P Utilization Efficiency Research Articles

Effects of phosphate fertilization and sulfadiazine on plant growth, root morphology, nitrogen and phosphorus uptake of soybean and maize

Low soil phosphorus (P) availability is a limiting factor for crop production. Application of livestock manure as organic fertilizer can increase soil P availability, but may cause soil contamination with antibiotics such as sulfadiazine (SD), thus adversely affecting plant growth and nutrient uptake. The effects of P (0 and 50 mg kg−1) and SD (0, 1, 10, and 100 mg kg−1) levels on plant growth, root development, and nitrogen (N) and P uptake of maize and soybean were examined in a pot experiment using a loess soil as the test soil. High levels of SD considerably inhibited plant growth of both crops. Both P fertilization and SD negatively affected root development of both crops, especially at higher SD levels. For both crops, the average root diameter and the proportion of thick roots increased with increasing soil SD level. When soil SD level was ≤10 mg kg−1, the effects of P fertilization and SD on plant N and P concentrations, and N:P, N- and P-utilization efficiency were not significant in most cases. The effects of SD on plant N and P nutrition could not be of a great concern when soil SD level was ≤10 mg kg−1. Overall, soil SD pollution could reduce plant biomass and inhibit root development of soybean and maize, with a stronger effect on root development than on plant biomass at a high soil SD level (≥10 mg kg−1). In agricultural production, attention should be paid to soil SD pollution via manure application.

Fertilizer Addition Modifies Utilization of Different P Sources in Upland Rice on Strongly P-fixing Andosols

AimsHigh Phosphorus (P) efficiencies such as internal P utilization efficiency (PUE) and P acquisition efficiency (PAE) are crucial for upland rice production, particularly on highly P-fixing soils like Andosols. While the effect of root traits associated with high PAE in upland rice has been studied intensively, less attention has been given to the origin of P (native soil-P versus fertilizer-P) taken up by plants when evaluating differences in P efficiency. Here we aim to evaluate the efficiency of different upland rice genotypes to acquire native soil-P and fertilizer-P.MethodsFour upland rice genotypes with varying PAE were grown in an Andosol at low- and high-P fertilization level and harvested 9 and 34 days after emergence. Fertilizer-P was labeled with 33P to distinguish between the efficiency to acquire P originating from native soil and fertilizer by measuring plant P uptake.ResultsIncreased fertilizer supply enhanced native soil-P uptake. Under low-P conditions the genotype DJ123 showed a superior PAE and an increased acquisition of native soil-P while AB199 was identified to have a superior internal PUE under P deficient conditions. Differences between genotypes in overall PAE under high-P conditions were not significant but the distinction of P sources showed that genotype DJ123 acquired significantly more native soil-P per unit root than all other genotypes.ConclusionsOur results indicate that variations in PAE among genotypes are associated with their ability to access native soil-P. DJ123 emerged as the most adept genotype in acquiring sparingly soluble native soil-P and future studies should unravel the rhizosphere processes underlying increased PAE of native soil-P.

Root Architectural Adaptations to Phosphorus Deficiency: Unraveling Genotypic Variability in Wheat Seedlings

Understanding the changes in the root system architecture of bread wheat under phosphorus (P)-limited conditions is critical for identifying specific traits contributing to improved P uptake. Phenotypic variability in root, biomass, and P index-related traits among 204 diverse wheat genotypes at the seedling stage was examined under low and optimum P treatments. Strong genotypic and phenotypic associations between P utilization efficiency (PUtE) and total root volume, dry weight of root and shoot, total P uptake, and total plant biomass were observed under optimum P. Under low P, strong positive correlations between PUtE and total root length, total root volume, total surface area, and total biomass were observed, while it was negatively correlated with average diameter. These traits exhibited medium to high heritability. Under low P, average root diameter, primary root length, root mass ratio, total root tips, and surface area showed high Shannon–Weaver diversity index (H’) values (>0.79). The agglomerative hierarchical clustering analysis grouped the genotypes into four distinct clusters. The best performing genotypes in Clusters I and II indicated their strong relationship with P use efficiency due to higher percent increases in total root length, total surface area, total root volume, total root tips, total biomass, P efficiency ratio, specific root length, and PUtE under low P as compared to optimum P conditions. The present study identified specific root system architectural traits and P use-efficient genotypes (SHANGHAI, Pavon F76, BWL 5233, SONALIKA, KHARCHIA LOCAL, WH 102, BWL 4425, HD 2888.2, CBW 12, MN75136/PGO, KRL 19, and WH 1022) associated with efficient P uptake and utilization. These identified genotypes and traits may be useful in wheat breeding programs to develop P-efficient varieties with better adaptations for sustainable agriculture.

