玉米株高和穗位高的QTL定位

摘要: 用玉米自交系掖478和丹340构建了397个F_2:3家系群体, 利用双亲间多态的150个共显性SSR标记绘制分子连锁图谱, 图谱总长度1 478.7 cM, 标记间平均距离10.0 cM。在5种环境下对株高和穗位高性状进行鉴定, 复合区间作图法检测到21个株高QTL和25个穗位高QTL。于第1和5染色体的umc2025－umc1035及umc1822－bnlg1118区域检测到平均贡献率分别为12.2%和14.9%的株高QTL。于第3和5染色体的phi029－umc1102及phi109188－bnlg1118区域检测到平均贡献率达到10.2%和22.8%的穗位高QTL。第5染色体的Bin5.05－5.07区域可能存在控制株高和穗位高的主效QTL。株高和穗位高的基因作用方式主要是加性和部分显性效应。文章还分析了群体大小及试验环境对株高和穗位高QTL定位结果的影响     

Quantitative trait loci analysis of plant height and ear height in maize (Zea mays L.)

Genetic map containing 103 microsatellite loci obtained on 200 F₂ plants derived from the cross R15 × 478 was used for quantitative trait loci (QTL) mapping in maize. QTLs were characterized in a population of 200 F_2:4 lines, derived from selfing the F₂ plants, and were evaluated with two replications in two environments. QTL determinations were made from the mean of these two environments. Plant height (PH) and ear height (EH) were measured. Using composite interval mapping (CIM) method, a total of 14 distinct QTLs were identified: nine for PH and five for EH. Additive, partial dominance, dominance, and overdominance actions existed among all detected QTLs affecting plant height and ear height. The QTLs explained 78.27% of the phenotypic variance of PH and 41.50% of EH. The 14 QTLs displayed mostly dominance or partial dominance gene action and mapped to chromosomes 2, 3, 4, 8, and 9. The text was submitted by the authors in English.     

QTL mapping and phenotypic variation for root architectural traits in maize (Zea mays L.)

Key message

QTL were identified for root architectural traits in maize.

Abstract

Root architectural traits, including the number, length, orientation, and branching of the principal root classes, influence plant function by determining the spatial and temporal domains of soil exploration. To characterize phenotypic patterns and their genetic control, three recombinant inbred populations of maize were grown for 28 days in solid media in a greenhouse and evaluated for 21 root architectural traits, including length, number, diameter, and branching of seminal, primary and nodal roots, dry weight of embryonic and nodal systems, and diameter of the nodal root system. Significant phenotypic variation was observed for all traits. Strong correlations were observed among traits in the same root class, particularly for the length of the main root axis and the length of lateral roots. In a principal component analysis, relationships among traits differed slightly for the three families, though vectors grouped together for traits within a given root class, indicating opportunities for more efficient phenotyping. Allometric analysis showed that trajectories of growth for specific traits differ in the three populations. In total, 15 quantitative trait loci (QTL) were identified. QTL are reported for length in multiple root classes, diameter and number of seminal roots, and dry weight of the embryonic and nodal root systems. Phenotypic variation explained by individual QTL ranged from 0.44 % (number of seminal roots, NyH population) to 13.5 % (shoot dry weight, OhW population). Identification of QTL for root architectural traits may be useful for developing genotypes that are better suited to specific soil environments.     

Molecular mapping in tropical maize (Zea mays L.) using microsatellite markers. 2. Quantitative trait loci (QTL) for grain yield, plant height, ear height and grain moisture

A previous genetic map containing 117 microsatellite loci and 400 F(2) plants was used for quantitative trait loci (QTL) mapping in tropical maize. QTL were characterized in a population of 400 F(2:3) lines, derived from selfing the F(2) plants, and were evaluated with two replications in five environments. QTL determinations were made from the mean of these five environments. Grain yield (GY), plant height (PH), ear height (EH) and grain moisture (GM) were measured. Variance components for genotypes (G), environments (E) and GxE interaction were highly significant for all traits. Heritability was 0.69 for GY, 0.66 for PH, 0.67 for EH and 0.23 for GM. Using composite interval mapping (CIM), a total of 13 distinct QTLs were identified: four for GY, four for PH and five for EH. No QTL was detected for GM. The QTL explained 32.73 % of the phenotypic variance of GY, 24.76 % of PH and 20.91 % of EH. The 13 QTLs displayed mostly partial dominance or overdominance gene action and mapped to chromosomes 1, 2, 7, 8 and 9. Most QTL alleles conferring high values for the traits came from line L-14-4B. Mapping analysis identified genomic regions associated with two or more traits in a manner that was consistent with correlation among traits, supporting either pleiotropy or tight linkage among QTL. The low number of QTLs found, can be due to the great variation that exists among tropical environments.     

