Molecular mapping of genomic regions associated with wheat seedling growth under osmotic stress

A quantitative trait loci (QTL) approach was applied to dissect the genetic control of the common wheat seedling response to osmotic stress. A set of 114 recombinant inbred lines was subjected to osmotic stress from the onset of germination to the 8^th day of seedling development, induced by the presence of 12 % polyethylene glycol. Root, coleoptile and shoot length, and root/shoot length ratio were compared under stress and control conditions. In all, 35 QTL mapping to ten chromosomes, were identified. Sixteen QTL were detected in controls, 17 under stressed conditions, and two tolerance index QTL were determined. The majority of the QTL were not stress-specific. In regions on five chromosome arms (1AS, 1BL, 2DS, 5BL and 6BL) the QTL identified under stress co-mapped with QTL affecting the same trait in controls, and these were classified as seedling vigour QTL, in addition to those expressed in controls. Tolerance-related QTL were detected on four chromosome arms. A broad region on chromosome 1AL, including five QTL, with a major impact of the gene Glu-A1 (LOD 3.93) and marker locus Xksuh9d (LOD 2.91), positively affected root length under stress and tolerance index for root length, respectively. A major QTL (LOD 3.60), associated with marker locus Xcdo456a (distal part of chromosome arm 2BS) determined a tolerance index for shoot length. Three minor QTL (LOD < 3.0) for root length and root/shoot length ratio under osmotic stress were identified in the distal parts of chromosome arms 6DL (marker locus Xksud27a) and 7DL (marker locus Xksue3b). Selecting for the favourable alleles at marker loci associated with the detected QTL for growth traits may represent an efficient approach to enhance the plants’ ability to maintain the growth of roots, coleoptile and shoots in drought-prone soils at the critical early developmental stages.     

水稻种子活力QTL定位及上位性分析

利用1个粳／籼交来源(Lemont／Teqing)、包含264个重组自交系的作图群体,采用纸卷法在18℃培养箱中进行2次重复的发芽实验,考察了种子发芽7d、9d和1ld的发芽率,种子发芽15d后的芽长及干重等种子活力的相关性状。结合一张含有198个DNA标记的连锁图谱,用作图软件QTLMapper1．0定位与种子活力相关的QTL。共检测到13个主效应QTL,这些QTL对性状的贡献率为2．9％～12．7％,平均贡献率为6．2％。同时检测到18对贡献率≥5％的互作位点,其贡献率为5．1％～11．8％,平均贡献率为6．9％,比检测到的主效应QTL的平均贡献率稍大。种子活力相关性状的大多数主效应和互作QTL成串分布于少数几个染色体区段(Chromosome Regions,CRs),并且成串分布在同一染色体区段的QTL效应的方向总是一致,该结果与这些性状在表型上的正相关相一致。若将成串分布有3个及3个以上种子活力相关性状QTL的CRs视为与种子活力高度相关的CRs,则共检测到7个上述与种子活力高度相关的CRs,分别分布在水稻12条染色体中的7条染色体上。根据所含QTL的种类(主效应QTL或／和上位性QTL)可将这些CRs分成以下3种：1)M-CRs：只含有主效应QTL,如CR^sv-7;2)E-CRs：所含位点没有主效应,但与其他位点发生互作,如CR^sv-1、CR^sv-6和CR^sv-12;3)ME-CRs：既含有主效应QTL、也含有与其他位点产生互作的互作位点,如CR^sv-2、CR^sv-5和CR^sv-8。另外还发现,有的CR上的位点同时与多个不同CR上的位点互作,影响种子活力的相关性状。与前入的研究结果相比较,发现有些与种子活力高度相关的CR可在不同研究者所用的不同定位群体中被检测到,而有的CR只在特定的定位群体中被检测到。由此表明,水稻种子活力具有丰富的遗传多样性和复杂的遗传基础,其主效QTL和互作位点可能基于遗传背景的不同而相互转化。     

Identification and fine mapping of quantitative trait loci for seed vigor in germination and seedling establishment in rice