Enhancing phosphorus use efficiency in wheat grown on alkaline calcareous soils

Phosphorus (P) use efficiency is crucial for sustainable wheat production, particularly on alkaline calcareous soils. This study investigates the relative importance of two factors; P acquisition efficiency (PAE) and P utilization efficiency (PUtE), in determining P use efficiency (PUE) in wheat. A field trial with ten wheat genotypes was conducted under two P levels (no P application and P application at 110 kg P2O5 ha−1). Results revealed significant genetic variability in PUE, PAE, and PUtE among wheat genotypes under varying P availabilities. Genotypes MK-4 and MK-8 exhibited superior PUE, making them ideal candidates for soils with differing P levels. PAE played a more substantial role in influencing PUE, with PUtE contributing less to the variability. The findings underscore the importance of improving PAE, particularly for wheat genotypes grown in P-deficient conditions. Moreover, selecting genotypes with lower grain P concentration can enhance PUtE, contributing to improved PUE. These insights can improve breeding efforts and crop management practices to enhance P use efficiency in wheat, ultimately reducing production costs and fertilizer demand, especially in P-limited alkaline calcareous soils.

Phosphorus partitioning contribute to phosphorus use efficiency during grain filling in Zea mays.

Lower phosphorus (P) availability limits crop productivity in agroecosystems. The remobilization of P from the source to the sink organs plays an important role in enhancing the P-utilization efficiency of crops. During the grain filling stage, phosphorus flow to the developing grains, the primary sink, determines crop yield. However, the specific contributions of different organs to grain P throughout the post-silking period in maize remain unclear. In our study, three maize inbred lines (CIMBL89, Ji846, and CML118) with contrasting P statuses were selected and grown in a field with high P (HP, 150 kg ha-1 P2O5) and low P (LP, 0 kg ha-1 P2O5) conditions. The grain yield of CIMBL89 was 69% and 169% greater under HP supply, and 83% and 309% greater than those of Ji846 and CML118 under LP supply, respectively. The ear length, ear diameter, and kernel row number of CML118 were lower than those of CIMBL89 and Ji846 under HP conditions. Most of the P (87%) in the grains of CIMBL89 came from P uptake at the LP supply, while almost all P (95%) came from P remobilization in various organs at the HP supply after silking. In contrast, 91% of the P found in the grain of CML118 came from P remobilization under LP supply, while 76% came from P uptake under HP supply after silking. In conclusion, our findings suggest that CIMBL89, with greater P acquisition efficiency, contributes to grain formation and production during the post-silking period under LP conditions. Additionally, CIMBL89 can fully remobilize P and avoid the extravagant absorption of P in P-sufficient soil, which sets it apart from Ji846 and CML118.

Breeding Milestones Correspond with Changes to Wheat Rhizosphere Biogeochemistry That Affect P Acquisition

Breeding wheat (Triticum aestivum L.) has resulted in small gains in improved nutrient acquisition and use as numerous traits are involved. In this study, we evaluated the impact of breeding on P-acquisition and identified both plant and soil variables that could be used to inform the selection of germplasm with increased P acquisition efficiency. We previously screened a historic panel of winter wheat cultivars for root system architecture and root tip organic acid content when grown in P-deficient solution/agar and used these characteristics together with breeding history to develop a predicted P extraction potential (PEP). We tested the validity of the PEP classification by growing cultivars under sufficient and insufficient soil P conditions. Old, wild-type cultivars had the greatest P utilization efficiency (PUtE) when grown under insufficient P, likely a result of the chemical potential of wild-type (with respect to Rht-B1) cultivars (greater organic acid production) rather than root system size. Wild-type plants had differences in rhizosphere microbial community structure, rhizosphere bicarbonate-extractable P, and bulk soil Fe and Al, indicating the utilization of typically less available P pools. The PEP classification based on the presence of dwarfing allele and era of release offers a path forward for breeding for improved P acquisition.

