Agronomy

Under both natural and agricultural conditions, plants are often exposed to various environmental stresses. Water stress and drought are the most important environmental factors inhibiting photosynthesis and decreasing growth and productivity of plants. To evaluate the effects of water stress on the physicochemical composition of barley, Tunisian cultivar Ardhaoui, several assays were performed on the leaves such as relative water, chlorophylls and proline contents. Our study showed that the water restriction affected significantly the physicochemical composition of barley leaves. In fact, plants which were subjected to the water stress, showed lower relative water and chlorophylls contents and higher level of proline, compared to the control.

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RESUMO -O presente trabalho teve por objetivo avaliar a germinação de sementes e o crescimento de plântulas de canola do híbrido Hyola 401 sob condições de estresse hídrico induzidas por soluções de manitol. Para tanto, os testes de germinação (primeira contagem e contagem final); classificação do vigor das plântulas; velocidade de germinação, comprimento da raiz primária e do hipocótilo, biomassa seca das plântulas e taxa de crescimento relativo foram conduzidos em substrato embebido com soluções de manitol + 0,2% de fungicida Vitavax-Thiram, utilizando os potenciais osmóticos de 0 (controle), -0,25; -0,5; -1,0 e -1,5MPa. Observou-se que potenciais osmóticos mais negativos promoveram redução acentuada na germinação das sementes e no crescimento das plântulas. As características primeira contagem e contagem final de germinação, biomassa seca das plântulas e taxa de crescimento relativo foram afetadas na mesma proporção com o aumento da concentração das soluções osmóticas. O potencial osmótico de -1,0MPa foi considerado crítico para a germinação das sementes. Termos para indexação: Brassica napus, potencial osmótico, germinação.

Aim: Deltamethrin (DM), a hydrophobic and lipophilic substance used for insect control, easily accumulates in the body, increasing ROS production and causing mucosal inflammation and damage. The aim of this study was to explore the prophylactic effects of hesperidin on DM toxicity in periodontal membrane. Methods: The study was conducted for 14 days on 21 male Wistar albino rats. The experimental animals were divided into three groups (n=7): The Sham group received 0.9% NaCl (1 mL). The deltamethrin group received 0.5 mg/kg DM (1 mL, dissolved in dimethyl sulfoxide). The deltamethrin + hesperidin group received DM (0.5 mg/kg) + hesperidin (100 mg/kg) (both drugs dissolved in 1 mL dimethyl sulfoxide). All treatments were administered daily via the orogastric route for 14 days. At the end of the experiment, the rats were euthanized by cervical dislocation, and biochemical and histological analyses were performed. Results: The biochemical tests showed significantly higher malondialdehyde (MDA) levels in the deltamethrin group than in the Sham group. Combined application of hesperidin and deltamethrin resulted in significantly lower MDA levels in the deltamethrin + hesperidin group than in the deltamethrin group. Histopathological examination of the periodontal tissues of the deltamethrin group revealed cell degeneration at the alveolar bone-tooth junction, including atypical cells, irregularity in collagen fibers, dilatation and congestion of the blood vessels, and inflammatory cell infiltrates distributed in aggregate and solitary forms. The deltamethrin + hesperidin group showed substantially less cell degeneration. Conclusion: Hesperidin application helped alleviate deltamethrin toxicity by preventing oxidative stress and reducing cell degeneration.

Land application of wastewater conserves fresh water and recycles nutrients, but little is known of its impacts on arid and semiarid landscapes. Lagoon treated salineÀsodic industrial effluent was applied from 2002-2005 to a 0.4-ha Chihuahuan Desert shrubland to assess the deposition and recovery of effluent components and changes in soil quality vis-a `-vis a non-irrigated area. Effluent irrigation supplied 26% of the average annual nonstressed evapotranspiration (ET) of the native shrubs [Larrea tridentata (DC.) Coville and Prosopis glandulosa Torr. var. glandulosa], and increased both soil stress factors (sodicity, salinity, and pH) and soil fertility (N, P, and K). After 3 yr, the soil saturation extract electrical conductivity (EC e ) reached as high as 6.1 dS m À1 and Cl À 76 mol c m À3 at 105 cm depth under irrigated L. tridentata. After 4 yr, saturation extract sodium adsorption ratio (SAR e ) reached 25-35 at 7.5 cm under the irrigated shrubs and intershrub spaces. There were 27 Mg ha À1 of cumulative ionic deposits to the site comprised mostly of Na þ , Cl À , and CaCO 3 equivalent alkalinity, with soil analysis recovering most of the deposits (>57%) except for K þ and Na þ (8% to 13%). Subsurface leaching of NO À 3 À N and P was detected within the upper 1 m soil depth after 4 yr, and a high downward mobility of Cl À revealed the potential for deeper NO À 3 À N leaching at higher N loading rates. While long-term effects on the natural vegetation are unknown, results contribute to a limited scientific database for sustainable wastewater land application in semiarid regions.

