Promote Rice Growth Research Articles

Molybdenum Sulfide Induce Growth Enhancement Effect of Rice ( Oryza sativa L.) through Regulating the Synthesis of Chlorophyll and the Expression of Aquaporin Gene.

Molybdenum sulfide (MoS2) has been applied widely in industrial and environmental application, leading to increasing release into environment. So far, no studies have been investigated with regard to the potential effect of MoS2 on plants. Herein, we studied the impact of MoS2 on the growth, chlorophyll content, lipid peroxidation, antioxidase system, and aquaporins of rice for the first time. Results showed that MoS2 did not significantly affect the germination of rice seeds, malonaldehyde (MDA) content, and the antioxidant enzyme activity. While the length and biomass of rice root and shoot, chlorophyll content index (CCI), and expression of aquaporin genes were significantly increased. Based on these results, we concluded that MoS2 promoted rice growth through (i) the promotion of nitrogen source assimilation, (ii) the enhancement of photosynthesis, enzymatic-related biochemical reactions, and metabolic processes, subsequently, (iii) the acceleration of cell division and expansion, furthermore (iv) no abiotic stress and favorable condition of antioxidant enzyme system. These results provided an important insight into the further application of MoS2 on agriculture and environment.

Grain yield responses of lowland rice varieties to increased amount of nitrogen fertilizer under tropical highland conditions in central Kenya

Tropical highland conditions in Mwea Kenya, ensure the high radiation and the large day–night temperature differences. Such conditions are generally believed to promote rice growth and yield, but the current grain yield is lower than the expectation. In the current standard N fertilizer practice in Mwea, 75 kg nitrogen (N) ha−1 is applied in three splits at fixed timing. The effects of increases in N fertilizer amount (125, 175, and 225 kg N ha−1) on rice growth and yield were evaluated to test the hypothesis that unachieved high rice grain yield in Mwea is due to insufficient amount of N fertilizer. Two popular lowland varieties in Mwea (Basmati 370 and BW196) and two varieties reported as high yielding in other countries (Takanari and IR72) were used. Shoot dry weight (DW) increased with increases in the amount of N fertilizer applied in three splits at fixed timing, irrespective of variety. It reached approximately 20 t ha−1 under increased N conditions (>75 kg N ha−1) in several cases, indicating that high biomass production could be achieved by increasing N application rate. However, the increased biomass did not increase grain yield, due to decreased grain filling under high N conditions in all varieties. Thus, N amounts above 75 kg ha−1 were ineffective for increasing grain yields in Mwea, where N fertilizer was applied in three splits at fixed timing. Increasing influence of low temperature under high N conditions may be one of the reasons for the decreased grain filling in Mwea.

Colonization by Cupriavidus taiwanensis KKU2500-3 Enhances the Growth and Yield of KDML105 Jasmine Rice

The effects of the cadmium-tolerant bacterium Cupriavidus taiwanensis KKU2500-3 on the growth and grain production of jasmine rice (Oryza sativa L. var. KDML105) were studied. Bacterial cells were inoculated onto rice seedlings before transplanting into a hydroponic system; the cells successfully colonized, became distributed, and multiplied in the range of 104 - 109 log CFU·g-1 plant. The bacterial cells were localized to the cell wall and the intercellular space of all plant parts. Moreover, inoculation of strain KKU2500-3 significantly promoted rice growth by increasing the length, dry mass of shoots and roots, and chlorophyll concentration in leaves, and improved yields by increasing the panicle length, number of seeds/panicle, number of filled grains/panicle, filled grain percentage, and 100-grain weight (13.57, 11.90, 48.20, 32.55, and 23.53 % over the control, respectively). The number of filled grains/panicle and grain weight accounted for the increase in total yield. C. taiwanensis KKU2500-3 fixed nitrogen, produced indole-3-acetic acid, and solubilized phosphate, affecting the growth and yield of all plants. Successful colonization of rice seedlings before transplanting is an important finding, as it will simplify bacterial inoculation of plants, especially when grown in cadmium-contaminated rice fields.