Integrated multi-omics reveals the molecular mechanisms underlying efficient phosphorus use under phosphate deficiency in elephant grass (Pennisetum purpureum).

Phosphorus (P) is an essential macronutrient element for plant growth, and deficiency of inorganic phosphate (Pi) limits plant growth and yield. Elephant grass (Pennisetum purpureum) is an important fodder crop cultivated widely in tropical and subtropical areas throughout the world. However, the mechanisms underlying efficient P use in elephant grass under Pi deficiency remain poorly understood. In this study, the physiological and molecular responses of elephant grass leaves and roots to Pi deficiency were investigated. The results showed that dry weight, total P concentration, and P content decreased in Pi-deprived plants, but that acid phosphatase activity and P utilization efficiency (PUE) were higher than in Pi-sufficient plants. Regarding Pi starvation-responsive (PSR) genes, transcriptomics showed that 59 unigenes involved in Pi acquisition and transport (especially 18 purple acid phosphatase and 27 phosphate transporter 1 unigenes) and 51 phospholipase unigenes involved in phospholipids degradation or Pi-free lipids biosynthesis, as well as 47 core unigenes involved in the synthesis of phenylpropanoids and flavonoids, were significantly up-regulated by Pi deprivation in leaves or roots. Furthermore, 43 unigenes related to Pi-independent- or inorganic pyrophosphate (PPi)-dependent bypass reactions were markedly up-regulated in Pi-deficient leaves, especially five UDP-glucose pyrophosphorylase and 15 phosphoenolpyruvate carboxylase unigenes. Consistent with PSR unigene expression changes, metabolomics revealed that Pi deficiency significantly increased metabolites of Pi-free lipids, phenylpropanoids, and flavonoids in leaves and roots, but decreased phospholipid metabolites. This study reveals the mechanisms underlying the responses to Pi starvation in elephant grass leaves and roots, which provides candidate unigenes involved in efficient P use and theoretical references for the development of P-efficient elephant grass varieties.

Relationship between phosphorus uptake via indigenous arbuscular mycorrhizal fungi and crop response: A 32P-labeling study

Arbuscular mycorrhizal (AM) fungi form potentially symbiotic associations with most crop species and potentially increase crop phosphorus (P) uptake in intensive cropping systems. Their widespread use, however, remains restrained by our limited understanding of the processes that determine the outcome of the associations. Here, we have used 32P to quantify the delivery of P to maize (Zea mays L.) and wheat (Triticum aestivum L.) via indigenous AM fungi in compartmented pots under high- and low-P conditions. Soil P level was important in driving shoot P uptake via the direct root pathway (DP) or the mycorrhizal pathway (MP). The MP contribution reached 81.8 and 75.8%, respectively, in maize and wheat at low P status but declined to 40.6 and 9.1% at high P. The abundance of intraradical and extraradical colonization and the relative abundance of Rhizophagus and shoot P utilization efficiency (PUE) significantly impacted the MP contribution. Larger mycorrhizal P and growth responses were closely related to a higher MP contribution and shoot PUE in maize but only P response was significantly related to the latter in wheat. These results suggest that crops can acquire considerable amounts of P via the MP with indigenous AM fungi, especially at low P levels, and highlight the importance of plant and AM fungal identity in regulating the relationship between hidden P uptake and symbiotic outcomes. Therefore, manipulation of fertilizer P application rates to optimize the abundance and assemblage of the indigenous AM fungi and crop PUE to increase MP activity and symbiotic outcomes may contribute to the efficient utilization of AM fungi in intensive cropping systems.

Combining analyses of metabolite profiles and phosphorus fractions to explore high phosphorus utilization efficiency in maize.

