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Although significant intraspecific variation in photosynthetic phosphorus (P) use efficiency (PPUE) has been shown in numerous species, we still know little about the biochemical basis for differences in PPUE among genotypes within a species. Here, we grew two high PPUE and two low PPUE chickpea (Cicer arietinum) genotypes with low P supply in a glasshouse to compare their photosynthesis-related traits, total foliar P concentration ([P]) and chemical P fractions (i.e. inorganic P (Pi), metabolite P, lipid P, nucleic acid P, and residual P). Foliar cell-specific nutrient concentrations including P were characterized using elemental X-ray microanalysis. Genotypes with high PPUE showed lower total foliar [P] without slower photosynthetic rates. No consistent differences in cellular [P] between the epidermis and mesophyll cells occurred across the four genotypes. In contrast, high PPUE was associated with lower allocation to Pi and metabolite P, with PPUE being negatively correlated with the percentage of these two fractions. Furthermore, a lower allocation to Pi and metabolite P was correlated with a greater allocation to nucleic acid P, but not to lipid P. Collectively, our results suggest that a different allocation to foliar P fractions, rather than preferential P allocation to specific leaf tissues, underlies the contrasting PPUE among chickpea genotypes.

Background and aims This study investigated whether root traits at the seedling stage are maintained at the flowering stage in two chickpea (Cicer arietinum) genotypes with contrasting root morphology and physiology; and whether the genotype with greater rhizosheath carboxylates mobilises more poorly-available phosphorus (P) pools to increase shoot P at flowering/podding and seed yield at maturity. Methods Two chickpea genotypes were grown in a low P soil with or without P addition (0 and 40 µg P g−1 soil as KH2PO4) under controlled glasshouse conditions and harvested at seedling, flowering/podding, physiological maturity. Results At the seedling and flowering/podding stages, ICC2884 had thinner roots and greater root mass ratio, specific root length and rhizosheath carboxylates per root dry weight (DW) than ICC456. Both genotypes had smaller root diameter, higher carboxylates and acid phosphatase activity in rhizosheath soil at flowering/podding than at seedling. In the rhizosheath soil of both genotypes, NaHCO3-Pi concentration was depleted under P0 only; under both P0 and P40, NaHCO3-Po concentration increased while NaOH-Pi and NaOH-Po concentrations decreased at the seedling stage but accumulated at the flowering/podding stage, relative to the bulk soil. ICC2884 did not mobilise more poorly available soil P or acquire more P at the seedling or flowering/podding stages, or produce higher seed yields than ICC456. Conclusion ICC2884 and ICC456 maintained the difference in root morphological and physiological characteristics from the seedling stage to the flowering/podding stage. The genotype with greater rhizosheath carboxylates (root DW basis) did not produce higher yield than genotype with less rhizosheath carboxylates.

Carboxylate release by roots has been considered a strategy for mobilisation and acquisition of phosphorus (P). However, recently, it was argued that carboxylate release may be a way to discharge surplus carbon produced under conditions that limit plant growth. Plant P status may not be the main factor driving carboxylate release by roots. Instead, plant nitrogen (N) status and/or N:P ratio of the soil or plant may play a more important role in enhancing carboxylate release. A greenhouse pot experiment was performed to grow alfalfa in a P-deficient soil, supplied with two rates of P (0 and 20 mg kg−1) in combination with four forms of nitrogen (N) at five rates (0, 25, 50, 75, and 100 mg kg−1), to explore the effects of P rate, N form, N rate, and their interactions on plant growth, P and N status, and carboxylate release, and to determine the factors driving carboxylate release. Nitrogen addition weakened the positive effect of P addition on plant growth, and increased plant N and P concentrations; P addition increased plant P concentration, but weakened the effect of N addition on plant N concentration. The amount of tartrate increased dramatically with increasing N rate, which decreased shoot growth, depending on N form. At high P supply, tartrate exudation correlated negatively with shoot biomass. Nitrogen addition to P-deficient alfalfa decreased shoot growth and enhanced the release of tartrate, likely to discharge surplus carbon; and the effects varied with N form.