QTL mapping of phosphorus efficiency and relative biologic characteristics in maize (Zea mays L.) at two sites

The phosphorus efficiency, relative biologic characteristics and relative root exudations as well as the quantitative trait loci associated with these traits were determined for an F_2:3 population derived from the cross of two contrasting maize (Zea mays L.) genotypes, 082 and Ye107. A total of 241 F_2:3 families were evaluated in replicated trials under normal phosphorus (50 kg P/ha) and low phosphorus (0 kg P/ha) conditions in 2007 at two sites (Kaixian and Southwest University). The genetic map constructed by 275 SSR and 146 AFLP markers spanned 1,681.3 cM in length with an average interval of 3.84 cM. The heritability of PE, PAE, RPH, RBW, RRW, RLA, TPS, RTW, RFN, RAP and RH was all high ( $h_{\text{b}}^2 > 60\% $ ) whereas the heritability of root exudations was all low ( $h_{\text{b}}^2 > 60\% $ ).By using composite interval mapping (CIM), a total of 30 and 45 distinct QTLs were identified at Kaixian and Southwest University. At two sites, the number of same QTL located on common region was 16, five for PE (bins 1.07, 4.09, 5.05, 5.07, 5.08), three for RBW (bins 3.04, 5.04, 6.05), three for RRW (bins 5.05, 5.06, 5.07), one for RLA (bins 3.04), two for TPS (bins 3.08, 5.07), two for RTW (bins 5.05, 5.06). These QTLs explained 21% of the phenotypic variation of PE, 5–9% of RBW, 13–16% of RRW, 9% of TPS, 7% of RTW, respectively. The 16 common QTLs displayed mostly partial dominance or over-dominance gene action. Most QTL alleles conferring high values for the traits came from two parents. Mapping analysis identified chromosomal regions associated with two or more traits in a cluster, which was consistent with correlation among traits. The result showed either pleiotropy or tight linkage among QTL. Five common regions for same QTL at different site were found in the interval bnlg1556-bnlg1564 (bins 1.06), mmc0341-umc1101 (bins 4.08), mmc0282-phi333597 (bins 5.05), bnlg1346-bnlg1695 (bins 5.07) and bnlg118a-umc2136 (bins 5.08), which were important for PE. The information reported in the present paper may be useful for improving phosphorus efficiency by means of marker-assisted selection.     

Epistasis in maize (Zea mays L.)

Summary Three flint and three dent maize (Zea mays L.) inbred lines, their possible F₁ crosses, F₂ and backcross progenies, and all possible three-way crosses were evaluated in a three-year experiment for yield, ear moisture, and plant height. The purpose was to estimate genetic parameters in European breeding materials from (i) generation means analysis, (ii) diallel analysis of generation means, and (iii) analysis of F₁ and three-way cross hybrids. Method (i) was based on the F-metric model and methods (ii) and (iii) on the Eberhart-Gardner (1966) genetic model; both models extended for heterotic maternal effects.Differences among generation means for yield and plant height were mainly attributable to dominance effects. Epistatic effects were significantly different from zero in a few crosses and considerably reduced heterosis in both traits. Additive x additive and domiance x dominance effects for yield were consistently positive and negative, respectively. Significant maternal effects were established to the advantage of generations with a heterozygous seed parent. In the diallel analysis, mean squares for dominance effects were greater than for additive effects for yield and plant height but smaller for ear moisture. Though significant for yield and plant height, epistatic variation was small compared to additive and dominance variation. Estimates of additive x additive epistasis for yield were significantly negative in 11 of 15 crosses, suggesting that advantageous gene combinations in the lines had been disrupted by recombination in the segregating generations. The analysis of hybrids supported the above findings regarding the analysis of variance. However, the estimates of additive x additive epistasis for yield were considerably smaller and only minimally correlated with those from the diallel analysis. Use of noninbred materials as opposed to materials with different levels of inbreeding is considered the main reason for the discrepancies in the results.     

Maturation of stamens and ovaries on cultured ear inflorescences of maize (Zea mays L.)