Effect of Nitrogen and Silicon on Rice Submerged at Tillering Stage

Core Ideas Basal silicon promotes rice growth and development at the tillering stage.After flooding, foliar spraying N or silicon timely had a better effect.Foliar spraying N had more advantages than silicon. Flooding is a major threat to rice (Oryza sativa L.) yields. We wondered if basal Si and foliar spraying fertilizer had an influence on rice submerged at tillering stage. The results showed that basal Si application promoted rice growth and development at the tillering stage, improving rice seedling tolerance to submergence stress. After the occurrence of flooding, timely foliar spraying of N or Si had significant remedial effects, and spraying N along with Si had a better effect. The combination of basal Si and post‐flooding N and Si spraying was the most promising method of nutrient application and as resistance to damage during submergence was enhanced, plants rapidly resumed growth and development. By maintaining a great number of green leaves and tillers as well as higher aboveground and belowground dry mass, sugar contents and antioxidant enzyme activities, these plants yielded significantly more grain. We conclude that reasonable use of Si leads to resistance and alleviation of the damaging effects of submergence and contributes to reducing yield losses in rice.

Molluscicidal activity of Arisaema erubescens mixed with fertilizers against Oncomelania hupensis and its effect on rice germination and growth

To explore a new molluscicide with dual effects of fertilization and molluscicidal activity, an organic-inorganic compound fertilizer molluscicide was prepared by mixing the water extract (or powder) of Arisaema erubescens tubers with nitrogen fertilizer, phosphate fertilizer, potash fertilizer, and three mixed fertilizers (hereinafter referred to as ANF, APF, AKF and ACF, respectively). Leaching using the mixture was performed to test for molluscicidal activity, and indoor rice germination, seedling growth, and pot experiments were monitored. ANF exhibited superior molluscicidal activity, with respective 24-h and 48-h Oncomelania mortality rates significantly increased, reaching up to 67.7% and 92.3%. ANF, APF, and AKF significantly promoted rice germination and growth of rice, with ANF showing superior effects. The respective 3-day and 5-day germination rate of rice seeds treated with ANF significantly increased by 25% and 21% relative to that of the control group, and the respective 10-day and 20-day growth length of rice seedlings (aboveground part) increased by 106.2% and 33.2%. A positive correlation between ACF molluscicidal activity and concentration and treatment time were observed. The Oncomelania mortality rate at 48 h after treatment with a low ACF concentration (0.25 g/L) was 70.7%, whereas that at 24 h after treatment using a higher concentration (0.5 g/L) was 80.7%. ACF promoted rice seed germination and seedling growth, whereas inhibitory effects were observed using a high ACF concentration. Therefore, the combined application of A. erubescens and chemical fertilizers not only enhances molluscicidal activity, but also promotes rice growth, with the combined application of A. erubescens and nitrogen fertilizer and mixed fertilizer showing superior dual effects (molluscicide and fertilization).

Diversity and characterization of Azotobacter isolates obtained from rice rhizosphere soils in Taiwan

Azotobacter species, free-living nitrogen-fixing bacteria, have been used as biofertilizers to improve the productivity of non-leguminous crops, including rice, due to their various plant growth-promoting traits. The purposes of this study were to characterize Azotobacter species isolated from rice rhizospheres in Taiwan and to determine the relationship between the species diversity of Azotobacter and soil properties. A total of 98 Azotobacter isolates were isolated from 27 paddy fields, and 16S rRNA gene sequences were used to identify Azotobacter species. The characteristics of these Azotobacter strains were analyzed including carbon source utilization and plant growth-promoting traits such as nitrogen fixation activity, indole acetic acid production, phosphate-solubilizing ability, and siderophore secretion. Of the 98 strains isolated in this study, 12 were selected to evaluate their effects on rice growth. Four species of Azotobacter were identified within these 98 strains, including A. beijerinckii, A. chroococcum, A. tropicalis, and A. vinelandii. Of these four species, A. chroococcum was predominant (51.0%) but A. beijerinckii had the highest level of nucleotide diversity. Strains within individual Azotobacter species showed diverse profiles in carbon source utilization. In addition, the species diversity of Azotobacter was significantly related to soil pH, Mn, and Zn. Members of the same Azotobacter species showed diverse plant growth-promoting traits, suggesting that the 98 strains isolated in this study may not equally effective in promoting rice growth. Of the 12 strains evaluated, A. beijerinckii CHB 461, A. chroococcum CHB 846, and A. chroococcum CHB 869 may be used to develop biofertilizers for rice cultivation because they significantly promoted rice growth. This study contributes to the selection of suitable Azotobacter strains for developing biofertilizer formulations and soil management strategies of Azotobacter for paddy fields.

