Combining field data and modeling to better understand maize growth response to phosphorus(P) fertilizer application and soil P dynamics in calcareous soils

We used field experimental data to evaluate the ability of the agricultural production system model (APSIM) to simulate soil P availability,maize biomass and grain yield in response to P fertilizer applications on a fluvo-aquic soil in the North China Plain.Crop and soil data from a 2-year experiment with three P fertilizer application rates(0,75 and 300 kg P_(2)O_(5) ha^(–1)) were used to calibrate the model.Sensitivity analysis was carried out to investigate the influence of APSIM SoilP parameters on the simulated P availability in soil and maize growth.Crop and soil P parameters were then derived by matching or relating the simulation results to observed crop biomass,yield,P uptake and Olsen-P in soil.The re-parameterized model was further validated against 2 years of independent data at the same sites.The re-parameterized model enabled good simulation of the maize leaf area index (LAI),biomass,grain yield,P uptake,and grain P content in response to different levels of P additions against both the calibration and validation datasets.Our results showed that APSIM needs to be re-parameterized for simulation of maize LAI dynamics through modification of leaf size curve and a reduction in the rate of leaf senescence for modern staygreen maize cultivars in China.The P concentration limits (maximum and minimum P concentrations in organs)at different stages also need to be adjusted.Our results further showed a curvilinear relationship between the measured Olsen-P concentration and simulated labile P content,which could facilitate the initialization of APSIM P pools in the NCP with Olsen-P measurements in future studies.It remains difficult to parameterize the APSIM SoilP module due to the conceptual nature of the pools and simplified conceptualization of key P transformation processes.A fundamental understanding still needs to be developed for modelling and predicting the fate of applied P fertilizers in soils with contrasting physical and chemical characteristics.

Does Global Agriculture Need Another Green Revolution？

1.引言科学和技术是社会变革的历史驱动力,这些变革大多是有益的,但有时会产生意想不到的(通常是环境方面的)后果,其中一些后果我们目前仍在努力应对。18世纪和19世纪的工业革命,带来的以化石燃料为动力的采矿和制造业机械化发展,以及航运和陆路运输的快速发展,导致城市化和人口不断增长。即使在18世纪,人口增长率也显然不能保持稳定。随着城市人口的增多和耕地的减少,除非农业生产率能够跟上发展的步伐。

梨小食心虫实时荧光定量PCR内参基因的筛选

【目的】本研究旨在探明梨小食心虫Grapholita molesta在不同发育阶段、成虫不同组织以及不同浓度的3种杀虫剂处理后成虫中稳定表达的内参基因,为后续对梨小食心虫目的基因表达的研究奠定基础。【方法】基于梨小食心虫转录组数据筛选10个候选内参基因(β-actin,18S rRNA,β-tubulin,EF-1α,RPL13,RPL32,RSPL40,UBC7,α-tubulin和RPS20);通过实时荧光定量PCR(qRT-PCR)测定候选内参基因在梨小食心虫不同发育阶段(卵、1-5龄幼虫、蛹和成虫)、成虫不同组织(头、前肠、中肠、后肠、脂肪体、马氏管、精巢和卵巢)以及不同浓度的3种杀虫剂(阿维菌素:19.819,72.897和179.663μg/mL;吡虫啉:17.638,163.323和762.986μg/mL以及高效氯氟氰菊酯:33.791,96.123和198.282μg/mL)通过玻璃管药膜法处理后成虫中的表达量;利用geNorm,NormFinder,ΔCt,BestKeeper和RefFinder对10个候选内参基因的表达稳定性进行评价。选择梨小食心虫细胞色素P450基因CYP354A 32进行验证。【结果】结合qRT-PCR结果和软件评价结果表明,梨小食心虫不同发育阶段内参基因表达稳定性从高到低依次为β-tubulin,18S rRNA,EF-1α,RPL13,β-actin,RPS20,UBC7,RPL32,α-tubulin和RSPL40;成虫不同组织内参基因表达稳定性从高到低依次为UBC7,β-tubulin,β-actin,18S rRNA,RSPL40,EF-1α,RPS20,RPL13,RPL32和α-tubulin;不同浓度阿维菌素、吡虫啉和高效氯氟氰菊酯处理后成虫中内参基因表达稳定性从高到低依次为RPS20,RPL13,β-tubulin,β-actin,RPL32,RSPL40,EF-1α,UBC7,α-tubulin和18S rRNA。用所获得的内参基因组合对CYP354 A2表达特性进行的分析结果表明,用β-tubulin,18S rRNA和EF-1α组合作为内参基因时CYP354 A2在高龄幼虫及成虫中表达量较高,用UBC7,β-tubulin和β-actin组合作为内参基因时在成虫精巢和卵巢中有较高表达,且用RPS20,RPL13和β-tubulin组合作为内参基因时不同浓度杀虫剂处理后仅有19.819μg/mL阿维菌素处理时CYP354 A2表达量高于对照,其余浓度杀虫剂处理时CYP354 A2表达量均低于对照。【结论】梨小食心虫不同发育阶段目的基因表达的研究推荐使用β-tubulin,18S rRNA和EF-1α组合作为内参基因;梨小食心虫成虫不同组织目的基因表达的研究推荐使用UBC7,β-tubulin和β-actin组合作为内参基因;不同浓度阿维菌素、吡虫啉和高效氯氟氰菊酯处理梨小食心虫成虫后目的基因表达的研究推荐使用RPS20,RPL13和β-tubulin组合作为内参基因。