Observations were made on the maturation of stamens and ovaries from cultured maize (Zea mays L.) ear inflorescences. Immature ears (5.1–10.0 mm long) of maize were cultured in kinetin medium to study microsporogenesis and pollen maturation in developing stamens. Male spikelets developed on ears cultured in kinetin medium. Meiosis-I began by 7 days of culture in the developing anthers and the mature tri-nucleate pollen grains were developed by 20 days of culture. Further, kinetin was required in the culture medium for at least initial 5 days to obtain the microspores in differentiated stamens.To observe the embryosac formation in developed ovaries, ears were cultured in control, kinetin (10.1–15.0 mm long ears) medium, and kinetin + gibberellic acid (5.1–10.0 mm long ears) medium. Formation of embryosacs was noticed in the developed ovaries which were sampled after 20 days of culture. This differential flower development using two growth regulators provides an opportunity to uncover the biochemistry and physiology of micro- and mega-gametophyte development in maize.     

Biochemical composition of maize (Zea mays L.) pollen

Summary Pollen grains containing either the Wx, wx, Su ₁, su ₁, Sh ₂ or sh ₂ alleles were stored at 0, 1, 2, 3, 4 and 5 days at 2 °C. After each storage period, a portion of pollen from each genotype was analyzed for free amino acid content. Over all genotypes, storage significantly altered the content of all 16 amino acids measured. With increasing storage, a relatively consistent increase in aspartic acid, isoleucine, leucine, phenylalanine, ethanolanine, aminobutyric acid, NH₃ and lysine was found. A relatively consistent decrease in glutamic acid, proline, glycine and alanine occurred with increasing storage. No consistent response to storage was obtained with threonine-serine, valine, histidine and the unknown. Apparently, storage or stage of viability loss has a pronounced effect on amino acid metabolism in maize pollen grains. The experiment was designed so that comparisons free of genetic background effects could be made between alleles at each locus. Significant allele X storage interactions at each locus were found as follows: at the waxy locus, aspartic acid, glycine, alanine and ethanolanine; at the sugary locus, aspartic acid, alanine, ethanolanine and aminobutyric acid; and at the shrunken locus, aspartic acid, alanine, valine, leucine and ethanolanine. Amino acid metabolism is apparently influenced by the action of the alleles at these loci. The differences between the loci in the amino acids affected indicate the different areas of amino acid metabolism are influenced by each locus.Journal Series Paper No. 4425, Florida Agricultural Experiment Station.     

Biochemical composition of maize (Zea mays L.) pollen

Summary Mean percentages of sugars, water-soluble polysaccharides, starch, total carbohydrates and lipids were 40.1, 7.4, 28.6, 76.1, and 1.8 respectively. Differences among the mutants were found only for water-soluble polysaccharides with both wx and sh ₂ decreasing the percentage a small but significant amount. In terms of the various carbohydrates measured, no correlation was found between the expression of these mutants in the pollen and the kernel.

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Zusammenfassung Die Untersuchung des Kohlenhydrat- und Lipid-Gehaltes im Pollen der Endosperm-Mutanten waxy, shrunken und sugary vom Mais ergab einen gemittelten Gehalt an Zucker von 40,1%, wasserlöslichen Polysacchariden 7,4%, Stärke 28,6, Gesamtkohlenhydraten 76,1% und Lipiden 1,8%.Unterschiede zwischen den Mutanten wurden lediglich hinsichtlich der wasserlöslichen Polysaccharide gefunden, und zwar bei wx und sh ₂, die einen signifikant niedrigeren Gehalt aufwiesen.Hinsichtlich der verschiedenen analysierten Kohlenhydrate wurde keine Korrelation zwischen der Expression der Mutanten im Pollen und in den Karyopsen gefunden.

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Herrn Professor Dr. J. Straub (Köln-Vogelsang) zu seinem 60. Geburtstag gewidmet.

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Journal Series Paper No. 3621, Florida Agricultural Experiment Station.     

