A simple screening procedure for selecting fungi with potential for use in the bioremediation of contaminated land

A simple initial screening procedure for selecting strains of white-rot fungi with potential for use in bioremediation of contaminated sites is described. Besides the ability to degrade low molecular weight PAHs, isolates were screened for their growth rate on straw-based agar media, their potential to tolerate high concentrations of phenanthrene and their ability to out-grow the cellulolytic fungus Trichoderma harzianum on straw agar plates. Results from simple in vitro tests were correlated with the ability of the different strains to degrade PAHs in sand microcosms. It was found that fungal growth rate on straw-based agar media in the presence of phenanthrene correlated well with the ability of the different fungi to degrade PAHs in sand microcosms. Whereas growth rate on straw-based agar plates per se was indicative of the ability of white-rot fungi to establish in the presence of a competing fungus, it was a poor indicator of the fungus’ ability to degrade PAHs.     

Genetic Basis of Variations in Nitrogen Source Utilization in Four Wine Commercial Yeast Strains

The capacity of wine yeast to utilize the nitrogen available in grape must directly correlates with the fermentation and growth rates of all wine yeast fermentation stages and is, thus, of critical importance for wine production. Here we precisely quantified the ability of low complexity nitrogen compounds to support fast, efficient and rapidly initiated growth of four commercially important wine strains. Nitrogen substrate abundance in grape must failed to correlate with the rate or the efficiency of nitrogen source utilization, but well predicted lag phase length. Thus, human domestication of yeast for grape must growth has had, at the most, a marginal impact on wine yeast growth rates and efficiencies, but may have left a surprising imprint on the time required to adjust metabolism from non growth to growth. Wine yeast nitrogen source utilization deviated from that of the lab strain experimentation, but also varied between wine strains. Each wine yeast lineage harbored nitrogen source utilization defects that were private to that strain. By a massive hemizygote analysis, we traced the genetic basis of the most glaring of these defects, near inability of the PDM wine strain to utilize methionine, as consequence of mutations in its ARO8, ADE5,7 and VBA3 alleles. We also identified candidate causative mutations in these genes. The methionine defect of PDM is potentially very interesting as the strain can, in some circumstances, overproduce foul tasting H₂S, a trait which likely stems from insufficient methionine catabolization. The poor adaptation of wine yeast to the grape must nitrogen environment, and the presence of defects in each lineage, open up wine strain optimization through biotechnological endeavors.     

Technological properties of indigenous wine yeast strains isolated from wine production regions of Turkey

The purpose of this study was to evaluate the important technological and fermentative properties of wine yeast strains previously isolated from different wine producing regions of Turkey. The determination of the following important properties was made: growth at high temperatures; fermentative capability in the presence of high sugar concentration; fermentation rate; hydrogen sulfide production; killer activity; resistance to high ethanol and sulfur dioxide; foam production; and enzymatic profiles. Ten local wine yeast strains belonging to Saccharomyces, and one commercial active dry yeast as a reference strain were evaluated. Fermentation characteristics were evaluated in terms of kinetic parameters, including ethanol yield (Y_P/S), biomass yield (Y_X/S), theoretical ethanol yield (%), specific ethanol production rate (q_p; g/gh), specific glucose uptake rate (q_s; g/gh), and the substrate conversion (%). All tested strains were able to grow at 37 °C and to start fermentation at 30° Brix, and were resistant to high concentrations of sulfur dioxide. 60 % of the strains were weak H₂S producers, while the others produced high levels. Foam production was high, and no strains had killer activity. Six of the tested strains had the ability to grow and ferment at concentrations of 14 % ethanol. Except for one strain, all fermented most of the media sugars at a high rate, producing 11.0–12.4 % (v/v) ethanol. Although all but one strain had suitable characteristics for wine production, they possessed poor activities of glycosidase, esterase and proteinase enzymes of oenological interest. Nine of the ten local yeast strains were selected for their good oenological properties and their suitability as a wine starter culture.     

