Metagenomic Analysis to Assess the Impact of Plant Growth-Promoting Rhizobacteria on Peanut (Arachis hypogaea L.) Crop Production and Soil Enzymes and Microbial Diversity.

Peanut production could be increased through plant growth-promoting rhizobacteria (PGPR). In this regard, the present field research aimed at elucidating the impact of PGPR on peanut yield, soil enzyme activity, microbial diversity, and structure. Three PGPR strains (Bacillus velezensis, RI3; Bacillus velezensis, SC6; Pseudomonas psychrophila, P10) were evaluated, along with Bradyrhizobium japonicum (BJ), taken as a control. PGPR increased seed yield by 8%, improving the radiation use efficiency (4-14%). PGPR modified soil enzymes (fluorescein diacetate activity by 17% and dehydrogenase activity by 28%) and microbial abundance (12%). However, PGPR did not significantly alter microbial diversity; nonetheless, it modified the relative abundance of key phyla (Actinobacteria > Proteobacteria > Firmicutes) and genera (Bacillus > Arthrobacter > Pseudomonas). PGPRs modified the relative abundance of genes associated with N-fixation and nitrification while increasing genes related to N-assimilation and N-availability. PGPR improved agronomic traits without altering rhizosphere diversity.

Animal pollination contributes to more than half of citrus production.

Animal pollination is crucial for the reproduction and economic viability of a wide range of crops. Despite the existing data, the extent to which citrus crops depend on pollinators to guarantee fruit production still needs to be determined. Here, we described the composition of potential pollinators in citrus (Citrus spp.) from the main growing areas of Argentina; moreover, we combined Bayesian models and empirical simulations to assess the contribution of animal pollination on fruit set and yield ha-1 in different species and cultivars of lemons, grapefruits, mandarins, and oranges. Honeybee (A. mellifera L.) was the most commonly observed potential pollinator, followed by a diverse group of insects, mainly native bees. Regardless of citrus species and cultivars, the probability of flowers setting fruit in pollinated flowers was 2.4 times higher than unpollinated flowers. Furthermore, our simulations showed that about 60% of the citrus yield ha-1 can be attributable to animal pollination across all species and cultivars. Therefore, it is crucial to maintain environments that support pollinator diversity and increase consumer and to producer awareness and demand in order to ensure the significant benefits of animal pollination in citrus production.

Circular fertilisers combining dehydrated human urine and organic wastes can fulfil the macronutrient demand of 15 major crops.

This study evaluated the potential for combining dehydrated human urine with one other form of organic waste to create circular fertilisers tailored to meet the macronutrient demand of 15 major crops cultivated globally. Through a reverse blending modelling approach, data on 359 different organic wastes were used to identify 38 fertiliser blends. Materials found to be particularly suitable as blending materials were various biochars and ashes, due to their low nitrogen and high phosphorus and/or potassium content, and byproduct concentrates, due to their high phosphorus content, since the nitrogen content of human urine is disproportionately higher than its phosphorus content. Several organic wastes were suitable for fertilising more than one crop. The macronutrient content of the simulated fertiliser blends was comparable to that of blended inorganic fertilisers, but only a few blends precisely matched the macronutrient demand of crops. Fertilising crops with some simulated fertilisers would potentially result in excess application of one or more macronutrients, and thus overfertilisation. For organic wastes with data available on their content of six or more heavy metals, it was found that the simulated fertilisers generally met European Union regulations on use of fertilisers of organic origin in agriculture. Overall, these findings suggest that fertiliser blends combining dehydrated human urine and organic wastes, both of which are widely available globally, could replace inorganic blended fertilisers in agriculture. Such recycling would help the global food system and water sector transition to circularity and promote better management of plant-essential nutrients in society.

Genomic insights of a native bacterial consortium for wheat production sustainability.

