This study assessed changes in nitrogen (N) and phosphorus (P) uptake and partitioning in response to selection for yield in milestone varieties of Chinese winter wheat (Triticum aestivum L.). We established a factorial trial combining 11 nutrient–water regimes with three (2013–14) and five (2014–15) varieties released from 1970 to 2005. Grain yield increased at a rate of 0.46% year^–1, with no apparent increase in the uptake of nutrients. Nitrogen harvest index did not change, and P harvest index increased at a rate of 0.15% year^–1. Consequently, yield per unit N uptake and yield per unit P uptake increased at similar rates (0.4% year^–1) at the expense of nutrient concentration in grain, which declined at a rate of 0.47% year^–1 for N and 0.31% year^–1 for P. No trends in N nutrition index were found. Selection for yield in wheat increased the yield per unit nutrient uptake at the expense of grain nutrient concentration. Further gains in yield need to be matched by increasing N uptake to maintain grain protein. Dilution of P in grain needs to be considered in terms of the putatively undesirable role of phytate for human nutrition, and the need for P reserves in seed for crop establishment.

DNA methylation is an important epigenetic modification that may contribute to environmentally induced phenotypic variations by regulating gene expression. Chemically induced male sterility (CIMS) lines in wheat (Triticum aestivum L.) can transform from sterile to fertile, induced by a chemical hybridising agent during anther development. So far, little is known about the DNA methylation variation of CIMS in wheat. TAA1 regulates pollen wall development, probably through converting fatty acids to fatty alcohol in wheat. We investigated the DNA methylation pattern of the TAA1 gene in the core promoter region by using the bisulfite genomic sequencing method, and higher methylation was observed in CIMS. The expression levels of the TAA1 gene were also evaluated by real time quantitative reverse transcriptase PCR analysis, which revealed that the expression levels of the TAA1 gene were downregulated in CIMS. The aliphatic composition of the anther underwent accumulation in line 1376-CIMS, revealed by gas chromatography–mass spectrometry, including increments of tetradecanoic acid, hexadecanoic acid and octadecanoic acid. Scanning electron microscopy revealed that anther and pollen wall formation was significantly altered in 1376-CIMS.These results suggested that DNA methylation of the TAA1 gene may be involved in the sterility–fertility transition of CIMS.

Drought and heat stress are two major constraints that limit chickpea (Cicer arietinum L.) yield, particularly during seed filling. The present study aimed (i) to assess the individual and combined effects of drought and heat stress on oxidative metabolism during seed filling, and (ii) to determine any genetic variation in oxidative metabolism among genotypes differing in drought and heat tolerance and sensitivity. The plants were raised in outdoor conditions with two different times of sowing, one in November (normal-sown, temperatures <32°C−20°C (day–night) during seed filling), and the other in February (late-sown, temperatures >32°C−20°C (day–night) during seed filling). Plants were regularly irrigated to prevent any water shortage until the water treatments were applied. At both sowing times, the drought treatment was applied during seed filling (at ∼75% podding) by withholding water from half of the pots until the relative leaf water content (RLWC) of leaves on the top three branches reached 42–45%, whereas leaves in the fully irrigated control plants were maintained at RLWC 85–90%. Drought-stressed plants were then rewatered and maintained under fully irrigated conditions until maturity. Several biochemical parameters were measured on the leaves and seeds at the end of the stress treatments, and seed yield and aboveground biomass were measured at maturity. Individual and combined stresses damaged membranes, and decreased PSII function and leaf chlorophyll content, more so under the combined stress treatment. The levels of oxidative molecules (malondialdehyde (MDA) and H₂O₂) markedly increased compared with the control plants in all stress treatments, especially across genotypes in the combined heat   drought stress treatment (increases in leaves: MDA 5.4–8.4-fold and H₂O₂ 5.1–7.1-fold; in seeds: MDA 1.9–3.3-fold and H₂O₂ 3.8–7.9-fold). The enzymatic and non-enzymatic antioxidants related to oxidative metabolism increased under individual stress treatments but decreased in the combined heat   drought stress treatment. Leaves had higher oxidative damage than seeds, and this likely inhibited their photosynthetic efficiency. Yields were reduced more by drought stress than by heat stress, with the lowest yields in the combined heat   drought stress treatment. Heat- and drought-tolerant genotypes suffered less damage and had higher yields than the heat- and drought-sensitive genotypes under the individual and combined stress treatments, suggesting partial cross-tolerance in these genotypes. A drought-tolerant genotype ICC8950 produced more seed yield under the combined heat   drought stress than other genotypes, and this was associated with low oxidative damage in leaves and seeds.

The uses and nutritional value of soybean (Glycine max (L.) Merrill) oil are largely influenced by the levels and relative proportions in the seed of the five major fatty acids: oleic (OA), palmitic (PA), stearic (SA), linoleic (LLA), linolenic (LNA). The present study was undertaken to identify quantitative trait loci (QTLs) that are associated with fatty acid content (particularly OA) and to determine the effects of epistasis and the environment. The mapping population included 134 recombinant inbred lines (RILs) derived from soybean varieties Suinong10 and L-9. Phenotypic data of the two parents and their RILs were obtained at Harbin in 2013, 2014 and 2015. Nineteen QTLs associated with individual fatty acid content (six for OA, four for LNA, three for PA, two for SA, four for LLA) were identified. Twelve of these QTLs (four for OA, three for LNA, two for PA, one for SA, two for LLA) were detected with an additive main effect and/or additive × environment interaction effect in certain environments. Epistatic QTLs were identified for contents of OA (two QTLs), LNA (one QTL) and LLA (one QTL) in different environments, and which exhibited significant epistatic effects. Our observation of these additive and epistatic QTLs suggested that soybean possesses a complex network for fatty acid accumulation, which is valuable for marker-assisted selection.

