Low Phosphorus Conditions Research Articles

Cloning and functional analysis of the promoter of purple acid phosphatase gene <italic>GmPAP14 </italic>in soybean

<p id="C3">The expression of <italic>GmPAP14</italic> was induced under low phosphorus condition, and its overexpression could significantly improve the utilization efficiency of organic phosphorus in <italic>Arabidopsis</italic>. In order to further explore its regulatory mechanism, the promoter sequence of <italic>GmPAP14</italic> was cloned according to the sequence of soybean reference genome. The regulatory elements of <italic>GmPAP14</italic> promoter were predicted by the database PLACE and PlantCARE, which showed that it contained enhancer regulatory elements, tissue-specific expression elements, root-specific expression elements, and P1BS elements (transcription factor PHR1 binding sites). <italic>P_GmPAP14-2568</italic>-<italic>GUS</italic>, <italic>P_GmPAP14-2238</italic>-<italic>GUS</italic>, and <italic>P_GmPAP14-1635</italic>-<italic>GUS</italic> were constructed and transferred into <italic>Arabidopsis thaliana</italic> via Floral dip method. The expressional activities of three fragments of <italic>GmPAP14</italic> promoter were analyzed through GUS staining and activity measurement. The results revealed that <italic>GmPAP14</italic> promoter was mainly expressed in root tip under Pi condition, and GUS staining was extended to the elongation area, mature area, and root hair after low phosphorus treatment. Additionally, <italic>Arabidopsis</italic> plants with <italic>P_GmPAP14-2238</italic>-<italic>GUS</italic> had the highest activity among them. These results lay an important foundation for the further study of gene regulation.

Chinese Cherry (Cerasus pseudocerasus Lindl.) ARF7 Participates in Root Development and Responds to Drought and Low Phosphorus

In this paper, an auxin-responsive transcription factor, CpARF7, was isolated from the roots of Chinese cherry (Cerasus pseudocerasus Lindl. Cv. “Manao Hong”). CpARF7 is highly homologous to AtARF7 or AtARF19 in Arabidopsis, and PavARF1 or PavARF14 in sweet cherry. However, in the phenotype of transgenic tomatoes, the root morphology changed, the main root elongated, and the lateral root increased. Both drought treatment and low-phosphorus conditions can elongate the roots of transgenic tomatoes. In addition, the drought resistance and low-phosphorus tolerance of the transgenic lines are improved, and the POD, SOD, and CAT activities under drought and low-phosphorus environments are increased. There is an effect on the tomato somatotropin suppressor gene, SlIAAs, in which SlIAA1/14/19/29 are up-regulated and SlIAA2/11/12/16 are down-regulated. These results indicate that CpARF7 plays an essential regulatory role in root formation and abiotic stress response, and deepens the understanding of auxin-responsive genes in root growth and abiotic stress.

Genome-wide association and linkage mapping strategies reveal genetic loci and candidate genes of phosphorus utilization in soybean

Insufficient available phosphorus in soil has become an important limiting factor for the improvement of yield and quality in soybean. The mining of QTLs and candidate genes controlling soybean phosphorus utilization related traits is a necessary strategy to solve this problem. In this study, 11 phosphorus utilization related traits of a natural population of 281 typical soybean germplasms and a recombinant inbred line (RIL) population of 270 lines were evaluated under different phosphorus conditions at two critical stages: the four-leaf stage as the seedling critical stage was designated as the T1 stage, and the six-leaf stage as the flowering critical stage was designated as the T2 stage. In total, 200 single nucleotide polymorphism (SNP) loci associated with phosphorus utilization related traits were identified in the natural population, including 91 detected at the T1 stage, and 109 detected at the T2 stage. Among these SNP loci, one SNP cluster (s715611375, ss715611377, ss715611379 and ss715611380) on Gm12 was shown to be significantly associated with plant height under the low phosphorus condition at the T1 stage, and the elite haplotype showed significantly greater plant height than the others. Meanwhile, one pleiotropic SNP cluster (ss715606501, ss715606506 and ss715606543) on Gm10 was found to be significantly associated with the ratio of root/shoot, root and total dry weights under the low phosphorus condition at the T2 stage, and the elite haplotype also presented significantly higher values for related characteristics under the phosphorus starvation condition. Furthermore, four co-associated SNP loci (ss715597964, ss715607012, ss715622173 and ss715602331) were identified under the low phosphorus condition at both the T1 and T2 stages, and 12 QTLs were found to be consistent with these genetic loci in the RIL population. More importantly, 14 candidate genes, including MYB transcription factor, purple acid phosphatase, sugar transporter and HSP20-like chaperones superfamily genes, etc., showed differential expression levels after low phosphorus treatment, and three of them were further verified by qRT-PCR. Thus, these genetic loci and candidate genes could be applied in marker-assisted selection or map-based gene cloning for the genetic improvement of soybean phosphorus utilization.