Although corn production is affected by several harmful insects, its most important pest in the southeastern region of Europe is the European corn borer (ECB), Ostrinia nubilalis Hübner, 1796 (Lepidoptera: Pyralidae). Chemical control of O. nubilalis remains the main strategy in conventional corn production. The key to successfully achieving a high efficiency of insecticides is determining the appropriate moment of application, including the exact time in the insect’s life cycle when it is most vulnerable. In this study, monitoring data on the flight dynamics of ECB adults from a seven-year period (2014–2020) were exploited for the development of a predictive model of adult numbers within the growing season. ECB monitoring was performed by using light traps at 15 different locations in the Vojvodina region (Serbia) during the specified time period. First, the calendar for Vojvodina was created based on the analytics of the collected monitoring data. Additionally, the calendar was co...

Flame-weeding is a very useful method for weed control, especially in organic production where the use of herbicides is prohibited. With this method heat sup?presses weeds in row within a second. Apart from this, heat also affects growing crop plants and surrounding soil. The aim of this paper was to determine the effect of different propane doses, on photosynthetic and polyphenolic (total flavonoids and anthocy?nins) pigments in soybean leaves, as well as the number of microorganisms in the soil. Soybean plants exposed to flame showed a different reaction to high temperature stress, which was reflected in differ?ent content of analyzed biochemical parameters, but the most responsive were anthocyanins. Actinomycetes turned out to be the most sensitive group of soil microorganisms affected by weed flaming, while fungi were the most tolerant.

In conventional agriculture, nitrogen is essential for plant growth and is usually supplied through fertilization. However, nitrogen can be lost through various pathways, signi cantly affecting soils with distinct compositions. This study focused on examining the effects of split urea application, along with the application of fertilizers containing the nitri cation inhibitor 3.4-dimethylpyrazole phosphate (DMPP) and the urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT) at full (100%) and reduced (75%) levels of the standard application rate. Conducted over two years, the eld trial aimed to assess the capacity of these treatments to mitigate nitrogen loss and meet the nitrogen requirements of maize effectively. The results of the study revealed that NBPT maintained the required nitrogen levels in the soil by meeting the nitrogen requirement of maize. On the other hand, DMPP caused nitrogen losses due to increasing ammonium levels in the soil during early plant growth stages. NBPT provided the best results in terms of plant yield and nitrogen content, whereas DMPP showed lower performance in these parameters. Reduced NBPT doses increased nitrogen use e ciency but were less effective in terms of yield compared to full doses. According to the result of the economic analysis, split urea treatment gave better results compared to all treatments. In conclusion, NBPT increased both yield and nitrogen use e ciency by providing nitrogen release by the nitrogen requirement of maize.

Efficient Use of Nitrogen in Cropping Systems Efficient use of N in cropping systems is often viewed from agronomic, economic, or environmental perspectives. A given N management system may provide highly efficient use of N from one perspective but be relatively inefficient from another. This chapter reviews basic factors affecting N use efficiency (NUE) from agronomic, economic, and environmental perspectives and discusses interrelationships among these perspectives. The agronomic section reviews ways of characterizing NUE based on yield and N recovery in relation to N inputs and discusses physical potentials and limitations for improving these relationships. Since Chapt. 17 (this book) deals with the role of N in attaining high yield potentials, the agronomic section in this chapter emphasizes factors affecting the slope of yield curves rather than factors affecting maximum yield levels with a nonlimiting N rate. The economic section reviews factors that determine optimum N rates and discusses economic considerations for optimizing inputs (e.g., application practices and nitrification inhibitors) that affect the slope of yield curves. The environmental section examines relationships between N fertilizer recovery and environmental impact of N fertilizer use and also environmental implications of maximizing return from N fertilizer use. I. AGRONOMIC PERSPECTIVE A. Characterizing Efficiency The phrase N use efficiency (NUE) usually has referred to relationships between yield and N rate (yield efficiency), N recovered and N rate (N recovery efficiency), or yield and N recovered (physiological efficiency). For

Maize (Zea mays L.) is one of the most important crops in East Africa serving both as a staple food and cash crop to millions of people. As a vegetable, it is produced as green maize cobs, sweet corn or baby corn. Yields under farmers' conditions in the Lake Victoria Basin average 1.3 t ha -1 which is less than 25% of the potential yield. This is attributed to several factors; the greatest being Striga (Striga hermonthica) which is a parasitic weed attacking several crops in the grass family. A medium term technological breakthrough in form of a herbicide (imazapyr) resistant maize variety has been developed to help reduce Striga infestation. The optimum maize plant population for effective seedbank reduction and optimum grain yield has however not been determined. The main objective of this study was therefore to evaluate the performance of imazapyr-resistant (IR) maize at different plant densities on Striga weed incidence and crop growth. The study was conducted for two seasons on a naturally infested Striga field in Western Kenya. The experiment was laid out as a split plot with three replications. Maize variety (treated IR maize, untreated IR maize and WH505/H516 commercial checks) was the main plot factor and density (44,444, 66,666 and 88,888 plants ha -1 ) as the sub-plot factor. Data was collected on maize stand, days to first Striga emergence, Striga incidence, Striga biomass, maize biomass and its yield components. Treated IR maize delayed Striga emergence on maize thus suppressing Striga parasitism. Any late Striga attachments had little or no effect on maize growth. Increasing the plant density of treated IR maize from 44,444 to 88,888 plants ha -1 did not affect Striga incidence but increased maize yield from 1.60 to 3.48 t ha -1 . It is therefore recommended that treated IR maize should be planted in Striga infested fields at 75cm x 15cm to hasten Striga seed bank reduction and maximize on maize yield to improve staple food availability.

