In three independent experiments in Turkey and Kazakhstan, winter wheat germplasm with variable degrees of resistance to leaf rust was subjected to fungicide protection. The yield loss of genotypes susceptible to leaf rust varied from 30% to 60% depending on the environment and severity of infection. Genotypes completely or moderately resistant to leaf rust also responded positively to fungicide protection, with average yield increases in the range 10–30%. This increase was observed even in one season without leaf rust infection. The main character affected by fungicide was 1000-kernel weight. There was stable expression of the magnitude of yield gain in resistant genotypes in different seasons, confirming genetic variation for this trait. Possible mechanisms of yield gain from fungicide protection in resistant genotypes are related to a positive physiological effect of the chemical used as well as a possible ‘cost of resistance’ to wheat plants. The magnitude of yield gain by resistant germplasm justifies its capture in breeding programs to develop varieties resistant to diseases and with greater benefits from the fungicide protection.

Plant height (PH) and yield components are important traits for yield improvement in wheat breeding. In this study, 207 F_2:4 recombinant inbred lines (RILs) derived from the cross Jingdong 8/Aikang 58 were investigated under limited and full irrigation environments at Beijing and Gaoyi, Hebei province, during the 2011–12 and 2012–13 cropping seasons. The RILs were genotyped with 149 polymorphic simple sequence repeat (SSR) markers, and quantitative trait loci (QTLs) for PH and yield components were analysed by inclusive composite interval mapping. All traits in the experiment showed significant genetic variation and interaction with environments. The range of broad-sense heritabilities of PH, 1000-kernel weight (TKW), number of kernels per spike (KNS), number of spikes per m² (NS), and grain yield (GY) were 0.97–0.97, 0.87–0.89, 0.59–0.61, 0.58–0.68, and 0.23–0.48. The numbers of QTLs detected for PH, TKW, KNS, NS, and GY were 3, 10, 8, 7 and 9, respectively, across all eight environments. PH QTLs on chromosomes 4D and 6A, explaining 61.3–80.2% of the phenotypic variation, were stably expressed in all environments. QPH.caas-4D is assumed to be the Rht-D1b locus, whereas QPH.caas-6A is likely to be a newly discovered gene. The allele from Aikang 58 at QPH.caas-4D reduced PH by 11.5–18.2% and TKW by 2.6–3.8%; however, KNS increased (1.2–3.7%) as did NS (2.8–4.1%). The QPH.caas-6A allele from Aikang 58 reduced PH by 8.0–11.5% and TKW by 6.9–8.5%, whereas KNS increased by 1.2–3.6% and NS by 0.9–4.5%. Genotypes carrying both QPH.caas-4D and QPH.caas-6A alleles from Aikang 58 showed reduced PH by 28.6–30.6%, simultaneously reducing TKW (13.8–15.2%) and increasing KNS (3.4–4.9%) and NS (6.5–10%). QTKW.caas-4B and QTKW.caas-5B.1 were stably detected and significantly associated with either KNS or NS. Major KNS QTLs QKNS.caas-4B and QKNS.caas-5B.1 and the GY QTL QGY.caas-3B.2 were detected only in water-limited environments. The major TKW QTKW.caas-6D had no significant effect on either KNS or NS and it could have potential for improving yield.

Although nitrate and ammonium transporter genes of wheat have been cloned, little is known about their expression characteristics. A greenhouse experiment was established to study temporal expression patterns over a growing season for four nitrate-transporter genes (TaNRT2.1, TaNRT2.2, TaNRT2.3 and TaNRT1.2) and two ammonium-transporter genes (TaAMT1.1 and TaAMT1.2) in wheat genotypes with different nitrogen (N)-uptake efficiencies. Genotypes that were N-efficient (XY107) and N-inefficient (XY6) were planted in soils that were N-limited (no N added) and N-adequate (added 0.3 g N kg^–1 soil). Roots were sampled at tillering, jointing, heading and grain-filling stages, and the expression of the six genes was quantified using real-time, reverse transcription PCR (polymerase chain reaction). Results indicated that maintaining active N uptake during reproduction was the main strategy used by genotype XY107 to sustain its high N-uptake efficiencies in both N treatments. The expression of all NRT and AMT genes showed significant temporal dynamics, and generally matched the pattern of in-season N uptake of wheat plants. Several NRT or AMT genes (especially TaNRT2.1) showed greater expression at reproduction in the N-efficient genotype, XY107, than in the N-inefficient genotype, XY6, suggesting that nitrate and ammonium transporters play important roles in determining the genotypic variation of N uptake in wheat.

