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Background and aims Large areas of paddy fields have been contaminated by cadmium (Cd) in both China and worldwide, resulting in excessive Cd accumulation in rice grains. Here, we investigated the effects of cultivars, water regimes, and growth stages on Cd accumulation in rice with different radial oxygen loss (ROL). Methods Two groups of experiments were conducted: pot trials with soil-added Cd and solution-added agar using 20 rice cultivars and a rhizobag trial with Cd-contaminated soil and pot trial with solution-added agar under flooded and non-flooded water regimes with three growth stages and two cultivars. Results Different rice cultivars exhibited different porosity, Cd tolerance, and Cd accumulation in grains, which were significantly correlated with ROL. Cd concentration in shoots was significantly lower under the flooded (0.13–1.01, mean 0.56 mg kg −1 ) than non-flooded regime (0.68–1.39, mean 0.97 mg kg −1 ). The low Cd-accumulating cultivar showed higher rates of ROL, higher Cd combined with Fe plaque formation, and lower Cd bioavailability in the rhizosphere soil than the high-Cd accumulating cultivar. Conclusions Rice cultivars grown under flooded regimes effectively reduced Cd accumulation in edible parts, and the later stage was crucial for reducing Cd accumulation. Low Cd-accumulating cultivars generally exhibited a higher ability to reduce Cd bioavailability in the rhizosphere soil.

This study evaluated grain anthocyanin, zinc (Zn) and iron (Fe) concentrations, and grain yield of eleven purple rice varieties (PP1-PP11) grown under wetland (W+) and aerobic conditions (W0) in 2 years. There was a significant variation in the concentrations of anthocyanin, Zn and Fe, by water regime and year among the varieties with a wide range of anthocyanin (1-117 mg 100 g −1 ) and narrower ranges of Zn (19-41 mg kg −1 ) and Fe (6-19 mg kg −1 ) concentrations. The nutritional quality in aerobic grown rice was lower than wetland grown among the varieties with higher levels of anthocyanin (>40 mg 100 g −1 ), Zn (>30 mg kg −1 ) and Fe (>15 mg kg −1 ), with smaller effects of water among varieties in the lower quality ranges. The lowering of anthocyanin in aerobic grown rice was observed in the two varieties of the upland ecotype that were highest in anthocyanin concentration, as well as some wetland varieties. The grain yield (1.4-6.7 Mg ha −1 ) was associated negatively with grain Zn concentration (r = −0.50, P ≤ 0.001), but not with grain Fe (r = −0.14, NS 0.05 ) or anthocyanin (r = −0.27, NS 0.05 ). The anthocyanin concentration in the purple rice increased with Zn concentration (r = 0.57, P ≤ 0.001). Wetland condition was shown to be more favorable than aerobic culture for intense pigmentation in the production of purple rice, as well as higher Zn and Fe concentrations.

Water availability is a crucial environmental factor on grain number in wheat, which is one of the important yield-related traits. In this study, a diverse panel of 282 wheat accessions were phenotyped for grain number per spike (GNS), spikelet number (SN), basal sterile spikelet number (BSSN), and apical sterile spikelet number (ASSN) under different water regimes across two growing seasons. Correlation analysis showed that GNS is significantly correlated with both SN and BSSN under two water regimes. A total of 9,793 single nucleotide polymorphism (SNP) markers from the 15 K wheat array were employed for genome-wide association study (GWAS). A total of 77 significant marker-trait associations (MTAs) for investigated traits as well as 8 MTAs for drought tolerance coefficient (DTC) were identified using the mixed linear model. Favored alleles for breeding were inferred according to their estimated effects on GNS, based on the mean difference of varieties. Frequency changes in favored alleles associated with GNS in modern varieties indicate there is still considerable genetic potential for their use as markers for genome selection of GNS in wheat breeding.

Hydrologic condition is a major driving force for wetland ecosystems. The influence of water regimes on vegetation distribution is of growing interest as wetlands are increasingly disturbed by climate change and intensive human activities. However, at large spatial scales, the linkage between water regimes and vegetation distribution remains poorly understood. In this study, vegetation communities in Poyang Lake wetland were classified from remote sensing imagery. Water regimes characterized by inundation duration (IDU), inundation depth (IDE), and inundation frequency were simulated using physics-based hydraulic models and were then linked with vegetation communities by a Gaussian regression model. The results showed that the Carex community was found to favor more hydrologic environments with longer IDU and deeper IDE in comparison to the Phragmites community. In addition, we found that the Carex community could survive in a relatively wider variety of hydrological conditions than the Phragmites community. For the typical sub-wetlands of the Poyang Lake National Nature Reserve (PLNNR), only the influence of IDU on the distribution of vegetation communities was significant. Outcomes of this research extend our knowledge of the dependence of wetland vegetation on hydrological conditions at larger spatial scales. The results provide practical information for ecosystem management.