Intensive soil tillage in sugarcane plantation may cause soil degradation including soil microorganism activities. The experiment was conducted at PT GMP to test the effect of soil tillage systems and bagasse application on arbuscular mycorrhiza fungi (AMF) population. The experimental design used was a completely randomized design arranged in a split plot with five replications. The main plot consisted of intensive soil tillage and no tillage system. The sub-plot consisted of 80 ton ha-1 bagasse application, and without bagasse application. The result showed that AMF population in intensive soil tillage was not signicantly different over no tillage system. AMF population in the soil applied with 80 t ha-1 bagasse was also not signicantly different over no bagasse. There was no interaction between soil tillage systems and bagasse application on arbuscular mycorrhiza fungi (AMF) population.

The abundance and biomass of earthworms are affected by soil tillage and fertilization. This research aimed to study long-term 32nd-year soil tillage and nitrogen fertilization on the population and biomass of earthworms under Zea mays L. The research was conducted using a randomized block design (RBD) which consisted of two factors. The first factor was the soil tillage that was Intensive Tillage (IT), Minimum Tillage (MT), and No-Tillage (NT). The Second factor was nitrogen fertilization that was N0 = 0 kg N ha-1 and N1= 200 kg N ha-1. Data of earthworm population and biomass were tested using analysis of variance and continued with the least significant difference (LSD) test at the 95% significant level. The population and biomass of earthworms at MT or NT were higher than IT. The population and biomass of earthworms in the plots without fertilization were higher than those at 200 kg N ha-1. There was an interaction between the soil tillage and N fertilization on earthworm biomas...

This research aimed to determine the effect of secondary metabolites from weed pathogenic fungi (Fusarium oxysporum. Curvularia sp., and Chaetomium sp.) on narrow leaf weeds and on cultivated plants. The research was conducted at the Laboratory of Plant Protection and the experimental farm, Faculty of Agriculture, Jenderal Soedirman University for five months. Split plot design was used with main plot consisted of the pathogenic fungi Fusarium  oxysporum, Curvularia sp., and Chaetomium sp. and subplots consisted of Imperata cylindrica, Cyperus kyllingia, and Cynodon dactylon, and maize, and rice. The variables observed were the incubation period, disease intensity, infection rate, disease area under progress curve (AUDPC), plant height, fresh plant weight, and dry plant weight. Results of the research showed that the secondary metabolites of three weed pathogenic fungi were able to infect narrow leaf weeds. From the single effect of the pathogen, the secondary metabolites of Curvula...

Research aiming for knowing ability of biological agents in remeding contaminated soil with Fusarium oxysporum f.sp. lycopersici and in controlling Fusarium wilt was carried out at the screen house for five months. Completely Randomized Block Design was used with 12 treatments and repeated three times. The agents tested were Trichoderma harzianum isoleted from ginger, ginseng, or banana, Bacillus subtilis, and Pseudomonas fluorescens P60. Result of the research showed that all the agents could decrease population density of F. oxysporum f.sp. lycopersici ranging from 21.01 to 40.03% applied two weeks before planting to the soil. The most effective agent was P. fluorescens P60 by decreasing the population of 35.08%, suppressing the disease of 28.15%, and increasing the agent itself for 50%.

Show simple item record Physiological traits associated with drought resistance in Andean and Mesoamerican genotypes of common bean (Phaseolus vulgaris L.) dc.contributor.author Polania, Jose Arnulfo dc.contributor.author Rao, Idupulapati M. dc.contributor.author Cajiao, César dc.contributor.author Rivera, Mariela dc.contributor.author raatz, bodo dc.contributor.author Beebe, Stephen E. dc.date.accessioned 20160408T21:46:16Z dc.date.available 20160408T21:46:16Z dc.date.issued 20160406 dc.identifier.citation

CIAT and its collaborators have an on-going breeding program to combine the desirable attributes from the three grasses . B. hybrid cv. Mulato is the product of three generations of crosses between B. ruziziensis, B. decumbens and B. brizantha. This grow well in low P, low fertility acid soils in both wet and dry seasons , and produces a large numbers of panicles with well synchronized flowering and good caryopsis formation, which leads to good-quality seed. Defining the specific physiological and biochemical mechanisms that are associated with greater adaptation to low fertility acid soils will contribute to developing rapid and reliable methods to select the phenotypes and to develop molecular markers for marker assisted breeding of brachiariagrasses. Developing superior Brachiaria hybrids from the on-going breeding programs that combine the desirable attributes including adaptation to major biotic and abiotic constraints, forage quality, and seed production will facilitate sustainable intensification of crop-livestock systems in the tropics Rao, 2001 a,b). This chapter reviews the progress made in defining the physiological and biochemical mechanisms of adaptation of brachiariagrasses to low fertility acid soils. There is limited knowledge on the comparative differences in Al resistance among B. decumbens, B. brizantha, B. ruziziensis and B. hybrids (Mulato and Mulato ) grown in hydroponic system. Identification of plant attributes that contribute to greater ability to acquire nutrients under low pH, low P and high Al conditions is critical to develop brachiariagrases that are productive and persistant under infertile acid soil conditions. There have been some discussions on the validity of short-term screening technique that uses simple solution of Al and Ca to test the effect of Al on relative root elongation of young seedlings: whether the results obtained by this short-term screening technique can apply to the behaviour of older plants is under discussion . However, significant positive correlations were observed on Al resistance of 15 cultivars of sorghum (Sorghum bicolor Moench) and 10 cultivars of maize (Zea mays L.) with data obtained using short-term (1 day) screening and long-term screening technique using hydroponic system . Similar results were also observed with 8 rice cultivars (unpublished data). In this chapter, we consider short-term vs long-term responses of several plant species including brachiariagrasses that differed widely in their level of Al resistance. B. decumbens is known for very high level of Al resistance, however, the mechanisms responsible for this high level of Al resistance was not associated with exudation capacity of organic acid anions from root tips . It is important to define the specific mechanism(s) contributing to the high level of Al resistance in B. decumbens. Higher level of Al exclusion was found in B. decumbens, however, the specific mechanisms related to Al exclusion are not known. Several mechanisms other than organic acid anion exudation were found and the related Al resistance genes have been reported (