Screening maize (Zea mays L.) genotypes for phosphorus deficiency at the seedling stage

A study was conducted at Bangladesh Agricultural Research Institute's greenhouse with 48 maize genotypes through hydroponic culture. Two levels of treatment, namely, low phosphorus (LP) (2.5 × 10-6 mol L-1 of KH2PO4) and normal phosphorus (NP) (2.5 × 10-4 mol L-1 of KH2PO4), were used for this study. Morphologically, plants behave differently in low phosphorus conditions than in normal phosphorus environments. Large augmented roots were found in the plant in low phosphorus conditions. The results revealed that chlorophyll contents, shoot length, root length shoot dry weight, root dry weight, leaf area, and root/shoot ratio might be considered critical traits for screening low phosphorus tolerant maize at the seedling stage. The first four principal components (PCs) described 89% of the total variation. Forty-eight maize genotypes formed four main groups or clusters. Among these four cluster groups, except for the SPAD value, the highest number of the mean values for root length, shoot length, root/shoot ratio, root volume, leaf area, root dry weight, shoot dry weight, and total dry weight were obtained from cluster group three. By constructing a genotype × trait biplot with nine traits recorded in 48 genotypes, the highest positive relationship was recorded in total dry weight (TDW) with root dry weight (RDW), shoot dry weight (SDW), and root volume (RV). The results revealed that the SPAD value was weakly correlated with other traits. In the current study, the studied characters were highly heritable. Based on the performance, G10, G18, G23, G27, G29, G33, and G34 could be considered low phosphorus tolerant genotypes. The results of combining abilities revealed that the genotypes G9, G13, G29, G31, and G39 could be used as parents in breeding activities. The present study offers guidelines for plant breeders to develop low phosphorus tolerant maize cultivars for the sustainability of maize production in the modern era of the changing climate.

Availability of Residual and/or Applied Inorganic Phosphorus for Sugarcane Uptake and Growth in a Post-Mined Reconstituted Soil

Mineral sands mining is worldwide an environmental issue and also at the Hillendale mine in KwaZulu-Natal, South Africa. The post-mined soil is to be rehabilitated to sugarcane cropping. One of the concerns with the post-mined soil which is reconstituted with a 70:30 mixture of sand: slimes (silt-plus-clay fraction), is its low phosphorus (P) status, which could be limiting for optimum sugarcane production. A field experiment was conducted on a reconstituted soil at Hillendale to establish the availability of either residual or applied inorganic P to the plant and first ratoon sugarcane crop. Four treatments were evaluated including those where P fertilizer was omitted, applied at half the recommended rate or introduced equal to the recommended rate according to chemical analysis of the soil. In the fourth treatment, no fertilizer was applied at all, whereas nitrogen (N) and potassium (K) were added at recommended rates in the first three treatments. Phosphorus application had a significant effect on sugarcane fractional light interception and aboveground biomass yield of the plant and first ratoon crops, and stalk length and diameter of the first ratoon crop. Pol, brix, purity and fibre content and tiller number were not affected by P application. The application of P increased the foliar N, P, K, calcium (Ca), magnesium (Mg) and sulphur (S) contents of both crops. However, foliar N, P and K were deficient in the first ratoon crop even in the case where fertilizer was applied at the recommended rates, which could have been because of waterlogging. The possible effect of waterlogging on P uptake needs to be addressed in future studies in this reconstituted soil.

