Root-released organic acids and phosphorus uptake of two barley cultivars in laboratory and field experiments

A major portion of phosphorus (P) applied as fertilizers is bound in soils as P compounds of variable adsorption strength, reducing the effectiveness of P fertilization. Plant genotypes equipped with mechanisms for utilizing the adsorbed P more efficiently can, therefore, enhance the effectiveness of P fertilization. Such genotypes will also enrich plant gene pools for further analysis and upgrading of P efficiency by selection and breeding. We studied the variation and the mechanisms of P uptake of two winter barley (Hordeum vulgare L.) cultivars Marinka and Sonate (parents of existing 200 haploid progeny lines), by laboratory and field experiments. After cultivation in nutrient solution for 21 days, Marinka produced more roots than Sonate, but similar amounts of dry shoots of lower P content (Marinka 3.4±0.4 mg g⁻¹, Sonate 4.9±0.6 mg g⁻¹). The total P uptake per plant did not differ between the cultivars. Marinka retained more P in roots as indicated by the higher concentration of P in the roots (Marinka 3.9±0.3 mg g⁻¹ and Sonate 3.0±0.4 mg g⁻¹). In sterile nutrient solution culture, the cultivars differed mainly in release of organic acids from the roots, with Marinka releasing three times more citric acid and nearly two times more acetic acid than Sonate. The cultivars had similar root hair lengths and they did not differ (P>0.05) in depletion of available soil P fraction (extracted with 0.5 M NaHCO₃) in the rhizosphere. Marinka absorbed nearly twice as much P from the strongly adsorbed soil P fraction (extracted with 0.1M NaOH). Also under field conditions, Marinka absorbed more P and produced more shoot dry matter. The higher P uptake by Marinka than Sonate can be attributed to its ability to acquire P from strongly adsorbed soil P by releasing more organic acids, especially citric acid, from its roots.     

土壤深松下磷肥施用深度对夏玉米根系分布及磷素吸收利用效率的影响

采用大田试验与土柱试验相结合的方式,设置距离地表-5 cm (P5)、-10 cm (P10)、-15 cm (P15)和-20 cm(P20)施用磷肥处理,以不施磷肥为对照(CK),研究磷肥施用深度对夏玉米根系分布、干物质积累与产量形成及磷肥吸收和利用效率的影响。结果表明,磷肥施用深度显著影响夏玉米根系干重及根长,表现为P15P10P20P5CK。与常规磷肥施用深度(P5)处理相比,P15处理玉米籽粒产量两年平均提高23.1%,根干重及总根长两年平均提高13.1%、22.9%; P15、P20处理均增加了-20 cm以下土层的根干重比例及根长比例,土柱试验分别达到35.4%和36.4%、58.7%和59.3%,大田试验根干重两年均达到19.0%,根长比重分别达到39.8%和39.9%。根系分布的优化促进了植株磷素积累与转运, P10、P15、P20处理较P5处理磷积累量2年平均提高10.6%、25.2%和14.7%,磷转运量平均提高46.9%、76.6%和57.6%,籽粒产量相应增加12.9%、23.1%和10.6%。P15比P5处理的磷肥偏生产力、农学利用效率和表观利用效率两年平均值分别提高19.1 kg kg~(–1)、19.1 kg kg~(–1)和25.2%。磷肥深施能够增加深层土壤根系的分布比例,提高植株对磷肥的吸收、利用效率,显著提高夏玉米产量,在本试验条件下以磷肥集中施用在-15 cm处效果最好。     

磷肥做种肥条施对棉花根系活力及产量的影响

为了提高磷肥利用率和棉花产量,在田间试验条件下研究了两种施磷方式对棉花根系活力和产量的影响。结果表明：在相同施磷量条件下,磷肥条施与传统施肥方式相比较棉花根系活力增加1.7倍,籽棉产量增加14.5%,磷肥农学利用率增加38.0%,磷肥偏生产力增加14.5%。通过试验研究得出磷肥条施不仅可以增加棉花根系活力和产量,而且还可以提高磷肥利用率。     