Seed vigor is an index of seed quality that is used to describe the rapid and uniform germination and the establishment of strong seedlings in any environmental conditions.Strong seed vigor in low-temperature germination conditions is particularly important in direct-sowing rice production systems. However, seed vigor has not been selected as an important breeding trait in traditional breeding programs due to its quantitative inherence. In this study, we identified and mapped eight quantitative trait loci(QTLs) for seed vigor by using a recombinant inbred population from a cross between rice(Oryza sativa L. ssp. indica) cultivars ZS97 and MH63.Conditional QTL analysis identified qSV-1, qSV-5b, qSV-6a, qSV-6b, and qSV-11 influenced seedling establishment and that qSV-5a, qSV-5c, and qSV-8 influenced only germination. Of these,qSV-1, qSV-5b, qSV-6a, qSV-6b, and qSV-8 were low-temperature-specific QTLs. Two major-effective QTLs, qSV-1, and qSV-5c were narrowed down to 1.13-Mbp and 400-kbp genomic regions, respectively. The results provide tightly linked DNA markers for the marker-assistant pyramiding of multiple positive alleles for increased seed vigor in both normal and low-temperature germination environments.     

水稻苗期生长对缺磷响应的QTL定位(英文)

缺磷是抑制全球水稻产量主要因素之一。本研究利用Asomonori(粳型)/IR24(籼型)杂交重组自交株系,对5个水稻苗期性状(相对苗高、相对根长、相对根重、相对苗重以及相对总重)在缺磷条件下的响应QTL进行定位。共检测到20个水稻苗期生长对缺磷响应的QTL位点,分别位于第1(4QTLs)、第4(4QTLs)、第5(2QTLs)、第7、第8(4QTLs)、第9(2QTLs)、第11(2QTLs)和第12号染色体上,其中13个QTLs位于与C3029C、XNpb302、C621B、C621C、R2976和C1263分子标记紧密连锁的6个基因组区域上。另外,每个性状均能从双亲中检测到正负效应QTL位点,这些能解释重组自交系群体中出现超亲和连续分布的现象。本文主要报道了水稻第5、第7和第11染色体上存在水稻苗期生长对缺磷响应的QTL位点。研究表明,该结果及其中检测到的QTLs两侧的连锁分子标记可用于水稻苗期耐低磷性分子育种。     

Quantitative trait loci associated with seed and seedling traits in Lactuca

Seed and seedling traits related to germination and stand establishment are important in the production of cultivated lettuce (Lactuca sativa L.). Six seed and seedling traits segregating in a L. sativa cv. Salinas x L. serriola recombinant inbred line population consisting of 103 F8 families revealed a total of 17 significant quantitative trait loci (QTL) resulting from three seed production environments. Significant QTL were identified for germination in darkness, germination at 25 and 35°C, median maximum temperature of germination, hypocotyl length at 72 h post-imbibition, and plant (seedling) quality. Some QTL for germination and early seedling growth characteristics were co-located, suggestive of pleiotropic loci regulating these traits. A single QTL (Htg6.1) described 25 and 23% of the total phenotypic variation for high temperature germination in California- and Netherlands-grown populations, respectively, and was significant between 33 and 37°C. Additionally, Htg6.1 showed significant epistatic interactions with other Htg QTL and a consistent effect across all the three seed production environments. L. serriola alleles increased germination at these QTL. The estimate of narrow-sense heritability (h²) of Htg6.1 was 0.84, indicating potential for L. serriola as a source of germination thermotolerance for lettuce introgression programs.     

QTL controlling root and shoot traits of maize seedlings under cold stress

The improvement of early vigour is crucial for the adaptation of maize (Zea mays L.) to the climatic conditions of central Europe and the northern Mediterranean, where early sowing is an important strategy for avoiding the effect of summer drought. The objectives of this study were to identify quantitative trait loci (QTL) controlling cold-related traits and to investigate the relationships among them. A set of 168 F_2:4 families of the Lo964 × Lo1016 cross was grown in a sand–vermiculite substrate at 15/13°C (day/night) until the one-leaf stage. Twenty QTL were identified for the four shoot and two seed traits examined. Analysis of root weight and digital measurements of the length and diameter of primary and seminal roots led to the identification of 40 QTL. The operating efficiency of photosystem II (_PSII) was related to seedling dry weight at both the phenotypic and genetic level (r=0.46, two matching loci, respectively) but was not related to root traits. Cluster analysis and QTL association revealed that the different root traits were largely independently inherited and that root lengths and diameters were mostly negatively correlated. The major QTL for root traits detected in an earlier study in hydroponics were confirmed in this study. The length of the primary lateral roots was negatively associated with the germination index (r=–0.38, two matching loci). Therefore, we found a large number of independently inherited loci suitable for the improvement of early seedling growth through better seed vigour and/or a higher rate of photosynthesis.This paper is dedicated to our friend and colleague Alberto Soldati, who passed away unexpectedly.     