Effects of maize and soybean intercropping on nodule growth, nitrogen fixation of soybean under low phosphorus condition

Effects of maize and soybean intercropping on nodule growth, nitrogen fixation of soybean under low phosphorus condition

Phosphorus availability increases pathobiome abundance and invasion of rhizosphere microbial networks by Ralstonia.

Soil disease-suppressiveness depends on complex interactions among pathogens, native microbiota, and physicochemical properties, while these interactions remain understudied. Comparing field and microcosm experiments, we investigated the significance of these interactions in disease emergence or suppression using structural equation modelling (SEM) and receiver operating characteristic curve (ROC) analyses. We observed significant differences in the relative abundance of pathogenic and beneficial microbes, alpha and beta diversity indices between disease-conducive and -suppressive rhizosphere soils. The pathogenic (Ralstonia) and beneficial (Bacillus) taxa dominated disease-conducive and -suppressive rhizosphere soils, respectively. Moreover, the co-occurrences of Ralstonia with native microorganisms were positive and negative in the disease-conducive and -suppressive soils, respectively. These results suggest the supportive (Rudaea) and suppressive (Enterobacter, Bacillus) role of indigenous microbes in the invasion of soil and plant systems by Ralstonia. The SEM and ROC analysis predicted that Ralstonia invaded rhizospheric microbial networks and caused peanut wilt under high than low soil phosphorus conditions. Our results suggest the importance of soil phosphorus availability in altering the microbial interactions, thus leading to soil invasion by Ralstonia. Thus, we conclude by saying that feeding soil with high amounts of available phosphorus could deplete plant-beneficial microbes and increase the pathobiome abundance that may compromise plant health.

Rice G protein γ subunit qPE9-1 modulates root elongation for phosphorus uptake by involving 14-3-3 protein OsGF14b and plasma membrane H+ -ATPase.

Heterotrimeric G protein is involved in plant growth and development, while the role of rice (Oryza sativa) G protein γ subunit qPE9-1 in response to low-phosphorus (LP) conditions remains unclear. The gene expression of qPE9-1 was significantly induced in rice roots under LP conditions. Rice varieties carrying the qPE9-1 allele showed a stronger primary root response to LP than the varieties carrying the qpe9-1 allele (mutant of the qPE9-1 allele). Transgenic rice plants with the qPE9-1 allele had longer primary roots and higher P concentrations than those with the qpe9-1 allele under LP conditions. The plasma membrane (PM) H+ -ATPase was important for the qPE9-1-mediated response to LP. Furthermore, OsGF14b, a 14-3-3 protein that acts as a key component in activating PM H+ -ATPase for root elongation, is also involved in the qPE9-1 mediation. Moreover, the overexpression of OsGF14b in WYJ8 (carrying the qpe9-1 allele) partially increased primary root length under LP conditions. Experiments using R18 peptide (a 14-3-3 protein inhibitor) showed that qPE9-1 is important for primary root elongation and H+ efflux under LP conditions by involving the 14-3-3 protein. In addition, rhizosheath weight, total P content, and the rhizosheath soil Olsen-P concentration of qPE9-1 lines were higher than those of qpe9-1 lines under soil drying and LP conditions. These results suggest that the G protein γ subunit qPE9-1 in rice plants modulates root elongation for phosphorus uptake by involving the 14-3-3 protein OsGF14b and PM H+ -ATPase, which is required for rice P use.

Cloning and expression pattern of phosphate transporter 1;1 cDNA sequence from Spirodela polyrrhiza