Biochemical composition of maize (Zea mays L.) pollen

Summary Proline was the most abundant amino acid with a mean value of 186.28 moles/mg dry pollen. The other amino acids tested were below 33 moles/mg dry pollen. The mutant wx significantly increased aspartic acid, valine, histidine and an unknown but significantly decreased aminobutyric acid. The mutant sh ₂ significantly increased glutamic acid, proline, lysine, histidine and an unknown but significantly decreased aspartic acid and aminobutyric acid. The effect of su ₁ was altered by the genetic background involved. In one genetic background, su ₁ did not significantly increase any amino acid but significantly decreased alanine and aminobutyric acid. However, in a distinctly different background, su ₁ significantly increased aminobutyric acid but significantly decreased aspartic acid and glutamic acid. Apparently the genetic background is capable of producing major shifts in the amino acid pattern in addition to the action of these mutants.The fatty acids, palmitic and linolenic were the most common with percentages of 54.1 and 34.4 respectively. The mutants tested did not affect the fatty acid distribution.

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Zusammenfassung Prolin war die am reichlichsten vorkommende Aminosäure mit einem mittleren Gehalt von 186,28 Mikromol per mg trockenen Pollen. Die anderen Aminosäuren erreichten weniger als 33 Mikrogramm per mg trockenen Pollen.Die Mutante wx zeigte einen signifikant erhöhten Gehalt an Asparaginsäure, Valin, Histidin, sowie einer nicht identifizierten Komponente, während der Gehalt an -Aminobuttersäure signifikant erniedrigt war. Die Mutante sh ₂ ist gekennzeichnet durch einen signifikant erhöhten Gehalt an Glutaminsäure, Prolin, Lysin, Histidin, sowie einer unbekannten Fraktion; der Gehalt an Asparaginsäure und -Aminobuttersäure war dagegen signifikant erniedrigt. Die Wirkung des mutierten Gens su ₁ wurde durch das übrige Genom, in dem es sich befand, geändert. In dem einen genetischen Milieu verursachte su ₁ keine signifikante Erhöhung des Gehaltes irgend einer Aminosäure, während der Gehalt an Alanin und -Aminobuttersäure signifikant erniedrigt war. In einem anderen genetischen Milieu jedoch zeigte su ₁ eine signifikante Erhöhung der -Aminobuttersäure; Asparaginsäure und Glutaminsäure waren signifikant erniedrigt.Offensichtlich ist das übrige Genom zusätzlich zu der Wirkung der genannten Mutanten in der Lage, wesentliche Verschiebungen im Verteilungsmuster der Aminosäuren zu verursachen.Von den Fettsäuren wurden am häufigsten Palmitin- und Linolen-Säure mit einem Gehalt von 54,1 bzw. 34,4% gefunden. Die untersuchten Endosperm-Mutanten zeigten keinen Einfluß auf die Fettsäureverteilung im Pollen.

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Journal Series Paper No. 3468, Florida Agricultural Experiment Station.     

Fine mapping a major QTL for kernel number per row under different phosphorus regimes in maize (Zea mays L.)

Phosphorus (P) is one of the essential macronutrients for plant growth and development. Grain yield is the primary trait of interest in maize breeding programs. Maize grain yield and yield-related traits are seriously affected by P deficiency. Kernel number per row (KN), as one of the major components of grain yield, has attracted the attention of more and more breeders. In our previous study, one major QTL (named qKN), controlling KN under different P regimes was mapped to the interval between molecular markers bnlg1360 and umc1645 on chromosome 10 using a F _2:3 population derived from the cross between maize inbreds 178 and 5,003 (107). In order to understand its genetic basis, we developed a population of near isogenic lines (NILs) and two P regimes were used to fine map and characterize qKN. The QTL qKN was finally localized in a region of ~480 kb. A single qKN allele of inbred 178 increased KN by 6.08–10.76 % in the 5,003 (107) background; qKN acted in a partially dominant manner. Our results will be instrumental for the future identification and isolation of the candidate gene underlying qKN. The tightly linked molecular markers that we developed for qKN will be useful in maize breeding programs for improving KN applying the marker-assisted selection.     

Proteomic analysis of shoot-borne root initiation in maize (Zea mays L.)

Postembryonically formed shoot-borne roots make up the major backbone of the adult maize root stock. In this study the abundant soluble proteins of the first node (coleoptilar node) of wild-type and mutant rtcs seedlings, which do not initiate crown roots, were compared at two early stages of crown root formation. In Coomassie Bluestained 2-D gels, representing soluble proteins of coleoptilar nodes 5 and 10 days after germination, 146 and 203 proteins were detected, respectively. Five differentially accumulated proteins (> two-fold change; t-test: 95% significance) were identified in 5-day-old and 14 differentially accumulated proteins in 10-day-old coleoptilar nodes of wild-type versus rtcs. All 19 differentially accumulated proteins were identified via ESI MS/MS mass spectrometry. Five differentially accumulated proteins, including a regulatory G-protein and a putative auxin-binding protein, were further analyzed at the RNA expression level. These experiments confirmed differential gene expression and revealed subtle developmental regulation of these genes during early coleoptilar node development. This study represents the first proteomic analysis of shoot-borne root initiation in cereals and will contribute to a better understanding of the molecular basis of this developmental process unique to cereals.     