磷肥用量对甜玉米磷素吸收利用的影响

明确磷素吸收利用特性,是磷素高效利用及作物高产的基础。本研究通过2年田间磷肥梯度定位试验,研究不同磷肥供应(0、37.5、75、150和300kghm^–2,分别用P0、P1、P2、P3和P4表示)对甜玉米产量、不同器官生物量和磷素累积与分配、磷素转运特征和磷肥利用效率的影响。结果表明,磷肥供应均显著提高2018年和2019年甜玉米的鲜穗产量,但不同磷肥供应处理(P1~P4)之间的产量差异不显著,磷肥供应显著提高甜玉米拔节期、吐丝期和鲜食期植株的生物量及磷素累积量,其中籽粒磷素累积量约占植株磷素累积量的42%。磷肥供应下花后磷同化对甜玉米穗部磷素累积量的贡献率达到57.3%~93.0%;而1kg磷素生产鲜穗量、磷素生理效率、农学效率、回收利用率和偏生产力均随着磷肥供应量增加而明显下降。综合考虑产量与磷肥利用效率,在本试验条件下,37.5 kg hm^–2磷肥供应可满足甜玉米高产和磷肥高效利用的需求。     

Molecular mapping of genes involved in root hair formation in barley

In the presented study, the existing AFLP and SSR maps of barley were used to find chromosomal position of four genes controlling different stages of root hair development. Four barley mutants were used in the analysis: the root hairless mutant rhl1.b, mutant rhp1.b with root hair development blocked at the initial bulge formation, mutant rhi1.a with irregular pattern of sparsely located root hairs and mutant rhs1.a with very short root hairs. Each mutant was crossed with parents of ‘Steptoe’/‘Morex’ mapping population and F₂ progenies of crosses: mutant × ‘Steptoe’ and mutant × ‘Morex’ were analyzed for segregation of root hair phenotype and polymorphic AFLP and SSR markers. It was possible to map all the analyzed genes on barley chromosomes: rhl1 gene on the short arm of chromosome 7H, rhp1 gene on chromosome 1H, rhs1 locus in the pericentromeric region of chromosome 5H and rhi1 gene on the long arm of chromosome 6H. Subsequently, the Bulk Segregant Analysis and AFLP technique were used for saturation of the identified regions with new markers. The joint maps were constructed using as common points the SSR markers located in the target regions. Linkage maps of the regions around the four genes involved in the root hair formation in barley were composed of 8–11 markers and spanned over 16.1–49.0 cM. The distances between localized genes and the closest markers ranged from 1.0 to 3.8 cM. The identified chromosomal locations of genes can be used for their fine mapping and future map-based cloning.     

磷肥用量对甜玉米磷素吸收利用的影响

Understanding the phosphorus (P) absorption mechanism is the premise for high P utilization and high crop yield. In this study, the effects of different P rates (0, 37.5, 75, 150, and 300 kg hm^-2, expressed as P0, P1, P2, P3, and P4, respectively) on sweet corn yield, biomass and P accumulation and tissue distribution, P transportation and P utilization were studied using a two-year P gradient positioning field experiment. Our results showed that P application significantly increased the fresh ear yield of sweet corn, but the yield difference among different P application rates (P1-P4) was not significant from 2018 to 2019 compared with P0 treatment. P application significantly increased the biomass and P accumulation of sweet corn plants at jointing, silking and fresh eating stages, respectively. In addition, P accumulation in grain was not significant different, which accounting for 42% of plant P accumulation. With P application, the contribution rate of P assimilation to the ear P accumulation was 57.3%-93.0% after anthesis, while the fresh ear yield per P accumulation, P physiological efficiency, agronomic efficiency, recovery efficiency and partial productivity decreased with P rates. Considering the yield and utilization efficiency of phosphate fertilizer, the supply of 37.5 kg hm^-2 of phosphate fertilizer can meet the needs of high yield and efficient utilization of phosphate fertilizer in sweet corn in this experiment.     

Inheritance of root traits and phosphorus uptake in common bean (Phaseolus vulgaris L.) under limited soil phosphorus supply

Heterosis is an important way to improve yield and quality for many crops. Hybrid rice and hybrid maize contributed to enhanced productivity which is essential to supply enough food for the increasing world population. The success of hybrid rice in China has led to a continuous interest in hybrid wheat, even when most research on hybrid wheat has been discontinued in other countries for various reasons including low heterosis and high seed production costs. The Timopheevii cytoplasmic male sterile system is ideal for producing hybrid wheat seeds when fertility restoration lines with strong fertility restoration ability are available. To develop PCR-based molecular markers for use in marker-assisted selection of fertility restorer lines, two F₂ populations derived from crosses R18/ND36 and R9034/ND36 were used to map fertility restoration genes in the two elite fertility restorer lines (R-lines) R18 and R9034. Over 678 SSR markers were analyzed, and markers closely linked to fertility restoration genes were identified. Using SSR markers, a major fertility restoration gene, Rf3, was located on the 1B chromosome in both populations. This gene was partially dominant in conferring fertility restoration in the two restorer lines. SSR markers Xbarc207, Xgwm131, and Xbarc61 are close to this gene. These markers may be useful in marker-assisted selection of new restorer lines with T. timopheevii cytoplasm. Two minor QTL conferring fertility restoration were also identified on chromosomes 5A (in R18) and 7D (in R9034) in two R-lines.     