The use of plant growth-promoting bacteria as bioinoculants is a powerful tool to increase crop yield and quality and to improve nitrogen use efficiency (NUE) from fertilizers in plants. This study aimed to bioprospecting a native bacterial consortium (Bacillus cabrialesii subsp. cabrialesii TE3T, Priestia megaterium TRQ8, and Bacillus paralicheniformis TRQ65), through bioinformatic analysis, and to quantify the impact of its inoculation on NUE (measured through 15N-isotopic techniques), grain yield, and grain quality of durum wheat variety CIRNO C2008 grown under three doses of urea (0, 120, and 240 kg N ha-1) during two consecutive agricultural cycles in the Yaqui Valley, Mexico. The inoculation of the bacterial consortium (BC) to the wheat crop, at a total N concentration of 123-225 kg N ha-1 increased crop productivity and maintained grain quality, resulting in a yield increase of 1.1 ton ha-1 (6.0 vs. 7.1 ton ha-1, 0 kg N ha-1 added, 123 kg N ha-1 in the soil) and of 2.0 ton ha-1 (5.9 vs. 7.9 ton ha-1, 120 kg N ha-1 added, 104 kg N ha-1 in the soil) compared to the uninoculated controls at the same doses of N. The genomic bioinformatic analysis of the studied strains showed a great number of biofertilization-related genes regarding N and Fe acquisition, P assimilation, CO2 fixation, Fe, P, and K solubilization, with important roles in agroecosystems, as well as genes related to the production of siderophores and stress response. A positive effect of the BC on NUE at the studied initial N content (123 and 104 kg N ha-1) was not observed. Nevertheless, increases of 14 % and 12.5 % on NUE (whole plant) were observed when 120 kg N ha-1 was applied compared to when wheat was fully fertilized (240 kg N ha-1). This work represents a link between bioinformatic approaches of a native bacterial inoculant and the quantification of its impact on durum wheat.

Phenogenetic profile and agronomic contribution of Azospirillum argentinense Az39T, a reference strain for the South American inoculant industry.

Azospirillum sp. is a plant growth-promoting rhizobacteria largely recognized for its potential to increase the yield of different important crops. In this work, we present a thorough genomic and phenotypic analysis of A. argentinense Az39T to provide new insights into the beneficial mechanisms of this microorganism. Phenotypic analyses revealed the following in vitro abilities: growth at 20-38 °C (optimum, 28 °C), pH 6.0-8.0 (optimum, pH 6.8), and in the presence of 1% (w/v) NaCl; production of variable amounts of PHB as intracellular granules; nitrogen fixation under microaerophilic conditions; IAA synthesis in the presence of L-tryptophan. Through biochemical (API 20NE) and carbon utilization profiling (Biolog) assays, we proved that A. argentinense Az39T is able to use 15 substrates and metabolize 19 different carbon substrates. Lipid composition indicated a predominance of medium and long-chain saturated fatty acids. A total of 6 replicons classified as one main chromosome, three chromids, and two plasmids, according to their tRNA and core essential genes contents, were identified. Az39T genome includes genes associated with multiple plant growth-promoting (PGP) traits such as nitrogen fixation and production of auxins, cytokinin, abscisic acid, ethylene, and polyamines. In addition, Az39T genome harbor genetic elements associated with physiological features that facilitate its survival in the soil and competence for rhizospheric colonization; this includes motility, secretion system, and quorum sensing genetic determinants. A metadata analysis of Az39T agronomic performance in the pampas region, Argentina, demonstrated significant grain yield increases in wheat and maize, proving its potential to provide better growth conditions for dryland cereals. In conclusion, our data provide a detailed insight into the metabolic profile of A. argentinense Az39T, the strain most widely used to formulate non-legume inoculants in Argentina, and allow a better understanding of the mechanisms behind its field performance.

Gene regulatory networks underlying sulfate deficiency responses in plants.