Background Soil salinization is a major constraint limiting agricultural development and affecting crop growth and productivity, especially in arid and semi-arid regions. Understanding the molecular mechanism of the adaptability of canola to salt stress is very important to improve the salt tolerance of canola and promote its cultivation in saline alkali soil. Results To identify the metabolomic and transcriptomic mechanisms of canola under alkaline salt stress, we collected roots of control (no salt treatment) and 72 h Na2CO3-stressed canola seedlings (hydroponics) for metabolic profiling of metabolites, supplemented with RNA-Seq analysis and real-time quantitative PCR validation. Metabolomic analysis showed that the metabolites of amino acids and fatty acids were higher accumulated under alkaline salt stress, including L-proline, L-glutamate, L-histidine, L-phenylalanine, L-citrulline, L-tyrosine, L-saccharopine, L-tryptophan, linoleic acid, dihomo gamma linolenic acid, alpha linolenic acid, Eric acid, oleic acid and neuronic acid, while the metabolism of carbohydrate (sucrase, alpha, alpha trehalose), polyol (ribitol), UDP-D-galactose, D-mannose, D-fructose and D-glucose 6-phosphate decreased. Transcriptomic and metabolomic pathway analysis indicated that carbohydrate metabolism may not play an important role in the resistance of canola to alkaline salt stress. Organic acid metabolism (fatty acid accumulation) and amino acid metabolism are important metabolic pathways in the root of canola under alkaline salt stress. Conclusions These results suggest that the genes and metabolites involved in fatty acid metabolism and amino acids metabolism in roots of canola may regulate salt tolerance of canola seedlings under alkaline salt stress, which improves our understanding of the molecular mechanisms of salt tolerance in canola.

Plants deploying a phosphorus (P)-mobilising strategy via carboxylate release have relatively high leaf manganese concentrations ([Mn]). Thus, leaf [Mn] is a proxy for the amount of rhizosheath carboxylates. Whether the concentrations of other leaf micronutrient, such as iron ([Fe]), zinc ([Zn]) and copper ([Cu]), show a similar signal for rhizosheath carboxylates is unclear. We grew a large number of chickpea genotypes in two glasshouse studies with different growth media, P sources and P levels. Seven weeks after sowing, we determined concentrations of micronutrients in mature leaves, and the quantity and composition of rhizosheath carboxylates. For 100 genotypes grown in river sand with low P supply, leaf [Fe] (R2 = 0.36) and [Zn] (R2 = 0.22), like leaf [Mn] (R2 = 0.38), were positively correlated with the total amount of rhizosheath carboxylates. For 20 genotypes grown in a soil mixture, leaf [Fe], [Zn], [Cu] and [Mn] showed positive correlations with total rhizosheath carboxylates that were stronger under moderately low P (R2 = 0.59, 0.59, 0.54, 0.72) than severely low P (R2 = 0.39, 0.28, 0.20, 0.36) or sufficient P (R2 = 0.36, 0.00, 0.01, 0.50) supply. Malonate was the predominant carboxylate in the rhizosheath and was significantly correlated with leaf micronutrient concentrations in both experiments. In addition to leaf [Mn], leaf [Fe] and [Zn] can be used as alternative and easily measurable proxies for belowground carboxylate-releasing processes in chickpea under low-P supply, particularly on moderately low-P soils.