The application of biochar to agricultural soils has been proven to have many advantages, including the improvement of soil water holding capacity and plant growth, particularly under limiting conditions of water supply. The response of quinoa (Chenopodium quinoa Willd.) to water shortage occurring during the vegetative growth stages is not well known. Therefore, the present study aimed to evaluate the combined effects of three wood chip biochar rates (0%, 2% and 4%) and two water regimes (100 and 50% evapotranspiration losses restitution) on the vegetative development and water status of quinoa (cultivar Titicaca). The results showed that the treatment with 2% wood chip biochar improved plant height, leaf and branch number and stem diameter during the vegetative growing cycle compared to the 0% (control) and 4% biochar treatments, which were not different from each other. At the end of the experiment, when the plants were at the flowering initiation stage, increases of 23% in leaf area, 22% in fresh biomass, 27% in main panicle length and 36% in sub-panicle number were observed. The application of woody biochar at a 4% rate, although improving the plant water status with increases of 10% in RWC and 18% in Ψ, did not enhance the vegetative development of the quinoa. The water shortage negatively affected both the growth performance and plant water status. The best growth response of quinoa was observed only when the plants were treated with a 2% biochar rate and were fully irrigated.

Little is known about the effects of temperature and drying–rewetting on soil phosphorus (P) fractions and microbial community composition in regard to different fertilizer sources. Soil P dynamics and microbial community properties were evaluated in a soil not fertilized or fertilized with KH2PO4 or swine manure at two temperatures (10 and 25 °C) and two soil water regimes (continuously moist and drying–rewetting cycles) in laboratory microcosm assays. The P source was the dominant factor determining the sizes of labile P fractions and microbial community properties. Manure fertilization increased the content of labile P, microbial biomass, alkaline phosphomonoesterase activity, and fatty acid contents, whereas KH2PO4 fertilization increased the content of labile inorganic P and microbial P. Water regimes, second to fertilization in importance, affected more labile P pools, microbial biomass, alkaline phosphomonoesterase activity, and fatty acid contents than temperature. Drying–rewetting cycles increased labile P pools, decreased microbial biomass and alkaline phosphomonoesterase activity, and shaped the composition of microbial communities towards those with greater percentages of unsaturated fatty acids, particularly at 25 °C in manure-fertilized soils. Microbial C and P dynamics responded differentially to drying–rewetting cycles in manure-fertilized soils but not in KH2PO4-fertilized soils, suggesting their decoupling because of P sources and water regimes. Phosphorus sources, temperature, and water regimes interactively affected the labile organic P pool in the middle of incubation. Overall, P sources and water availability had greater effects on P dynamics and microbial community properties than temperature.

Perennial ryegrass (Lolium perenne) is widely cultivated around the world for turf and forage. However, the plant is highly susceptible to disease and is sensitive to drought. The present study aims to determine the effect of the fungal endophyte Epichloë festucae var. lolii of perennial ryegrass on the combined stresses of drought and disease caused by Bipolaris sorokiniana in the greenhouse. In the experiment, plants infected (E+) or not infected (E−) with the fungal endophyte were inoculated with Bipolaris sorokiniana and put under different soil water regimes (30%, 50%, and 70%). The control treatment consisted of E+ and E− plants not inoculated with B. sorokiniana. Plant growth, phosphorus (P) uptake, photosynthetic parameters, and other physiological indices were evaluated two weeks after pathogen infection. The fungal endophyte in E+ plants increased P uptake, plant growth, and photosynthetic parameters but decreased the malondialdehyde concentration, proline content, and disease incidence of perennial ryegrass (p < 0.05). E+ plants had the lowest disease incidence at 70% soil water (p < 0.05). The study demonstrates that the fungal endophyte E. festucae var. lolii is beneficial for plant growth and stress tolerance in perennial ryegrass exposed to the combined stresses of drought and B. sorokiniana.