Sulfur (S) is an essential macronutrient for plants and its availability in soils is an important determinant for growth and development. Current regulatory policies aimed at reducing industrial S emissions together with changes in agronomical practices have led to a decline in S contents in soils worldwide. Deficiency of sulfate-the primary form of S accessible to plants in soil-has adverse effects on both crop yield and nutritional quality. Hence, recent research has increasingly focused on unraveling the molecular mechanisms through which plants detect and adapt to a limiting supply of sulfate. A significant part of these studies involves the use of omics technologies and has generated comprehensive catalogs of sulfate deficiency-responsive genes and processes, principally in Arabidopsis together with a few studies centering on crop species such as wheat, rice, or members of the Brassica genus. Although we know that sulfate deficiency elicits an important reprogramming of the transcriptome, the transcriptional regulators orchestrating this response are not yet well understood. In this review, we summarize our current knowledge of gene expression responses to sulfate deficiency and recent efforts towards the identification of the transcription factors that are involved in controlling these responses. We further compare the transcriptional response and putative regulators between Arabidopsis and two important crop species, rice and tomato, to gain insights into common mechanisms of the response to sulfate deficiency.

Effect of Co-Application of Azospirillum brasilense and Rhizobium pisi on Wheat Performance and Soil Nutrient Status under Deficit and Partial Root Drying Stress.

Water management techniques are improving at the farm level, but they are not enough to deal with the limited availability of water and increased crop yields. Soil microbes play a vital role in nitrogen fixation, improving soil fertility and enhancing plant growth hormones under drought conditions. Therefore, this study was conducted to investigate the impact of water management combined with Azospirillum brasilense and Rhizobium pisi on wheat crop productivity and soil properties in dry regions. Three water management techniques were compared, normal irrigation as a control (C), deficit irrigation (DI), and partial root drying irrigation (PRD), together with the interaction of plant-growth-promoting rhizobacteria (PGPR). Experiments were conducted with six treatments in total: T1 = C + No PGPR, T2 = C + PGPR, T3 = DI + No PGPR, T4 = DI + PGPR, T5 = PRD + No PGPR, and T6 = PRD + PGPR. The highest grain yield was achieved in the control irrigation treatment using seeds inoculated with rhizobacteria, followed by control treatment without any inoculation, and the lowest was recorded with deficit irrigation without rhizobacteria inoculated in the seeds. However, PRD irrigation resulted in significantly higher plant growth and grain yield than the DI treatment. PGPR inoculation combined with PRD resulted in a 22% and 20% higher number of grains per spike, a 19% and 21% higher grain yield, and a 25% and 22% higher crop growth rate compared to rhizobacteria inoculation combined with the DI system in 2021-22 and 2022-23, respectively. This increase was due to the higher production of growth hormones and higher leaf area index under water-limited conditions. A greater leaf area index leads to a higher chlorophyll content and higher food production for plant growth.

Response of 'criolla' potato (Solanum tuberosum) cultivar Colombia to mineral organic fertilization

The 'Criolla' potato (Solanum tuberosum) phureja group cultivated in the inter-Andean valleys of the high tropics, is commonly fertilized only with mineral nutrients in conventional production, without the use of soil test and use of organic fertilizers. The purpose of this study was to determine the potential of organic chicken manure as a source of nutrients to increase yield and quality in 'Criolla' potatoes compared to conventional fertilization. Treatments evaluated were organic chicken manure, mineral nutrition based on soil tests, organic manure mixed with mineral nutrition, and conventional nutrition based on farmers' typical nutrition plans. In plant response conventional and mineral treatments mixed with organic matter were the best in leaf area and dry weight of shoot and tuber. Treatment with mineral nutrition mixed with organic manure (2 and 6 t) obtained the largest length of the main stems. The best yield response was obtained with conventional nutrition, while the major size was obtained with mineral and mineral combined with organic treatments. According to the results, the best response was obtained with the application of mineral nutrition in the combination of 6 t ha-1 organic manure.