The rhizosheath is a belowground area that acts as a communication hub at the root–soil interface to promote water and nutrient acquisition. Certain crops, such as white lupin (Lupinus albus), acquire large amounts of phosphorus (P), owing partially to exudation of acid phosphatases (APases). Plant growth-promoting rhizobacteria also increase soil P availability. However, potential synergistic effects of root APases and rhizosheath-associated microbiota on P acquisition require further research. In this study, we investigated the roles of root purple APases (PAPs) and plant growth-promoting rhizobacteria in rhizosheath formation and P acquisition under conditions of soil drying (SD) and P treatment (+P: soil with P fertilizer; –P: soil without fertilizer). We expressed purple acid phosphatase12 (LaPAP12) in white lupin and rice (Oryza sativa) plants and analyzed the rhizosheath-associated microbiome. Increased or heterologous LaPAP12 expression promoted APase activity and rhizosheath formation, resulting in increased P acquisition mainly under SD–P conditions. It also increased the abundance of members of the genus Bacillus in the rhizosheath-associated microbial communities of white lupin and rice. We isolated a phosphate-solubilizing, auxin-producing Bacillus megaterium strain from the rhizosheath of white lupin and used this to inoculate white lupin and rice plants. Inoculation promoted rhizosheath formation and P acquisition, especially in plants with increased LaPAP12 expression and under SD–P conditions, suggesting a functional role of the bacteria in alleviating P deficit stress via rhizosheath formation. Together, our results suggest a synergistic enhancing effect of LaPAP12 and plant growth-promoting rhizobacteria on rhizosheath formation and P acquisition under SD–P conditions.

Seeds of crops contain large amounts of phosphorus (P), mostly as phytate. To lower seed phytate concentration is the ultimate breeding aim and highly desirable as the benefit of humans and many animals, given seed size is not sacrificed, i.e. leading to reduced seed P content. This study tested whether low seed P content affects early chickpea growth, and whether P supply during early growth compensates for early growth from seeds with low seed P content. Twenty-three chickpea genotypes with contrasting seed P content were selected for three treatments that were compared with a control: 1) seedlings supplied with a small amount of starter P (P10), 2) one cotyledon removed to reduce P content (Remove 1), and 3) both cotyledons removed to further reduce P content (Remove 2). Genotypes with higher seed P content had more vigorous early growth than genotypes with lower seed P, as did intact seedlings compared with those cotyledons removed. Application of P fertiliser significantly enhanced early growth. Low seed P genotypes had a more economic strategy, with a greater specific leaf area and specific root length, than genotypes with medium or high seed P content. Our results provided useful information for breeders that breeding chickpea genotypes with reduced seed P, does not affect germination and seedling vigour, provided starter P is supplied at the early development stage.

Zinc (Zn) and phosphorus (P) often interact negatively with each other in soil-plant systems. We investigated the effects of P-Zn interaction on Zn and P accumulation and partitioning in alfalfa. Plants were grown in a calcareous soil supplied with different rates of Zn (0, 200, and 800 mg kg−1) and P (0, 20, and 80 mg kg−1). Plant dry mass, Zn and P concentrations in shoots and roots, bulk soil and rhizosheath pH, rhizosheath carboxylates, and DTPA-extractable Zn concentration in the bulk soil were determined. Phosphorus-Zn interaction significantly affected DTPA-extractable Zn concentration, plant dry mass, accumulation of Zn and P, and partitioning of Zn in alfalfa, but did not affect rhizosheath pH or the amounts of rhizosheath carboxylates. Increasing P rate promoted plant growth at all soil Zn rates and might enhance the plants’ capacity to cope with excessive Zn; it resulted in a lower rhizosheath pH, which likely contributed to greater Zn and P uptake. Zinc deficiency enhanced exudation of citrate, malonate and malate, while the release of tartrate was related with P deficiency. There are strong P-Zn interactions in calcareous soil-plant system, such interactions significantly affect Zn bioavailability, plant growth, accumulation of Zn and P, and partitioning of Zn in alfalfa. Rational P fertilization should be considered for efficient Zn biofortification on Zn-deficient soils and phytoremediation of Zn-contaminated soils.