Phosphorus (P) limitation is a significant factor restricting crop production in agricultural systems, and enhancing the internal P utilization efficiency (PUE) of crops plays an important role in ensuring sustainable P use in agriculture. To better understand how P is remobilized to affect crop growth, we first screened P-efficient (B73 and GEMS50) and P-inefficient (Liao5114) maize genotypes at the same shoot P content, and then analyzed P pools and performed non-targeted metabolomic analyses to explore changes in cellular P fractions and metabolites in maize genotypes with contrasting PUE. We show that lipid P and nucleic acid P concentrations were significantly lower in lower leaves of P-efficient genotypes, and these P pools were remobilized to a major extent in P-efficient genotypes. Broad metabolic alterations were evident in leaves of P-efficient maize genotypes, particularly affecting products of phospholipid turnover and phosphorylated compounds, and the shikimate biosynthesis pathway. Taken together, our results suggest that P-efficient genotypes have a high capacity to remobilize lipid P and nucleic acid P and promote the shikimate pathway towards efficient P utilization in maize.

Effects of Scion Variety on the Phosphorus Efficiency of Grafted Camellia oleifera Seedlings

Grafting provides a way to improve tolerance to low phosphorus (P) stress for plants, and has been extensively applied in commercial cultivars grafted onto appropriate rootstocks. However, little literature is available concerning the scion-mediated effect on P efficiency in grafted plants. In this study, three different Camellia oleifera Abel. scion cultivars (G8, G83-1, and W2) were grafted onto the same rootstock (W2) under controls (0.5 mM) and low-P (0 mM) availability for eight months. The results showed that the scions significantly affected root-to-shoot weight ratios, the root morphology with a diameter larger than 1 mm, P accumulation, and the P utilization efficiency (PUE) of the root. A higher increase in the root-to-shoot weight ratio under the low-P supply was observed in the G83-1/W2 (26.15%) than in the G8/W2 (0%) and the W2/W2 (5.32%). Root PUE of the scion G8, G83-1, and W2 was improved by up to 113.73%, 45.46%, and 20.97% under the low-P supply. Moreover, G8/W2 exhibited higher shoot P accumulation and the highest root PUE under the low-P supply, indicating a high capability to tolerate P deficiency by maximizing the cost-effectiveness of P remobilization to photosynthetic organs. This suggested the vigorous variety of G8 could be a promising scion to improve grafted C. oleifera tolerance to low-P stress. Our results would have important implications for exploration and identification of a superior scion variety to enhance the ability of resistance concerning P deficiency stress in C. oleifera.

Combined Transcriptome and Proteome Analysis of Maize (Zea mays L.) Reveals A Complementary Profile in Response to Phosphate Deficiency.

A deficiency in the macronutrient phosphate (Pi) brings about various changes in plants at the morphological, physiological and molecular levels. However, the molecular mechanism for regulating Pi homeostasis in response to low-Pi remains poorly understood, particularly in maize (Zea mays L.), which is a staple crop and requires massive amounts of Pi. Therefore, in this study, we performed expression profiling of the shoots and roots of maize seedlings with Pi-tolerant genotype at both the transcriptomic and proteomic levels using RNA sequencing and isobaric tags for relative and absolute quantitation (iTRAQ). We identified 1944 differentially expressed transcripts and 340 differentially expressed proteins under low-Pi conditions. Most of the differentially expressed genes were clustered as regulators, such as transcription factors involved in the Pi signaling pathway at the transcript level. However, the more functional and metabolism-related genes showed expression changes at the protein level. Moreover, under low-Pi conditions, Pi transporters and phosphatases were specifically induced in the roots at both the transcript and protein levels, and increased amounts of mRNA and protein of two purple acid phosphatases (PAPs) and one UDP-sulfoquinovose synthase (SQD) were specifically detected in the roots. The new insights provided by this study will help to improve the P-utilization efficiency of maize.