Identification of early ammonium nitrate-responsive genes in rice roots

Ammonium has long been used as the predominant form of nitrogen source for paddy rice (Oryza sativa). Recently, increasing evidence suggests that nitrate also plays an important role for nitrogen acquisition in the rhizosphere of waterlogged paddy rice. Ammonium and nitrate have a synergistic effect on promoting rice growth. However, the molecular responses induced by simultaneous treatment with ammonium and nitrate have been less studied in rice. Here, we performed transcriptome analysis to identify genes that are rapidly regulated by ammonium nitrate (1.43 mM, 30 min) in rice roots. The combination of ammonium and nitrate preferentially induced the expression of nitrate-responsive genes. Gene ontology enrichment analysis revealed that the early ammonium nitrate-responsive genes were enriched in “regulation of transcription, DNA-dependent” and “protein amino acid phosphorylation” indicating that some of the genes identified in this study may play an important role in nitrogen sensing and signaling. Several defense/stress-responsive genes, including some encoding transcription factors and mitogen-activated protein kinase kinase kinases, were also rapidly induced by ammonium nitrate. These results suggest that nitrogen metabolism, signaling, and defense/stress responses are interconnected. Some of the genes identified here may be involved in the interaction of nitrogen signaling and defense/stress-response pathways in plants.

Silicon application promotes rice growth and negatively affects development of Spodoptera frugiperda (J. E. Smith)

AbstractSilicon (Si) has been reported to enhance plant resistance against biotic and abiotic stressors and also benefit plant growth. These effects are more pronounced in grass species, especially with soil‐applied Si. This study investigated the effects of Si application on rice resistance to Spodoptera frugiperda development and plant vegetative growth. Effects of Si on rice were assessed via soil and foliar applications and compared with untreated plants (control). Si was soil‐ and foliar‐applied as 1% silicic acid solution at a dosage equivalent to 1.4 t Si per ha. After application, leaf material was collected from Si‐treated and untreated plants and placed in Petri dishes with individual S. frugiperda neonate larvae, where development was followed to adult emergence and biological parameters recorded. Vegetative growth parameters recorded in rice plants were the height, chlorophyll content, fresh and dry weights of shoots, and shoot Si content. No effects of Si application were observed on the durations of larval and pupal stages, larval and pupal survival, and sex ratio of S. frugiperda. Insects fed leaves from Si‐treated plants exhibited lower leaf consumption, larval and pupal weights, longevity of males and females, number of eggs, and egg viability. The negative effects were correlated with higher rice Si content. Si application to rice increased plant height, chlorophyll content and dry weight. Our study demonstrates that foliar‐applied Si is as efficient as soil‐applied Si in negatively affecting S. frugiperda development and providing beneficial effects on rice plant growth.

Growth and Cd uptake by rice (Oryza sativa) in acidic and Cd-contaminated paddy soils amended with steel slag

Contamination of rice (Oryza sativa) by Cd is of great concern. Steel slag could be used to amend Cd-contaminated soils and make them safe for cereal production. This work was conducted to study the effects of steel slag on Cd uptake and growth of rice plants in acidic and Cd-contaminated paddy soils and to determine the possible mechanisms behind these effects. Pot (rhizobag) experiments were conducted using rice plants grown on two acidic and Cd-contaminated paddy soils with or without steel slag amendment. Steel slag amendment significantly increased grain yield by 36–45% and root catalase activity, and decreased Cd concentrations in brown rice by 66–77% compared with the control, in both soils. Steel slag amendment also markedly decreased extractable soil Cd, Cd concentrations in pore-water and Cd translocation from roots to above-ground parts. It also significantly increased soil pH, extractable Si and Ca in soils and Ca concentrations in roots. Significant positive correlations were found between extractable soil Cd and Cd concentrations in rice tissues, but it was negatively correlated with soil pH and extractable Si. Calcium in root tissues significantly and negatively correlated with Cd translocation factors from roots to straw. Overall, steel slag amendment not only significantly promoted rice growth but decreased Cd accumulation in brown rice. These benefits appear to be related to improvements in soil conditions (e.g. increasing pH, extractable Si and Ca), a reduction in extractable soil Cd, and suppression of Cd translocation from roots to above-ground parts.