La papa criolla (Solanum tuberosum) grupo phureja es cultivada en los valles interandinos del trópico alto, comúnmente fertilizada con nutrientes minerales en la producción convencional, sin hacer uso de análisis de suelos y nutrición con fertilizantes orgánicos. El objetivo de este estudio fue determinar el potencial de la materia orgánica de gallinaza, como fuente de nutrientes, para incrementar el rendimiento y la calidad en la papa criolla, comparándola con la nutrición convencional. Los tratamientos evaluados fueron gallinaza, nutrición mineral, basado en análisis de suelos; nutrición mineral, combinada con materia orgánica y un tratamiento soportado en la fertilización convencional, con base en los planes nutricionales, típicos de los agricultores. En las respuestas de la planta, los tratamientos convencionales y minerales mezclados con nutrición mineral obtuvieron los valores más altos en área foliar y peso seco de la parte aérea y el tubérculo. En longitud de tallo, la mejor respuesta se obtuvo con los tratamientos minerales mezclados con materia orgánica (2 y 6 toneladas). La mejor respuesta en rendimiento fue obtenida en la nutrición mineral convencional, mientras que las papas con mayor calibre, se lograron con los tratamientos mineral y mineral mezclado con orgánico. De acuerdo con los resultados, la mejor respuesta en cultivo se puede obtener con la nutrición mineral, en combinación con 6 toneladas de materia orgánica.

Valoración de un método de osmoguiado a flores de durazno (Prunus persica) aplicado en abejas Apis mellifera

Diversos estudios demuestran que la inclusión de polinizadores, como las abejas Apis mellifera, generan efectos positivos sobre la productividad de cultivos de durazno (Prunus persica). Esto lleva a probar metodologías que estimulen a las abejas para visitar, con mayor frecuencia, el cultivo de interés, sugiriendo el uso de la técnica de osmoguiado, como herramienta para potencializar el efecto de la polinización. Este estudio valoró un protocolo de osmoguiado, para estimular híbridos africanizados de Apis mellifera, a recolectar polen de flores de durazno, utilizando, como indicador indirecto, el análisis palinológico en muestras de polen. Los tratamientos utilizados fueron con osmoguiado y sin osmoguiado. Cada tratamiento contó con tres colmenas y el periodo de evaluación fue de cinco semanas, coincidiendo con el mayor periodo de floración del durazno. Los resultados evidenciaron que este protocolo no logró estimular a las abejas a visitar la flor de durazno para la búsqueda de polen. La disponibilidad permanente de otras plantas productoras de polen, reportadas previamente como importantes en el aporte de este recurso, pudo influir en la selección de fuentes por parte de las abejas. El polen obtenido provino, principalmente, de plantas de las familias Fabaceae, Asteraceae, Malvaceae y Passifloraceae.

Several studies show that the inclusion of pollinators such as honeybee Apis mellifera generates positive effects in the productivity of peach (Prunus persica) crops. It led to test methodologies that stimulate bees to improve the visit of crops of interest, suggesting the use of the osmoguiding technique, as a tool to potentiate the effect of pollination. This study evaluated an osmoguided protocol to stimulate Africanized hybrids of Apis mellifera to collect pollen from peach flowers, using palynological analysis of pollen samples as an indirect indicator. The treatments used were with osmoguided and without osmoguided. Each treatment had three hives, and the evaluation period was five weeks, coinciding with the peak flowering period of the peach. The results showed that this protocol did not stimulate the bees to visit the peach blossom to search pollen. The permanent availability of other pollen-producing plants, previously reported as significant in the contribution of this resource, could influence bee source selection. The pollen obtained came mainly from plants of the families Fabaceae, Asteraceae, Malvaceae, and Passifloraceae.

