo-Gangetic Plain.

Extreme heat-stress events are becoming more frequent under anticipated global warming, which is having devastating effect on grain yield, as well as quality, of rice (Oryza sativa L.). The effects of heat stress at booting stage on grain quality of two japonica varieties, Nanjing41 and Wuyunjing24, were investigated in phytotrons during 2014 and 2015. Rice plants were subjected to four mean temperature regimes 27°C, 31°C, 35°C and 39°C of 2, 4 and 6 days’ duration. The results showed that high temperatures of 35°C and 39°C for 4 and 6 days significantly reduced panicle size, seed-setting rate, grain size, chalky grain rate, milling characteristics and amylose content, but increased protein content. Severe heat stress decreased values of peak viscosity and breakdown, and increased pasting temperature. An increase in heat degree-days decreased the percentage of chalky grains exponentially, and decreased amylose content and increased protein content linearly. Sensitivity of grain quality to heat stress in the two varieties differed among quality traits and with heat stress intensity. This study indicates that rice-grain quality had some resistance to mild heat stress, but it could not withstand severe heat stress at booting. Short-term heat stress at booting stage deteriorates most grain-quality traits, posing a potential risk to rice quality. The impacts on grain quality could be well quantified by the combined effects of the intensity and duration of heat stress at booting stage.

Foliar zinc (ZnSO₄) application is an effective agronomic tool for Zn biofortification of wheat (Triticum aestivum L.) and hence for overcoming human Zn deficiency. It is unclear how the methods used to apply phosphorus (P) fertilisers affect the uptake and availability of Zn in wheat plants. Here, a solution-culture experiment and a 2-year field experiment were conducted to determine the influence of P applied to leaves or roots on total, soluble and insoluble Zn in winter wheat plants (cv. Xiaoyan-22) also receiving foliar Zn. Foliar Zn application, regardless of P application, significantly improved grain total Zn (primarily water-soluble) by 79.4% under both growth conditions, and reduced grain phytic acid : Zn (PA : Zn) molar ratio by 54.4% in the field. In solution culture, root-applied P did not affect plant uptake of foliar-applied Zn; however, foliar application of Zn plus P reduced the soluble fraction of Zn in wheat tissues, and thus decreased grain Zn concentration by 13.2% compared with Zn-only foliar application. Similarly, in the field, foliar-applied Zn plus P resulted in lower grain total and soluble Zn concentration and higher grain PA and PA : Zn molar ratio than foliar Zn alone. Overall, foliar Zn application is efficient in increasing grain Zn concentration and bioavailability under varied methods of P application. Although foliar-applied P slightly reduces the ability of plants to use foliar-applied Zn to increase grain Zn, foliar Zn combined with commonly applied foliar P application represents an easily adoptable practice for farmers that will help to alleviate Zn deficiency in human populations.

Textural property is one of the most important factors influencing the quality of northern-style Chinese steamed bread (CSB). We detected quantitative trait loci (QTLs) for the textural properties of CSB by using 184 recombinant inbred lines derived from a cross between two Chinese winter wheat (Triticum aestivum L.) varieties, Linmai6 and Tainong18. Eighteen putative QTLs were detected on 14 chromosomes: 1B, 1D, 2A, 2B, 2D, 3A, 3B, 4A, 4B, 5B, 6A, 6B, 7B, and 7D. Six textural quality traits, one QTL for hardness (QHa-4A), three QTLs for springiness (QSp-3B, QSp-4B, and QSp-5B), seven QTLs for cohesiveness (QCo-6A, QCo-7B.1, QCo-7B.2, QCo-3A, QCo-1D, QCo-2B.1, and QCo-2B.2), four QTLs for resilience (QRe-2D, QRe-2A, QRe-7D, and QRe-1B), two QTLs for gumminess (QGu-6B, and QGu-3B), and one QTL for chewiness (QCh-7D) were detected. The contributions of the QTLs ranged from 6.19% to 15.74%. The present study enhances understanding of the genetic basis for the textural properties of northern-style CSB and provides the basis for gene mapping of these traits.

Uptake of potassium (K) in crops depends mainly on the root system. Field, pot and hydroponic experiments were carried out to characterise root morphological traits and examine their roles in K uptake and utilisation of vegetable soybean (edamame) (Glycine max (L.) Merr.). Of 40 genotypes, two high K-efficiency (HKE) and two low K-efficiency (LKE) genotypes were identified and compared at two levels of K application: nil or 120 kg K₂SO₄ ha^–1. HKE genotypes had shorter total root length and smaller root surface area and root volume than LKE genotypes, but responded earlier to low-K conditions by adjusting root architecture. In plants receiving nil K, total root length was increased by 10.4–21.8% for HKE genotypes but decreased by 5.5–9.5% for LKE genotypes at the V4 stage relative to plants receiving applied K. HKE genotypes were more efficient in redistributing K from source to sink tissue, especially from leaf. Of the total K in vegetative tissues, 35.0–46.4% was redistributed to seed in HKE genotypes, whereas only 19.7–28.2% was redistributed in LKE genotypes. HKE genotypes also had a higher specific K uptake rate (K uptake per unit root length), 1.6–1.7 times higher than LKE genotypes at the R5 stage. This indirectly indicated a stronger root K acquisition in HKE genotypes. This study suggests that future vegetable soybean improvement with greater K efficiency should be focused on the selection of higher K-redistribution rate and specific K-uptake rate.