Flooding is the major abiotic stress in flood-prone rice ecosystems, where duration, severity and turbidity of flooding are the factors negatively affecting survival and crop growth worldwide. Advances in physiology, genetics, and molecular biology have greatly improved our understanding of plant responses to stresses, but nutrient-management options are still lacking. This study was conducted to investigate the combined effect of silica (Si), phosphorus (P) and nitrogen (N) with Sub1 and non-Sub1 cultivars of rice under clear and turbid water submergence. Submergence tolerance effects on allometry, metabolic changes, photosynthetic rate and ethylene accumulation were evaluated. Application of Si reduced elongation, lodging and leaf senescence, with more prominent effects when applied with basal P. Combined effect of Si, N and P significantly improved, growth, photosynthetic rate, concentrations of chlorophyll and soluble sugars of rice after flood recovery, which led to higher plant survival. The findings of the study suggest that combined application of Si, N and P can significantly contribute to higher survival of rice seedlings and establishment thereafter in flash-flood prone areas.

Nitrous oxide (N₂O) is a potent greenhouse gas, contributing to global warming. Most of the N₂O emitted from cropping systems is derived from the soil and is closely related to the use of nitrogen (N) fertiliser. However, several reports have shown that small, yet significant, portions of the N₂O flux from cropping systems are emitted from the crop foliage. This research aimed to quantify N₂O emissions from the foliage of field-grown cotton (Gossypium hirsutum L.), and included maize (Zea mays L.) and soybean (Glycine max L.) for comparison. We also aimed to identify differences in the timing of N₂O emissions from foliage during the day and over an irrigation cycle. Individual plants were isolated from the soil, and the atmosphere surrounding the encapsulated plants was sampled over a 30-min period. Subplots that were previously fertilised with urea at 0, 80, 160, 240 and 320 kg N ha^–1 and then sown to cotton were used to measure N₂O flux from plants on three occasions. N₂O flux from cotton foliage was also measured on five occasions during an 11-day irrigation cycle and at five times throughout one day. N₂O flux from foliage accounted for a small but significant portion (13–17%) of the soil–crop N₂O flux. N₂O flux from foliage varied with plant species, and the time of day the flux was measured. N₂O flux from cotton plants was closely related to soil water content. Importantly, the application of N fertiliser was not related to the N₂O flux from cotton plants. The most plausible explanation of our results is that a proportion of the N₂O that was evolved in the soil was transported through the plant via evapotranspiration, rather than being evolved within the plant. Studies that exclude N₂O emissions from crop foliage will significantly underestimate the N₂O flux from the system.

Arbuscular mycorrhizal fungi (AMF) play an important role in protecting plant growth against such stresses as phytotoxic aluminium (Al) in soil. To understand some of the AMF interactions that relate to amelioration of Al phytotoxicity and phosphorus (P)-uptake efficiency in barley (Hordeum vulgare L.), this study examined the effect of soil Al levels and mycorrhizal symbiosis on plant response, including root colonisation, AMF propagules and glomalin production. A greenhouse experiment was conducted using two native barley cultivars, Sebastián and Aurora, grown in an acidic soil at two Al-saturation levels (80% Al-sat, unlimed soil; 7% Al-sat, limed soil) with and without AMF propagules. Root dry weight, total and colonised root lengths, and root P and Al contents were determined at 60 and 150 days after sowing. AMF spore density, total hyphal length, glomalin-related soil protein (GRSP) and Al bound to GRSP (Al-GRSP) were analysed at final harvest. AM root colonisation was not inhibited in limed soil, mycorrhizal propagule numbers increased at high Al levels, and Al-GRSP ranged from 5.6% to 8.3% of the total GRSP weight. These values also increased in unlimed soil, particularly those associated with cv. Aurora. Root Al concentration correlated inversely with AMF spores (r = –0.85, P < 0.001) and Al-GRSP (r = –0.72, P < 0.01), but only in plants growing in limed soil. Conversely, the AMF treatments in which Al was present showed a greater relationship between total root length and both root Al (r = –0.72, P < 0.01) and root P (r = 0.66, P < 0.01) concentrations. Sebastián showed a greater response to lime, whereas Aurora responded better to mycorrhizal presence. The relative growth rate of roots, P uptake efficiency and mycorrhizal parameters such as root colonisation, spores, hyphae and GRSP showed Aurora to be more Al-tolerant than Sebastián. In conclusion, the greater rate of increase of AM propagules, GRSP and Al-GRSP associated with cv. Aurora supports the hypothesis that AMF play an important role in the Al-tolerance capacity and P-uptake efficiency of H. vulgare growing in soils with high Al levels.