Spirodela polyrrhiza is a floating plant widely used in biomass utilization and eutrophication phytoremediation. It becomes a common aquatic plant everywhere with the increasingly serious eutrophication. It has been reported that S. polyrrhiza has a good effect on the remediation of eutrophication water. In order to study the absorption and transportation of phosphorus in S. polyrrhiza, we extracted RNA from S. polyrrhiza and then reverse transcribed it into cDNA, which was used as a template to amplify a specific fragment. The full-length sequence of the open reading frame (ORF) was 1 620 bp, encoding 539 amino acids, named SpPHT1;1, and the accession number in GenBank was MN720003. Bioinformatical analysis showed that SpPHT1;1 had no intron. The protein it encoded was a stable, hydrophobic protein with 11 transmembrane domains. SpPHT1;1 structure was similar to that of major facilitator superfamily (MFS) superfamily members. The cluster analysis showed that SpPHT1;1 was closely related to ZMPHT2 in maize and SBPHT1-8 in sorghum. So, it might belong to plant PHT1 family. The expression of SpPHT1;1 in leaf was significantly more than that of root under normal phosphorus condition. Low phosphorus condition could promote gene expression, and the relative expression level of SpPHT1;1 arrived at the peak at 48 h both in root and leaf. High phosphorus condition could inhibit gene expression. These results indicated that SpPHT1;1 expression would be affected by external phosphorus concentration. The results of this study are helpful for further research on the function of phosphate transporter. It also can provide theoretical basis for further development and utilization of S. polyrrhiza.

Customizing the leaf tissue nutrient ranges for blue and pink hydrangeas

Pink, blue, and red hydrangea [(Hydrangea macrophylla subsp. Macrophylla var. macrophylla (Thunb.)] cultivars contain the anthocyanin pigment delphinidin-3-glucoside that color the sepal. Without aluminum (Al), the natural color of the pigment is pink or red depending on the cultivar. To produce blue sepals, plants are fertilized with Al2(SO4)3 (AS) under low phosphorus (P) conditions. To determine the effect of AS on nutrient tissue concentrations ‘Early Blue’, ‘Hor Tivoli’, ‘Jip’, and ‘Mathilda Gutges’ plants were treated with 0 (pink), 12, or 15 g (blue) of AS. Pre-bloom leaf tissue concentrations were analyzed with blue cultivars generally having higher concentrations of sulfur (S), iron (Fe), manganese (Mn), zinc (Zn), boron (B), copper (Cu), and Al, while the pink plants had higher nitrogen (N), P, calcium (Ca), and magnesium (Mg) concentrations. Concentrations of N, potassium (K), Mg, B and Cu were consistent with published sufficiency ranges regardless of color or cultivar, while S, Fe, Mn and Zn concentrations were below sufficiency in some pink cultivars. The P concentrations in both pink and blue cultivars and Ca in some blue cultivars were lower than the published sufficiency range. The difference in leaf tissue nutrient concentrations among cultivars and coloration, suggest that nutrient uptake in hydrangeas varies and that lab recommendations should be customized depending on cultivar and color production system.

Low nitrogen and phosphorus effects on wheat Fe, Zn, phytic acid and phenotypic traits

In sub-Saharan Africa, crops are often grown under low nitrogen (N) and low phosphorus (P) conditions, which may impact on the nutritional components of the grains. The aim of this study was to investigate the effect of low N and low P and a combination of the two on iron (Fe), zinc (Zn) and phytic acid content in two commercial South African spring wheat cultivars (PAN3497 and SST806). Phenotypic traits were also investigated. Although cultivar effects were not significant, treatment effects were highly significant for the phenotypic and nutritional traits. Low P stress increased Fe and Zn levels, whereas low N stress had the opposite effect. In addition, low P stress inhibited phytic acid accumulation the most, suggesting that under this treatment, Fe and Zn were more available because of less interaction with phytic acid. Compared to the low N treatment, the low P treatment led to lower reductions in the number of tillers, plant height, stem thickness, number of seeds, weight of seeds and dry weight for both cultivars. While low P had positive effects on the nutritional value of wheat, the combination of low N and P treatment had a negative impact on most of the measured characteristics. Low N conditions had more negative effects on all measured characteristics than low P conditions and was very detrimental to wheat nutritional value and yield.Significance:&#x0D; &#x0D; Results from this study emphasise the impact of fertilisation and the impact of insufficient nitrogen and phosphorus fertiliser on wheat productivity.&#x0D; Low nitrogen and phosphorus fertilisation impact grain microelement content and bioavailability which impact nutritional value.&#x0D;

Screening and identification of soybean varieties with high phosphorus efficiency at seedling stage