Crop wild relatives represent an important agronomic resource for crop improvement and biodiversity conservation. The wild squash Cucurbita argyrosperma subsp. sororia. (Cucurbitaceae) has been considered the wild ancestor of cultivated forms of C. argyrosperma. In order to characterise the geographic patterns of genetic variation in this wild cucurbit and to identify priority areas for conservation, we analysed the genetic diversity and structure of natural populations along the Mexican Pacific coast. By using 14 polymorphic microsatellites, we genotyped 378 individuals sampled from 61 locations. Standard population genetics analyses and group testing were conducted on the genotypes with the aid of principal coordinate analysis and Bayesian analysis. Overall, we found an average of 12.3 alleles per locus and an expected heterozygosity of 0.756. We found greater genetic diversity in southern populations. The fixation index was 0.113, suggesting a mixed mating system. The Mantel test revealed a minor distance effect on genetic differentiation between individuals (r = 0.321). Finally, we found three main groups of populations arranged in a mostly latitudinal pattern, from Sinaloa (north-west) to Oaxaca–Guerrero (south-east). The greater genetic diversity and heterogeneity among southern populations (Guerrero–Oaxaca), suggests that this region is an important centre of diversity of this wild squash with important implications for conservation.

The aim of this study was to evaluate the effects of shading on structural characteristics and herbage accumulation of palisade grass (Brachiaria brizantha cv. Piatã), in a crop–livestock–forest integration area. Three shade regimes were evaluated: no shade (NS), moderate shade (MS, 338 trees ha^–1), and intense shade (IS, 714 trees ha^–1). The effects of shade regime on soil-water content and nitrogen nutrition index were also evaluated. Grazing management was established based on sward light interception targets (95% LI pre-gazing). The MS and IS regimes were divided into two shade strips (central and lateral) in order to describe the variation in light availability within the paddocks. Two methods for taking the reference readings of LI were tested in IS paddocks: LI reading inside (under the tree canopy) and outside (under full sunlight) the experimental area. Increased tree density reduced photosynthetically active radiation on lateral and central shade strips by 37% and 12% for MS, and 52% and 50% for IS, respectively. For NS, MS, IS (outside) and IS (inside), grazing intervals were 23, 26, 28 and 35 days, pre-grazing heights corresponded to 33, 35, 43 and 52 cm, and pre-grazing herbage mass to 5.37, 4.44, 2.96 and 3.23 t ha^–1, respectively. Leaf percentage remained relatively stable across shade regimes, but stem percentage was greater and dead material percentage was smaller for IS than for NS and MS. Soil water content was lower near the trees, especially during the dry season. Relative to NS, herbage accumulation decreased by 39% and 68% for MS and IS, respectively. Under natural shade, small variations in light availability affect sward structure and herbage production. The use of the 95% LI target developed under full sunlight conditions is not suitable for use under trees, emphasising the need to generate specific grazing-management targets for pastures cultivated under trees.

Soil and water salinity is a major environmental problem in the dry Mediterranean regions, affecting rangeland production. This study investigated the effects of salinity on the wild perennial grass (Poaceae) species Stipa lagascae R. & Sch., a potential forage plant that could be used to rehabilitate degraded rangelands in dry areas. In a laboratory, 3-month-old S. lagascae seedlings were subjected to increasing salt treatments (0–400 mm NaCl) for 45 days. Physiological and biochemical parameters such as leaf water potential (Ψw), leaf relative water content (RWC), proline, total soluble sugars, Na , K and Ca² contents, and catalase, ascorbate peroxidase and glutathione reductase activities were measured.

Total soluble sugars and proline concentrations increased and Ψw and RWC decreased with increasing salt concentrations. Lower salt concentrations induced a non-significant degradation of chlorophyll pigments. Shoot Na content increased with a salinity level, whereas shoot K and Ca² concentrations decreased and the K  : Na ratio was lower. The salinity threshold, above which S. lagascae showed signs of damage, occurred at 300 mm. Plants have evolved reactive oxygen species (ROS) scavenging enzymes including catalase, ascorbate peroxidase and glutathione reductase, which provide cells with an efficient mechanism to neutralise ROS. The tolerance strategies of S. lagascae to moderate salinity seem to include osmotic adjustment through total soluble sugars and proline accumulation, and highly inducible antioxidative defence. Further investigations are necessary to study the effect of salt stress on distribution of ions (Na , K , Ca² , Mg² , Cl^–, NO₃^–, SO₄^2–) and osmotic adjustment. Photosynthesis and water-use efficiency parameters could be also useful tools.

Trifolium repens L. (white clover) is an important component of temperate pastures, but its root morphology makes it vulnerable to drought and pest attack. T. uniflorum is a wild species, adapted to dry environments, with deep woody roots but poor vegetative growth and only 1–3 florets per inflorescence (head). Interspecific hybridisation to incorporate the drought tolerance and root characteristics of T. uniflorum into white clover led to primary hybrids (F₁ and BC₁) with poor seed production. Advanced-generation hybrids expressed high variation for almost all seed-production traits, and seed production responded to selection. To inform future breeding programs, trait associations and heritabilities were analysed. Numbers of heads per plant, florets per head and seeds per floret were important factors with moderate–high heritabilities. The derived traits, numbers of seeds per head, florets per plant and seeds per plant, expressed low–moderate heritabilities. No negative associations between seed production and root traits were found in the hybrids, nor were there any negative associations among head production, persistence and foliage production. Selection for improved seed-production traits should be effective without adversely affecting vegetative traits.