Genetic variation in specific root length in Scandinavian wheat and barley accessions

Specific root length (SRL, m root g^–1 root dry matter) was studied in a broad selection of old and current accessions of spring wheat and barley from Norway and Sweden, at sub-optimal phosphorus conditions in nutrient solution and soil. The results indicated that genotype did not have a significant effect on SRL. A close relationship between root length (RL) and root weight (RW) was found, and more than 70% of the variation in root length was explained by root weight of representative and homogenous root samples. In nutrient solution, the relationship between RL and RW was described by the regression equations RL = 0.32 RW—0.19 (R ²= 0.74) for wheat and RL = 0.20RW + 0.73 (R ²= 0.56) for barley. In the soil experiment, the relationships between RL and RW were described by the equations RL = 0.15RW + 0.95 (R ²= 0.67) for barley and RL = 0.16 RW + 0.50 (R ²= 0.77) for wheat. Hence, in screenings of a large number of cereal genotypes, the root length may be estimated with good accuracy by records of root weight and an appropriate regression equation.     

不同连作年限对大豆根际土壤养分的影响

本试验通过对不同连作年限大豆根际土壤养分的测定,明确了连作对大豆根际土壤养分的影响,研究结果表明,连作处理根际土壤pH值随连作年限增长呈下降趋势,各连作大豆根际土壤中氮、磷、钾、镁、锌、硼、钼、有机质等养分含量均低于正茬,不同连作年限对大豆根际土壤中铁、钙、锰含量的影响未表现出线形规律。     

Biometrical analysis of phosphorus use efficiency in lettuce cultivars adapted to high temperatures

With the objective of selecting phosphorus efficient lettuce cultivars adapted to high temperatures, one hundred and thirteen lettuce genotypes from the vegetable germplasm bank at CCTA-UENF, Rio de Janeiro, Brazil, were initially selected for resistance to bolting under greenhouse temperature ranging from 20 to 32 ^°C. Nineteen greater longevity genotypes were further selected and evaluated for efficiency and responsiveness to phosphorus in soils with 10 and 60 mg dm^-3 of P. The estimated genetic parameters indicated that genetic gains from selection should be expected for all traits. Based on leaf and root dry weight, Mimosa and Regina genotypes were identified as efficient users of phosphorus in soils with low P content, while BGH 292 was inefficient. The genotype graphic dispersion based on the first three canonic variables confirmed Mimosa and Regina as efficient cultivars in soil with 10 mg dm^-3 of P. Their efficiency seemed to be linked to greater capacity for phosphorus use by the plant top as well as greater root growth. Similarly, the poor performance of BGH 292 in the low P soil seemed to be associated with its low capacity of phosphorus use in the plant top and its small root growth. The α parameter identified the Mimosa genotype as efficient user but not responsive to high P levels and the Regina and BGH4064 genotypes as efficient and responsive. Mimosa is, therefore, best suited for low P-input production systems, while Regina and BGH 4064 are indicated for production systems that use P-fertilization. This revised version was published online in August 2006 with corrections to the Cover Date.     

A rapid technique for determining common root rot reaction in barley

The reaction of two barley cultivars (‘Thibaut’ and ‘Arizona’) and three lines (AECS 76,‘Tadmor’ and WI 2291) to infection by Cochliobolus sativus was evaluated by three methods. Deep seeding of inoculated seeds was performed in pots and field. Gibberellin (GA3) was applied to inoculated seeds in vitro. Susceptibility assessments were made in vitro at 2 weeks, and in pots at 7 weeks after inoculation, using a scale of 1 (very resistant) to 5 (very susceptible) according to the percentage infected area of the subcrown internodes. There were no differences between the results using the three methods.‘Arizona’ was the most susceptible, whereas ‘Thibaut’ and AECS 76 were partially resistant genotypes. The WI 2291 line and ‘Tadmor’ were moderately susceptible and moderately resistant, respectively. In vitro tests yielded the same order as tests from pot and field experiments.     

Influence of genotype on phosphate uptake and utilization efficiencies in spring barley

To investigate the genetic variation of phosphate (P) uptake and P utilization efficiency, 24 high-yielding spring barley cultivars were grown in two pot experiments on a loess loam-sand mixture. In the first experiment, the plants grew until maturity under P stress (50% of the maximum yield), and in the second experiment, the plants grew until the stage of tillering (DC 25) at a low or at a high P supply.