Are yarn quality prediction tools useful in the breeding of high yielding and better fibre quality cotton(Gossypium hirsutum L.)?

Results The population had large variations for lint yield,fibre properties,predicted yarn properties,and composite fibre quality values.Lint yield with all fibre quality traits was not correlated.When the selection was conducted first to keep those with improved fibre quality,and followed for high yields,a large proportion in the resultant populations was the same between selections based on Cottonspec predicted yarn quality and HVI-measured fibre properties.They both exceeded the selection based on FQI and Background The approach of directly testing yarn quality to define fibre quality breeding objectives and progress the selection is attractive but difficult when considering the need for time and labour.The question remains whether yarn prediction tools from textile research can serve as an alternative.In this study,using a dataset from three seasons of field testing recombinant inbred line population,Cottonspec,a software developed by the Commonwealth Scientific and Industrial Research Organisation(CSIRO)for predicting ring spun yarn quality from fibre properties measured by High Volume Instrument(HVI),was used to select improved fibre quality and lint yield in the population.The population was derived from an advanced generation inter-crossing of four CSIRO conventional commercial varieties.The Cottonspec program was able to provide an integrated index of the fibre qualities affecting yarn properties.That was compared with selection based on HVI-measured fibre properties,and two composite fibre quality variables,namely,fibre quality index(FQI),and premium and discount(PD)points.The latter represents the net points of fibre length,strength,and micronaire based on the Premiums and Discounts Schedule used in the market while modified by the inclusion of elongation.PD points.Conclusions The population contained elite segregants with improved yield and fibre properties,and Cottonspec predicted yarn quality is useful to effectively capture these elites.There is a need to further develop yarn quality prediction tools through collaborative efforts with textile mills,to draw better connectedness between fibre and yarn quality.This connection will support the entire cotton value chain research and evolution.

A 2-bp frameshift deletion at GhDR,which encodes a B-BOX protein that co-segregates with the dwarf-red phenotype in Gossypium hirsutum L.

Plant architecture and leaf color are important factors influencing cotton fiber yield.In this study,based on genetic analysis,stem paraffin sectioning,and phytohormone treatments,we showed that the dwarf-red(DR)cotton mutant is a gibberellin-sensitive mutant caused by a mutation in a single dominant locus,designated GhDR.Using bulked segregant analysis(BSA)and genotyping by target sequencing(GBTS)approaches,we located the causative mutation to a~197-kb genetic interval on chromosome A09 containing 25 annotated genes.Based on gene annotation and expression changes between the mutant and normal plants,GH_A09G2280 was considered to be the best candidate gene responsible for the dwarf and red mutant phenotypes.A 2-nucleotide deletion was found in the coding region of GhDR/GH_A09G2280 in the DR mutant,which caused a frameshift and truncation of GhDR.GhDR is a homolog of Arabidopsis AtBBX24,and encodes a B-box zinc finger protein.The frameshift deletion eliminated the C-terminal nuclear localization domain and the VP domain of GhDR,and altered its subcellular localization.A comparative transcriptome analysis demonstrated downregulation of the key genes involved in gibberellin biosynthesis and the signaling transduction network,as well as upregulation of the genes related to gibberellin degradation and the anthocyanin biosynthetic pathway in the DR mutant.The results of this study revealed the potential molecular basis by which plant architecture and anthocyanin accumulation are regulated in cotton.