Assessment of Rice Associated Bacterial Ability to Enhance Rice Seed Germination and Rice Growth Promotion

ABSTRACT The application of beneficial bacteria has recently been used for sustainable agriculture. In current research, 71 bacterial isolates were obtained from rice plant and the rhizosphere soil of different paddy fields in Guilan province, Iran. After primitive investigation, 40 bacteria with typical predominant characteristics were selected. By PCR-RFLP of their 16S r-DNA gene, 8 Operational Taxonomic Units (OTUs) totally consisted of 33 isolates were obtained. From all of them, 8 isolates were selected for rice seed germination experiment, then, effective isolates were used for pot experiment to evaluate their ability for promoting rice growth. All of them were able to increase rice growth and yield, but in different potential. These tested isolates were identified as Alcaligenes faecalis (DEp8, O1R4), Pantoea ananatis (AEn1), Bacillus vietnamensis (MR5), Bacillus idriensis (MR2) and Stenotrophomonas maltophilia by partial sequencing of their 16S r-DNA gene. Among them, AEn1 and MR5 produced indole-3- acetic acid (IAA) in larger amounts than the other isolates and the isolates AEn1 and O1R4 were able to solubilize phosphate in higher amounts. According to the results obtained, it can be concluded that AEn1, O1R4 and MR5 can be considered as bacterial inoculants to use as alternatives for chemical fertilizers.

Evaluation of soil water percolation under different irrigation practices, antecedent moisture and groundwater depths in paddy fields

Understanding soil water percolation in paddy fields is helpful to optimize irrigation schedule for rice production and improve water use efficiency under various irrigation practices and groundwater depths. Calibrated HYDRUS-1D model was used to simulate soil water movement and water balance in this study. We conducted scenario analyses based on the model to evaluate the combined effects of irrigation amount in an irrigation event (irrigation amount), irrigation duration, antecedent soil moisture, and groundwater depth on deep percolation (DP) in paddy fields. Results showed that during an irrigation event, there would be higher DP in paddy fields with higher antecedent soil moisture (≥−10kPa), larger irrigation amount (7cm) and/or free drainage in the bottom of rice root zones. We also used a classification and regression tree model to analyze the relative contribution of different factors to DP. Results indicated that antecedent soil moisture was the primary factor that contributed 46.3% of DP variation. Groundwater depth contributed 32.5% of DP variation, while irrigation amount (18.7%) and irrigation duration (2.5%) contributed least for DP variation. Furthermore, effects of these factors on DP interacted with each other. In scenario analysis, the contribution of antecedent soil moisture increased from 16.1% to 65.2% as the groundwater depth increased. When irrigation amount rose from 1cm to 5cm, the contributions of antecedent soil moisture increased to 77.6% from 57.1%; when irrigation amount was 7cm, the contributions of antecedent soil moisture decreased to 46.4%. The contribution of irrigation amount rose to 55.7% from 28.4% with the increase of antecedent soil moisture, while the contributions of groundwater depth to DP showed opposite variation to irrigation amount as antecedent soil moisture altered. Based on relative contribution of these factors, optimal combinations of irrigation practices, antecedent soil moisture and groundwater depth were screened out to control DP for promoting rice growth and improving water use efficiency.

De novo Transcriptome Assembly of Phomopsis liquidambari Provides Insights into Genes Associated with Different Lifestyles in Rice (Oryza sativa L.).