Dietary P regulates phosphate transporter expression,phosphatase activity,and effluent P partitioning in trout culture

Phosphate utilization by fish is an important issue because of its critical roles in fish growth and aquatic environmental pollution. High dietary phosphorus (P) levels typically decrease the efficiency of P utilization, thereby increasing the amount of P excreted as metabolic waste in effluents emanating from rainbow trout aquaculture. In mammals, vitamin D₃ is a known regulator of P utilization but in fish, its regulatory role is unclear. Moreover, the effects of dietary P and vitamin D₃ on expression of enzymatic and transport systems potentially involved in phosphate utilization are little known. We therefore monitored production of effluent P, levels of plasma vitamin D₃ metabolites, as well as expression of phosphatases and the sodium phosphate cotransporter (NaPi2) in trout fed semipu diets that varied in dietary P and vitamin D₃ levels. Mean soluble P concentrations varied markedly with dietary P but not with vitamin D₃, and constituted 40–70% of total effluent P production by trout. Particulate P concentrations accounted for 25–50% of effluent P production, but did not vary with dietary P or vitamin D₃. P in settleable wastes accounted for <10% of effluent P. The stronger effect of dietary P on effluent P levels is paralleled by its striking effects on phosphatases and NaPi2. The mRNA abundance of the intestinal and renal sodium phosphate transporters increased in fish fed low dietary P; vitamin D₃ had no effect. Low-P diets reduced plasma phosphate concentrations. Intracellular phytase activity increased but brushborder alkaline phosphatase activity decreased in the intestine, pyloric caeca, and gills of trout fed diets containing low dietary P. Vitamin D₃ had no effect on enzyme activities. Moreover, plasma concentrations of 25-hydroxyvitamin D₃ and of 1,25-dihydroxyvitamin D₃ were unaffected by dietary P and vitamin D₃ levels. The major regulator of P metabolism, and ultimately of levels of P in the effluent from trout culture, is dietary P.Communicated by: C.-H. Wang     

Nitrogen availability limits phosphorus uptake in an intertidal macroalga

Nutrients such as nitrogen (N) and phosphorus (P) limit primary productivity, and recent anthropogenic activities are changing the availability of these nutrients, leading to alterations in the type and magnitude of nutrient limitation. Recent work highlights the potential for N and P to interact to limit primary production in terrestrial and freshwater systems. However, mechanisms underlying co-limitation are not well described. Documentation of ambient nutrient levels and tissue nutrients of the intertidal macroalga Fucus vesiculosus for 2 years in the southern Gulf of Maine, USA, indicates that N availability may be impacting the ability of F. vesiculosus to access P, despite relatively high ambient P concentrations. To experimentally validate these observations, F. vesiculosus individuals were enriched with N or P for 6 weeks, followed by an uptake experiment to examine how the interactions between these nutrients affected macroalgal N and P uptake efficiency. Results illustrate that exposure of seaweed to different nutrient regimes influenced nutrient uptake efficiency. Notably, seaweeds enriched with N displayed the highest P uptake efficiency at low, biologically relevant, P concentrations. Our results confirm that N availability may be mediating the ability of primary producers to access P. These interactions between limiting nutrients have implications for not only the growth and functioning of primary producers who rely directly on these nutrients but also the entire communities that they support.     

Rhamnolipids are conserved biosurfactants molecules: implications for their biotechnological potential

A range of isolates of Pseudomonas aeruginosa from widely different environmental sources were examined for their ability to synthesise rhamnolipid biosurfactants. No significant differences in the quantity or composition of the rhamnolipid congeners could be produced by manipulating the growth conditions. Sequences for the rhamnolipid genes indicated low levels of strain variation, and the majority of polymorphisms did lead to amino acid sequence changes that had no evident phenotypic effect. Expression of the rhlB and rhlC rhamnosyltransferase genes showed a fixed sequential expression pattern during growth, and no significant up-regulation could be induced by varying producer strains or growth media. The results indicated that rhamnolipids are highly conserved molecules and that their gene expression has a rather stringent control. This leaves little opportunity to manipulate and greatly increase the yield of rhamnolipids from strains of P. aeruginosa for biotechnological applications.     

Glutathione Preservation during Storage of Rat Lenses in Optisol-GS and Castor Oil

Background

Glutathione concentration in the lens decreases in aging and cataractous lenses, providing a marker for tissue condition. Experimental procedures requiring unfrozen lenses from donor banks rely on transportation in storage medium, affecting lens homeostasis and alterations in glutathione levels. The aim of the study was to examine the effects of Optisol-GS and castor oil on lens condition, determined from their ability to maintain glutathione concentrations.