We investigated the effects of water stress under low phosphorus (P) supply on P-acquisition by chickpea, and identified a genotype with faster relative growth and P-acquisition rates. We grew four genotypes in pots filled with a sand and soil mixture with a low P availability in a glasshouse. Plants were either well-watered or water-stressed, imposed at the reproductive stage. Plants were harvested when water-stressed plants fully closed their stomata. For all four genotypes, water stress reduced shoot and root growth, root mass ratio, and shoot P content, while it increased specific root length (except in ICC 456), water-use efficiency and the amount of rhizosheath carboxylates per gram root dry weight. A faster relative shoot P-acquisition rate in ICC 2884 was associated with a greater specific root length, a smaller mean root diameter and a greater increase in the amount of rhizosheath carboxylates in response to water stress under low P supply. Interestingly, under water stress ICC 2884 also maintained a similar physiological P-use efficiency to that of the well-watered plants. ICC 2884 is recommended as a parental genotype in chickpea breeding programs to develop cultivars for low-P and terminal drought environments.

Plant growth is often limited by low soil phosphorus (P) availability, soil nitrogen (N) availability may affect plants’ responses to P supply. We studied the growth and physiological responses of alfalfa to soil P supply at different N levels. Alfalfa (Medicago sativa L.) plants were grown in an alkaline soil supplied with different levels of P (0, 5, and 20 mg kg−1) as monopotassium phosphate, and N (50 and 100 mg kg−1) as ammonium nitrate. Plant biomass and P concentrations always showed positive responses to P addition but not to N addition, nodulation was inhibited by lower P supply and higher N supply. Roots released more phosphatase and carboxylates, mainly tartrate, into the rhizosheath at lower soil P supply and higher N supply. Roots always acidified the rhizosheath, but rhizosheath pH did not vary considerably among treatments. This study demonstrates the release of tartrate as a major carboxylate as affected by soil P supply and N supply, and highlights the importance of investigating plant adaptive strategies for P acquisition from soil with different N availability for proper application of P and N fertilizers.

Soil alkalinity imposes important limitations to lupin productivity; however, little attention has been paid to investigate the effects of soil alkalinity on plant growth and development. Many lupins are sensitive to alkaline soils, butLupinus albusmaterial from Egypt was found to have tolerance to limed soils. The aim of this study was to compare the growth response of two cultivars ofL.albusL. – an Egyptian cultivar, P27734, and an Australian cultivar, Kiev Mutant, to different soil pH levels and to understand the physiological mechanisms underlying agronomic alkalinity tolerance of P27734. Plants were grown under three pH levels (5.1, 6.7, and 7.8) in a temperature-controlled glasshouse. For both cultivars, the greatest dry mass production and carboxylate exudation from roots were observed at alkaline pH. The better performance of the Egyptian cultivar at high pH was entirely accounted for by its greater seed weight. From a physiological perspective, the Australian cultivar was as alkaline-tolerant as the Egyptian cultivar. These findings highlight the agronomic importance of seed weight for sowing, and both cultivars can be used in alkaline soils.

Salinity is a major constraint to crop growth and productivity, limiting sustainable agriculture production. Planting canola (Brassica napus L.) variety with salinity-alkalinity tolerance as a green manure on the large area of salinity-affected land in Xinjiang could alleviate feed shortage. To investigate the differential effects of neutral and alkaline salt stress on seed germination and seedling growth of canola, we used two salts at varying concentrations, i.e., NaCl (neutral salt at 100, 150, and 200 mM) and Na2CO3 (alkaline salt at 20, 30, and 40 mM). To further explore the effects of Na+ and pH on seed germination, we included combined of NaCl (0, 100, 150, and 200 mM) and pH (7.1, 8.0, 9.0, 10.0, and 11.0). Shoot growth was promoted by low concentrations of NaCl and Na2CO3 but inhibited at high salt concentrations. Given the same Na+ concentration, Na2CO3 inhibited seed germination and seedling growth more than NaCl. The results showed that the main factor affecting seed germination and seedling growth is not pH alone, but the interaction between pH and salt ions. Under NaCl stress, canola increased the absorption of K+, Ca2+, and Mg2+ in roots and K+ in leaves. However, under Na2CO3 stress, canola maintained a high K+ concentration and K+/Na+ ratio in leaves and increased Ca2+ and Mg2+ in roots. Our study showed that alkaline salts inhibit canola seed germination and seedling growth more significantly than neutral salts and salt species, salt concentration, and pH significantly affected on seed germination and seedling growth. However, pH affected seed germination and seedling growth mainly through an interaction with salt ions.