The mechanisms that trigger the switch from endophytic fungi to saprophytic fungi are largely unexplored. Broad host range Phomopsis liquidambari is established in endophytic and saprophytic systems with rice (Oryza sativa L.). Endophytic P. liquidambari promotes rice growth, increasing rice yield and improving the efficiency of nitrogen fertilizer. This species's saprophytic counterpart can decompose rice litterfall, promoting litter organic matter cycling and the release of nutrients and improving the soil microbial environment. Fluorescence microscopy, confocal laser scanning microscopy and quantitative PCR investigated the colonization dynamics and biomass of P. liquidambari in rice in vivo. P. liquidambari formed infection structures similar to phytopathogens with infected vascular tissues that systematically spread to acrial parts. However, different from pathogenic infection, P. liquidambari colonization exhibits space restriction and quantity restriction. Direct comparison of a fungal transcriptome under three different habitats provided a better understanding of lifestyle conversion during plant-fungi interactions. The isolated total RNA of Ck (pure culture), EP (endophytic culture) and FP (saprophytic culture) was subjected to Illumina transcriptome sequencing. To the best of our knowledge, this study is the first to investigate Phomopsis sp. using RNA-seq technology to obtain whole transcriptome information. A total of 27,401,258 raw reads were generated and 22,700 unigenes were annotated. Functional annotation indicated that carbohydrate metabolism and biosynthesis of secondary metabolites played important roles. There were 2522 differentially expressed genes (DEGs) between the saprophytic and endophytic lifestyles. Quantitative PCR analysis validated the DEGs of RNA-seq. Analysis of DEGs between saprophytic and endophytic lifestyles revealed that most genes from amino acids metabolism, carbohydrate metabolism, fatty acid biosynthesis, secondary metabolism and terpenoid and steroid biosynthesis were up-regulated in EP. Secondary metabolites of these pathways may affect fungal growth and development and contribute to signaling communication with the host. Most pathways of xenobiotic biodegradation and metabolism were upregulated in FP. Cytochrome P450s play diverse vital roles in endophytism and saprophytism, as their highly specialized functions are evolutionarily adapted to various ecological niches. These results help to characterize the relationship between fungi and plants, the diversity of fungi for ecological adaptations and the application prospects for fungi in sustainable agriculture.

Impacts of Steel-Slag-Based Silicate Fertilizer on Soil Acidity and Silicon Availability and Metals-Immobilization in a Paddy Soil.

Slag-based silicate fertilizer has been widely used to improve soil silicon- availability and crop productivity. A consecutive early rice-late rice rotation experiment was conducted to test the impacts of steel slag on soil pH, silicon availability, rice growth and metals-immobilization in paddy soil. Our results show that application of slag at a rate above higher or equal to 1 600 mg plant-available SiO2 per kg soil increased soil pH, dry weight of rice straw and grain, plant-available Si concentration and Si concentration in rice shoots compared with the control treatment. No significant accumulation of total cadmium (Cd) and lead (Pb) was noted in soil; rather, the exchangeable fraction of Cd significantly decreased. The cadmium concentrations in rice grains decreased significantly compared with the control treatment. In conclusion, application of steel slag reduced soil acidity, increased plant–availability of silicon, promoted rice growth and inhibited Cd transport to rice grain in the soil-plant system.

Hydrogen sulfide alleviates mercury toxicity by sequestering it in roots or regulating reactive oxygen species productions in rice seedlings

Soil mercury (Hg) contamination is a major factor that affects agricultural yield and food security. Hydrogen sulfide (H2S) plays multifunctional roles in mediating a variety of responses to abiotic stresses. The effects of exogenous H2S on rice (Oryza sativa var ‘Nipponbare’) growth and metabolism under mercuric chloride (HgCl2) stress were investigated in this study. Either 100 or 200 μM sodium hydrosulfide (NaHS, a donor of H2S) pretreatment improved the transcription of bZIP60, a membrane-associated transcription factor, and then enhanced the expressions of non-protein thiols (NPT) and metallothioneins (OsMT-1) to sequester Hg in roots and thus inhibit Hg transport to shoots. Meanwhile, H2S promoted seedlings growth significantly even in the presences of Hg and superoxide dismutase (SOD, EC 1.15.1.1) or catalase (CAT, EC 1.11.1.6) inhibitors, diethyldithiocarbamate (DDC) or 3-amino-1,2,4-triazole (AT). H2S might act as an antioxidant to inhibit or scavenge reactive oxygen species (ROS) productions for maintaining the lower MDA and H2O2 levels, and thereby preventing oxidative damages. All these results indicated H2S effectively alleviated Hg toxicity by sequestering it in roots or by regulating ROS in seedlings and then thus significantly promoted rice growth.