At maturity, the range between cultivars with the highest and the lowest values were 30% for total dm yield (grain and straw), 28% for grain yield, 24% for P uptake efficiency (P in grain and straw), 26% for P concentration in grains and 24% for P utilization efficiency quotient PEQ (g dm grain per mg P in shoots) (mean of all cultivars = 100%). Grain yield was correlated with P uptake per plant, r = 0.71^***, and with PEQ, r = 0.60^**. Between P uptake and PEQ, there was only a weak relationship (r = −0.14). Therefore, a combination of high uptake efficiency and high PEQ in a cultivar may be possible.

At growth stage DC 25, the cultivars showed a significant variability in shoot biomass, P concentration, P removal, P influx, acitvity of acid phophatases (P_ase) and root length. The ranking of the cultivars, however, was very different at the two P levels, but the root-length and the P_ase activity were more influenced by genotype than by the P supply.

As the relationships between grain yield, P removal, PEQ and the characters of the young plants cultivated under P stress were very weak (r < 0.43), selection for P efficiency at the stage of tillering cannot be recommended.     

Genetic analysis of the nitrogen and phosphorus utilization efficiencies in mature spring barley plants

Inheritance of the efficiency of nitrogen and phosphorus utilization in grain production was studied in diallel hybrids of spring barley. Effects of varied NPK fertilization and soil moisture on the genetic variance was evaluated at maturity in pot‐ and field‐grown plants. A preponderance of general combining ability effects was found for the efficiency ratios and utilization efficiencies, suggesting that the generative efficiency indices were mainly controlled by an additive genetic system. However, the relatively high narrow‐sense heritabilities (0.33‐0.81) found under optimal conditions tended to decline to 0.00‐0.36 following water and nutrient shortages. The importance of non‐additive gene effects for utilization efficiencies was demonstrated in the field under reduced nutrition. This leads to the conclusion that the involvement of additive gene action should facilitate selection efforts only under favourable environments. Selection delayed until later hybrid generations should be used when trying to improve the nutrient efficiency of barley under less favourable nutrition conditions.     

Genotypic Variation in Root Systems of Chickpea (Cicer arietinum L.) across Environments

Root systems of various chickpea genotypes were studied over time and in diverse environments, – varying in soil bulk density, phosphorus (P) levels and moisture regimes. In a pot study comparing a range of chickpea genotypes, ICC 4958 and ICCV 94916‐4 produced higher root length density (RLD) and root dry weight (RDW), which were better expressed under P stress conditions. In two field experiments in soils of intermediate and high soil bulk densities, ICC 4958 also had greater RLD and RDW, particularly under soil moisture stress conditions. The expression of greater rooting ability of ICC 4958 under a wide range of environmental conditions confirms its suitability as a parent for genetically enhancing drought resistance and P acquisition ability. The superiority of ICC 4958 over other genotypes was for root proliferation expressed through RLD. Thus, the variation in RLD can be the most relevant root trait that reflects chickpea's potential for soil moisture or P acquisition.     

Segregation distortion for agronomic traits in doubled haploid lines of barley

Four barley doubled haploid populations were produced by anther culture from the reciprocal crosses between two six‐row barley cultivars, ‘Plaisant’ and ‘Orria’; the doubled haploid lines (DHLs) derived from each cross were subsequently assigned to weak or vigorous populations according to the weak or vigorous nature of the originating embryos. Well‐formed embryos at day 25 on the induction medium were considered vigorous, whereas embryos maturing later were considered weak. The classification of vigorous and weak was closely associated with the ratio of green to albino plantlets regenerated. A random set of 25 DHLs from each of the four populations were selected for field testing in a replicated trial. Furthermore, a second set consisting of a total of 454 unreplicated DHLs from the four populations were also field assessed for grain yield. Distortion during in vitro culture may impede regeneration of a random array of microspores from a given cross, and may bias genetic estimates of specific trait/marker association in genetic studies. However, no significant differences were detected in this study among the four populations for days to heading, height, grain yield and thousand‐kernel‐weight when measured on the replicated trial of 100 DHLs, nor for grain yield in the second collection of 454 entries. This suggests that the likelihood of producing improved agronomic pure lines is independent of the direction of crossing and, more importantly, independent of the time when embryos matured in the induction media, at least for these particular six‐row cultivars and for the anther culture method used.     