Methodology/Principal Findings

Rat lenses were stored in the two types of storage media at varying time intervals up to 3 days. Glutathione concentration was afterwards determined in an enzymatic detection assay, specific for both reduced and oxidized forms. Lenses removed immediately after death exhibited a glutathione concentration of 4.70±0.29 mM. In vitro stored lenses in Optisol-GS lost glutathione quickly, ending with a concentration of 0.60±0.34 mM after 3 days while castor oil stored lenses exhibited a slower decline and ended at 3 times the concentration. A group of lenses were additionally stored under post mortem conditions within the host for 6 hours before its removal. Total glutathione after 6 hours was similar to that of lenses removed immediately after death, but with altered GSH and GSSG concentrations. Subsequent storage of these lenses in media showed changes similar to those in the first series of experiments, albeit to a lesser degree.

Conclusions/Significance

It was determined that storage in Optisol-GS resulted in a higher loss of glutathione than lenses stored in castor oil. Storage for more than 12 hours reduced glutathione to half its original concentration, and was considered unusable after 24 hours.     

Influence of invertase activity and glycerol synthesis and retention on fermentation of media with a high sugar concentration by Saccharomyces cerevisiae.

In the past, the fermentation activity of Saccharomyces cerevisiae in substrates with a high concentration of sucrose (HSuc), such as sweet bread doughs, has been linked inversely to invertase activity of yeast strains. The present work defines the limits of the relationship between invertase activity and fermentation in hyperosmotic HSuc medium. Fourteen polyploid, wild-type strains of S. cerevisiae with different invertase levels gave a similar ranking of fermentation activity in HSuc and in medium in which glucose and fructose replaced sucrose (HGF medium). Thus, invertase is unlikely to be the most important determinant of fermentation in sweet doughs. Yeasts produce the compatible solute-osmoprotective compound glycerol when exposed to hyperosmotic environments. Under low sugar concentrations (and nonstressing osmotic pressure), there was no correlation between glycerol and fermentation activities. However, there was a strong correlation between the ability of yeasts to ferment in HSuc or HGF medium and their capacity to produce and retain glycerol intracellularly. There was also a strong correlation between intracellular glycerol and fermentation activity of yeasts in a medium in which the nonfermentable sugar alcohol sorbitol replaced most of the sugars (HSor), but the ability to produce and retain glycerol was greater when yeasts were incubated in HGF medium under the same osmotic pressure. The difference between the amounts of glycerol produced and retained in HSor and in HGF media varied with strains. This implies that high fermentable sugar concentrations cause physiological conditions that allow for enhanced glycerol production and retention, the degree of which is strain dependent. In conclusion, one important prerequisite for yeast strains to ferment media with high concentrations of sugar is the ability to synthesize glycerol and especially to retain it.     

Phosphorus absorption and utilization efficiency of pigeon pea (Cajanus cajan (L) Millsp.) in relation to dry matter production and dinitrogen fixation

The effect of P supply on absorption and utilization efficiency of P in relation to dry matter production and dinitrogen fixation was examined in 8 pigeon pea cultivars with different growth duration and a soybean cultivar under field conditions. In all the pigeon pea cultivars, the maximum whole plant dry weight was obtained in a P-deficient soil at 100 kg P ha⁻¹ application. The short duration cultivars had smaller whole plant dry weights at low P rates (5 and 25 kg P ha⁻¹) and poor response to P application compared with the medium and long duration cultivars. Increasing the P application rate significantly increased dinitrogen fixation in all the cultivars. At the low P rates, the total nodule activity (TNA) was lower in the short than in the medium and the long duration cultivars. However, at 200 kg P ha⁻¹ application, dinitrogen fixation did not vary among these cultivars except for one short duration cultivar whichregistered very low values. Dry matter production and dinitrogen fixation are strongly controlled by P absorption ability rather than P utilization efficiency. The low absorption ability of the short duration cultivars is mainly due to poor root development. The high P concentrations in the nodules of all the cultivars suggest that nodules have advantage over host plant interms of P distribution under P deficient conditions. Our results suggest that P plays an important role in dinitrogen fixation through an effective translocation of P to the leaf. Thus when P supply is limited, efficient cultivars obtained reasonably high yield through an effective translocation of the absorbed P to the leaf.     