Photosynthetic modification of plants through recent technologies: a valuable way to ensure crop fortification / Modificação fotossintética de plantas por meio de tecnologias recentes: uma forma valiosa de garantir a fortificação das culturas

The 2030 Sustainable Development Goals of the United Nations include a strong emphasis on ending hunger worldwide. According to the 2019 Global Food Security Index, while 88% of countries claim there is sufficient food supply in their country, the sad reality is that 1 in 3 countries is facing insufficient availability of food supply, which means that in those countries, more than 10% of the population is malnourished. Since nutrition is crucial to leading a healthy life and satisfying food security needs, several governments have turned to national nutrition surveys to gauge the extent of malnutrition in their populations. Plants are able to grow, develop, and store nutrients by photosynthesis, which convert light into chemical energy through cell redox regulatory networks. A photosynthesis system's electron flow may be adjusted to accommodate varying light and environmental circumstances. Many techniques exist for controlling the flow of electrons emitted during light processes in order to save or waste energy. The two protein molecules TROL and flavoenzyme ferredoxin (oxidoreductase+NADP) (FNR) interact dynamically to form an excellent molecular switch capable of splitting electrons from the photosystem. The TROL-FNR bifurcation may be limited by either generating NADPH or preventing reactive oxygen species from propagating. TROL-based genome editing is an experimental method for enhancing plant stress and defensive responses, efficiency, and ultimately agricultural production.

Os Objetivos de Desenvolvimento Sustentável de 2030 da Organização das Nações Unidas incluem uma forte ênfase em acabar com a fome em todo o mundo. De acordo com o Índice Global de Segurança Alimentar de 2019, enquanto 88% dos países afirmam que há abastecimento alimentar suficiente em seu país, a triste realidade é que 1 em cada 3 países enfrenta disponibilidade insuficiente de alimentos, o que significa que, nesses países, mais de 10% da população está desnutrida. Uma vez que a nutrição é crucial para levar uma vida saudável e satisfazer as necessidades de segurança alimentar, vários governos recorreram a pesquisas nacionais de nutrição para avaliar a extensão da desnutrição em suas populações. As plantas são capazes de crescer, desenvolver e armazenar nutrientes pela fotossíntese, que converte luz em energia química por meio de redes reguladoras redox celulares. O fluxo de elétrons de um sistema de fotossíntese pode ser ajustado para acomodar luz variável e circunstâncias ambientais. Existem muitas técnicas para controlar o fluxo de elétrons emitidos durante os processos de luz, a fim de economizar ou desperdiçar energia. As duas moléculas de proteína TROL e a flavoenzima ferredoxina (oxidorredutase+NADP) (FNR) interagem dinamicamente para formar um excelente interruptor molecular capaz de separar elétrons do fotossistema. A bifurcação TROL-FNR pode ser limitada, gerando NADPH ou impedindo a propagação de espécies reativas de oxigênio. A edição do genoma baseada em TROL é um método experimental para aumentar o estresse da planta, as respostas defensivas, a eficiência e, finalmente, a produção agrícola.

Chickpeas from a Chilean Region Affected by a Climate-Related Catastrophe: Effects of Water Stress on Grain Yield and Flavonoid Composition.

The Valparaiso region in Chile was decreed a zone affected by catastrophe in 2019 as a consequence of one of the driest seasons of the last 50 years. In this study, three varieties ('Alfa-INIA', 'California-INIA', and one landrace, 'Local Navidad') of kabuli-type chickpea seeds produced in 2018 (control) and 2019 (climate-related catastrophe, hereafter named water stress) were evaluated for their grain yield. Furthermore, the flavonoid profile of both free and esterified phenolic extracts was determined using liquid chromatography-mass spectrometry, and the concentration of the main flavonoid, biochanin A, was determined using liquid chromatography with diode array detection. The grain yield was decreased by up to 25 times in 2019. The concentration of biochanin A was up to 3.2 times higher in samples from the second season (water stress). This study demonstrates that water stress induces biosynthesis of biochanin A. However, positive changes in the biochanin A concentration are overshadowed by negative changes in the grain yield. Therefore, water stress, which may be worsened by climate change in the upcoming years, may jeopardize both the production of chickpeas and the supply of biochanin A, a bioactive compound that can be used to produce dietary supplements and/or nutraceuticals.

