Trichoderma–plant–pathogen interactions

Biological control involves the use of beneficial organisms, their genes, and/or products, such as metabolites, that reduce the negative effects of plant pathogens and promote positive responses by the plant. Disease suppression, as mediated by biocontrol agents, is the consequence of the interactions between the plant, pathogens, and the microbial community. Antagonists belonging to the genus Trichoderma are among the most commonly isolated soil fungi. Due to their ability to protect plants and contain pathogen populations under different soil conditions, these fungi have been widely studied and commercially marketed as biopesticides, biofertilizers and soil amendments. Trichoderma spp. also produce numerous biologically active compounds, including cell wall degrading enzymes, and secondary metabolites. Studies of the three-way relationship established with Trichoderma, the plant and the pathogen are aimed at unravelling the mechanisms involved in partner recognition and the cross-talk used to maintain the beneficial association between the fungal antagonist and the plant. Several strategies have been used to identify the molecular factors involved in this complex tripartite interaction including genomics, proteomics and, more recently, metabolomics, in order to enhance our understanding. This review presents recent advances and findings regarding the biocontrol-resulting events that take place during the Trichoderma–plant–pathogen interaction. We focus our attention on the biological aspects of this topic, highlighting the novel findings concerning the role of Trichoderma in disease suppression. A better understanding of these factors is expected to enhance not only the rapid identification of effective strains and their applications but also indicate the potentials for improvement of natural strains of Trichoderma.     

Treatment of Olive Oil Mill Wastewater by Silica–Alginate–Fungi Biocomposites

Olive oil mill wastewater (OMW) generates a wide variety of pollutants depending on the production process and other factors such as olive varieties and cultivation system. Efforts to mitigate the impact of these effluents in the environment have been made by developing more efficient treatment systems in terms of removal of chemical oxygen demand (COD), color, organic compounds, and toxicity. This study is the first that reports the potential of a treatment of OMW by biocomposites of silica?Calginate?Cfungi (Pleurotus sajor caju and Trametes versicolor). The treatment by biocomposites can be considered as a three-step process responsible for the removal of the compounds: (1) adsorption of reactants on the monolithic structure and diffusion to the biological active sites, (2) biodegradation by the fungi, and (3) diffusion of the products resulting from the biodegradation. Both treatments tested showed potential capacity to remove organic compounds, color, COD, and toxicity. The T. versicolor biocomposites were the most effective and responsible for the reduction in color (from 38.4 to 44.9?%), COD (from 42.8 to 63.8?%), and total phenolic content (from 85.3 to 88.7?%) after 29?days of treatment. The toxicity reduction on Portuguese OMW was minimal, but the use of composites on the Moroccan OMW caused a 9.5- to 19-fold reduction in toxicity. Furthermore, the biocomposites showed potential for re-utilization for more 29?days of treatment.     

15N2–DNA–stable isotope probing of diazotrophic methanotrophs in soil

Nucleic acid stable isotope probing (SIP) is a powerful tool that can identify and characterize the microorganisms that mediate specific soil processes and explore the flow of C and N through functional groups in the soil food web. While ¹³C–SIP has been used successfully in a range of applications, methodological constraints have limited the applicability of ¹⁵N-labelled compounds in nucleic acid SIP. However, ¹⁵N–DNA–SIP can now be achieved and this method when used with ¹⁵N₂ provides a powerful new tool for characterizing free-living diazotrophs in natural ecosystems. A diverse array of non-cultivated diazotrophs have been observed in soil and yet the characteristics of these organisms and their environmental significance remain almost completely unknown. ¹⁵N₂–DNA–SIP can identify those diazotrophs that are active in situ while providing access to gene sequences and genome fragments that can yield insights on their evolutionary history and functional capacities. Further insights on the ecology of free-living diazotrophs in soil can be provided by performing ¹⁵N₂–DNA–SIP on microcosms in which the response of the diazotrophic community is determined in relation to experimental manipulation. We describe the use of ¹⁵N₂–DNA–SIP to explore linkages between different C sources and N-fixation by specific diazotroph populations in soil. Methane addition to soil was observed to stimulate N-fixation and the organisms that were found to be responsible for this activity were Type II methanotrophs most closely related to the genus Methylocystis. This report provides insights on the use of nucleic acid SIP to identify and characterize microorganisms that mediate specific soil processes and represents the first time that a specific group of methanotrophs has been shown to mediate N-fixation while in the soil environment.     