Mycorrhizal-mediated seedling establishment may reduce dependency on chemical fertilizers, but the effectiveness of infection for growth may differ depending on species with different eco-physiological adaptations. The infection of arbuscular mycorrhizal fungi (AMF) and P uptake were compared between rice (Oryza sativa L.) (Koshihikari (ricek), Togo4 (ricet)), and pearl millet (Pennisetum glaucum (L.) R. Br.) (ICMB89111 (millet891), ICMB95444 (millet954)) seedlings (i) in response to three different commercial AMF inoculants of Rhizoglomus irregulare (popular inoculant Dr. Kinkon (I1); two new inoculants Rootella P (I2) and Rootella F (I3)) in comparison with indigenous AMF from Andosol upland and paddy topsoils (Exp. 1–2 as the inoculant experiments) and (ii) across different water regimes from upland to flooded lowland conditions for I1 inoculant (Exp. 3–4 as the water regime experiments). The new inoculants I2 and I3 with higher propagule numbers showed a higher infection rate than the control seedlings in both rice and pearl millet, with a tendency for slower leaf development and no seedling growth enhancement. I1 inoculant had more significant positive effects on the root transversal area and shoot growth parameters than the control. The infection rates of all three inoculants were lower than the indigenous AMF from upland Andosol in rice and pearl millet, in which a higher infection rate led to higher P uptake found in millet954. I1 inoculant increased the infection rate in pearl millet and rice but had no clear indication of interaction with water regimes. A higher infection rate led to higher P uptake and shoot dry weight in pearl millet but not in rice with higher root length density. This study provided the significance of inoculants for seedling establishment and highlighted more mycorrhizal-mediated P uptake in pearl millet than in rice.

Although the information on the Normalized Difference Vegetation Index (NDVI) in plants under water deficit is often obtained from sensors attached to satellites, the increasing data acquisition with portable sensors has wide applicability in agricultural production because it is a fast, nondestructive method, and is less prone to interference problems. Thus, we carried out a set of experiments to investigate the influence of time, spatial plant arrangements, sampling size, height of the sensor and water regimes on NDVI readings in different soybean cultivars in greenhouse and field trials during the crop seasons 2011/12, 2012/13 and 2013/14. In experiments where plants were always evaluated under well-watered conditions, we observed that 9 a.m. was the most suitable time for NDVI readings regardless of the soybean cultivar, spatial arrangement or environment. Furthermore, there was no difference among NDVI readings in relation to the sampling size, regardless of the date or cultivar. We also observed that NDVI tended to decrease according to the higher height of the sensor in relation to the canopy top, with higher values tending to be at 0.8 m, but with no significant difference relative to 1.0 m—the height we adopted in our experiments. When different water regimes were induced under field conditions, NDVI readings measured at 9 a.m. by using a portable sensor were successful to differentiate soybean cultivars with contrasting responses to drought.

Six months-old seminal plants of 36 cacao genotypes grown under greenhouse conditions were subjected to two soil water regimes (control and drought) to assess, the effects of water deficit on growth, chemical composition and oxidative stress. In the control, soil moisture was maintained near field capacity with leaf water potentials (ΨWL) ranging from -0.1 to -0.5 MPa. In the drought treatment, the soil moisture was reduced gradually by withholding additional water until ΨWL reached values of between -2.0 to -2.5 MPa. The tolerant genotypes PS-1319, MO-20 and MA-15 recorded significant increases in guaiacol peroxidase activity reflecting a more efficient antioxidant metabolism. In relation to drought tolerance, the most important variables in the distinguishing contrasting groups were: total leaf area per plant; leaf, stem and total dry biomass; relative growth rate; plant shoot biomass and leaf content of N, Ca, and Mg. From the results of these analyses, six genotypes were selected with contrasting characteristics for tolerance to soil water deficit [CC-40, C. SUL-4 and SIC-2 (non-tolerant) and MA-15, MO-20, and PA-13 (tolerant)] for further assessment of the expression of genes NCED5, PP2C, psbA and psbO to water deficit. Increased expression of NCED5, PP2C, psbA and psbO genes were found for non-tolerant genotypes, while in the majority of tolerant genotypes there was repression of these genes, with the exception of PA-13 that showed an increased expression of psbA. Mutivariate analysis showed that growth variables, leaf and total dry biomass, relative growth rate as well as Mg content of the leaves were the most important factor in the classification of the genotypes as tolerant, moderately tolerant and sensitive to water deficit. Therefore these variables are reliable plant traits in the selection of plants tolerant to drought.