Ample room for reducing agrochemical inputs without productivity loss: The case of vegetable production in Uruguay.

Vegetables are commonly produced with high inputs of pesticides and fertilisers to boost production and meet cosmetic market standards. Yet, reports on the relationships between agrochemical inputs and crop productivity are scattered and an overview is missing. We assessed the relationship between pesticide and nutrient inputs and crop productivity for five vegetable crops in the south of Uruguay at field and farm level and explored the relation with farm resource endowment. We analysed crop yield and input use for tomato, onion, sweet potato, and strawberry with a dataset of 82 farms and 428 fields constructed between 2012 and 2017. Clear crop-specific patterns in pesticide and nutrient input levels were found, despite considerable variation across fields within the same crop. Strawberry and long cycle tomato had the greatest pesticide input regarding of the number of applications (20 and 18, respectively) and pesticide load (21 kg AI ha-1). Cumulative nutrient inputs were greatest for long cycle tomato (1127 kg ha-1). The relationships between inputs and yield were weak or non-significant, indicating inefficiencies and overuse of inputs, and there was no agronomical rationale for input use. We found substantial variation in management practices between fields and farms. In several cases, 21% of the fields and 17% of the farms producing onion, strawberry and tomato, attained relatively high yield levels with limited input levels. Yield and input use levels were not related to farm resource endowment. Our findings question the efficiency of the current high levels of pesticide and nutrient inputs in Uruguayan vegetable systems. The inputs may pose environmental and human health risks and in most cases did not increase yields. Learning from positive deviant farmers in combination with guided farm redesign, high-quality extension services, and use of context-specific knowledge and technologies may equip farmers to use more sustainable management practices.

Biochar impacts on soil chemical properties, greenhouse gas emissions and forage productivity: A field experiment.

Biochar is a promising alternative to agricultural productivity and climate change mitigation. However, quantitative data are needed to better understand the productivity and greenhouse gas (GHG) emissions from agricultural fields amended with biochar. To assess the impacts of the four biochars on soil properties, forage productivity, and GHG emissions, a 1-year field experiment was conducted in a Humic Haploxerands (Andisol). Three manure-derived biochars and one wood residue biochar (all pyrolyzed at 550 °C) were applied at rates of 1% (equivalent to 11 t ha-1) in two parallel and independent experiments. The changes in (i) soil chemical properties and yield of Sorghum sudangrass (S. bicolor×S. bicolor var. Sudanese) and (ii) soil CO2 and N2O emissions were monitored. Two controls, with and without NPK, were included. The added amendments produced from residues of poultry and pig systems increased soil pH by 0.73 and 0.19 units, respectively. Increased sorghum yield were associated with fertilizer and the liming potential of the added biochar. Soil total carbon (TC) increased with the addition of different biochars, especially during the wood biochar treatment. Biochar application, regardless of the feedstock, had no significant impact on the cumulative soil CO2 emitted after a year. Soil N2O fluxes decreased (23%-50%) in treatments containing biochars with low mineral N contents and high C stability (i.e., low H:OC and Cox:TC ratios). NPK treatment resulted in the highest N2O emissions. Wood residue-derived biochar has a great potential in mitigating climate change, reducing soil N2O emissions, and promoting soil C storage. Manure-derived biochars could be instrumental in circular economy livestock systems, where pyrolyzed animal manure can satisfy the demand for nutrients and/or liming of Andisols under sustainable forage models.

Time to Integrate Pollinator Science into Soybean Production.

Soybeans cover 129 million hectares globally. Soybean productivity can increase with pollinator management, but soybean cultivation practices commonly ignore biotic pollination. If pollinator habitats are created within soybean landscapes and policies to limit agricultural expansion are implemented, millions of hectares could be restored for biodiversity without loss of soybean production.

Assessing the performance of two gridded weather data for sugarcane crop simulations with a process-based model in Center-South Brazil.