基于粮食安全的乌鲁木齐市人口–粮食–耕地系统态势分析及预测

基于统计数据在分析了乌鲁木齐市近16年人口、粮食和耕地动态变化的基础上,运用耕地压力指数模型和耕地资源人口承载指数模型,揭示了乌鲁木齐市耕地压力和粮食供给状况;同时集成曲线估计模型和时间序列平滑法对2014—2020年人口–粮食–耕地系统进行了预测。结果表明:1996—2011年,乌鲁木齐市人口–粮食–耕地系统整体逐渐呈不平衡态势;16年来乌鲁木齐市人口超载、耕地压力明显,其中,2003年耕地压力最大、耕地资源承载力最小,1996年与之相反;未来7年乌鲁木齐市人口将持续增长,粮食产量波动式减少,耕地面积和人均耕地缓慢减少,耕地压力指数和耕地资源承载指数继续变大,乌鲁木齐市人、地、粮矛盾将更加尖锐。据此提出应对措施:控制人口数量并提高人口素质;完善耕地保护制度的同时重视现代生态农业发展;重视基本农田保护的基础上优化都市圈内部耕地资源。     

利用螯合–缓冲营养液对小麦苗期磷–锌关系的研究

采用螯合缓冲营养液培养技术（Chelator-buffer culture solution）,对小麦幼苗植株的磷锌营养进行了探讨。结果表明,高磷条件下小麦出现的缺锌黄化与磷中毒症状之间存在着明显区别,本研究结果支持高磷条件下作物出现的黄化是锌缺乏症状而非磷中毒的观点。与缺磷相比,正常供磷促进了小麦的生长,但过量磷对小麦生长有阻碍作用,而且锌的供应加剧了促进或抑制的程度。正常供应磷、锌条件下,小麦幼苗根系或地上部的磷、锌含量、吸收量及转运率均处于相对较高的水平,其余各处理则因为磷或锌供应量不适宜而使植株的磷、锌营养受到不同程度的影响。另外,磷锌相互拮抗的作用方式及大小程度不同:磷主要影响小麦根系对锌的吸收,而锌对小麦磷营养的影响主要是通过对其从根系向地上部转运的抑制来实现的;磷对锌的影响要明显大于锌对磷的影响,磷素水平在小麦的磷、锌营养平衡中起着更为重要的作用。磷锌拮抗作用只在双方供应不适宜的情况下发生,而且相互作用的方式及程度存在明显差异。     

A Note on the Royle–Nichols Model for Repeated Detection–Nondetection Data

In this note, it is shown that the integrated likelihood for the Royle–Nichols model with a Poisson mixing distribution can be expressed as a finite rather than an infinite sum of terms. The advantages which so accrue are discussed and explored by means of two examples. The finite sum formulation of the likelihood is also shown to hold for negative binomial and zero-inflated mixing distributions. Results based on these two mixing distributions proved disappointing however and their use is not recommended unless extensive data are available.     

巢湖藻–草–泥堆制有机肥对土壤性质的影响

通过田间试验,研究施用由巢湖取出物蓝藻、水草和底泥高温堆肥制作成的有机肥对作物产量、土壤理化性质及微生物学特性的影响。结果表明:施用藻-草-泥有机肥对大豆、花生有明显增产效应。施肥土壤中总氮、碱解氮、总磷、有效磷、有机质、腐殖酸、阳离子交换量和土壤孔隙度均显著高于未施肥土壤,而容重显著降低。与未种植未施肥处理(T1)相比,种植大豆施肥(T4)和种植花生施肥处理(T5)中微生物生物量碳分别增加116.5%、97.8%,微生物生物量氮增加196.7%、170.6%;T4处理的转化酶、脲酶和过氧化氢酶活性分别提高183%、392%和8.9%,T5处理中相应酶活性分别提高116%、268%、1.01%。相关性分析表明,微生物生物量碳、氮和转化酶、脲酶活性都与多种肥力因子呈显著相关,且转化酶及脲酶活性间存在显著相关性。T4处理中过氧化氢酶活性与肥力因子间无显著相关性,而T5处理过氧化氢酶活性与有效磷、有机质、腐殖酸、微生物生物量碳、微生物生物量氮间呈显著相关。巢湖取出物蓝藻、水草和底泥可作为生产有机肥的良好材料以达到资源化利用目的。     