Relationship between plant type and canopy apparent photosynthesis in maize (Zea mays L.)

Experiments were conducted to study the effect of plant type on canopy photosynthesis under field conditions. A chamber made of aluminium frame covered with clear plastic material was used to estimate canopy CO₂-exchange rates over a land area of 1.33 m². The plant type of maize “Shendan 7” [planophile type, original-type (OT)] was changed to erectophile type [altered-type (AT)] at silking stage. The rates of canopy apparent photosynthesis (CAP) were measured in both types of maize grown at five plant densities during the reproductive phase. It was shown that AT canopies had greater rates (about 17.2%) of CAP than did OT canopies and the yield increased by about 5.9–8.6% in AT canopies. The vertical distribution of photosynthetic photon flux density and CO₂ concentration in AT canopies were more uniform than those in OT ones. It was suggested that the compact architecture of maize canopy was excellent for photosynthesis and yield formation.     

Thiols in cadmium- and copper-treated maize (Zea mays L.)

Maize plants (Zea mays L. cv. Honeycomb F-1) were grown on quartz sand containing amounts of Cd or Cu which resulted in comparable internal contents in the roots. Fresh and dry weights and the content of Cd or Cu were measured in roots and shoots after eight weeks. In addition, cysteine, γ-glutamylcysteine (γEC), glutathione (GSH) and the thiols in heavy-metal-binding peptides (HMBPs) were determined in the roots. At low internal contents, Cd and Cu inhibited root growth to the same extent. Inhibition by Cu was enhanced, however, at high internal contents, indicating that Cu was more toxic than Cd. Separation of extracts from roots of Cd- and Cutreated plants on a Sephadex G-50 column resulted in HMBP complexes with relative molecular masses (M_rs) of 6200 and 7300, respectively. Separation of these HMBP-complexes using HPLC resulted in a distinct pattern of thiol compounds for each heavy metal. The accumulation of HMBPs was linearly dependent on the content of Cd at all values examined. In Cu-treated roots, HMBP accumulation was linearly dependent on the internal Cu content only up to 7.1 μmol·g^?1 dry weight. At internal contents which caused an enhanced inhibition of root growth, no further significant increase in the HMBP content was detected. At these internal Cu contents an increased transport of Cu to the shoot was measured. This result indicates that HMBPs are involved in reducing heavy-metal transport from roots to shoots.     

A re-examination of corn (Zea mays L.) ear volatiles

Helicoverpa zea (Boddie) is a major insect pest of corn and other agricultural crops. An improved understanding of semiochemcials that control adult behavior is needed to develop alternative control measures. In this study, overnight SPME collection of volatiles from corn ears enclosed in Teflon bags in the field at two stages of development were made. C₈–C₁₀ aldehydes, a C₈-alcohol, C₆–C₉ alcohol acetates, and numerous monoterpenes, sesquiterpenes, sequiterpene alcohols, and geosmin were identified after thermal desorption and GC/MS. Structural assignments of the alcohol acetates, Z-3-hexenyl acetate, 2-heptyl acetate, 2-nonyl acetate, and 4-nonyl acetate, the monoterpenes, α- and β-ocimene, and geosmin were made by analysis of standards that were purchased or prepared in the laboratory. All other assignments were based on published Kovat’s retention time indices (KI) and mass spectra. Pair-wise comparison of the relative amounts of each component between two groups of corn ears defined by silk weight did not identify significant differences, thus it is unknown whether or not silk weight impacted volatile emission composition and rate. To our knowledge three compounds detected in SPME collections, 2-heptyl acetate, 2-nonyl acetate, and 4-nonyl acetate have not been previously reported in corn ear or silk volatiles. Their impact on the flight response of gravid earworm females was evaluated in a flight chamber. No significant response to the individual compounds or a blend of all three was observed. Thus, their impact on moth behavior remains uncertain.