High-quality measured weather data (MWD) are essential for long-term and in-season crop model applications. When MWD is not available, one alternative for crop simulations is to employ gridded weather data (GWD), which needs to be evaluated a priori. Therefore, this study aimed to evaluate the impact of weather data from two GWD sources (NASA and XAVIER), in the way that they are available for end users, on simulating sugarcane crop performance within the APSIM-Sugar model at traditional sites where sugarcane is grown in Center-South Brazil, compared to simulations with MWD. Besides, this study also evaluated the impact of replacing GWD rainfall by the site-specific measured data on such simulations. A common sugarcane cropping system was repeatedly simulated between 1997 and 2015 for different combinations of climate input. Both NASA and XAVIER appear to be interesting for applications that only require temperature and solar radiation for predictions, such as crop phenology and potential yield. Nonetheless, GWD should be used with caution for crop model applications that rely on accurate estimation of crop water balance, canopy development, and biomass accumulation, at least with crop models that run at a daily time-step. The replacement of gridded rainfall with measured rainfall was pivotal for improving sugarcane simulations, as observed for cane yield, by increasing both agreement (NASA d index from 0.67 to 0.90; XAVIER d from 0.73 to 0.93) and R2 (NASA from 0.35 to 0.76; XAVIER from 0.43 to 0.79) and reducing root mean square errors (RMSE) from 32.8 to 16.3 t/ha when simulated with other variables of NASA data and from 27.9 to 12.7 t/ha when having XAVIER data as input. Therefore, while using both GWD sets without any correction, it is recommended to replace gridded rainfall by measured values, whenever possible, to improve sugarcane simulations in Center-South Brazil.

Nitrogen and Stem Development: A Puzzle Still to Be Solved.

High crop yields are generally associated with high nitrogen (N) fertilizer rates. A growing tendency that is urgently demanding the adoption of precision technologies that manage N more efficiently, combined with the advances of crop genetics to meet the needs of sustainable farm systems. Among the plant traits, stem architecture has been of paramount importance to enhance harvest index in the cereal crops. Nonetheless, the reduced stature also brought undesirable effect, such as poor N-uptake, which has led to the overuse of N fertilizer. Therefore, a better understanding of how N signals modulate the initial and late stages of stem development might uncover novel semi-dwarf alleles without pleiotropic effects. Our attempt here is to review the most recent advances on this topic.

Hormesis in plants: Physiological and biochemical responses.

Hormesis is a favorable response to low level exposures to substance or to adverse conditions. This phenomenon has become a target to achieve greater crop productivity. This review aimed to address the physiological mechanisms for the induction of hormesis in plants. Some herbicides present a hormetic dose response. Among them, those with active ingredients glyphosate, 2,4-D and paraquat. The application of glyphosate as a hormesis promoter is therefore showing promess . Glyphosate has prominent role in shikimic acid pathway, decreasing lignin synthesis resulting in improved growth and productivity of several crops. Further studies are still needed to estimate optimal doses for other herbicides of crops or agricultural interest. Biostimulants are also important, since they promote effects on secondary metabolic pathways and production of reactive oxygen species (ROS). When ROS are produced, hydrogen peroxide act as a signaling molecule that promote cell walls malleability allowing inward water transport causing cell expansion. . Plants'ability to overcome several abiotic stress conditions is desirable to avoid losses in crop productivity and economic losses. This review compiles information on how hormesis in plants can be used to achieve new production levels.

Cropland trees need to be included for accurate model simulations of land-atmosphere heat fluxes, temperature, boundary layer height, and ozone.