Effect of freeze–thaw cycles on carbon stocks of saline–alkali paddy soil

This study aims to provide basic data to support accurate estimation of carbon stocks and reveal the physicochemical factors that influence the carbon cycle in saline–alkali soils. Soil samples were collected during initial freezing, complete freezing, initial thawing and complete thawing stages. Levels of soil organic carbon (SOC), soil inorganic carbon (SIC), moisture, salinity, pH and available nitrogen were determined, and variations were observed during the freezing and thawing periods. Correlation analysis and regression analysis of carbon contents and physicochemical properties were performed. The results showed that freeze–thaw cycles have significant effects on carbon contents. The SOC content initially decreased in the freezing stage and then increased in the thawing stage. However, the SIC content initially increased in the freezing stage, decreased in the initial thawing stage and finally increased in the complete thawing stage. The migration and transformation of SOC and SIC were observed both temporally and spatially. SOC was positively correlated with available nitrogen, moisture and salinity and negatively correlated with pH; while SIC was negatively correlated with available nitrogen, moisture and salinity and positively correlated with pH. Among the factors evaluated, available nitrogen and salinity exerted the greatest effects on SOC and SIC contents, respectively.     

Coupled model of stomatal conductance–photosynthesis–transpiration for paddy rice under water-saving irrigation

To improve the performance of a coupled model based on a Leuning–Ball stomatal conductance (g_s) model for rice under water deficit conditions, leaf temperature rising (ΔT) was incorporated into the Leuning–Ball model and a revised coupled model for simulation of stomatal conductance g_s–net photosynthesis rate (P_n)–transpiration rate (T_r) was developed based on data collected from a rice paddy with nonflooded controlled irrigation in 2003 and 2004. Both a Leuning–Ball and revised Leuning–Ball and coupled model based on both were evaluated with internal conductance (g_ic) determined by different equations. The performance of the Leuning–Ball model was improved under water deficit condition by incorporating ΔT, and the revised Leuning–Ball model performed better than the Leuning–Ball model in the coupled model of stomatal conductance–photosynthesis–transpiration for rice under water deficit conditions. Meanwhile, accuracy in g_ic calculation is essential for simulation of P_n, but not for simulation of T_r. Thus, leaf temperature rising ΔT is suitable as a leaf water status indicator in a simulation of rice leaf gas exchange response to water deficit conditions.     

Meeting the challenge of scaling up processes in the plant–soil–microbe system

The scaling up of processes in the plant–soil–microbe system represents one of the greatest challenges facing environmental scientists and yet is essential for sustainable land management worldwide. The latter encompasses, for example, the mitigation of and adaptation to anthropogenic climate change, the bioremediation of industrially contaminated sites, catchment management of human pathogens such as Escherichia coli O157 and integrated crop management on the farm. Scaling up is also essential for the regional and global biogeochemical modelling that will inform policy-makers of the critical environmental factors driving climate change. Despite increasing understanding of the links between gene expression and process on a microscale, there is still much progress to be made when relating this to processes at the macroscale. In this paper, we explore the challenges this poses and examine key case studies of successful up-scaling.

Long–term effect of crop rotation and nutrient management on soil–plant nutrient cycling and nutrient budgeting in Indo–Gangetic plains of India

In the present investigation, the long-term effect of pulse crop inclusion in the maize-wheat rotation was assessed for the nutrient availability and soil-plant nutrient cycling under different nutrient management practices. Including pulses in the maize-wheat rotation improved soil organic carbon (SOC) and plant available macronutrients being higher in maize-wheat-mungbean rotation. Inclusion of mungbean to maize-wheat rotation enhanced the nitrogen (33.9%), phosphorus (46.4%), potassium (36.3%), and sulphur (55.5%) uptake in maize crop; likewise, alternate-year chickpea inclusion increased the uptake of these nutrients by 18.2, 19.1, 21.7, 32.1%, respectively. Inorganic fertilization maintained the positive annual balance of nitrogen, phosphorus, and zinc. By contrast, the nutrient balance under organic nutrient management was mostly negative. The magnitude of negative balance of potassium and sulphur was higher in inorganic than that of organic nutrient management. The low nutrient supply (particularly nitrogen) in organic fertilization largely inhibited the yield of cereal crops but not that of pulses. In view of this, the inclusion of pulses in the cereal-cereal systems could cause substantial improvement in soil fertility and sustainability in Indo-Gangetic plains. We infer that supply of nutrients like nitrogen and phosphorus in organic, and potassium and sulphur in recommended inorganic fertilization merit special attention.     