中国柱花草炭疽病原菌遗传多态性的RAPD分析

在对中国柱花草炭疽病进行广泛调查和病原采样收集的基础上 ,利用RAPD分子标记技术对 43个代表性菌株进行了基因组DNA分析 ,并与 2 76份国外菌株进行了综合聚类分析。结果表明所用 8个引物的扩增片段位于 0 3～ 2 8kb之间 ,菌株间呈现显著的DNA多态性。以柱花草起源中心———南美的柱花草炭疽菌分类为基础 ,中国柱花草炭疽菌可划分成 3大类型即Ⅱ、Ⅲ、Ⅵ类。中国菌株与来自柱花草起源中心———南美的菌株相比之下 ,其生物多样性和遗传变异性则相对简单。就中国菌株而言海南菌株与广西、广东菌株相比多样性较丰富 ,中国柱花草胶孢炭疽菌正在出现种内遗传分化。从聚类结果看 ,通常来自于同一个地理区域或同一个寄主基因型的菌株聚成一类 ,即同一RAPD聚类组内的菌株通常来自于同一寄主基因型或同一地理区域。说明来自不同寄主基因型或物种的炭疽菌在遗传基因上具有专化性 ,而地理上隔离的国家或地区的柱花草炭疽病原菌各自具有相对独立的进化途径。

Construction of an integrated map and location of a bruchid resistance gene in mung bean

Bruchid beetle(Callosobruchus chinensis) poses a serious threat to the production and storage of mung bean(Vigna radiata). Mapping bruchid resistance(Br) will provide an important basis for cloning the responsible gene(s) and elucidating its functional mechanism, and will also facilitate marker-assisted selection in mung bean breeding. Here, we report the construction of the genetic linkage groups of mung bean and mapping of the Br1 locus using an RIL population derived from a cross between Berken, a bruchid-susceptible line, and ACC41, a bruchid-resistant line. A total of 560 markers were mapped onto 11 linkage groups,with 38.0% of the markers showing distorted segregation. The lengths of the linkage groups ranged from 45.2 to 117.0 c M with a total coverage of 732.9 c M and an average interval of1.3 c M between loci. Br1 was located on LG9 between BM202(0.7 c M) and Vr2-627(1.7 c M).Based on 270 shared SSR markers, most of the linkage groups were assigned to specific chromosomes. These results should further accelerate the genetic study of this crop.

不同磷水平下大麦分蘖期磷效率相关性状QTL定位分析

磷素营养与大麦品质及产量密切相关,磷高效遗传机制和品种改良是近年的研究热点之一。本研究利用由大麦栽培品种Baudin和种质材料CN4079杂交构建的重组自交系(RIL)群体,低磷胁迫(0.02 mmol L^(-1) KH_2PO_4)与正常供磷(0.2 mmol L^(-1) KH_2PO_4)条件下,对地上部和地下部磷素利用效率、磷素吸收效率和干重,以及分蘖数相关的QTL定位,并预测相关位点基因。表型鉴定结果表明,各性状在RIL群体中表现连续变异,并存在超亲分离。两种磷水平下,共检测到16个QTL,分布在2H、3H和5H染色体上,表型贡献率14.1%~28.5%。3H染色体上含有3个磷素利用效率位点,其增效等位基因均来源于Baudin,其中Qspue.sau-3H.1和Qrpue.sau-3H与控制磷素吸收效率的Qspae.sau-3H和Qrpae.sau-3H处于同一区段,而Qspue.sau-3H.2与控制分蘖数的位点Qtn.sau-3H处于同一区段。5H染色体上含有3个磷素吸收效率位点,其中Qspae.sau-5H.2和Qrpae.sau-5H的增效等位基因来自CN4079,且与控制磷素利用效率的Qspue.sau-5H和Qrpue.sau-5H,以及控制干重的Qsdw.sau-5H和Qrdw.sau-5H处于同一区段。在磷效率相关的4个区段中,除Qspue.sau-3H.1所处区间仅含有磷酸代谢与磷脂代谢相关基因外,其他区间均包含磷酸盐转运蛋白基因、磷酸代谢与磷脂代谢相关基因。