Effects of Biochar on Cadmium Accumulation in Rice and Cadmium Fractions of Soil: A Three-Year Pot Experiment

A three-year rice pot experiment was conducted to investigate the effects of biochar on cadmium (Cd) accumulation in rice and Cd fractions of soil. The biochar was derived from farmland waste and applied to contaminated paddy soil at various application rates (0, 1, 2, and 4%). The dry matter accumulations in rice, Cd contents of various rice organs, and fraction distributions of Cd in soil were measured. In a 3-year experiment, the results indicated that biochar treatments reduced the exchangeable Cd concentrations by 28.5 to 59.4% in soil, the total Cd accumulations in rice by 2.7 to 23.8%, and promoted rice growth by 0.7 to 3.9%. The application rates of 2% to 4% were considered to be reasonable for both rice growth and remediation of Cd-contaminated soil. Meanwhile, the Cd-contaminated biochar and straw were studied in the above manner for two years. Contaminated biochar reduced the Cd content of individual rice plants and ensured the normal growth of rice, but it had little effect on the Cd contents in specific organs of rice and Cd fractions of soil. However, this indicated that contaminated biomass materials have the possibility to be reused after pyrolysis for remediation of contaminated paddy soil.

Cultivable Methylobacterium species diversity in rice seeds identified with whole-cell matrix-assisted laser desorption/ionization time-of-flight mass spectrometric analysis

Methylobacterium species are methylotrophic bacteria that widely inhabit plant surfaces. In addition to studies on methylotrophs as model organisms, research has also been conducted on their mechanism of plant growth promotion as well as the species-species specificity of plant-microbe interaction. We employed whole-cell matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (WC-MS) analysis, which enables the rapid and accurate identification of bacteria at the species level, to identify Methylobacterium isolates collected from the rice seeds of different cultivars harvested in Japan, Thailand, and Kenya. Rice seeds obtained from diverse geographical locations showed different communities of Methylobacterium species. We found that M.fujisawaense, M.aquaticum, M.platani, and M.radiotolerans are the most frequently isolated species, but none were isolated as common species from 18 seed samples due to the highly biased communities in some samples. These findings will contribute to the development of formulations containing selected species that promote rice growth, though it may be necessary to customize the formulations depending on the cultivars and farm conditions.

Silicate application decreased methane emission from paddy soil under elevated UV‐B radiation

AbstractA pot experiment was conducted to investigate the effects of silicate application quantity and silicate fertilizer type on rice growth and methane (CH4) emission under elevated UV‐B radiation. The experiment was designed with two UV‐B radiation levels, i.e., reference UV‐B radiation (Ambient, A, 12.0 kJ·m−2·d−1), and elevated UV‐B radiation (Elevated by 20%, E, 14.4 kJ·m−2·d−1); with four silicate fertilizer levels, i.e., Si0 (no silicate application, 0 kg SiO2·ha−1), Si1 (sodium silicate, 100 kg SiO2·ha−1), Si2 (sodium silicate, 200 kg SiO2·ha−1) and Si3 (slag silicate fertilizer, 200 kg SiO2·ha−1). The results show that, silicate application could mitigate the depressive effect of elevated UV‐B radiation on rice growth and increase the tiller number, and dry weight of shoot and root biomass. Silicate application promoted rice growth, which increased with silicate application quantity (sodium silicate); slag silicate fertilizer was better than sodium silicate in promoting rice growth. Elevated UV‐B radiation could increase the emission flux and accumulative emission of CH4 in rice soil, but silicate application significantly decreased the emission flux and accumulative emission of CH4 and the methane emission decreased with the increase in silicate application quantity. At one silicate application quantity, slag silicate fertilizer was better than sodium silicate in respect of emission reduction effect. This indicates that application of slag silicate fertilizer in rice production can realize waste reuse and can effectively decrease the CH4 emission in rice field under elevated UV‐B radiation. © 2016 Society of Chemical Industry and John Wiley & Sons, Ltd

In situ stabilization of heavy metals in multiple-metal contaminated paddy soil using different steel slag-based silicon fertilizer.