Genetic Dissection of Phosphorous Uptake and Utilization Efficiency Traits Using GWAS in Mungbean

Mungbean (Vignaradiata L. Wilczek) is an early maturing legume grown predominantly in Asia for its protein-rich seeds. P deficiency can lead to several physiological disorders which ultimately result in a low grain yield in mungbean. The genetic dissection of PUpE (Puptake efficiency) and PUtE (P utilization efficiency) traits are essential for breeding mungbean varieties with a high P uptake and utilization efficiency. The study involves an association mapping panel consisting of 120 mungbean genotypes which were phenotyped for total dry weight, P concentration, total P uptake, and P utilization efficiency under low P (LP) and normal P (NP) conditions in a hydroponic system. A genotyping-by-sequencing (GBS) based genome-wide association study (GWAS) approach was employed to dissect the complexity of PUpE and PUtE traits at the genetic level in mungbean. This has identified 116 SNPs in 61 protein-coding genes and of these, 16 have been found to enhance phosphorous uptake and utilization efficiency in mungbeans. We identified six genes with a high expression (VRADI01G04370, VRADI05G20860, VRADI06G12490, VRADI08G20910, VRADI08G00070 and VRADI09G09030) in root, shoot apical meristem and leaf, indicating their role in the regulation of P uptake and utilization efficiency in mungbean. The SNPs present in three genes have also been validated using a Sanger sequencing approach.

Decline of seedling phosphorus use efficiency in the heterotic pool of flint maize breeding lines since the onset of hybrid breeding

AbstractImproved management and breeding increased maize (Zea mays L.) yields over the last century, but nutritional efficiency was usually not the focus. This study investigates whether old and recently released flint and dent maize seedlings vary in the phosphorus (P) acquisition and utilization. P use efficiency (PUE) and related traits were measured and compared at two P levels in a calcareous soil. PUE and P acquisition efficiency (PAE) from founder flints to elite flints declined over the last decades. This was associated with smaller root systems, reduced ability to exploit external P, decreased rhizosphere pH and shorter root hairs in low P. Comparing flints with doubled haploid landraces (DH_LR), old and elite dents and hybrids revealed that dents started to acquire exogenous P earlier and had improved PUE. Most DH_LRs had similar PUE as elite flints. When evaluating root traits associated with P efficiency, seed P was also critical, and it is important to stack different root traits to optimize PUE, P utilization efficiency (PUtE) and PAE in breeding programmes. The root hair length, the ability to acidify the rhizosphere and the root diameter in flint and dent pools may be utilized to improve P use in maize germplasm.

Novel QTL Conferring Phosphorus Acquisition and Utilization Efficiencies in Barley.

Phosphorus (P) deficiency in agricultural soil is a major constraint for crop production and increasing P acquisition efficiency (PAE) of plants is considered as one of the most cost-effective solutions for yield increase. The objective of this study was to detect quantitative trait loci (QTL) controlling (PAE) and P utilization efficiency (PUE) in barley under applied (+P) and non-applied P (−P) conditions. Based on the analysis of a recombinant inbred lines (RILs) population derived from a cross between a malting barley variety and a wild barley accession, 17 QTL controlling PAE, PUE and yield traits were detected. The phenotypic variation explained by each of these QTL ranges from 11.0 to 24.7%. Significant correlation was detected between most of P-related traits and yield traits. Five QTL clusters were identified on four different chromosomes (1H, 3H, 5H, and 7H). Two of the QTL clusters, located on chromosome 1H (for GPUP/PUP) and 7H (for SPUE/SPC), respectively, are novel. Fourteen genes located in the interval harboring the major QTL were identified as candidates associated with P efficiency. The stable QTL for PAE, PUE and yield-related traits could be important for breeding P-efficient barley varieties.

Detection of QTL for phosphorus efficiency and biomass traits at the seedling stage in wheat