In order to simplify the workload and find a reliable method for screening soybeans with different phosphorus (P) efficiencies, 47 soybean varieties were screened from 90 varieties according to yield under normal phosphorus, and 10 indicators including root phenotype, phosphorus utilization efficiency at the seedling stage and yield were measured. Through single-index cluster analysis, the performance value and relative value of the above-mentioned indexes under low-phosphorus conditions were analyzed, and then, the combined indexes were analyzed by principal components method. The membership function method and the cluster analysis method was used to calculate and analyze the comprehensive score value. Three indexes of root P utilization efficiency (X1), relative value of root P utilization efficiency (X2), and root volume (X3) under low P at the seedling stage were selected as the most consistent with the yield screening results under low P condition, and the mathematical model of the comprehensive score value was obtained: D ​= ​1.218X1+ 0.320X2+ 0.007X3-0.664 (P ​= ​0.000, R2 ​= ​1.000). The comprehensive score can screen and identify the P efficiency of soybeans with fewer indexes in the early growth stages, which provides a more rapid and reliable mathematical model for screening and identifying a larger number of germplasm resources for P efficiency.

Effect of Aluminum on Phosphate Absorption in Saccharomyces cerevisiae and Nicotiana tabacum L.

Soil acidification has become an increasingly serious problem. In this study, the mechanism involved in aluminum toxicity and reduction of phosphorus absorption under acidic conditions was investigated using Saccharomyces cerevisiae as a model organism. The high-affinity phosphate transporter PHO84 was sensitive to aluminum under low-phosphorus conditions, and the addition of phosphate alleviated this sensitivity. The reduction of phosphate absorption induced by aluminum is dependent on PHO84. Moreover, the effect of aluminum on PHO84 is regulated by PHO4/PHO2; however, aluminum did not affect the pho84p transport mediated by Pho86p. Our results corroborate the finding that aluminum reduces phosphorus absorption and inhibits the growth of the plant in acidic media. Additionally, the high-affinity phosphate transporter NtPT1 in tobacco exhibits a similar role to PHO84 in yeast cells. Altogether, our results may provide basis for the engineering of aluminum-resistant microorganisms or plants and the treatment of acidic soil.

Unravelling the phosphorus use efficiency associated traits in mungbean (Vigna radiata L.) under low phosphorus condition

Phosphorus (P) deficiency is one of the serious problems affecting plant growth in mungbean in different parts of the world. The root, shoot and biomass related traits were investigated for identifying P-efficient genotypes in 54 mungbean genotypes under low-P (LP) and normal-P (NP) conditions. In this study, the membership function value of P use efficiency of studied traits was used as a compendious index for studying P use efficiency (PUE) in mungbean. Among the studied traits, mean values of total root volume, chlorophyll concentration, root dry weight (RDW) and root to shoot ratio increased &gt;25% under LP condition indicating that these traits are highly responsive to P deficiency. Correlation and stepwise regression analysis revealed that RDW explained most of the variation and could be used as a clear indicator of PUE. The five highly P-efficient genotypes namely, MH 805, M 42, PUSA 9531, EC 398885 and M 209 with high MFVP values may be used for PUE improvement in mungbean.

Genome-Wide Association Analysis for Phosphorus Use Efficiency Traits in Mungbean (Vigna radiata L. Wilczek) Using Genotyping by Sequencing Approach.

Mungbean (Vigna radiata L. Wilczek) is an annual grain legume crop affected by low availability of phosphorus. Phosphorus deficiency mainly affects the growth and development of plants along with changes in root morphology and increase in root-to-shoot ratio. Deciphering the genetic basis of phosphorus use efficiency (PUE) traits can benefit our understanding of mungbean tolerance to low-phosphorus condition. To address this issue, 144 diverse mungbean genotypes were evaluated for 12 PUE traits under hydroponics with optimum- and low-phosphorus levels. The broad sense heritability of traits ranged from 0.63 to 0.92 and 0.58 to 0.92 under optimum- and low-phosphorus conditions, respectively. This study, reports for the first time such a large number of genome wide Single nucleotide polymorphisms (SNPs) (76,160) in mungbean. Further, genome wide association study was conducted using 55,634 SNPs obtained by genotyping-by-sequencing method. The results indicated that total 136 SNPs shared by both GLM and MLM models were associated with tested PUE traits under different phosphorus regimes. We have identified SNPs with highest p value (–log10(p)) for some traits like, TLA and RDW with p value (–log10(p)) of more than 6.0 at LP/OP and OP condition. We have identified nine SNPs (three for TLA and six for RDW trait) which was found to be present in chromosomes 8, 4, and 7. One SNP present in Vradi07g06230 gene contains zinc finger CCCH domain. In total, 71 protein coding genes were identified, of which 13 genes were found to be putative candidate genes controlling PUE by regulating nutrient uptake and root architectural development pathways in mungbean. Moreover, we identified three potential candidate genes VRADI11G08340, VRADI01G05520, and VRADI04G10750 with missense SNPs in coding sequence region, which results in significant variation in protein structure at tertiary level. The identified SNPs and candidate genes provide the essential information for genetic studies and marker-assisted breeding program for improving low-phosphorus tolerance in mungbean.