The integrated soil–crop system management (ISSM) approach can potentially mitigate the loss of biodiversity in agricultural landscapes, ensuring crop yield with lower nitrogen (N) fertiliser input and minimised environmental pollution. The aim of this study was to test the hypotheses that overuse of N fertiliser could reduce the biodiversity of arbuscular mycorrhizal fungi (AMF) and that ISSM could help to maintain higher AMF biodiversity than the conventionally managed system in maize (Zea mays L.). The AMF community composition under three different treatments (conventionally managed, N-optimised and non-N-fertilised fields) was assessed by using both spore-based morphological taxonomy and DNA-based T-RFLP fingerprinting approaches. Maize roots in intensively managed fields formed functioning mycorrhizal symbioses even when a high rate of N fertiliser was applied. AMF diversity was higher under optimised N input, whereas AMF richness decreased when more N fertiliser was used. The N-optimised farms had AMF communities similar to those in the conventionally managed fields. The ISSM approach is recommended for sustaining crop yields without incurring continuing environmental costs and for maintaining AMF communities in intensively managed agro-ecosystems, especially in rapidly developing countries.

Genotypic variation in crop response to drought depends on agronomic, environmental and genetic factors, and only limited work has compared responses of crop species to water limitation. Twenty genotypes of peanut (Arachis hypogaea L.) and of cowpea (Vigna unguiculata (L.) Walp) were tested in lysimeters under well-watered (WW) and water-stress (WS) conditions during two seasons, a post-rainy season with high evapotranspiration and a rainy season with low evapotranspiration (ET), in order to assess: (i) variability in the agronomic response to stress within and between species across the seasons; (ii) the water requirement of the two crops in each season; and (iii) the stress effect on harvest index (HI), transpiration efficiency (TE), pod yield and haulm yield. Cowpea required less water than peanut during the two seasons, and water use in cowpea varied less across seasons than in peanut. Peanut yield was more sensitive to water stress than cowpea yield, although its water use under WS was higher than in cowpea. Also, under WS conditions, TE, HI and pod yield were more stable across season in cowpea than in peanut. In the post-rainy season, the decrease in pod yield and HI under WS was higher in peanut (95% and 80%, respectively) than in cowpea (70% and 35%). In addition, TE was less affected by WS in cowpea (5%) than in peanut (24%). HI explained a large part of yield variation in both crops, especially under WS. Under WW, water use explained a large portion of the residual yield variations unexplained by HI, although TE also explained a substantial part of the variation in cowpea. Under WS, the main determinant of residual yield variations in both crops was TE. Generally, genetic variation for water use, TE and HI was found in both species across water regimes and seasons. A notable exception was the absence of variation in peanut water use and TE in the rainy season. Our results showed that cowpea, with lower water requirement and efficient water use under a high-ET season, was more resilient to water-limited and high-ET conditions than peanut.