Glyphosate-tolerant genetically modified (GM) soybeans (Glycine max (L.) Merr.), known commercially as Roundup Ready soybeans, dominate oil consumption and are partly used for protein intake in China. Chemical composition of soybean seed determines its nutritional value, its processing suitability for various protein products, and market decisions. We conducted a compositional comparison of eight GM and 16 conventional Chinese representative soybean varieties. Crude protein, crude fat, moisture, ash, carbohydrate, crude fibre, amino acid and fatty acid contents of the different soybean genotypes were compared and analysed. The GM soybeans had the highest oil concentration but poorer quality, whereas conventional soybeans from the Huanghuaihai region of China showed significantly higher protein, total amino acid, essential amino acid and oleic acid contents, and lower n-6 : n-3 ratio and carbohydrate content, which suggested superior nutritional value. Principal component analysis indicated that protein, carbohydrates and amino acids (except tryptophan, methionine, tyrosine, histidine and proline) contributed most to distinguishing GM soybeans from conventional Chinese soybeans. Differences among the GM and conventional soybeans collected from two major producing regions in China can help to guide manufacturing processes and market decisions with respect to soybeans. High protein and amino acid content in conventional Chinese soybeans mean the potential to expand and improve the International Life Sciences Institute Crop Composition Database used for safety assessment of GM soybean.

Brassinosteroids (BRs), as a class of plant growth regulators, have been shown to affect different physiological traits of plants and counteract various stresses. We studied the possibility of increasing seed and protein yields of two genotypes of common bean (Phaseolus vulgaris L.) with the exogenous application of 24-epibrassinolide (EBL) in an experiment conducted during 2016 and 2017. Two levels of irrigation (optimal and drought stress) were applied to the main plots, and two genotypes of common bean (cv. Kusha and genotype COS16) and four concentrations of EBL (0, 2, 4 and 6 μm) were allocated to subplots in a factorial arrangement. At the flowering stage, drought stress was applied and bean plants were sprayed with EBL. The results indicate that drought stress reduced leaf area, yield components, seed yield and protein content. Moreover, substantial increase in intercellular CO₂ concentration and decrease in transpiration rate, stomatal conductance and net photosynthetic rate were also recorded. However, exogenous application of EBL remarkably improved gas exchange attributes, leaf area, yield components, seed yield and protein content both under optimal irrigation and drought-stress conditions. Analysis of regression showed that, under both water-supply conditions, genotype COS16 would have highest seed yield when receiving 4.05 and 4.52 µm EBL, and cv. Kusha would have the highest seed yield by receiving 3.27 and 3.62 µm EBL. Therefore, EBL can be used as a plant growth regulator to enhance drought tolerance and minimise yield loss of common bean caused by water deficits.

Forage breeding is essential for animal production, and its effectiveness depends on available genetic diversity. However, breeding is challenged when there is limited evaluation of genebank accessions. Predictive characterisation based on ecogeographic information is a promising approach to address the urgent need to expedite evaluation of target traits in existing collections of forage genetic resources. Using white clover (Trifolium repens L.) as an example, we applied predictive characterisation to model the expression of cyanogenesis, an important process related to the generation of anti-quality compounds. Data on genebank accessions and other population occurrences were divided into two subsets, one including accessions that had been evaluated for this trait, and the other with those that had not. The occurrence sites of the records with the best geo-referencing quality were characterised ecogeographically. The cyanogenesis trait was predicted using the calibration method, in which some selected ecogeographic variables were used as independent variables. Thus, we identified 470 populations with high probability of being acyanogenic. A small sample of populations (18 accessions) was evaluated to ratify the usefulness of this approach. Seventeen of the evaluated accessions showed a complete acyanogenic response and one showed 95% acyanogenic plants. Our study also expanded the areas previously rated as highly acyanogenic. In conclusion, our results contribute in a predictive way and with minimum cost to increase the knowledge of wild populations and genebank accessions in relation to a target trait. This facilitation in the generation of evaluation data may encourage greater investment in forage plant breeding and boost germplasm utilisation.

Plant morphology and architecture are essential characteristics for all plants, but perhaps most importantly for agricultural species because economic traits are linked to simple features such as blade length and plant height. Key morphological traits likely respond to CO₂ concentration ([CO₂]), and the degree of this response could be influenced by water availability; however, this has received comparatively little research attention. This study aimed to determine the impacts of [CO₂] on gross morphology of perennial ryegrass (Lolium perenne L.), the most widespread temperate pasture species, and whether these impacts are influenced by water availability. Perennial ryegrass cv. Base AR37 was grown in a well-fertilised FACE (free-air carbon dioxide enrichment) experiment in southern Tasmania. Plants were exposed to three CO₂ concentrations (∼400 (ambient), 475 and 550 µmol mol^–1) at three watering-treatment levels (adequate, limited and excess). Shoot dry weight, height, total leaf area, leaf-blade separation, leaf size, relative water content and specific leaf area were determined, as well as shoot density per unit area as a measure of tillering. Plant morphology responded dramatically to elevated [CO₂], plants being smaller with shorter leaf-blade separation lengths and smaller leaves than in ambient (control) plots. Elevated [CO₂] increased tillering but did not substantially affect relative water content or specific leaf area. Water supply did not affect any measured trait or the response to elevated [CO₂]. Observed impacts of elevated [CO₂] on the morphology of a globally important forage crop could have profound implications for pasture productivity. The reductions in plant and leaf size were consistent across a range of soil-water availability, indicating that they are likely to be uniform. Elucidating the mechanisms driving these responses will be essential to improving predictability of these changes and may assist in breeding varieties suited to future conditions.