Heavy grazing disrupts positive effects of arbuscular mycorrhizae symbiosis on community productivity and stability under low and high phosphorus conditions

We quantified the potential influence of arbuscular mycorrhizal fungi (AMF) on primary productivity and community stability and tested whether the effects of AMF depend on soil phosphorus (P) availability and grazing intensity in a semiarid grassland. We manipulated the abundance of AMF and soil P availability (P addition and no P addition) under four levels of grazing intensity. The aboveground biomass of plant species, functional groups and community, as well as community temporal stability were examined under these conditions. Under no to moderate grazing, benomyl decreased the aboveground biomass in C4 grasses and forbs, but increased the aboveground biomass in C3 grasses under low P conditions; thus no obvious changes in community primary productivity were observed. These results indicated that the mycorrhizal dependency of C4 grasses and forbs is higher than that of C3 grasses under low P conditions. However, community primary productivity was greatly enhanced by benomyl due to the increased biomasses of C3 grasses and forbs under high P conditions. Under heavy grazing conditions, benomyl increased community primary productivity under both low and high P conditions. AMF presence increased the community temporal stability by promoting the compensatory effects between plant species under no to moderate grazing conditions; whereas AMF decreased the community stability by forming a parasitic symbiosis with their plant hosts under heavy grazing conditions. Our findings demonstrate that the effects of benomyl application to suppress AMF on primary productivity and community stability are strongly mediated by soil P availability and grazing intensity, which improves our understanding for the roles of AMF-plant symbiosis on ecosystem functioning in grazed systems.

Lower nodule biomass with increased nitrogenase efficiency in Robinia pseudoacacia seedlings when grown under low soil phosphorus conditions

Symbiotic nitrogen (N) fixation is the largest non-anthropogenic N input to many terrestrial ecosystems. The energetic expense of symbiotic N fixation suggests soil phosphorus (P) availability may regulate symbiotic nitrogen fixation directly through nodule development and function, and/or indirectly through plant growth. Since P availability is heterogenous in the landscape, we sought to understand if symbiotic nitrogen fixation responds to both P availability and heterogeneity. To test how P availability affects symbiotic nitrogen fixation, we grew Robinia pseudoacacia seedlings under high (8.1 g P m−2) and low (0.2 g P m−2) conditions. Soil P heterogeneity was simulated by splitting roots into soil patches receiving P or no-P fertilizer. At the whole plant level, P availability limited seedling and nodule biomass. However, the low P treatment had higher nitrogenase efficiency (acetylene reduced (AR) g−1 nodule; a nodule efficiency proxy). High P seedlings had significantly more root and nodule biomass in the patches directly receiving P fertilizer, but patch proliferation was absent in the low P treatment. AR g−1 seedling did not differ between P treatments, suggesting P indirectly limited symbiotic nitrogen fixation through plant growth, rather than directly limiting symbiotic nitrogen fixation. This relatively consistent AR g−1 seedling across treatments demonstrates the ability of seedlings to respond to low P conditions with increased nitrogenase efficiency.