Fusarium oxysporum f. sp. medicaginis (Fom) and Rhizoctonia solani (Rs) are the major soil-borne fungal pathogens that pose severe threats to commercial alfalfa production in China. However, the effects of Fom and Rs co-infection on alfalfa and whether co-infection alters disease resistance responses among diverse varieties remain unknown. A collection of 80 alfalfa varieties (Medicago sativa) originated from seven countries were used to study the effects of Fom and Rs co-infection on alfalfa and host resistance responses. The co-infection resulted in more severe disease and reductions in growth and biomass allocation across varieties in comparison with either single infection by Fom or Rs; in addition, root morphology was much more strongly altered by the co-infection. Principal component analysis based on all plant traits showed that varieties under the co-infection were related to the single infection by Rs, being separated from Fom, and hierarchical clustering found differential response patterns among varieties upon co-infection compared with either single infection, with most varieties being highly susceptible to the co-infection. Furthermore, varieties that were most resistant to either single infection were not effective to co-infection, and there was no individual variety with resistance to both pathogens singly and co-infected. This study reveals for the first time that the co-infection by Fom and Rs alters disease resistance responses among diverse alfalfa varieties and provides useful information for developing alfalfa varieties with resistance to the co-occurrence of different soil-borne pathogens.

Aims Carboxylate release by roots has been considered a strategy for mobilization and acquisition of phosphorus (P). However, recently, it was argued that carboxylate release may be a way to discharge surplus carbon produced under conditions that limit plant growth. Plant P status may not be the main factor driving carboxylate release by roots. Instead, plant nitrogen (N) status and/or N:P ratio of the soil or plant may play a more important role in enhancing carboxylate release. Methods A greenhouse pot experiment was performed to grow alfalfa in a P-deficient soil, supplied with two rates of P (0 and 20 mg kg− 1) in combination with four forms of nitrogen (N) at five rates (0, 25, 50, 75, and 100 mg kg− 1), to explore the effects of P rate, N form, N rate, and their interactions on plant growth, P and N status, and carboxylate release, and to determine the factors driving carboxylate release. Results Nitrogen addition weakened the positive effect of P addition on plant growth, and increased plant N ([N]) and P concentrations ([P]); P addition increased plant [P], but weakened the effect of N addition on plant [N]. The amount of tartrate increased dramatically with increasing N rate, which decreased shoot growth, depending on N form. At high P supply, tartrate exudation correlated negatively with shoot biomass. Conclusions Nitrogen addition to P-deficient alfalfa decreased shoot growth and enhanced the release of tartrate, likely to discharge surplus carbon; and the effects varied with N form.

Background and Aims Soil phosphorus (P) deficiency and salinity are constraints to crop productivity in arid and semiarid regions. Salinity may weaken the effect of P fertilization on plant growth. We investigated the interactive effects of soil P availability and salinity on plant growth, P nutrition and salt tolerance of two alfalfa (Medicago sativa) cultivars. Methods A pot experiment was carried out to grow two cultivars of alfalfa in a loess soil under a combination of different rates of added P (0, 40, 80 and 160 mg P kg−1 soil as monopotassium phosphate) and sodium chloride (0, 0.4, 0.8 and 1.6 g NaCl kg−1 soil). Plant biomass, concentrations of P ([P]), sodium ([Na]) and potassium ([K]) were determined, and rhizosheath carboxylates were analysed. Key Results There were significant interactions between soil P availability and salinity on some, but not all, of the parameters investigated, and interactions depended on cultivar. Plant growth and P uptake were enhanced by P fertilization, but inhibited by increased levels of salinity. Increasing the salinity resulted in decreased plant P-uptake efficiency and [K]/[Na]. Only soil P availability had a significant effect on the amount of tartrate in the rhizosheath of both cultivars. Conclusions Increased salinity aggravated P deficiency. Appropriate application of P fertilizers improved the salt tolerance of alfalfa and increased its productivity in saline soils.