Current understanding of grapevine defense mechanisms against the biotrophic fungus (Erysiphe necator), the causal agent of powdery mildew disease

The most economically important disease of cultivated grapevines worldwide is powdery mildew(PM)caused by the ascomycete fungus Erysiphe necator.The majority of grapevine cultivars used for wine,table grape,and dried fruit production are derived from the Eurasian grape species Vitis vinifera because of its superior aroma and flavor characteristics.However,this species has little genetic resistance against E.necator meaning that grape production is highly dependent on the frequent use of fungicides.The integration of effective genetic resistance into cultivated grapevines would lead to significant financial and environmental benefits and represents a major challenge for viticultural industries and researchers worldwide.This review will outline the strategies being used to increase our understanding of the molecular basis of V.vinifera susceptibility to this fungal pathogen.It will summarize our current knowledge of different resistance loci/genes that have evolved in wild grapevine species to restrict PM infection and assess the potential application of these defense genes in the generation of PM-resistant grapevine germplasm.Finally,it addresses future research priorities which will be important in the rapid identification,evaluation,and deployment of new PM resistance genes which are capable of conferring effective and durable resistance in the vineyard.

Creating a novel herbicide-tolerance OsALS allele using CRISPR/Cas9-mediated gene editing

Weeds and weedy rice plague commercial rice fields in many countries. Developingherbicide-tolerance rice is the most efficient strategy to control weed proliferation. CRISPR/Cas9-mediated gene editing, which generates small InDels and nucleotide substitutions atand around target sites using error-prone non-homologous end joining DNA repairing, hasbeen widely adopted for generation of novel crop germplasm with a wide range of geneticvariation in important agronomic traits. We created a novel herbicide-tolerance allele inrice by targeting the acetolactate synthase (OsALS) gene using CRISPR/Cas9-mediated geneediting. The novel allele (G628W) arose from a G-to-T transversion at position 1882 of OsALSand conferred a high level of herbicide tolerance. Transgene-free progeny carryinghomozygous G628W allele were identified and showed agronomic performance similar tothat of wild-type plants, suggesting that the G628W allele is a valuable resource fordeveloping elite rice varieties with strong herbicide tolerance. To promote use of the G628Wallele and to accelerate introgression and/or pyramiding of the G628W allele with other elitealleles, we developed a DNA marker for the G628W allele that accurately and robustlydistinguished homozygous from heterozygous segregants. Our result further demonstratesthe feasibility of CRISPR/Cas9-mediated gene editing in creating novel genetic variation forcrop breeding.

The community structure and microbial linkage of rumen protozoa and methanogens in response to the addition of tea seed saponins in the diet of beef cattle

Background: This study investigated changes in rumen protozoal and methanogenic communities, along with the correlations among microbial taxa and methane(CH_4) production of six Belmont Red Composite beef steers fed tea seed saponins(TSS). Animals were fed in three consecutive feeding periods, a high-grain basal diet for 14 d(BD period) then a period of progressive addition of TSS to the basal diet up to 30 g/d for 20 d(TSS period), followed by the basal diet for 13 d without TSS(BDP post-control period).Results: The study found that TSS supplementation decreased the amount of the protozoal genus Entodinium and increased Polyplastron and Eudiplodinium genera. During BDP period, the protozoa community of steers did not return to the protozoal profiles observed in BD period, with higher proportions of Metadinium and Eudiplodinium and lower Isotricha. The addition of TSS was found to change the structure of methanogen community at the subgenus level by decreasing the abundance of methanogens in the SGMT clade and increasing the abundance of methanogens in the RO clade. The correlation analysis indicated that the abundance of SGMT clade methanogens were positively correlated with Isotricha, and Isotricha genus and SGMT clade methanogens were positively correlated with CH_4 production. While RO clade were positively correlated with the proportion of Metadinium genus, which was negatively correlated with CH_4 emission.Conclusions: These results suggest that different genera of rumen protozoa ciliates appear to be selectively inhibited by TSS, and the change in methanogen community at the subgenus level may be due to the mutualistic relationships between methanogens and rumen ciliates.