Common bean (Phaseolus vulgaris L.) is sensitive to different types of abiotic stresses (drought, high temperature, low soil fertility, and acid soil), and this may limit its adaptation and consequently to its yield under stress. Because of this, a sister species, tepary bean (Phaseolus acutifolius A. Gray), has recently gained attention in breeding for improved abiotic stress tolerance in common bean. In this study, we evaluated the adaptation of 302 accessions of tepary bean (Phaseolus acutifolius A. Gray) and its wild relatives (grouped in four types of tepary bean genetic resource: cultivated, acutifolius regressive, acutifolius wild, tenuifolius wild) when grown under high temperature and acid soil conditions with aluminum toxicity in the Amazon region of Colombia. Our objective was to determine differences among four types of tepary bean genetic resource in their morpho-phenological, agronomic, and physiological responses to combined high temperature and acid soil stress condi...

Forage grass nutritional quality directly affects animal feed intake, productivity, and enteric methane (CH4) emissions. This study evaluated the nutritional quality, in vitro enteric CH4 emission potential, and optimization of diets based on two widely grown tropical forage grasses either alone or mixed with legumes. The grasses Urochloa hybrid cv. Cayman (UHC) and U. brizantha cv. Toledo (UBT), which typically have low concentrations of crude protein (CP), were incubated in vitro either alone or mixed with the legumes Canavalia brasiliensis (CB) and Leucaena diversifolia (LD), which have higher CP concentrations. Substitution of 30% of the grass dry matter (DM) with CB or LD did not affect gas production or DM degradability. After 96 h of incubation, accumulated CH4 was 87.3 mg CH4 g−1 DM and 107.7 mg CH4 g−1 DM for the grasses alone (UHC and UBT, respectively), and 100.7 mg CH4 g−1 DM and 113.2 mg CH4 g−1 DM for combined diets (70% grass, 15% CB, and 15% LD). Diets that combined ...

Intercropping the common bean (Phaseolus vulgaris L.) with maize (Zea mays L.) is a widely used agronomic practice in smallholder farms in different regions of the world. Although it is a common practice in the Colombian Amazon region, crop yields are low due to the degradation of low fertility, acidic soil and high-temperature stress. Studies are needed on how the integration of genetically adapted common bean breeding lines into an intercropping system can benefit smallholders. The objective of this study was to: (i) evaluate differences in agronomic performance of two common bean lines when intercropped with maize in two different patterns under two types of fertilizer applications; and (ii) identify which intercropping pattern is better to maximize productivity and land use in the Colombian Amazon region. To achieve these aims, 2 field experiments (October 2018 to January 2019, season 1; April to June 2019, season 2) were conducted in the Colombian Amazon region. A randomized co...

Brachiaria grass is an important tropical forage of African origin with desirable attributes of agricultural and environmental significance. Brachiaria has been extensively cultivated as a pasture across the tropics except in its endemic provenance of Africa. In 2013, a collaborative research program was initiated in Kenya and Rwanda with the aim of improving the availability of quality livestock feeds adapted to drought and low fertility soils using Brachiaria. The outcomes sought were increased livestock productivity leading to improved farmer income and the development of seed production opportunities. The program has identified five preferred cultivars, and four of them are currently being evaluated on-farm by over 2000 small-holder farmers in Kenya and Rwanda for livestock productivity. Preliminary milk production data has shown a 15 to 40% increase in milk production in Kenya and an average increase of 36% in Rwanda. The substitution of Napier grass by Brachiaria in the feed h...