Nutrient uptake and growth responses of three intertidal macroalgae with perennial, opportunistic and summer-annual strategies

An important life history trait of macroalgae species is the physiological ability to cope with nutrient limiting conditions, which seasonally occur in temperate coasts while other environmental factors are adequate (e.g., sufficient light). Nitrogen (N) and Phosphorus (P) uptake kinetics and field growth limitation were investigated in the perennial Bifucaria bifurcata, the opportunistic Ulva intestinalis, and the summer-annual Nemalion helminthoides from Asturian coasts (N Spain). We performed 4 nutrient uptake experiments (ammonium, nitrate, nitrate + ammonium, and phosphate) and monitored the growth and N content of field individuals in the presence/absence of artificial nutrient supply to assess potential growth limitations. B. bifurcata was not actively growing during summer thus low nutrient demands probably relied on stored pools and/or the low background nutrient levels in seawater, as generally observed for perennials. Corresponding N content and uptake rates in this species were the lowest. The opportunistic U. intestinalis showed kinetics suitable for assimilating N quickly at high external concentrations in order to fulfill the high nutrient demands that support its fast-growing strategy. This response is well adapted to seasons and sites of high nutrient loading but signs of nutrient starvation during summer (decreasing growth and N content) were found in the pristine studied area. N. helminthoides showed an intermediate response in terms of thallus N content and uptake affinity, together with an inducible activation of nitrate uptake. This response assured the uptake of transient nutrient pulses without the nutrient storage response of perennials, or the costly enzymatic machinery of opportunistics. This allows N. helminthoides to effectively exploit low background nutrient conditions interrupted by transient peaks during spring-summer, when most ephemerals found difficulties to survive and perennials suspend their active growth. P uptake did not differ greatly between species suggesting its secondary importance compared to N in the tested algae.     

Storage ofCandida albicans,C. tropicalis and related species in liquid nitrogen

Storage in liquid nitrogen of a collection ofC. albicans, C. tropicalis and related species checked by numerical and classical taxonomy is described. Strains stored for 3 years in liquid nitrogen were thawed and their survival was tested. After adaptation and regeneration, their fermentation and assimilation spectra, production of chlamydospores and pseudomycelia, appearance and radial growth rate of giant colonies were investigated and compared with the properties of cultures stored under paraffin oil. It follows from the results obtained that two different media —with an increased content of a nitrogen source and with an increased carbon source content —should be used for the post-heating adaptation and regeneration of yeast cells. In some strains it is useful to store them at 4 °C for additional time intervals in order to increase survival of the cells. The above strains can be successfully stored in liquid nitrogen.     

Use of bacterial acc deaminase to increase oil (especially poly aromatic hydrocarbons) phytoremediation efficiency for maize (zea mays) seedlings

Oil presence in soil, as a stressor, reduces phytoremediation efficiency through an increase in the plant stress ethylene. Bacterial 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase, as a plant stress ethylene reducer, was employed to increase oil phytoremediation efficiency. For this purpose, the ability of ACC deaminase-producing Pseudomonas strains to grow in oil-polluted culture media and withstand various concentrations of oil and also their ability to reduce plant stress ethylene and enhance some growth characteristics of maize and finally their effects on increasing phytoremediation efficiency of poly aromatic hydrocarbons (PAHs) in soil were investigated. Based on the results, of tested strains just P9 and P12 were able to perform oil degradation. Increasing oil concentration from 0 to 10% augmented these two strains population, 15.7% and 12.9%, respectively. The maximum increase in maize growth was observed in presence of P12 strain. Results of high-performance liquid chromatography (HPLC) revealed that PAHs phytoremediation efficiency was higher for inoculated seeds than uninoculated. The highest plant growth and PAHs removal percentage (74.9%) from oil-polluted soil was observed in maize inoculated with P12. These results indicate the significance of ACC deaminase producing bacteria in alleviation of plant stress ethylene in oil-polluted soils and increasing phytoremediation efficiency of such soils.     

Growth but Not Photosynthesis Response of a Host Plant to Infection by a Holoparasitic Plant Depends on Nitrogen Supply