Rice bioinformatics in the genomic era: Status and perspectives

Rice is one of cereal crops and a model species for monocots.Since the release of the first draft rice genome sequences in 2002,considerable progress has been achieved in rice genomic researches,thanks to rapid development and efficient utilization of bioinformatics methods and tools.In this review,we summarize the progress of studies of rice genome sequencing and other omics and introduce the wellmaintained bioinformatics databases and tools developed for rice genome resources and breeding.After reviewing the history of rice bioinformatics,we use single-cell sequencing and machine learning as examples showing how bioinformatics integrates emerging technologies and how it continues to develop for future rice research.

Intron-targeted gene insertion in rice using CRISPR/Cas9: A case study of the Pi-ta gene

Intron-targeted gene insertion strategy using CRISPR/Cas9(clustered regularly interspaced short palindromic repeats/CRISPR-associated Cas9) has been shown to be a potential tool for crop genetic improvement by targeted mutagenesis or gene replacement of an elite allele into widely cultivated rice varieties. The rice blast resistant protein Pi-ta, differs from its susceptible counterpart, pi-ta, by a single amino acid in exon 2. To create new materials resistant to the rice blast disease, we inserted a genomic fragment containing the exon 2 and 3′ untranslated region(3′ UTR) of Pi-ta into intron 1 of pi-ta in rice materials susceptible to rice blast using the intron-targeted insertion strategy. The gene insertion frequency was3.8%. Several novel transgene-free progeny with stably inherited homozygous insert were identified in the T_1 generation, which have been crossed to rice germplasm bearing other resistance gene(R gene) for pyramiding of R genes. This work verified the feasibility of using the genome editing technology in improvement of qualitative agronomic trait in crops.

Triple bottom-line consideration of sustainable plant disease management:From economic,sociological and ecological perspectives

Plant disease management plays an important role in achieving the sustainable development goals of the United Nations(UN)such as food security,human health,socio-economic improvement,resource conservation and ecological resilience.However,technologies available are often limited due to different interests between producers and society and lacks of proper understanding of economic thresholds and the complex interactions among ecology,productivity and profitability.A comprehensive synergy and conflict evaluation of economic,sociological and ecological effects with technologies,productions and evolutionary principles as main components should be used to guide sustainable disease management that aims to mitigate crop and economic losses in the short term while maintaining functional farm ecosystem in the long term.Consequently,there should be an increased emphasis on technology development,public education and information exchange among governments,researchers,producers and consumers to broaden the options for disease management in the future.

In Vitro Evaluation of the Antimethanogenic Potency and Effects on Fermentation of Individual and Combinations of Marine Macroalgae

Contribution of ruminants to total greenhouse gas emissions in Australia is approximately 10% and likely to increase with demand for livestock products, thus an efficient method of mitigation must be implemented. The red marine macroalgae Asparagopsis taxiformis reduces enteric methane production by up to 99% in vitro. Other macroalgae with less potent antimethanogenic properties may complement inclusion of Asparagopsis in livestock feeds. Adoption of environmental based changes in livestock systems must provide benefits to producers if change in management is to be adopted. This study used 72 h in vitro fermentations with rumen inoculum to characterize and rank seven species of macroalgae at low inclusion that previously demonstrated some degree of antimethanogenesis at higher inclusion concentration. The seven were assessed at 5% inclusion (OM basis) and in combination with Asparagopsis to evaluate beneficial effects on fermentation. When tested individually, improvements in volatile fatty acids were generally observed, however, minimal effect on gas production and no clear justification for a ranking order were demonstrated. When tested in combination with Asparagopsis, the effects on fermentation were dominated by presence of Asparagopsis at 2% and no further benefits demonstrated. Therefore, Asparagopsis remains the only macroalga inducing near elimination of methane in vitro and benefit of combinations with other macroalgae evaluated in this study was not demonstrated. However, combination with high protein macroalgae is proposed to provide productivity enhancement during seasonal lows in grass quality and thus reduce methane emissions intensity providing a stronger conduit for environmental responsibility while increasing productivity.