Phosphorus (P) is one of the most vital nutrient elements in crop output and quality formation. In this study, four biomass, four P uptake efficiency (PupE), and three P-utilization efficiency (PutE) traits were investigated using a set of recombinant inbred lines (RILs) derived from a cross of “SN0431 × LM21”, under hydroponic culture trials at low P (LP) and normal P (NP) levels in two different seasons, respectively. A total of 85 QTL were identified on 18 chromosomes except for 1D, 2A, and 3D. Among them, 36 and 42 QTL were detected under LP and NP, respectively, and seven QTL were simultaneously detected under LP and NP. Seventeen relatively high-frequency QTL (RHF-QTL) were detected. The average contributions of 13 major RHF-QTL were over 10.00%. Five important QTL clusters were detected on chromosomes 4D, 5A, and 5B. Among them, positive linkages were observed between PutE and biomass traits at four QTL clusters, C1, C2, C3, and C6, showing these loci may be hot spots for genetic control of both phosphorus utilization and biomass accumulation in wheat seedlings. In addition, correlation analysis indicated that three biomass traits (SDW, RDW, and TDW) should be used as primary selection indexes for PE at the seedling stage.

Metabolomic markers and physiological adaptations for high phosphate utilization efficiency in rice.

Utilizing phosphate more efficiently is crucial for sustainable crop production. Highly efficient rice (Oryza sativa) cultivars have been identified and this study aims to identify metabolic markers associated with P utilization efficiency (PUE). P deficiency generally reduced leaf P concentrations and CO2 assimilation rates but efficient cultivars were reducing leaf P concentrations further than inefficient ones while maintaining similar CO2 assimilation rates. Adaptive changes in carbon metabolism were detected but equally in efficient and inefficient cultivar groups. Groups furthermore did not differ with respect to partial substitutions of phospholipids by sulfo- and galactolipids. Metabolites significantly more abundant in the efficient group, such as sinapate, benzoate and glucoronate, were related to antioxidant defence and may help alleviating oxidative stress caused by P deficiency. Sugar alcohols ribitol and threitol were another marker metabolite for higher phosphate efficiency as were several amino acids, especially threonine. Since these metabolites are not known to be associated with P deficiency, they may provide novel clues for the selection of more P efficient genotypes. In conclusion, metabolite signatures detected here were not related to phosphate metabolism but rather helped P efficient lines to keep vital processes functional under the adverse conditions of P starvation.

Strategic timing and rate of phosphorus fertilization improves phosphorus-use efficiency in two contrasting cultivars of subirrigated greenhouse-grown chrysanthemum

Greenhouse floriculture operations pose significant environmental risk due to extensive inputs of fertilizer, especially nitrogen and phosphorus (P). Recent evidence shows that the use efficiency for nitrogen or sulphur is markedly improved in subirrigated potted chrysanthemums (Chrysanthemum morifolium Ramat.) by supplying a moderate level of the nutrient during vegetative growth, and removing the entire nutrient suite at the onset of reproductive growth, without adverse effects on plant quality. Here, two split-plot experiments were conducted with subirrigated, potted, disbudded chrysanthemums grown in a peat:perlite mixture under greenhouse conditions (high- or low-ambient light) with inorganic orthophosphate (Pi) treatment (2.6 mmol L−1 Pi supplied during the vegetative and reproductive stages, and 2.6, 1.95, or 1.3 mmol L−1 Pi supplied during the vegetative stage only) as the main plot and cultivar (‘Olympia’ and ‘Covington’) as the subplot. Market quality plants with sufficient tissue P were produced even when Pi delivery was reduced by approximately 75% over the crop cycle, compared with industry standards. The primary mechanism for sustaining plant growth with decreasing Pi delivery was improved acquisition or uptake efficiency, although some changes in internal P-utilization efficiency were evident, including the remobilization of both organic P and Pi during inflorescence development. Differences in biomass yields, tissue P concentrations, content-based P-use efficiency (PUEC = mg shoot dry mass/mg shoot P content) with constant Pi acquisition, and uptake- versus remobilization-based P supply for inflorescence growth established that ‘Olympia’ has a greater P-utilization efficiency than ‘Covington’. This modified subirrigation practice could contribute significantly to low-input production of floricultural crops.