Parasitic plants can adversely influence the growth of their hosts by removing resources and by affecting photosynthesis. Such negative effects depend on resource availability. However, at varied resource levels, to what extent the negative effects on growth are attributed to the effects on photosynthesis has not been well elucidated. Here, we examined the influence of nitrogen supply on the growth and photosynthesis responses of the host plant Mikania micrantha to infection by the holoparasite Cuscuta campestris by focusing on the interaction of nitrogen and infection. Mikania micrantha plants fertilized at 0.2, 1 and 5 mM nitrate were grown with and without C. campestris infection. We observed that the infection significantly reduced M. micrantha growth at each nitrate fertilization and more severely at low than at high nitrate. Such alleviation at high nitrate was largely attributed to a stronger influence of infection on root biomass at low than at high nitrate fertilization. However, although C. campestris altered allometry and inhibited host photosynthesis, the magnitude of the effects was independent of nitrate fertilizations. The infection reduced light saturation point, net photosynthesis at saturating irradiances, apparent quantum yield, CO₂ saturated rate of photosynthesis, carboxylation efficiency, the maximum carboxylation rate of Rubisco, and maximum light-saturated rate of electron transport_, and increased light compensation point in host leaves similarly across nitrate levels, corresponding to a similar magnitude of negative effects of the parasite on host leaf soluble protein and Rubisco concentrations, photosynthetic nitrogen use efficiency and stomatal conductance across nitrate concentrations. Thus, the more severe inhibition in host growth at low than at high nitrate supplies cannot be attributed to a greater parasite-induced reduction in host photosynthesis, but the result of a higher proportion of host resources transferred to the parasite at low than at high nitrate levels.     

Growth of Pseudomonas aeruginosa mutants lacking glutamate synthase activity.

Mutant strains SU1, SU4, and US1 lacking glutamate synthase (GOGAT) activity were isolated from strains of P. aeruginosa for which histidine is a growth rate-limiting source of nitrogen. Strains SU1 and SU4 were unable to grow when a low concentration of ammonia and a variety of compounds, including histidine, were supplied as sole sources of nitrogen. A revertant of strain SU1, strain 39, produced no GOGAT but high levels of nicotinamide adenine dinucleotide-dependent glutamate dehydrogenase and had restored ability to grow on a limited number of nitrogen sources. Strain US1 grew at the same rate in histidine medium as did its parent; it was derepressed for glutamine synthase synthesis, and histidase was less sensitive to repression by ammonia than in the parent strain. We conclude that GOGAT is not essential for growth on histidine but high levels of glutamine synthase are required nd high levels of nicotinamide adenine dinucleotide-dependent glutamate dehydrogenase can sustain growth at low concentrations of ammonia in the absence of GOGAT.     

Comparison of Several Selective Media for Isolation and Differentiation of Coagulase-Positive Strains of Staphylococcus aureus

Six coagulase-positive strains of Staphylococcus aureus which had been cultivated in Brain Heart Infusion broth, milk, and brine were plated on seven isolation media. A significant difference in the growth patterns of the individual strains was found as well as a significant effect resulting from the previous cultivation history before plating. Brine and, to a lesser extent, milk were found to reduce maximal cell concentrations attained, but strains grown in brine and milk showed greater ability to withstand the selective action of the isolation media. Fibrinogen applied to the surface of five of the media allowed the formation of characteristic halos by coagulase-positive strains of S. aureus. Only half of the strains studied produced a zone of precipitation on SM110-Egg Yolk agar. The isolation medium containing cycloheximide and a high level of polymxin B was most inhibitory to the organisms.     

Influence of Calcium, Iron, and pH on Phosphate Availability for Microbial Mineralization of Organic Chemicals

A study was conducted to determine some of the factors affecting the P requirement for the biodegradation of p-nitrophenol, phenol, and glucose by Pseudomonas and Corynebacterium strains. Mineralization of glucose was rapid and the Pseudomonas sp. grew extensively in solutions with 5 and 10 mM phosphate, but the rate and extent of degradation were low and the bacterial population never became abundant in media with 0.2 mM phosphate. Similar results were obtained with the Corynebacterium sp. growing in media containing p-nitrophenol or phenol and in solutions with a purified phosphate salt. The extent of growth of the Corynebacterium sp. was reduced with 2 or 10 mM phosphate in media containing high Fe concentrations. Ca at 5 mM but not 0.5 mM inhibited p-nitrophenol mineralization by the Corynebacterium sp. with phosphate concentrations from 0.2 to 5.0 mM. Phenol mineralization by the Pseudomonas sp. in medium with 0.2 mM phosphate was rapid at pH 5.2, but the bacteria had little or no activity at pH 8.0. In contrast, the activity was greater at pH 8.0 than at pH 5.2 when the culture contained 10 mM phosphate. These effects of pH were similar in media with 5 mM Ca or no added Ca. We conclude that the effect of P on bacterial degradation can be influenced by the pH and the concentrations of Fe and Ca.     