Laboratory phenomics predicts field performance and identifies superior indica haplotypes for early seedling vigour in dry direct-seeded rice

Seedling vigour is an important agronomic trait and is gaining attention in Asian rice (Oryza sativa) as cultivation practices shift from transplanting to forms of direct seeding. To understand the genetic control of rice seedling vigour in dry direct seeded (aerobic) conditions we measured multiple seedling traits in 684 accessions from the 3000 Rice Genomes (3K-RG) population in both the laboratory and field at three planting depths. Our data show that phenotyping of mesocotyl length in laboratory conditions is a good predictor of field performance. By performing a genome wide association study, we found that the main QTL for mesocotyl length, percentage seedling emergence and shoot biomass are co-located on the short arm of chromosome 7. We show that haplotypes in the indica subgroup from this region can be used to predict the seedling vigour of 3K-RG accessions. The selected accessions may serve as potential donors in genomics-assisted breeding programs.     

Molecular mapping of quantitative trait loci in japonica rice.

Rice (Oryza sativa L.) molecular maps have previously been constructed using interspecific crosses or crosses between the two major subspecies: indica and japonica. For japonica breeding programs, however, it would be more suitable to use intrasubspecific crosses. A linkage map of 129 random amplified polymorphic DNA (RAPD) and 18 restriction fragment length polymorphism (RFLP) markers was developed using 118 F2 plants derived from a cross between two japonica cultivars with high and low seedling vigor, Italica Livorno (IL) and Labelle (LBL), respectively. The map spanned 980.5 cM (Kosambi function) with markers on all 12 rice chromosomes and an average distance of 7.6 cM between markers. Codominant (RFLP) and coupling phase linkages (among RAPDs) accounted for 79% of total map length and 71% of all intervals. This map contained a greater percentage of markers on chromosome 10, the least marked of the 12 rice chromosomes, than other rice molecular maps, but had relatively fewer markers on chromosomes 1 and 2. We used this map to detect quantitative trait loci (QTL) for four seedling vigor related traits scored on 113 F3 families in a growth chamber slantboard test at 18 degrees C. Two coleoptile, five root, and five mesocotyl length QTLs, each accounting for 9-50% of the phenotypic variation, were identified by interval analysis. Single-point analysis confirmed interval mapping results and detected additional markers significantly influencing each trait. About two-thirds of alleles positive for the putative QTLs were from the high-vigor parent, IL. One RAPD marker (OPAD13720) was associated with a IL allele that accounted for 18.5% of the phenotypic variation for shoot length, the most important determinant of seedling vigor in water-seeded rice. Results indicate that RAPDs are useful for map development and QTL mapping in rice populations with narrow genetic base, such as those derived from crosses among japonica cultivars. Other potential uses of the map are discussed. Key words : QTL mapping, RAPD, RFLP, seedling vigor, japonica, Oryza sativa.     

Epistasis for fitness-related quantitative traits in Arabidopsis thaliana grown in the field and in the greenhouse

The extent to which epistasis contributes to adaptation, population differentiation, and speciation is a long-standing and important problem in evolutionary genetics. Using recombinant inbred (RI) lines of Arabidopsis thaliana grown under natural field conditions, we have examined the genetic architecture of fitness-correlated traits with respect to epistasis; we identified both single-locus additive and two-locus epistatic QTL for natural variation in fruit number, germination, and seed length and width. For fruit number, we found seven significant epistatic interactions, but only two additive QTL. For seed germination, length, and width, there were from two to four additive QTL and from five to eight epistatic interactions. The epistatic interactions were both positive and negative. In each case, the magnitude of the epistatic effects was roughly double that of the effects of the additive QTL, varying from -41% to +29% for fruit number and from -5% to +4% for seed germination, length, and width. A number of the QTL that we describe participate in more than one epistatic interaction, and some loci identified as additive also may participate in an epistatic interaction; the genetic architecture for fitness traits may be a network of additive and epistatic effects. We compared the map positions of the additive and epistatic QTL for germination, seed width, and seed length from plants grown in both the field and the greenhouse. While the total number of significant additive and epistatic QTL was similar under the two growth conditions, the map locations were largely different. We found a small number of significant epistatic QTL x environment effects when we tested directly for them. Our results support the idea that epistatic interactions are an important part of natural genetic variation and reinforce the need for caution in comparing results from greenhouse-grown and field-grown plants.     