The current status of nitrogen fertiliser use efficiency and future research directions for the Australian cotton industry

Fifty years of sustained investment in research and development has left the Australian cotton industry well placed to manage nitrogen(N) fertiliser. The average production in the Australian cotton industry today is greater than two tonnes of lint per hectare due to improved plant genetics and crop management. However, this average yield is well below the yield that would be expected from the amount of N fertiliser used. It is clear from the recent studies that across all growing regions, conversion of fertiliser N into lint is not uniformly occurring at application rates greater than 200-240 kg·hm^(-2) of N. This indicates that factors other than N availability are limiting yield, and that the observed nitrogen fertiliser use efficiency(NFUE) values may be caused by subsoil constraints such as sodicity and compaction. There is a need to investigate the impact of subsoil constraints on yield and NFUE.Gains in NFUE will be made through improved N fertiliser application timing, better targeting the amount of fertiliser applied for the expected yield, and improved soil N management. There is also a need to improve the ability and confidence of growers to estimate the contribution of soil N mineralisation to the crop N budget. Many Australian studies including data that could theoretically be collated in a meta-analysis suggest relative NFUE values as a function of irrigation technique; however, with the extensive list of uncontrolled variables and few studies using non-furrow irrigation, this would be a poor substitute for a single field-based study directly measuring their efficacies. In irrigated cotton, a re-examination of optimal NFUE is due because of the availability of new varieties and the potential management and long-term soil resilience implications of the continued removal of mineralised soil N suggested by high NFUE values. NFUE critical limits still need to be derived for dryland systems.

Characterization of peach tree crown by using high-resolution images from an unmanned aerial vehicle

In orchards, measuring crown characteristics is essential for monitoring the dynamics of tree growth and optimizing farm management. However, it lacks a rapid and reliable method of extracting the features of trees with an irregular crown shape such as trained peach trees. Here, we propose an efficient method of segmenting the individual trees and measuring the crown width and crown projection area (CPA) of peach trees with time-series information, based on gathered images. The images of peach trees were collected by unmanned aerial vehicles in an orchard in Okayama, Japan, and then the digital surface model was generated by using a Structure from Motion (SfM) and Multi-View Stereo (MVS) based software. After individual trees were identified through the use of an adaptive threshold and marker-controlled watershed segmentation in the digital surface model, the crown widths and CPA were calculated, and the accuracy was evaluated against manual delineation and field measurement, respectively. Taking manual delineation of 12 trees as reference, the root-mean-square errors of the proposed method were 0.08 m (R^(2) = 0.99) and 0.15 m (R^(2) = 0.93) for the two orthogonal crown widths, and 3.87 m2 for CPA (R^(2) = 0.89), while those taking field measurement of 44 trees as reference were 0.47 m (R^(2) = 0.91), 0.51 m (R^(2) = 0.74), and 4.96 m2 (R^(2) = 0.88). The change of growth rate of CPA showed that the peach trees grew faster from May to July than from July to September, with a wide variation in relative growth rates among trees. Not only can this method save labour by replacing field measurement, but also it can allow farmers to monitor the growth of orchard trees dynamically.

Contrasting patterns of accumulation,partitioning,and remobilization of biomass and phosphorus in a maize cultivar