Trees significantly impact land-atmosphere feedbacks through evapotranspiration, photosynthesis and isoprene emissions. These processes influence the local microclimate, air quality and can mitigate temperature extremes and sequester carbon dioxide. Despite such importance, currently only 5 out of 15 atmospheric chemistry climate models even partially account for the presence of cropland trees. We first show that the tree cover over intensely farmed regions in Asia, Australia and South America is significantly underestimated (e.g. only 1-3% tree cover over north-India) in the Model of Emissions of Gases and Aerosol from Nature (MEGAN) and absent in Noah land-surface module of the Weather Research and Forecasting (WRF-Chem) Model. By including the actual tree cover (~10%) over the north-west Indo Gangetic Plain in the Noah land-surface module of the WRF-Chem and the MEGAN module, during the rice growing monsoon season in August, we find that the latent heat flux alone increases by 100%-300% while sensible heat flux reduces by 50%-100%, leading to a reduction in daytime boundary layer height by 200-400 m. This greatly improves agreement between the modelled and measured temperature, boundary layer height and surface ozone, which were earlier overestimated and isoprene and its oxidation products which were earlier underestimated. Mitigating peak daytime temperatures and ozone improves rice production by 10 to 20%. Our findings from north west Indo-Gangetic Plain establish that such plantations mitigate heat stress, and have beneficial effects on crop yields while also sequestering carbon. Expanding agroforestry practices to 50% of the cropland area could result in up to 40% yield gain regionally. Implementing such strategies globally could increase crop production and sequester 0.3-30 GtC per year, and therefore future climate mitigation and food security efforts should consider stakeholder participation for increased cropland agroforestry in view of its beneficial effects.

Spatial variability of the green water footprint using a medium-resolution remote sensing technique: The case of soybean production in the Southeast Argentine Pampas.

Agriculture accounts for about 70% of the fresh water use in the world, dominating rainfed production systems. As meeting future food demand will require an increase in crop production, new techniques are necessary to monitor the spatial variability of agricultural water use. However, the use of remote sensing for the water footprint estimation is limited. This study aims at evaluating the spatial variability of the soil-water consumption in soybean crops, also termed as green water footprint (WFgreen), in a sector of the Argentine Pampas using satellite data. WFgreen was evaluated at spatial resolution of 250 m, estimating the soil water availability through the evaporative fraction and crop yield from Moderate-Resolution Imaging Spectroradiometer (MODIS/Aqua) data. In the analysed soybean plots, the WFgreen varied from 900 m3 t-1 to 1800 m3 t-1. The preliminary comparison of the method with field measurements showed a RMSE = 494 m3 t-1 and Bias = -410 m3 t-1, respectively. The high spatial variability reflected the heterogeneity of soil-water use efficiency. The proposed technique can be useful to obtain WFgreen maps at medium spatial resolutions (250 m-1000 m). Also, it can be applied in regions with poor ground data coverage to estimate the WFgreen, after a parameterization of the model. The contribution to our understanding of the relationship between soil-water availability, rainfed-crop productivity and then WFgreen is expected.

Sensitivity of global major crop yields to climate variables: A non-parametric elasticity analysis.

Climate variability controls crop yield variability with impacts on food security at the local, regional and global levels. This study uses non-parametric elasticity to investigate the sensitivity of crop yields of the top four global crops (wheat, rice, maize, and soybean) to three climate variables (precipitation (PRE), potential evapotranspiration (PET), and mean air temperature (TMP)). Trends and serial correlations exist in both climate variables and crop yields over the study period (1961 to 2014). To overcome this limitation, the Trend Free Pre-Whitening (TFPW) method was applied. Crop yields are most sensitive to TMP globally. But the exact sensitivity varies across continents. The highest sensitivity regions are located in parts of the Southeast Asia. Wheat yields are more sensitive to TMP in Western Europe and Northern America, whereas maize has higher sensitivity to TMP for regions located in South America and parts of Eastern and Western Africa. Soybean is more sensitive in North and South America. The elasticities of wheat and rice yields to TMP are negative in most of the regions (i.e. increased TMP decreases yield), whereas maize witnessed positive and soybean witnessed mixed positive and negative signals depending on the region. PRE has lower influence on crop yields. The non-parametric elasticity concept is a simple and an efficient approach that complements the existing linear models methods used to detect climate change impacts on crop yields and can be used to investigate the future consequences of climate change on local to global scale agricultural production.