Use of a large multiparent wheat mapping population in genomic dissection of coleoptile and seedling growth

Identification of alleles towards the selection for improved seedling vigour is a key objective of many wheat breeding programmes. A multiparent advanced generation intercross (MAGIC) population developed from four commercial spring wheat cultivars (cvv. Baxter, Chara, Westonia and Yitpi) and containing ca. 1000 F₂‐derived, F_6:7 RILs was assessed at two contrasting soil temperatures (12 and 20 °C) for shoot length and coleoptile characteristics length and thickness. Narrow‐sense heritabilities were high for coleoptile and shoot length (h² = 0.68–0.70), indicating a strong genetic basis for the differences among progeny. Genotypic variation was large, and distributions of genotype means were approximately Gaussian with evidence for transgressive segregation for all traits. A number of significant QTL were identified for all early growth traits, and these were commonly repeatable across the different soil temperatures. The largest negative effects on coleoptile lengths were associated with Rht‐B1b (?8.2%) and Rht‐D1b (?10.9%) dwarfing genes varying in the population. Reduction in coleoptile length with either gene was particularly large at the warmer soil temperature. Other large QTL for coleoptile length were identified on chromosomes 1A, 2B, 4A, 5A and 6B, but these were relatively smaller than allelic effects at the Rht‐B1 and Rht‐D1 loci. A large coleoptile length effect allele (a = 5.3 mm at 12 °C) was identified on chromosome 1AS despite the relatively shorter coleoptile length of the donor Yitpi. Strong, positive genetic correlations for coleoptile and shoot lengths (r_g = 0.85–0.90) support the co‐location of QTL for these traits and suggest a common physiological basis for both. The multiparent population has enabled the identification of promising shoot and coleoptile QTL despite the potential for the confounding of large effect dwarfing gene alleles present in the commercial parents. The incidence of these alleles in commercial wheat breeding programmes should facilitate their ready implementation in selection of varieties with improved establishment and early growth.     

Comparison of quantitative trait loci controlling seedling characteristics at two seedling stages using rice recombinant inbred lines

A better understanding of the genetics of seedling characteristics in rice could be helpful in improving rice varieties. Zhenshan 97 and Minghui 63, the parents of Shanyou 63, an elite hybrid developed during the last decade in China, vary greatly with respect to their physiological and morphological traits at the seedling growth stage. In this study, we used a population of 240 recombinant inbred lines derived from a cross between Zhenshan 97 and Minghui 63 to identify quantitative trait loci (QTL) for seedling characteristics. All plant material was grown in hydroponic culture. Data for the following characters were collected at 30 days and 40 days post-sowing: plant height, shoot dry matter weight (SDW), maximum root length, root dry weight (RDW), total dry weight , and root-shoot ratio (the ratio of SDW to RDW). Analysis using composite interval mapping detected 16 QTL for the six traits in 30-day-old seedlings. Of these 16 QTL, Minghui 63 alleles increased trait values at only two of them. The QTL in the vicinity of R3166 on chromosome 5 simultaneously influenced PH, SDW, MRL, RDW, and TDW in the same direction. Twenty QTL were detected for the same traits in the 40-day-old seedlings. However, at this stage Minghui 63 alleles increased trait values at eight QTL. The QTL linked to R3166 also affected PH, SDW, MRL, RDW, and TDW. Only four QTL were common to the two stages. These results clearly indicate that different genes (QTL) control the same traits during different time intervals. Zhenshan 97 alleles had positive effects during the first 30 days of seedling growth, but thereafter the positive effects of Minghui 63 alleles on seedling growth gradually became more pronounced.     