Part of the Plant Sciences Commons, and the Soil Science Commons This document is available at https://uknowledge.uky.edu/igc/23/4-1-3/5 The XXIII International Grassland Congress (Sustainable use of Grassland Resources for Forage Production, Biodiversity and Environmental Protection) took place in New Delhi, India from November 20 through November 24, 2015. Proceedings Editors: M. M. Roy, D. R. Malaviya, V. K. Yadav, Tejveer Singh, R. P. Sah, D. Vijay, and A. Radhakrishna Published by Range Management Society of India

In our study, we analyzed 30years of climatological data revealing the bean production risks for Western Amazonia. Climatological profiling showed high daytime and nighttime temperatures combined with high relative humidity and low vapor pressure deficit. Our understanding of the target environment allows us to select trait combinations for reaching higher yields in Amazonian acid soils. Our research was conducted using 64 bean lines with different genetic backgrounds. In high temperatures, we identified three water use efficiency typologies in beans based on detailed data analysis on gasometric exchange. Profligate water spenders and not water conservative accessions showed leaf cooling, and effective photosynthate partitioning to seeds, and these attributes were found to be related to higher photosynthetic efficiency. Thus, water spenders and not savers were recognized as heat resistant in acid soil conditions in Western Amazonia. Genotypes such as BFS 10, SEN 52, SER 323, differe...

The degradation of tropical pastures sown with introduced grasses (e.g., Urochloa spp.) has dramatic environmental and economic consequences in Latin America. Nitrogen (N) limitation to plant growth contributes to pasture degradation. The introduction of legumes in association with grasses has been proposed as a strategy to improve N supply via symbiotic N2 fixation, but the fixed N input and N benefits for associated grasses have hardly been determined in farmers’ pastures. We have carried out on-farm research in ten paired plots of grass-alone (GA) vs. grass-legume (GL) pastures. Measurements included soil properties, pasture productivity, and sources of plant N uptake using 15N isotope natural abundance methods. The integration of legumes increased pasture biomass production by about 74%, while N uptake was improved by two-fold. The legumes derived about 80% of their N via symbiotic N2 fixation. The isotopic signature of N of grasses in GA vs. GL pastures suggested that sources o...

The progress in identification of genotypes with roots showing greater ability to penetrate compacted soils under moisture stress and understanding the physiological basis and morphological expression of the characteristics associated is fundamental to improving crop's tolerance to drought and to increase productivity under individual and combined stress conditions. Our objectives were to: (i) determine genotypic differences in root penetration ability of common bean (Phaseolus vulgaris L.) using two methods (compacted soil layers and wax-petrolatum layers) to simulate soil compaction; and (ii) identify the morpho-physiological characteristics associated with the ability to penetrate compacted layers under well-watered and intermittent drought conditions in a greenhouse environment. Six common bean genotypes of different origin (Andean, Mesoamerican and interspecific) were tested in two trials. In the first trial, we evaluated genotypic differences in morpho-physiological characteristics that were associated with the root's ability to penetrate compacted soil layers of 1.2, 1.4, and 1.6 g cm -3 bulk densities. In the second trial, we used another method to determine genotypic differences in root's ability to penetrate wax-petrolatum layers of low, medium, and high mechanical impedance. The conditions for root growth were severely restricted by compaction and aggravated by drought stress. The medium level of mechanical impedance of wax petrolatum layer method showed the best results to evaluate bean genotypes for soil compaction tolerance. Among the six genotypes tested, ALB 91 (an interspecific line) was identified as the one with the greatest root penetration ability compared with A774 which showed the lowest root penetration ability under both well-watered and drought conditions.

Background: Common bean is the most important staple grain legume for direct human consumption and nutrition. It complements major sources of carbohydrates, including cereals, root crop, or plantain, as a source of dietary proteins. It is also a significant source of vitamins and minerals like iron and zinc. To fully play its nutritional role, however, its robustness against stresses needs to be strengthened. Foremost among these is drought, which commonly affects its productivity and seed quality. Previous studies have shown that photosynthate remobilization and partitioning is one of the main mechanisms of drought tolerance and overall productivity in common bean. Results: In this study, we sought to determine the inheritance of pod harvest index (PHI), a measure of the partitioning of pod biomass to seed biomass, relative to that of grain yield. We evaluated a recombinant inbred population of the cross of ICA Bunsi and SXB405, both from the Mesoamerican gene pool, to determine the effects of intermittent and terminal drought stresses on the genetic architecture of photosynthate allocation and remobilization in pods of common bean. The population was grown for two seasons, under well-watered conditions and terminal and intermittent drought stress in one year, and well-watered conditions and terminal drought stress in the second year. There was a significant effect of the water regime and year on all the traits, at both the phenotypic and QTL levels. We found nine QTLs for pod harvest index, including a major (17% of variation explained), stable QTL on linkage group Pv07. We also found eight QTLs for yield, three of which clustered with PHI QTLs, underscoring the importance of photosynthate remobilization in productivity. We also found evidence for substantial epistasis, explaining a considerable part of the variation for yield and PHI. Our results highlight the genetic relationship between PHI and yield and confirm the role of PHI in selection of both additive and epistatic effects controlling drought tolerance. These results are a key component to strengthen the robustness of common bean against drought stresses.