Steel slag has been widely used as amendment and silicon fertilizer to alleviate the mobility and bioavailability of heavy metals in soil. The objective of this study was to evaluate the influence of particle size, composition, and application rate of slag on metal immobilization in acidic soil, metals uptake by rice and rice growth. The results indicated that application of slag increased soil pH, plant-available silicon concentrations in soil, and decreased the bioavailability of metals compared with control treatment, whereas pulverous slag (S1) was more effective than granular slag (S2 and S3). The acid-extractable fraction of Cd in the spiked soil was significantly decreased with application of S1 at rates of 1 and 3%, acid-extractable fractions of Cu and Zn were decreased when treated at 3%. Use of S1 at both rates resulted in significantly lower Cd, Cu, and Zn concentrations in rice tissues than in controls by 82.6-92.9, 88.4-95.6, and 67.4-81.4%, respectively. However, use of pulverous slag at 1% significantly promotes rice growth, restricted rice growth when treated at 3%. Thus, the results explained that reduced particle size and suitable application rate of slag could be beneficial to rice growth and metals stabilization.

An autophagy gene, HoATG5, is involved in sporulation, cell wall integrity and infection of wounded barley leaves

The endophytic fungus Harpophora oryzae is a beneficial endosymbiont isolated from wild rice. H. oryzae can not only promote rice growth and biomass accumulation but also protect rice roots from invasion by its close relative Magnaporthe oryzae. Autophagy is a highly evolutionary conserved process from lower to higher eukaryotic organisms, and is involved in the maintenance of normal cell differentiation and development. In this study, we isolated a gene (HoATG5) which encodes an essential protein required for autophagy from the beneficial endophyte fungus H. oryzae. Using targeted gene replacement, a ΔHoATG5 mutant was generated and used to investigate the biological functions of autophagy in H. oryzae. We found that the autophagic process was blocked in the HoATG5 deletion mutant. The mutant showed increased vegetative growth and sporulation, and was sensitive to nutrient starvation. The ΔHoATG5 mutant lost its ability to penetrate and infect the wounded barley leaves. These results provide new knowledge to elaborate the molecular machinery of autophagy in endophytic fungi.

Biofertilizers from Rhodopseudomonas palustris strains to enhance rice yields and reduce methane emissions

Flooded rice fields either organic or saline share common problems of low productivity and emission of methane (CH4) that contributes to global warming. Among various biofertilizers, purple nonsulfur bacteria (PNSB) are of good candidates to solve such problems since they could promote rice growth and yield, and also compete with methane producing bacteria for substrates. The goals of this work were to investigate the potential of Rhodopseudomonas palustris strains TN114, PP803 and TK103 identified as a biofertilizer to enhance rice yield and reduce CH4 emissions in both types of the rice fields. The efficiency of each PSNB biofertilizer were compared with a commercial organic fertilizer (COF), a carrier control (carrier with no added PNSB), and control without the addition of any fertilizer (control). In both paddy fields, no significant difference in the growth of rice was found based on the maximal height of plants, but there was a significant difference in rice grain yields. In saline paddy field, all PNSB biofertilizers produced higher grain yield at statistically significant level; however, in the organic paddy field only TN114 biofertilizer showed a promising result at 48% increase followed by COF treatment. The lowest grain yield was observed in both controls. COF treatment generated the highest CH4 emissions followed by both controls, and the least was in PNSB biofertilizer treatments, particularly PP803 which was 24% and 28% lower than COF in organic and saline paddy fields, respectively. Both paddy fields showed a strong negative correlation between PNSB cell density and CH4 emissions (rp=−0.90). It can be concluded that all biofertilizers from the selected R. palustris were able to enhance rice yields in both the organic and saline flooded paddy fields and concurrently reduce CH4 emissions.