Identification of quantitative trait loci associated with salt tolerance at seedling stage from Oryza rufipogon

Soil salinity is one of the major abiotic stresses affecting plant growth and crop production.In the present study,salt tolerance at rice seedling stage was evaluated using 87 introgression lines (ILs),which were derived from a cross between an elite indica cultivar Teqing and an accession of common wild rice (Oryza rufipogon Griff.).Substantial variation was observed for four traits including salt tolerance score (STS),relative root dry weight (RRW),relative shoot dry weight (RSW) and relative total dry weight (RTW).STS was significantly positively correlated with all other three traits.A total of 15 putative quantitative trait loci (QTLs) associated with these four traits were detected using single-point analysis,which were located on chromosomes 1,2,3,6,7,9 and 10 with 8％-26％ explaining the phenotypic variance.The O.rufipogon-derived alleles at 13 QTLs (86.7％) could improve the salt tolerance in the Teqing background.Four QTL clusters affecting RRW,RSW and RTW were found on chromosomes 6,7,9 and 10,respectively.Among these four QTL clusters,a major cluster including three QTLs (qRRW10,qRSW10 and qRTW10) was found near the maker RM271 on the long arm of chromosome 10,and the O.rufipogon-derived alleles at these three loci increased RRW,RSW and RTW with additive effects of 22.7％,17.3％ and 18.5％,respectively,while the phenotypic variance explained by these three individual QTLs for the three traits varied from 19％ to 26％.In addition,several salt tolerant ILs were selected and could be used for identifying and utilizing favorable salt tolerant genes from common wild rice and used in the salt tolerant rice breeding program.     

A butenolide, isolated from smoke, can overcome the detrimental effects of extreme temperatures during tomato seed germination

The butenolide, 3-methyl-2H-furo[2, 3-c]pyran-2-one, is an highly active compound isolated from plant-derived smoke. This compound is known to stimulate seed germination in a wide range of plants akin to smoke or aqueous extracts of smoke. The present study attempted to elucidate the role of the butenolide in overcoming detrimental effects of low and high temperatures on tomato seed germination and seedling growth. The germination percentage followed a parabolic curve for temperatures ranging from 10 to 40°C, with 25°C being the optimum for all treatments. Control seeds showed radicle emergence at two extreme temperatures (10 and 40°C) and seedlings failed to develop further, even upon prolonged incubation. By comparison the butenolide-treated seeds grew into phenotypically normal seedlings at these non-optimum temperatures. The smoke–water-treated seeds had an intermediate response as only a fraction of germinated seed developed into normal seedlings. Seedling vigour indices as well as seedling weight were significantly higher (p ≤ 0.05) for butenolide-treated seeds at all temperatures. Furthermore, seedlings developed in the presence of the butenolide had about a 1:1 correspondence between root and shoot length. Butenolide-treated seeds grew better than the control seeds in the temperature shift experiments. A gradual decline in the vigour index values was recorded with an increased duration of incubation at the extreme temperatures. Results of the present study are very important from an horticultural point of view as they indicate the potential use of the butenolide compound in restoring normal seed germination and seedling establishment in tomato below and above optimum temperatures.     

Mapping quantitative trait loci associated with arsenic accumulation in rice (Oryza sativa)

The quantitative trait loci (QTLs) associated with arsenic (As) accumulation in rice were mapped using a doubled haploid population established by anther culture of F1 plants from a cross between a Japonica cultivar CJ06 and an Indica cultivar TN1 (Oryza sativa). Four QTLs for arsenic (As) concentrations were detected in the map. At the seedling stage, one QTL was mapped on chromosome 2 for As concentrations in shoots with 24.4% phenotypic variance and one QTL for As concentrations in roots was detected on chromosome 3. At maturity, two QTLs for As concentrations in grains were found on chromosomes 6 and 8, with 26.3 and 35.2% phenotypic variance, respectively. No common loci were detected among these three traits. Interestingly, the QTL on chromosome 8 was found to be colocated for As concentrations in grain at maturity and shoot phosphorus (P) concentrations at seedling stage. These results provide an insight into the genetic basis of As uptake and accumulation in rice, and will be useful in identifying genes associated with As accumulation.     