Maize growth,organ development,and yield formation are highly controlled by the manner in which the plant captures,partition,and remobilizes biomass and phosphorus(P).Better understanding of biomass and P accumulation,partition,and remobilization processes will improve modeling of crop resource use.However,there is still a lack of detailed data to parameterize the modeling of these processes,particula rly for modern maize cultivars.A two-year(2016 and 2017)field experiment with three P fertilization treatments(0(P0),75(P75),and 300(P300)kg P_(2)O_(5)ha^(-1))was conducted on a Fluvo-aquic soil(Quzhou,Hebei province,China)to collect data and quantify key processes for a representative modern maize cultivar(Zhengdan 958)widely grown in China.The proportions of biomass and P partitioned into various maize organs were unaffected by P application rate.Zhengdan 958 showed a much lower leaf-senescence rate than older cultivars,resulting in post-silking leaf photosynthesis being sufficient to meet grain biomass demand.In contrast,50%-85%of leaf P and 15%-50%of stem P accumulated pre-silking were remobilized into grain,in spite of the large proportion of post-silking P uptake.Our results are consistent with the theory that plants use resources according to the priority order of re-allocation from senescence followed by assimilation and uptake,with the re-translocation of reserves last.The results also enabled us to estimate the threshold P concentrations of Zhengdan 958 for modeling crop P demand.The critical leaf P concentration for individual leaves was 0.25%-0.30%,with a corresponding specific leaf P(SLP)of 75-100 mg P m^(-2).The structural P concentration for leaf was 0.01%,corresponding to an SLP of 3.8 mg P m^(-2).The maximum P concentrations of leaves and stems were 0.33%and 0.29%.The residual P concentration for stems was 0.006%.

Testing a bell-shaped function for estimation of fully expanded leaf area in modern maize under potential production conditions

Accurate leaf area simulation is critical for the performance of crop growth models. Area of fully expanded individual leaves of maize hybrids released before 1995 (defined as old hybrids) has been simulated using a bell-shaped function (BSF) and the relationship between its parameters and total leaf number (TLNO). However, modern high-yielding maize hybrids show different canopy architectures. The function parameters calibrated for old hybrids will not accurately represent modern hybrids. In this study, we evaluated these functions using a dataset including old and modern hybrids that have been widely planted in China in recent years. Maximum individual leaf area (Y_0) and corresponding leaf position (X_0) were not predicted well by TLNO (R^2= 0.56 and R^2= 0.70) for modern hybrids. Using recalibrated shape parameters a and b with values of Y_0 and X_0 for modern hybrids, the BSF accurately predicted individual leaf area (R^2= 0.95–0.99) and total leaf area of modern hybrids (R^2= 0.98). The results show that the BSF is still a robust way to predict the fully expanded leaf area of maize when parameters a and b are modified and Y_0 and X_0 are fitted. Breeding programs have led to increases in TLNO of maize but have not altered Y_0 and X_0, reducing the correlation between Y_0, X_0, and TLNO. For modern hybrids, the values of Y_0 and X_0 are hybrid-specific. Modern hybrids tend to have less-negative values of parameter a and more-positive values of parameter b in the leaf profile. Growth conditions, such as plant density and environmental conditions, also affect the fully expanded leaf area but were not considered in the original published equations. Thus, further research is needed to accurately estimate values of Y_0 and X_0 of individual modern hybrids to improve simulation of maize leaf area in crop growth models.

A major quantitative trait locus controlling phosphorus utilization efficiency under different phytate-P conditions at vegetative stage in barley

Organic phosphorus（P） is an important component of the soil P pool, and it has been proven to be a potential source of P for plants. The phosphorus utilization efficiency（PUE） and PUE related traits（tiller number（TN）, shoot dry weight（DW）, and root dry weight） under different phytate-P conditions（low phytate-P, 0.05 mmol L^-1 and normal phytate-P, 0.5 mmol L^-1） were investigated using a population consisting of 128 recombinant inbred lines（RILs） at the vegetative stage in barley. The population was derived from a cross between a P-inefficient genotype（Baudin） and a P-efficient genotype（CN4027, a Hordeum spontaneum accession）. A major locus（designated Qpue.sau-3 H） conferring PUE was detected in shoots and roots from the RIL population. The quantitative trait locus（QTL） was mapped on chromosome 3 H and the allele from CN4027 confers high PUE. This locus explained up to 30.3 and 28.4% of the phenotypic variance in shoots under low and normal phytate-P conditions, respectively. It also explains 28.3 and 30.7% of the phenotypic variation in root under the low and normal phytate-P conditions, respectively. Results from this study also showed that TN was not correlated with PUE, and a QTL controlling TN was detected on chromosome 5 H. However, dry weight（DW） was significantly and positively correlated with PUE, and a QTL controlling DW was detected near the Qpue.sau-3 H locus. Based on a covariance analysis, existing data indicated that, although DW may affect PUE, different genes at this locus are likely involved in controlling these two traits.