Biochar amendment of soil is well known to improve soil fertility and microbial function. However, little is known about the effect of biochar addition to reclaimed soil in coal mining subsidence area on microbial community. A plant soil cultivation experiment was conducted with wheat grown and four treatments were included: P and K fertilizer (CK); NPK inorganic fertilizer (NPK); NPK inorganic fertilizer and straw (NPKS); and NPK inorganic fertilizer and biochar (NPKB). The results indicated that biochar amendment significantly increased the concentrations of NH4+-N, total N, and available P and K compared with the NPK. Biochar addition also significantly increased the grain yield and total biomass of wheat. Furthermore, biochar amendment treatment increased the absolute abundance and altered the community structure of soil bacteria and fungi in the reclaimed soil. Illumina MiSeq sequencing showed that the addition of biochar increased α-diversity of bacteria and relative abundances of Proteobacteria, Actinobacteria, and Bacteroidetes, whereas the relative abundance of Firmicutes were decreased by 61%. However, biochar addition did not change the relative abundance of dominant fungal phyla. Redundancy analysis (RDA) suggested that total N, available P, and K contents were the key factors correlated with changes in microbial community structure. Overall, our results suggest that biochar amendment in reclaimed soil in coal mine subsidence area could increase wheat yield and abundance and alter microbial community compositions.

The objectives of this study were to assess how Arachis hypogaea L. (peanut or groundnut) responds to different P supplies in terms of growth and photosynthesis, and to determine the optimum P supply and differential P stress thresholds. We investigated biomass production, leaf expansion, photosynthetic parameters, relative chlorophyll concentration, P700 parameters and chlorophyll fluorescence in a climate-controlled chamber at different P supplies (0.1, 0.5, 1, 1.5, 2 mM). Both deficient and excessive exogenous P supplies significantly reduced leaf growth, relative chlorophyll concentration and dry matter production in two high-yielding peanut cultivars. The optimum P range was 0.8–1.1 mM for peanut seedlings. Through principal component analysis (PCA) and data fitting, we found that the trade-off of the normalised actual quantum yield [Y(II)] and non-regulatory quantum yield [Y(NO)] in photosystem II (PSII) under light is one of the best proxies to determine the suboptimal, supraoptimal, deficient and toxic P supplies, because they are the two key factors with major positive and negative effects of PC1, accounting for 75.5% of the variability. The suboptimal P range was 0.41–0.8 mM and the supraoptimal P range was 1.1–1.72 mM. The suboptimal P supplies corresponded with a leaf P concentration range of 4.8–8.1 mg P g−1 DW, while the supraoptimal P supplies corresponded with a leaf P concentration range of 9.9–12.2 mg P g−1 DW. Both deficient and toxic P levels severely inhibited leaf growth and photosynthesis of peanut, and these unfavourable conditions were associated with significant reduction of biomass and photosynthesis, and photodamage extending beyond PSII. The trade-off of the normalised Y(II) and Y(NO) is a useful benchmark to demarcate deficient, suboptimal, supraoptimal and toxic P-fertilisations levels in A. hypogaea.

The expression of drought responsive genes were enhanced by N application and they contributed to drought acclimation. The interactive effects of water and nutrient are crucial for plants. The aim of this study was to elucidate how nitrogen (N) status influence drought acclimation of Populus. A two-factorial design consisting of two N levels (adequate-N and low-N) and two watering treatments (drought stress and well-watered) was used, and an integrative investigation was conducted at the anatomical, physiological and molecular levels. Adequate N supply alleviated the adverse effects of drought stress on root growth in poplars, which may increase water uptake under drought. Nitrogen enhanced leaf anatomical changes and stomata adjustment upon drought stress, lead to less water losses and better growth performance under drought stress. The expression levels of phytohormone signaling components and genes responsible for antioxidative systems and secondary metabolites such as phenylpropanoids were promoted by N application. The expression of abscisic acid (ABA) signaling components was induced by drought when soil N was adequate, which participated in stomata regulation and drought acclimation. The expression of indole acetic acid (IAA) signaling components also was enhanced by N application, which participated in anatomical changes of leaves under drought. These adaptive changes at molecular and anatomical levels contributed to drought acclimation in a synergistic way. Under adequate-N condition, nitrogen and carbon metabolism pathways are being recruited to combat drought, and the C-N interaction play a pivotal role in drought acclimation.