Changes in Germination and Seedling Traits of Sesame under Simulated Drought

Drought is considered one of the leading abiotic constraints to agricultural crop production globally. Present study was conducted to assess the effects of different drought treatments (viz. Control, 10% PEG, and 20% PEG) on seed germination, germination indices, seedling traits, and drought tolerance indices of sesame. Our results showed that maximum reduction in the studied parameters was observed at higher PEG concentration (i.e., 20% PEG). As compared to control, the drought treatments viz. 10% and 20% PEG decreased the values for germination indices, such as germination percentage, coefficient of variation of germination time, germination index, and seedling vigor index. Similarly, for seedling traits, the values were decreased for root length, shoot length, root shoot ratio, root fresh weight, shoot fresh weight, root dry weight and shoot dry weight under 10% and 20% PEG treatments significantly in comparison with control. Furthermore, relative to control, the values for drought tolerance indices, such as germination drought tolerance index, root length drought tolerance index, shoot length drought tolerance index, total seedling length drought tolerance index, root fresh weight drought tolerance index, shoot fresh weight drought tolerance index, total fresh weight drought tolerance index, root dry weight drought tolerance index, shoot dry weight drought tolerance index and total dry weight drought tolerance index were also reduced under 10% and 20% PEG treatments, respectively. Our results confirms that drought impact on seed germination and seedling traits could be quantified by using different indices which can further help to design drought adaptation and mitigation strategies. Based on these results it can be concluded that germination indices, seedling traits, and drought tolerance indices have great potential to simulate drought stress impacts on different crop traits thus they should be used in all kinds of stress related studies.     

Mapping quantitative trait loci for seedling vigor in rice using RFLPs

Improving seedling vigor is an important objective of modern rice (Oryza saliva L.) breeding programs. The purpose of this study was to identify and map quantitative trait loci (QTL) underlying seedling vigor-related traits using restriction fragment length polymorphisms (RFLPs). An F₂ population of 204 plants was developed from a cross between a low-vigor japonica cultivar Labelle (LBL) and a high-vigor indica cultivar Black Gora (BG). A linkage map was constructed of 117 markers spanning 1496 Haldane cM and encompassing the 12 rice chromosomes with an average marker spacing of 14 cM. The length of the shoots, roots, coleoptile and mesocotyl were measured on F₃ families in slantboard tests conducted at two temperatures (18° and 25°C). By means of interval analysis, 13 QTLs, each accounting for 7% to 38% of the phenotypic variance, were identified and mapped in the two temperature regimes at a log-likelihood (LOD) threshold of 2.5. Four QTLs controlled shoot length, 2 each controlled root and coleoptile lengths and 5 influenced mesocotyl length. Single-point analysis confirmed the presence of these QTLs and detected additional loci for shoot, root and coleoptile lengths, these latter usually accounting for less than 5% of the phenotypic variation. Only 3 QTLs detected both by interval and singlepoint analyses were expressed under both temperature regimes. Additive, dominant and overdominant modes of gene action were observed. Contrary to what was predicted from parental phenotype, the low-vigor LBL contributed 46% of the positive alleles for shoot, root and coleoptile lengths. Positive alleles from the high-vigor parent BG were identified for increased root, coleoptile and mesocotyl lengths. However, BG contributed alleles with only minor effects for shoot length, the most important determinant of seedling vigor in water-seeded rice, suggesting that it would not be an ideal donor parent for introducing faster shoot growth alleles into temperate japonica cultivars.     

Molecular marker dissection of rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L.) plant architecture under temperate and tropical climates