Exploiting the natural variability of Brachiaria forage germplasm to identify forage grasses adapted to infertile acid soils that contain very low available phosphorus (P) is an important research objective for improving livestock production in the tropics. The objective of this study was to determine the differences in the release of root biochemical markers, i.e. carboxylates and acid phosphatases (APases), during the development of P deficiency in signalgrass and ruzigrass. We used the hydroxyapatite pouch system in hydroponics to simulate conditions of low P supply in acid soils to test the response of well-adapted signalgrass (Brachiaria decumbens cv. Basilisk, CIAT 606) and less-adapted ruzigrass (B. ruziziensis cv. Kennedy, CIAT 654). We monitored shoot and root growth and other physiological and biochemical components that are important for root functionality at weekly intervals for 3 weeks. We found that monocarboxylate exudation was not associated with the plant's physiological P status, while exudation of oxalate and secreted-APases increased with declining plant P concentrations in both grasses. Ruzigrass showed higher exudation rates and grew faster than signalgrass, but could not maintain its initial fast growth rate when P concentrations in plant tissue declined to 1.0 mg P/g dry matter. Oxalate was the dominant exuded carboxylate for signalgrass after 21 days of growth and this response might confer some eco-physiological advantages in signalgrass when grown in low-P acid soils.

The International Center for Tropical Agriculture (CIAT) believes that open access contributes to its mission of reducing hunger and poverty, and improving human nutrition in the tropics through research aimed at increasing the eco-efficiency of agriculture. CIAT is committed to creating and sharing knowledge and information openly and globally. We do this through collaborative research as well as through the open sharing of our data, tools, and publications.

Nitrogen (N) accumulation in legumes is one of the main determinants of crop yield. Although N accumulation from symbiotic nitrogen fixation or N absorption from the soil has been widely investigated, there is no clear consensus on timing of the beginning of N accumulation and the termination of N accumulation and the physiological events that may be associated with these two events. The analyses conducted in this study aimed at identifying the determinant of N accumulation in two grain legume species. Nitrogen accumulation dynamics and mass accumulation and development stages were recorded in the field for several genotypes of common bean (Phaseolus vulgaris) and faba bean (Vicia faba) under different growing conditions. This study showed that during the vegetative stages, N accumulation rate was correlated with mass accumulation rate. However, the maximum accumulation of N did not correspond to the time of the maximum mass accumulation. In fact, for both species, N accumulation wa...

Brachiaria species have the ability to suppress nitrification in soil by releasing an inhibitory compound called 'brachialactone' from its roots; a process termed biological nitrification inhibition (BNI). This study tested the hypothesis that endophytic association with Brachiaria grass improves BNI activity of root tissues and reduces nitrification in Brachiaria-cultivated soil. Four cultivars of Brachiaria [i.e., B. decumbens (Basilisk), B. humidicola (Tully), B. brizantha (Marandu), and hybrid Cayman] were evaluated for their BNI potentials under greenhouse and field conditions. In each experiment, plants were grown with (E+) and without (E-) endophyte inoculation, and harvested after eight months of growth. Root tissues and rhizosphere soil were taken from 0-30 cm depth and analyzed for BNI activity and nitrification, using bioluminescence assays and soil incubation, respectively. In the greenhouse experiment, endophyte association reduced BNI activity of root tissues in at least two cultivars (Basilisk and Marandu; by 13% and 6%, respectively); and this corresponded with 9% and 10% higher rates of nitrification (for Basilisk and Marandu, respectively) in soils grown with endophyte-infected plants than in the control. Under field conditions, endophyte association increased rates of nitrification in Marandu and Cayman by a similar magnitude of 12%, compared with endophyte-free control. In both experiments, Tully and Basilisk were essentially the most outstanding candidates for low-nitrifying forage systems, as shown by their high BNI activity and/or low rates of nitrification. The study also showed that cultivating soils with Brachiaria grasses could offer more agronomic and environmental benefits due to low N loss through nitrification than leaving the soils bare. However, further research to identify endophyte species that could suppress soil nitrifying microbes may enhance BNI process in Brachiaria.

Improving adaptation to drought stress in white pea bean (Phaseolus vulgaris L.): Genotypic effects on grain yield, yield components and pod harvest index The International Center for Tropical Agriculture (CIAT) believes that open access contributes to its mission of reducing hunger and poverty, and improving human nutrition in the tropics through research aimed at increasing the eco-efficiency of agriculture. CIAT is committed to creating and sharing knowledge and information openly and globally. We do this through collaborative research as well as through the open sharing of our data, tools, and publications.

Drought stress limits growth and yield of crops, particularly under smallholder production systems with minimal use of inputs and edaphic limitations such as nitrogen (N) deficiency. The development of genotypes adapted to these conditions through genetic improvement is an important strategy to address this limitation. The identification of morpho-physiological traits associated with drought resistance contributes to increasing the efficiency of breeding programs. A set of 36 bean genotypes belonging to the Middle American gene pool was evaluated. A greenhouse study using soil cylinders was conducted to determine root vigor traits (total root length and fine root production) under drought stress. Two field trials were conducted to determinate grain yield, symbiotic nitrogen fixation (SNF) ability and other shoot traits under drought stress. Field data on grain yield and other shoot traits measured under drought were related with the greenhouse data on root traits under drought conditions to test the relationships between shoot traits and root traits. Response of root vigor to drought stress appeared to be related with ideotypes of water use (water savers and water spenders). The water spender ideotypes presented deeper root system, while the water saver ideotypes showed a relatively shallower root system. Increase in SNF ability under drought stress was associated with greater values of mean root diameter while greater acquisition of N from soil was associated with finer root system. We identified seven common bean lines (SEA 15, NCB 280, SCR 16, SMC 141, BFS 29, BFS 67 and SER 119) that showed greater root vigor under drought stress in the greenhouse and higher values of grain yield under drought stress in the field. These lines could serve as parents for improving drought resistance in common bean.