Background Drought and nitrogen (N) deficiency are two major limiting factors for forest productivity in many ecosystems. Elucidating the mechanisms underlying the influence of soil N availability on drought responses of tree species is crucial to improve tree growth under drought. Results The root proliferation under drought was enhanced by adequate N application. Vessel frequency in xylem increased upon drought, with more significant increase under adequate N conditions compared with that under low N conditions, possibly leading to increased hydraulic safety. Nitrogen application under drought increased indole acetic acid (IAA), which contributed to the adaptive changes of xylem. Nitrogen application increased leaf abscisic acid (ABA) concentration, therefore regulated stomata adjustment, and promoted intrinsic water use efficiency (WUEi). Moreover, N application promoted antioxidant defense in leaves by showing increased level of free proline and carotenoid, which improved drought tolerance and growth performance of poplars. Conclusions Anatomical and physiological responses of Populus to drought were suppressed by N deficiency. Adequate N application promoted adaptive changes of root and xylem under drought and increased hydraulic safety. Nitrogen addition under drought also increased leaf ABA level which may regulate stomata adjustment and promote WUEi. Moreover, nitrogen application improved antioxidant defense in leaves with increased levels of antioxidants. These positive regulations improved drought tolerance and growth performance of poplars. Electronic supplementary material The online version of this article (10.1186/s12870-019-1667-4) contains supplementary material, which is available to authorized users.

At a global scale, phosphorus (P) deficiency comprises a large area of cropland, while P has also been used in excess of crop requirements in many other regions. Improved crop P-acquisition efficiency would allow lower target critical soil P values and provide savings in P-fertiliser use. At the same time, it would reduce P lost through erosion, leaching and/or soil sorption. This chapter summarises the progress in research on root traits associated with P acquisition, including root morphology, architecture, biochemistry, colonisation by arbuscular mycorrhizal fungi, and fine root endophytes, and the trade-offs among all these traits. Farming-management practices to improve P acquisition under current intensive agricultural systems are also discussed. The chapter summarises breeding progress in improving P-acquisition efficiency. In the face of soil P deficiency or legacy P globally, the chapter suggests future directions to improve P acquisition in five key areas.

Chickpea—the second most important grain legume worldwide—is cultivated mainly on marginal soils. Phosphorus (P) deficiency often restricts chickpea yields. Understanding the genetics of traits encoding P-acquisition efficiency and P-use efficiency will help develop strategies to reduce P-fertilizer application. A genome-wide association mapping approach was used to determine loci and genes associated with root architecture, root traits associated with P-acquisition efficiency and P-use efficiency, and any associated proxy traits. Using three statistical models—a generalized linear model (GLM), a mixed linear model (MLM), and a fixed and random model circulating probability unification (FarmCPU) —10, 51, and 40 marker-trait associations (MTAs), respectively were identified. A single nucleotide polymorphism (SNP) locus (Ca1_12310101) on Ca1 associated with three traits, i.e., physiological P-use efficiency, shoot dry weight, and shoot P content was identified. Genes related to shoot P concentration (NAD kinase 2, dynamin-related protein 1C), physiological P-use efficiency (fasciclin-like arabinogalactan protein), specific root length (4-coumarate–CoA ligase 1) and manganese concentration in mature leaves (ABC1 family protein) were identified. The MTAs and novel genes identified in this study can be used to improve P-use efficiency in chickpea.