Rice (Oryza sativa L.) plants develop vertically with shoot elongation and horizontally with tillering. The purpose of this study was to identify and characterize genomic regions influencing the rice plant architecture by quantitative trait locus (QTL) analysis for the component traits: culm length (CL), panicle length (PnL), panicle number (PnN) and tiller number (TN). For this QTL analysis, 191 recombinant inbred lines (F₇) derived from a cross of Milyang 23 (M23) and Akihikari (AK) were grown in 1995, 1996 and 1997 (May–Oct) in Joetsu, Japan (temperate climate), and in the 2000 dry season (Jan–Apr), the 2000 wet season (Jun–Oct) and the 2001 dry season in Los Baños, The Philippines (tropical climate). Results showed that rice plant architecture was influenced by 19 genomic regions categorized into five groups. In Group I, two regions (on chrs. 6 and 11) affected shoot elongation (CL and PnL) and tillering (PnN and TN) in opposite directions more significantly in Los Baños than in Joetsu. In Group II, two regions (chrs. 3 and 12) affected shoot elongation, whereas in Group III, five regions [chrs. 1 (two), 2, 3 and 9] affected only culm length (CL). Expressions of four regions of Group III were influenced by either tropical or temperate environments. In Group IV, seven regions (chrs. 1, 2, 4, 5, 6, 8 and 9) controlled panicle development (PnN or PnL), and in Group V, three regions (chrs. 1, 2 and 3) regulated tillering (PnN or TN). Characterizing these 19 genomic regions provided a detailed analysis of rice plant architecture with emphasis on the multiple effect and environmental responsive regions.Communicated by D. Mackill     

直播条件下水稻6个穗部性状的QTL分析

在大田直播条件下,利用来源于＂Lemont/特青＂的重组自交系群体,对水稻6个穗部性状及其相互间遗传相关的分子基础进行了QTL分析,共检测到19个QTL,各性状QTL数为2～4个,单个QTL贡献率为4%～22%。共检测到3个染色体区段能同时影响多个穗部性状,其中第1染色体RM212-RM104和第2染色体RM263-RM221区段的QTL能同时影响单株产量、每穗颖花数、着粒密度和二次枝梗数中的3个或4个性状,且这2个区段的QTL对各性状的效应方向相同,增效等位基因均来自‘特青’,为各性状间表型正相关提供了重要的遗传解释。第11染色体RG1022附近的QTL对着粒密度的效应值为负,来自‘特青’的等位基因增加性状值,而对穗长的效应值为正,来自‘特青’的等位基因降低性状值,为这2个性状间表型负相关也提供了一定的遗传解释。此外,对水稻穗部性状QTL在多种环境和遗传背景下的稳定表达及其在分子标记辅助育种中的应用进行了讨论。     

Effect of vitamin C and folic acid on seed vigour response and phenolic-linked antioxidant activity

Folic acid and vitamin C were used in the concentration range of 0-500muM as exogenous growth enhancers to stimulate pea (Pisum sativum) seedling vigour. The results suggest that a concentration of 50muM folic acid and 500muM vitamin C were optimum in maximally enhancing seed vigour and potentially seedling performance according to both agronomic and biochemical seed vigour parameters. Results indicated that germination percentage, shoot weight, shoot height, and root length were enhanced in folic acid and vitamin C treated plants compared to control plants. The levels of enhanced phenolic content in response to folic acid and vitamin C treatments were highest on days 8 and 10. Evaluation of critical biochemical parameters indicated that the average glucose-6-phosphate dehydrogenase (G6PDH) activity and proline content in response to treatments were higher than control and correlated to enhanced phenolic content and DPPH-based antioxidant activity. Key enzymes, guaiacol peroxidase (GPX), superoxide dismutase (SOD), and catalase (CAT) were also higher in response to treatments and correlated to enhanced phenolic content and DPPH-based antioxidant activity. Taken together, these studies support the hypothesis that the proline-linked pentose phosphate pathway stimulates phenolic synthesis and related free-radical scavenging antioxidant activity. Further, this proline-linked pentose phosphate pathway stimulation in response to folic acid and vitamin C was also correlated to antioxidant enzyme response indicated by the stimulation of GPX, SOD, and CAT activities. Therefore, this study indicates the enhancement of seed vigour response by folic acid and vitamin C as reflected in both agronomic and biochemical responses, and this occurred through the stimulation of phenolic-linked antioxidant response that is likely positively modulated through the proline-linked pentose phosphate pathway.     

穗颈维管性状与产量相关性状的遗传分析

穗颈维管性状是实现"源"合成的同化物输送至籽粒中的唯一通道.本研究利用来源于籼稻93-11(受体)和粳稻日本晴(供体)构建的染色体片段代换系群体,调查穗颈维管性状与穗部产量性状.结果表明,大部分穗颈维管性状与穗部产量性状呈显著相关;7个穗颈维管性状共检测到42个QTL,其中16个位点日本晴等位基因起增效作用;6个穗部产...