The forage grass Brachiaria humidicola (Bh) has been shown to reduce soil microbial nitrification. However, it is not known if biological nitrification inhibition (BNI) also has an effect on nitrogen (N) cycling during cultivation of subsequent crops. Therefore, the objective of this study was to investigate the residual BNI effect of a converted long-term Bh pasture on subsequent maize (Zea mays L.) cropping, where a long-term maize monocrop field (M) served as control. Methods Four levels of N fertilizer rates (0, 60, 120 and 240 kg N ha -1 ) and synthetic nitrification inhibitor (dicyandiamide) treatments allowed for comparison of BNI effects, while 15 N labelled micro-plots were used to trace the fate of applied fertilizer N. Soil was incubated to investigate N dynamics. Results A significant maize yield increase after Bh was evident in the first year compared to the M treatment. The second cropping season showed an eased residual effect of the Bh pasture. Soil incubation studies suggested that nitrification was significantly lower in Bh soil but this BNI declined one year after pasture conversion. Plant N uptake was markedly greater under previous Bh compared with M. The N balance of the 15 N micro-plots revealed that N was derived mainly (68-86%) from the mineralized soil organic N pool in Bh while plant fertilizer N recovery (18-24%) was not enhanced. Conclusions Applied N was strongly immobilized due to long-term root turnover effects, while a significant residual BNI effect from Bh prevented re-mineralized N from nitrification resulting in improved maize performance. However, a significant residual Bh BNI effect was evident for less than one year only.

Brachiaria grasses are sown in tropical regions around the world, especially in the Neotropics, to improve livestock production. Waterlogging is a major constraint to the productivity and persistence of Brachiaria grasses during the rainy season. While some Brachiaria cultivars are moderately tolerant to seasonal waterlogging, none of the commercial cultivars combines superior yield potential and nutritional quality with a high level of waterlogging tolerance. The Brachiaria breeding program at the International Center for Tropical Agriculture, has been using recurrent selection for the past two decades to combine forage yield with resistance to biotic and abiotic stress factors. The main objective of this study was to test the suitability of normalized difference vegetation index (NDVI) and image-based phenotyping as non-destructive approaches to identify Brachiaria hybrids tolerant to waterlogging stress under field conditions. Nineteen promising hybrid selections from the breedin...

SUMMARYCommon bean (Phaseolus vulgaris L.) is the most important food legume for human consumption. Drought stress is the major abiotic stress limitation of bean yields in smallholder farming systems worldwide. The current work aimed to determine the role of enhanced photosynthate mobilization to improve adaptation to intermittent and terminal drought stress and to identify a few key adaptive traits that can be used for developing drought-resistant genotypes. Field studies were conducted over three seasons at Centro Internacional de Agricultura Tropical, Palmira, Colombia to determine genotypic differences in adaptation to intermittent (two seasons) and terminal (one season) drought stress compared with irrigated conditions. A set of 36 genotypes, including 33 common bean, two wild bean and one cowpea were evaluated using a 6 × 6 lattice design under irrigated and rainfed field conditions. Three common bean elite lines (NCB 226, SEN 56, SER 125) were identified with superior levels ...

Common bean (Phaseolus vulgaris L.) is the most important food legume, cultivated by small farmers and is usually exposed to unfavorable conditions with minimum use of inputs. Drought and low soil fertility, especially phosphorus and nitrogen (N) deficiencies, are major limitations to bean yield in smallholder systems. Beans can derive part of their required N from the atmosphere through symbiotic nitrogen fixation (SNF). Drought stress severely limits SNF ability of plants. The main objectives of this study were to: (i) test and validate the use of 15 N natural abundance in grain to quantify phenotypic differences in SNF ability for its implementation in breeding programs of common bean with bush growth habit aiming to improve SNF, and (ii) quantify phenotypic differences in SNF under drought to identify superior genotypes that could serve as parents. Field studies were conducted at CIAT-Palmira, Colombia using a set of 36 bean genotypes belonging to the Middle American gene pool for evaluation in two seasons with two levels of water supply (irrigated and drought stress). We used 15 N natural abundance method to compare SNF ability estimated from shoot tissue sampled at mid-pod filling growth stage vs. grain tissue sampled at harvest. Our results showed positive and significant correlation between nitrogen derived from the atmosphere (%Ndfa) estimated using shoot tissue at mid-pod filling and %Ndfa estimated using grain tissue at harvest. Both methods showed phenotypic variability in SNF ability under both drought and irrigated conditions and a significant reduction in SNF ability was observed under drought stress. We suggest that the method of estimating Ndfa using grain tissue (Ndfa-G) could be applied in bean breeding programs to improve SNF ability. Using this method of Ndfa-G, we identified four bean lines (RCB 593, SEA 15, NCB 226 and BFS 29) that combine greater SNF ability with greater grain yield under drought stress and these could serve as potential parents to further improve SNF ability of common bean.