Effect of in situ storage,light, and moisture on the germination of two wetland tropical trees

Seed germination was evaluated for Annona glabra L. and Pachira aquatica Aubl. in the wetland conditions of La Mancha, Veracruz, Mexico. These species have recalcitrant seeds and hydrochoral dispersal. Germination experiments were carried out under varying moisture (high, middle, and low) and light (below canopy and open sky) levels as well as after being stored in contrasting natural conditions. Seeds were stored both floating in water and buried in wetland soil for 15, 30, 60, and 90 days. P. aquatica seeds germinated faster in low and medium moisture, regardless of light intensity. After 45 days, for example, they exhibited 87–73% germination in medium-moisture/canopy and low-moisture/canopy treatments, respectively. In high moisture, seeds reached similar percentages after 60 days (80%). Storage by burial caused the death of seeds regardless the time they spent underground, while those stored in water germinated at a rate of over 90%. A. glabra seeds germinated better (98%) in low-moisture/sunny conditions. As to storage, they responded favorably to both burial and water techniques but germinated more readily in treatments that involved a long storage period. Evaluation of the germination behavior of A. glabra and P. aquatica seeds subject to varying in situ storage and germination conditions illustrates the response capacity of each species during early phases of development.     

Brevibacillus as a biological tool: a short review

The significance of Brevibacillus has been documented scientifically in the published literature and commercially in heterologous recombinant protein catalogs. Brevibacillus is one of the most widespread genera of Gram-positive bacteria, recorded from the diverse environmental habitats. The high growth rate, better transformation efficiency by electroporation, availability of shuttle vectors, production of negligible amount of extracellular protease, and the constitutive expression of heterologous proteins make some strains of this genus excellent laboratory models. Regarding biotechnological applications, this genus continues to be a source of various enzymes of great biotechnological interest due to their ability to biodegrade low density polyethylene, ability to act as a candidate bio-control agent, and more recently acknowledged as a tool for the overexpression. This article reviews the properties of Brevibacillus spp. as better biological tools with varied applications.     

Effect ofin vitro storage at 4°C on survival and proliferation of two apple rootstocks

One cm long shoot explants of dwarf apple rootstocks P 2 and M.9 taken from 2 year-old cultures were stored at 4°C in the dark in three media differing in concentration of growth regulators. Every 6 weeks, some explants were transferred into proliferation medium and multiplication rate was observed during three or four consecutive passages. In a second experiment, the influence of explant type (1 cm long shoot tips, 1 cm long middle part of shoots or three-shoot tufts smaller than 1 cm) and transfer time to the cold room (immediately, 10 days, or 20 days after subculture) on explant survival and proliferation were analysed.Survival of explants was influenced by composition of the storage media. On medium without 6-benzylaminopurine, 70% of P 2 and 17% of M.9 explants became necrotic during 18 weeks of storage. P 2 rootstock proliferated better in three passages after storage than did unstored controls. Storage of M.9 rootstock reduced proliferation in the first and second passages if stored in media containing 6-benzylaminopurine in comparison with unstored controls. Explants stored as tufts and transferred to the cold room directly after subculture produced more shoots during two passages than cultures stored as single shoots.     

耐低磷水稻基因型筛选指标的研究

采用溶液培养试验,并结合大田试验,研究和探讨了耐低磷水稻基因型的筛选指标.结果表明,溶液培养试验中,在正常供磷和低磷胁迫条件下,在所有调查性状中水稻单株干重都具有较大的基因型间变异(CV分别为21.73%和19.54%).在所有调查性状的相对值中,相对单株干重(低磷胁迫/正常供磷)也具有较大的基因型间变异(CV为19.60%);相关分析表明,相对单株干重与相对根干重、相对株高、相对单株吸磷量、相对地上部磷积累、相对磷利用效率和相对植株磷浓度均呈极显著正相关(P＜0.01).因此,水稻相对单株干重可以作为苗期筛选水稻耐低磷基因型的一个筛选指标.溶液培养试验中水稻的相对单株干重和大田试验中水稻的相对稻谷产量(不施磷/施磷)没有显著相关性,因此溶液培养试验的相对单株干重不能作为评价大田试验中水稻耐低磷能力的指标.低磷营养液培养的水稻体内磷利用效率与缺磷土壤生长的水稻体内磷利用效率呈极显著正相关.因此,直接以低磷营养液培养水稻苗期体内磷利用效率作为筛选指标,然后进行大田试验验证,是一条筛选水稻磷高效利用基因型的有效途径.