NITROGEN–PHOSPHORUS–POTASSIUM EFFECTS ON FORMS OF SULFUR IN LEAVES AND FRUITS OF CUCUMBER

ABSTRACT

The impact that nitrogen (N), phosphorus (P), and potassium (K) application rates on the sulfur (S) fractions in leaves and fruits of greenhouse-grown cucumbers plants (Cucumis sativus L. cv. Brunex) are presented. The treatments were as follows: N (N1=5 g NO₃NH₄/m², N2=10 g NO₃NH₄/m², N3=20 g NO₃NH₄/m², N4=40 g NO₃NH₄/m²), two levels of P (P1=8 g H₃PO₄/m² and P2=16 g H₃PO₄/m²), and two levels of K (K1=20 g K₂SO₄/m² and K2=40 g K₂SO₄/m²). The foliar and fruit contents were determined for total S, organic S and sulfate. The influence of the N treatments on the total S (St: organic S +sulfate) concentration, proved significant, showing a progressive increase in the leaf and fruit concentrations. In the leaves, the P slightly diminished the St concentration but values in the fruits did not appreciably differ from control. The K dosage did not cause the St concentration to differ from that of P, although in the fruit a slightly lower St concentration appeared in the K2 treatment. The response of the organic-S concentration in the leaves resembled that of St, and thus organic S should not be used as a diagnostic method for S status. In the relationship SO₄ ^2-/St, the SO₄ ^2- concentration proved more influential than did the St form, providing a more accurate representation of the potential status of this nutrient in the plant.     

Relative Efficiency of Zinc Sulfate and Zinc Oxide–Coated Urea in Rice–Wheat Cropping System

Abstract

Rice–wheat cropping system covers about 24 million hectares in China, India, Pakistan, Nepal, and Bangladesh, and zinc deficiency is widespread in rice–wheat belts of all these five countries. The current practice of applying zinc sulfate heptahydrate (ZnSO₄ · 7H₂O) to soil is problematic because of the poor quality of the nutrients available in the market to the farmers. Zinc (Zn)–coated urea is therefore being manufactured to guarantee a good‐quality Zn source. This article reports the results from a field study conducted to study the relative efficiency of zinc sulfate and zinc oxide (ZnO)–coated ureas in rice–wheat cropping system. The highest grain yield of rice–wheat cropping system was obtained with 2.0% coating of urea. Zinc sulfate was also a better coating material than ZnO. Partial factor productivity, agronomic efficiency, apparent recovery, and physiological efficiency of applied Zn decreased as the level of Zn coating was increased.     

成都东部“城–郊–乡”梯度绿地土壤碳氮磷化学计量特征

选取成都东部5个不同交通环线区域(一环内、一环至二环、二环至三环、三环至绕城、绕城外)的绿地土壤为研究对象,采集0~20 cm和20~40 cm土层的土壤样品,测定其总有机碳(C)、全氮(N)、全磷(P)的含量并分析其化学计量特征。结果表明:成都东部绿地土壤C、P含量在沿"城–郊–乡"梯度上总体有降低趋势。各环线区域绿地土壤C、N、P含量基本随着土层的加深而降低,其中以C、P降低最为明显。绿地土壤C:P和N:P在成都东部"城–郊–乡"梯度下有升高趋势,但均低于国内平均水平;绿地土壤C:N在"城–郊–乡"梯度变化不明显。快速的城市化进程导致了C、N、P化学计量比的空间分异。     

Integrated Analysis of Capture–Recapture–Resighting Data and Counts of Unmarked Birds at Stop-Over Sites

The models presented in this paper are motivated by a stop-over study of semipalmated sandpipers, Calidris pusilla. Two sets of data were collected at the stop-over site: a capture–recapture–resighting data set and a vector of counts of unmarked birds. The two data sets are analyzed simultaneously by combining a new model for the capture–recapture–resighting data set with a binomial likelihood for the counts. The aim of the analysis is to estimate the total number of birds that used the site and the average duration of stop-over. The combined analysis is shown to be highly efficient, even when just 1 % of birds are recaptured, and is recommended for similar investigations. This article has supplementary material online.