Genotypic Variation in Cotton Genotypes for Phosphorus-Use Efficiency

Low phosphorus (P) availability is a major constraint for cotton production. Consequently, P-efficient genotypes can improve productivity under conditions where the higher application of P is not economical. This study was conducted to characterize cotton genotypes for P-use efficiency under various P concentrations (0, 10, 20, 40, 80, and 500 μM KH2PO4). The results showed large genotypic variation in five selected traits, such as root dry weight, shoot dry weight, photosynthetic activity, P-utilization efficiency, and P-uptake efficiency. Based on these five selected traits, the genotypes were grouped into three main classes as efficient, moderate efficient, and inefficient genotypes as proposed by different researchers. Most of the genotypes behaved in a similar pattern under different P concentrations. Among the genotypes, Xinluzao-49 and Xinluzao-48 were considered as P efficient while CCRI-64 and Yumian-21 as inefficient genotypes. However, the rest of the genotypes were considered as moderately P efficient. The results prove that a large genetic potential exists in cotton genotypes for P-use efficiency, and the use of P-efficient genotypes for cultivation will reduce the application of phosphatic fertilizers. Furthermore, the use of P-efficient genotypes will improve cotton breeding activities and help in improving the environmental sustainability of cotton production.

Genotype-Specific Differences in Phosphorus Efficiency of Potato (Solanum tuberosum L.).

Potato is considered to have a low phosphorus (P) efficiency compared to other crops. Therefore, P fertilization requirements are high. New cultivars with improved P efficiency may contribute to save limited mineral P sources and to reduce eutrophication of surface water bodies. The present study aims to characterize the P efficiency of different potato genotypes and to identify mechanisms that improve P efficiency in cultivated potato. A diversity set of 32 potato accessions was used to assess their P efficiency. From this set, five cultivars were selected and two pot experiments with different P-fertilization strategies including a non-fertilized control were conducted to estimate effects of P deficiency on general agronomic and P related traits, root development, phosphatase activity and micro RNA 399 (miR399) expression. Significant differences between the 32 genotypes were found for P utilization efficiency (PUtE). P acquisition efficiency (PAE) as P content in low P in relation to P content in high P was positively correlated to relative biomass production while PUtE was not. Selected genotypes displayed a strong relation between total root length and P content. Root phosphatase activity and miR399 expression increased under P deficiency. However, tuber yields of four cultivars, grown on a soil with suboptimal content of plant available P, were not significantly affected in comparison to yields of well-fertilized plots. We conclude from the present study that PUtE and PAE are important traits when selecting for plants requiring less fertilizer inputs but PAE might be more important for cropping on deficient soils. A large root system might be the most important trait for P acquisition on such soils and therefore in breeding for P efficient crops. Lowering P fertilizer inputs might not necessarily reduce tuber yields.

Coincidence of QTLs determining foliar phosphorus fractionation patterns and phosphorus utilization efficiency in barley under low phosphorus stress

Plants can optimize the allocation of phosphorus (P) among their foliar P fractions to increase the P utilization efficiency (PUE). Identifying the genetic relationships between foliar P fractionation and PUE could provide opportunities to improve the P efficiency of barley (Hordeum vulgare L.). The differences in the concentrations and proportions of inorganic P, ester P, nucleic acid P and insoluble P between a wild barley cultivar CN4027 and a commercial cultivar Baudin were studied, and their quantitative trait loci (QTLs) at normal P (NP) and low P (LP) fertilisations were mapped. The PUE that was determined in the previous study was used to analyze the relationship between PUE and foliar P fractionation in this research. Both cultivars of barley could increase their metabolic P fractions as an LP stress tolerance strategy to ensure their continued metabolic activities in response to LP stress. Cultivar CN4027 showed higher nucleic acid P concentration (NPC), nucleic acid P proportion (NPP) and insoluble P proportion (IPP) than cultivar Baudin under LP stress. This abundant organic P (Po) pool of CN4027 ensured the normal functioning of its metabolic pathways under LP stress. The close relationships between the foliar P fractionation and PUE could be explained by two QTL clusters, Cl-3H.02 and Cl-5H.01. The QTL cluster Cl-3H.02 is flanked by the markers bPb3256099-bPb3255630 on chromosome 3H and controls the ester P concentration (EPC), ester P proportion (EPP), insoluble P concentration (IPC) and IPP. The QTL cluster Cl-3H.02 might have great potential for the future genetic improvement of barley PUE and may offer clues for the genetic relationships between the foliar P fractionation and PUE.