Changes in the mycorrhizal fungal community in host roots over five host generations under low and high phosphorus conditions

We tested whether arbuscular mycorrhizal fungal (AMF) community might shift as host plant generations advance under a low phosphorus (P) soil. Two greenhouse experiments were conducted using Medicago truncatula as the host plant, six AMF species, and two soil P levels. Experiment 1 assessed changes in AMF composition in roots and soil during five generations of host plant grown in low-P (5.7 mg kg−1) and high-P soil (24.0 mg kg−1). Experiment 2 tested the effects of single AMF species on host plant growth in low-P and high-P soil. Experiment 1 showed that AMF species composition at the OTU level in roots and soil significantly changed as host generations advanced, and that the pattern of change differed in low-P vs. high-P soil. In low-P soil, the dominant OTU in both roots and soil shifted from OTU-50 (Glomus tortuosum) to OTU-49 (Funneliformis geosporum) as host generations advanced. In high-P soil, the AMF community in roots and soil was dominated by OTU-50 in first two generations but OTU-49 and OTU-50 were co-dominant in the last three generations. Experiment 2 showed that mycorrhizal dependency indices based on plant biomass and P content in plant biomass, and spore numbers were higher in host plants with F. geosporum than other AMF fungal treatments in low-P soil. As the host M. truncatula grew in a low-P soil over five generations, AMF community in root and soil shifted to a composition with F. geosporum as dominant species who was effective in foraging for P.

Mechanism of Low Phosphorus Inducing the Main Root Lengthening of Rice

Root lengthening is regarded as a strategy for rice to adapt to the low phosphorus level. Namely, by increasing the length and surface area of root, rice has an opportunity to enhance its phosphorus adsorption efficiency under low phosphorus conditions. The relationship between main root lengthening of rice seedlings under low phosphorus conditions with the endogenous hormone contents and expression of expansin genes were examined by using methods of the hormone content determination and transcriptome sequencing. The experimental results suggested that after low phosphorus treatment for 15 days, the main root length of Tongjing981 (TJ981) and Zhendao99 (ZD99) was considerably longer than that of the control. However, the main root length of Zhenghan6 (ZH6) was shorter compared to the control. It reveals that the main root length of different rice varieties had different response modes to low phosphorus treatment. After low phosphorus treatment, the IAA content of TJ981 and ZD99 had dramatically increased IAA contents compared to the control, while the IAA content in the root system of ZH6 evidently decreased compared to the control. This finding indicates that the response mode of the IAA content in the roots of three rice varieties for the test to low phosphorus treatment was consistent with that of the main root length. Meanwhile, low-concentrated (5 mg L−1) exogenous IAA markedly elongated the main root of TJ981. Consequently, a higher IAA content in rice roots than that of the control may result in lengthening the rice main root induced by low phosphorus treatment. Low phosphorus treatment induced the expression of multiple expansin genes in TJ981 and ZD99 roots; meanwhile, exogenous IAA treatment at various doses also promoted the expression of expansin genes. Hence, the expression of expansin genes in rice roots induced by low phosphorus treatment was related to the increased IAA content caused by low phosphorus stress. Moreover, low phosphorus treatment promoted the length of cells in the elongation zone of TJ981 compared with the control.

Genetic variation for root architectural traits in response to phosphorus deficiency in mungbean at the seedling stage.

Roots enable the plant to survive in the natural environment by providing anchorage and acquisition of water and nutrients. In this study, root architectural traits of 153 mungbean genotypes were compared under optimum and low phosphorus (P) conditions. Significant variations and medium to high heritability were observed for the root traits. Total root length was positively and significantly correlated with total root surface area, total root volume, total root tips and root forks under both optimum P (r = 0.95, r = 0.85, r = 0.68 and r = 0.82 respectively) and low P (r = 0.95, r = 0.82, r = 0.71 and r = 0.81 respectively). The magnitudes of the coefficient of variations were relatively higher for root forks, total root tips and total root volume. Total root length, total root surface area and total root volume were major contributors of variation and can be utilized for screening of P efficiency at the seedling stage. Released Indian mungbean varieties were found to be superior for root traits than other genotypic groups. Based on comprehensive P efficiency measurement, IPM-288, TM 96–25, TM 96–2, M 1477, PUSA 1342 were found to be the best highly efficient genotypes, whereas M 1131, PS-16, Pusa Vishal, M 831, IC 325828 were highly inefficient. Highly efficient genotypes identified would be valuable genetic resources for P efficiency for utilizing in the mungbean breeding programme.