Utilization of molecular markers for improving the phosphorus efficiency in crop plants

Phosphorus (P) is the second most growth limiting macronutrient after nitrogen and plays several important roles in all organisms including plants. In soil, P is available in both organic and inorganic forms. P deficiency reduces the growth and yield of several crop plants. Plants respond to P deficiency by the phenotypic changes especially by the modification of root architecture. Molecular marker‐assisted breeding (MAB) has been proposed as an important tool to identify and develop improved varieties of crop plants with efficient P‐use efficiency (PUE). Identification of quantitative trait loci (QTLs) for traits related to PUE has been considered as the first step in marker‐assisted selection (MAS) and improvement of crop yield programmes. In this review, we describe in detail on architectural changes of roots under P deficiency that are reported in various crops and discuss the efforts made to improve PUE using molecular marker tools. Details on QTLs identified for low P‐stress tolerance in various crop plants are presented. These QTLs can be used to improve PUE in crop plants through MAS and breeding, which may be beneficial to improve the yields under P‐deficient soil. Development of new and improved varieties using MAB will limit the use of non‐renewable fertilizers and improve PUE of key crop plants in low input agriculture.     

In vitro quantification of the reaction of barley to common root rot

An in vitro technique was used to quantify the infection level of common root rot. This disease produces a brown to black discoloration of the subcrown internodes of barley. Quantification was based on the percentage of germinated infected pieces (1.5 mm) of subcrown internodes cultured on potato dextrose agar media. The disease severity was apparent among four different visually classified categories and numerical values for each category were applied. The results were highly correlated (r = 0.97, P < 0.01) among the different in vitro experiments, indicating that this testing procedure is repeatable. Highly significant differences (P < 0.001) were found for the length of first leaf and fresh weight between plants inoculated and uninoculated with common root rot. However, the effect of inoculation on fresh weight only differed significantly (P < 0.02) among the genotypes.     

Phosphorus uptake and utilization efficiency in response to potato genotype and phosphorus availability

Increased phosphorus (P) use efficiency (PUE) of potato production systems through P uptake and P utilization efficiency (PUPE and PUTE, respectively) is one of the main challenges for potato breeding and crop management programs. The aim of this study was to assess PUE, PUPE, PUTE and related traits in different potato genotypes (Solanum tuberosum L.) in response to P availability. Three field experiments were carried out in southern Chile in Andisol soils. In each experiment treatments were the factorial combination of (i) 22 genotypes of potatoes and (ii) two P fertilization rates (0 and 130 kg P ha⁻¹, −P and +P, respectively). On average, biomass, P concentrations and P uptakes were reduced (P < 0.05) 32, 13 and 41% by −P, respectively. Conversely, −P increased PUTE (1.2-fold), PUPE (7-fold) and consequently PUE (8.3-fold). All traits were consistently affected (P < 0.01) by genotype (G), and the coefficient of variation (up to 47%) for each trait reflects the genotypic variability under both +P and −P. In all experiments, PUE and its main components were affected (P < 0.01) by P × G interaction. PUE was highly correlated with tuber yield, total biomass, P uptake and PUPE (P < 0.01; r = 0.74 − 0.99) but not to PUTE. In addition, PUPE was well correlated to yield and highly correlated with total P uptake (P < 0.01; r = 0.94–0.99). By contrast, PUTE was strongly negatively correlated (P < 0.01; r = −0.85 − 0.89) with P concentration in tubers. Genotypes from native (1 and 4), national cultivar (Puren-INIA, Yagana-INIA and Patagonia-INIA) and advanced line (R 89063 and RD 36–35) groups were among the best regarding PUE under −P. The PUPE was found to be more important than PUTE in determining PUE across a broad range of genotypes. Moreover, there is important genotypic variability in these traits with the potential to be used to improve PUE in potato crops through breeding and crop management programs.     

Relationship between vernalization requirement and winter hardiness in doubled haploids of barley

Summary Progeny lines of chromosome-doubled haploids from crosses between one winter and four spring barley varieties were analysed for winter hardiness and vernalization requirement in the field. About one quarter or less of the offspring lines required vernalization under field conditions showing that winter versus spring habit of growth is controlled by at least two pairs of genes. The vernalization requirement could be measured quantitatively by testing a few plants in a greenhouse after artificial cold treatment during germination. The individual winter lines tested required from two to seven weeks of vernalization in order to flower as early as possible. The cold treatment had no effect on the time of flowering in the spring lines.Winter hardiness varied from zero to 100% plant survival in the field. The majority of the lines requiring vernalization survived better than 90% and the survival of the rest was at least 60%. The winter survival of the spring lines varied from zero per cent (about one third of the lines) to 100%. Hence, it is possible to obtain lines of good winter hardiness without requirements for cold treatment. Conversely, a selection for vernalization requirement has a positive effect on winter hardiness.