Plants depend on their root systems to acquire the water and nutrients necessary for their survival in nature, and for their yield and nutritional quality in agriculture. Root systems are complex and a variety of root phenes have been identified as contributors to adaptation to soils with low fertility and aluminium (Al) toxicity. Phenotypic characterization of root adaptations to infertile soils is enabling plant breeders to develop improved cultivars that not only yield more, but also contribute to yield stability and nutritional security in the face of climate variability. In this review the adaptive responses of root systems to soils with low fertility and Al toxicity are described. After a brief introduction, the purpose and focus of the review are outlined. This is followed by a description of the adaptive responses of roots to low supply of mineral nutrients [with an emphasis on low availability of nitrogen (N) and phosphorus (P) and on toxic levels of Al]. We describe progre...

Drought severely limits forage productivity of C 4 grasses across the tropics. The avoidance of water deficit by increasing the capacity for water uptake or by controlling water loss are common responses in forage C 4 grasses. Napier grass (Pennisetum purpureum) and Brachiaria hybrid cv. Mulato II are tropical C 4 grasses used for livestock production due to their reputed resistance to drought conditions. However, there is scant information on the mechanisms used by these grasses to overcome water-limited conditions. Therefore, assessments of cumulative transpired water, shoot growth, leaf rolling, leaf gas exchange, dry mass production and a number of morpho-physiological traits were recorded over a period of 21 days under well-watered or drought conditions. Drought reduced shoot dry mass of both grasses by 35 %, yet each grass exhibited contrasting strategies to cope with water shortage. Napier grass transpired most available water by the end of the drought treatment, whereas a significant amount of water was still available for Mulato II. Napier grass maintained carbon assimilation until the soil was fairly dry, whereas Mulato II restricted water loss by early stomatal closure at relatively wet soil conditions. Our results suggest that Napier grass exhibits a 'waterspending' behaviour that might be targeted to areas with intermittent drought stress, whereas Mulato II displays a 'water-saving' nature that could be directed to areas with longer dry periods.

Common bean (Phaseolus vulgaris L.) yields are severely limited by abiotic stresses, including drought and aluminum toxicity. Work at CIAT (the International Center for Tropical Agriculture) seeks to develop resistance to these stresses, employing both intraspecific and interspecific genetic variability. The analysis of physiological mechanisms is more advanced in the case of drought. Although deep rooting offers access to more moisture, as evidenced by higher values of stomatal conductance and canopy temperature depression, in many genotypes this does not result in greater yield. Photosynthate partitioning to grain plays a major role in drought resistance. Partitioning has been quantified as pod partitioning index (pod biomass at harvest as a percent of total biomass at mid-pod fill), and pod harvest index (grain as percent of total pod biomass). Both parameters consistently present significant correlations with yield under stress. Pod harvest index measured in a drought trial also...

As a consequence of global warming, rainfall is expected to increase in several regions around the world. This, together with poor soil drainage, will result in waterlogged soil conditions. Brachiaria grasses are widely sown in the tropics and, these grasses confront seasonal waterlogged conditions. Several studies have indicated that an increase in nutrient availability could reduce the negative impact of waterlogging. Therefore, an outdoor study was conducted to evaluate the responses of two Brachiaria sp. grasses with contrasting tolerances to waterlogging, B. ruziziensis (sensitive) and B. humidicola (tolerant), with two soil fertility levels. The genotypes were grown with two different soil fertilization levels (high and low) and under well-drained or waterlogged soil conditions for 15 days. The biomass production, chlorophyll content, photosynthetic efficiency, and macro- (N, P, K, Ca, Mg and S) and micronutrient (Fe, Mn, Cu, Zn and B) contents in the shoot tissue were determi...

Nitrogen (N), being the most critical and essential nutrient for plant growth, largely determines the productivity in both extensive-and intensive-grassland systems. Nitrification and denitrification processes in the soil are the primary drivers generating reactive-N: NO 3 -, N 2 O, and NO, and is largely responsible for Nloss and degradation of grasslands. Suppressing nitrification can thus facilitate the retention of soil-N to sustain long-term productivity of grasslands and forage-based production systems. Certain plants can suppress soil nitrification by releasing inhibitors from roots, a phenomenon termed 'biological nitrification inhibition' (BNI). Recent methodological developments (e.g. bioluminescence assay to detect BNIs from plant-root systems) led to significant advances in our ability to quantify and characterize BNI function in pasture grasses. Among grass-pastures, BNI-capacity is strongest in low-N adapted grasses such as Brachiaria humidicola and weakest in high-N environment grasses such as Italian ryegrass (Lolium perenne) and B. brizantha. The chemical identity of some of the BNIs produced in plant tissues and released from roots has now been established and their mode of inhibitory action determined on nitrifying bacteria Nitrosomonas. Synthesis and release of BNIs is a highly regulated and localized process, triggered by the presence of NH 4 + in the rhizosphere, which facilitates the release of BNIs close to soil-nitrifier sites. Substantial genotypic variation is found for BNI-capacity in B. humidicola, which opens the way for its genetic manipulation. Field studies suggest that Brachiaria grasses suppress nitrification and N 2 O emissions from soil. The potential for exploiting BNI function (from a genetic improvement and a system perspective) to develop production systems that are low-nitrifying, low N 2 O-emitting, economically efficient and ecologically sustainable, will be the subject of discussion.