Anthracnose, caused by Colletotrichum acutatum, is the most destructive fungal disease of Andean lupin (Lupinus mutabilis Sweet) in Ecuador and of other lupin species around the world. Symptoms of necrotic spots occur throughout the main stem, and infection progresses to cause bending of the main stem and lateral branches, resulting in yield loss. Although there is no known anthracnose resistance, this study aims to assess tolerance of Andean lupin and investigate lupin–C. acutatum interactions. Two Andean lupin genotypes, I-450 Andino and I-451 Guaranguito, were inoculated on the meristematic section of the main stem, either by spraying or by pipetting C. acutatum spores on to an artificial wound. Although the two methods gave similar results, spraying is the preferred method because it mimics natural pathogen infection. Plant-pathogen interactions were assessed at five different phenological stages (leaf stages 2–3, 4–5, 6–7, 8–9, and 10–11) with three C. acutatum isolates by using a 0–5 scale to assess disease symptoms. In both genotypes, anthracnose symptoms were greater at early seedling stage (2–3-leaf stage), decreasing significantly in early vegetative phase (6–7-leaf stage) and increasing again when the flower stage began (10–11-leaf stage). However, the tolerance of these two Andean lupin genotypes to anthracnose was not equally expressed at all developmental stages. We recommend, in a breeding program, that screening for anthracnose first occurs at the 6–7-leaf stage (6 weeks old) and again when flowering starts at the 10–11-leaf stage (10 weeks old) so that the overall tolerance can be determined. This method could be used in lupin breeding programs for improving resistance to anthracnose.

In an attempt to find biological fungicides, we screened 18 medicinal plants used in Chinese traditional medicine for their activity against Embellisia astragali, the causative fungus of yellow dwarf and root-rot disease in standing milkvetch (Astragalus adsurgens Pall.). The antifungal efficacy of ethanolic extracts of these plants was tested in vitro. Our results show that among the 18 plants tested, the ethanolic extracts of Saposhnikovia divaricata, Allium sativum and Juglans regia totally inhibited mycelial growth of E. astragali. These three extracts also significantly inhibited spore germination of E. astragali, with inhibition rates ranging from 86% to 88%. In addition, the same extract from the same plant part indicated the strongest antifungal activity against E. astragali, with a minimal inhibitory concentration value of 50 mg mL^–1. These results demonstrate that plant-derived products have a high potential to control yellow dwarf and root-rot disease in standing milkvetch.

Low temperature and flooding are severe stresses to cotton plant growth and development in some parts of the world. This study was conducted to determine the interactive effects of low temperature and flooding on physiological and growth parameters of cotton plants, and yield of seed cotton. Transgenic Bt cotton plants at the boll-setting stage were treated with low temperature, flooding, and their combinations. The stresses decreased photosynthetic rate, stomatal conductance, transpiration rate, and intercellular CO₂ concentration by up to 37%, 71%, 52%, and 60%, respectively. The content of soluble protein and insecticidal protein was also decreased by up to 65% and 53%, respectively. By contrast, malondialdehyde (MDA) content increased by up to 114%. The length of fruiting branch was shortened by combined low temperature and flooding stress. Boll number and weight were decreased by 3.2% and 28.1%, respectively. Seed cotton yield was decreased by up to 43.2%. Our results suggest that concurrent low temperature and flooding at the boll-setting stage negatively influenced leaf photosynthetic activities and insecticidal protein production, leading to poor protection and yield. We recommend that agronomic measures be designed to stabilise physiological activities and insecticidal protein production in Bt cotton plants under stress conditions.

The potential of biochar to improve crop productivity has received interest in recent years; however, little is known about the effects of biochar on crop nutritional quality. In this study, effects of three different biochars (wheat straw biochar, poplar biochar and olive residues biochar) were determined on the major fruit-size parameters, physico-chemical and nutritional properties of tomato (Lycopersicon esculentum L.) cv. Rio Grande. Application of biochar alone was sufficient to sustain the fruit growth, but results were affected by feedstock source of biochar. There were no significant differences in size and weight parameters and the sugar content was not significantly modified by biochar amendment. On the other hand, secondary metabolites showed changes relating to biochar type. Total phenol and flavonoid contents, as well as antioxidant activity, were higher in fruits grown in substrate amended with straw biochar and olive residues biochar. Lycopene, β carotene and lutein concentrations from tomato fruits grown on substrates amended with different biochars were significantly lower than from the control. The data require confirmation in field experiments; however, this study offers new knowledge about the biochar effects on horticultural crops.