Analysis of factors influencing milling yield and their association to other traits by QTL analysis in two hexaploid oat populations

Milling yield, or the grain weight from which 100 kg of rolled groats is obtained upon milling, is an important quality characteristic of cultivated oat (Avena sativa L.). Kernel morphology and the groat (caryopsis) percentage of the whole kernel including hull are factors that influence milling yield. We mapped QTLs for kernel area, kernel length, kernel width, and groat percentage in two populations of 137 recombinant inbred lines by RFLP and AFLP analysis to evaluate the prospects of marker-assisted selection (MAS). Phenotypic correlations between kernel morphology traits and groat percentage were not significant. For kernel morphology traits and groat percentage, one to five QTLs were detected, explaining 7.0–60.7% of the total phenotypic variance depending on the trait. One QTL for kernel length in each population and one QTL for kernel width in one population were found at the same location as a QTL for groat percentage, indicating that a change in kernel size or shape could have an influence on groat percentage. The positions and effects of QTLs for kernel morphology and groat percentage were compared to QTLs detected previously for chemical grain composition (oil andβ-glucanconcentration) and agronomic traits to evaluate the selection response on these traits through MAS. Several regions of the oat genome were identified that contained clusters of QTLs influencing two or more traits. While the allele from one parent at a QTL could simultaneously improve two or more traits in one population, it could have opposite effects on the same traits at another QTL or in the other population. Associations among traits were complex and will require careful consideration when employing QTL-marker associations in MAS to avoid negative selection response. Future research to discover candidate genes for those QTL clusters could provide information about trait associations and help in designing selection programs. Received: 17 February 2000 / Accepted: 27 October 2000     

裸燕麦Ty1-copia类反转录转座子反转录酶序列的分离、鉴定与分析

本研究根据Ty1-copia类反转录转座子反转录酶的保守区设计简并引物,通过PCR扩增,从裸燕麦(Avena nuda L.)品种‘品燕1号’基因组中分离获得23条Ty1-copia类反转录转座子序列,并对序列特征、系统发育关系及其转录活性进行分析。结果显示,23条Ty1-copia类反转录转座子存在较高的异质性,序列间的一致性为45%～98%,存在插入、移码和终止密码突变,但频率不高;系统发育分析结果表明,燕麦Ty1-copia类反转录转座子在进化过程中主要为垂直传递。本研究通过检索燕麦基因表达数据库,发现了5个有转录活性的Ty1-copia类反转录转座子。     

大粒裸燕麦(Avena nuda L.)遗传连锁图谱的构建

以“元莜麦”和“555”杂交得到的281个F2单株为作图群体,利用20对AFLP引物、3对SSR引物和1个穗型性状构建了一张大粒裸燕麦遗传连锁图。该图谱全长1544.8cM,包含19个连锁群,其上分布有92个AFLP标记、3个SSR标记和1个穗型形态标记,不同连锁群标记数为2-14个,长度在23.7-276.3cM之间,平均长度为81.3cM,标记间平均距离为20.1cM。穗型标记分离比符合3：1,11个AFLP标记表现为偏分离,偏分离比为11.5%。该图谱符合遗传连锁框架图的要求,为今后大粒裸燕麦的QTL定位、分子标记辅助育种和比较基因组学等研究奠定基础。     

黄花棘豆水提液对燕麦的化感作用及其机理研究

以燕麦种子和幼苗为受体,采用室内培养皿法、室内盆栽法和生化分析法,研究了甘肃天祝草地有毒植物黄花棘豆水浸提液对燕麦种子、幼苗的化感作用及其作用机理.结果表明:(1)黄花棘豆水提液均可抑制燕麦种子萌发和幼苗生长,且化感抑制作用随着水提液浓度的增大显著增强;燕麦幼苗根在高浓度的黄花棘豆水提液作用下表现出畸形.(2)随着水提液浓度的增大,根尖有丝分裂逐渐减弱及分裂高峰时间逐渐推迟,种子淀粉酶活性也逐渐下降.(3)燕麦幼苗茎叶部和根部的可溶性糖、可溶性蛋白和叶绿素的含量随着水提液浓度的增大以及作用时间的延长逐渐降低,丙二醛含量则逐渐升高.(4)随着黄花棘豆水提液浓度的增大,其对燕麦幼苗过氧化物酶(POD)、过氧化氢酶(CAT)和超氧化物歧化酶(SOD)活性的抑制作用逐渐增强,随着作用时间的延长抑制作用逐渐减弱.研究发现,黄花棘豆水提液通过降低燕麦幼苗渗透调节物质含量,抑制保护性酶活性,增加膜脂过氧化伤害,导致根尖细胞分裂缓慢,抑制燕麦种子萌发和幼苗生长,从而表现出化感作用,且化感作用随着浓度的增加而增强.     

In vivo labelling of the proteins in the first leaf of intact oat plants (Avena sativa)

In order to label the primary leaves of intact oat plants ( Avena sativa L. cv. Victory) for studying protein turnover using two-dimensional polyacrylamide gel electrophoresis, the following methods were tested: growth of seedlings on ³⁵S-sulfate-containing Knop medium, labelling with ³⁵S-methionine by vacuum infiltration of the leaf, injection into the leaf base or into the seed near the embryo, or wiping the surface of the leaf with ethanol followed by incubation in the labelled solution. A specific activity of 1.6 kBq per 20 μg of leaf protein applied was minimally necessary to obtain a well-resolved fluorogram of the gels. This level of labelling was reached only upon the treatment with ethanol, which did not require more than 0.55 MBq of ³⁵S-methionine per leaf. The method may be useful locally to apply compounds to intact plants.     

Dormancy-associated embryonic mRNAs and proteins in imbibing Avena fatua caryopses

The mechanisms controlling seed dormancy maintenance and release are not understood. To characterize the molecular events accompanying dormancy release, two-dimensional gel electrophoresis was used to monitor changes in soluble proteins and in vitro translation products of embryonic mRNA populations during imbibition of dormant and nondormant (after-ripened) Avena fatua L. caryopses. No differences were observed between in vitro translation products of mRNA extracted from dry dormant and nondormant embryos. However, the expression patterns of several imbibition- and germination-associated mRNAs were temporally modulated during the first 24 h of imbibition. Two dormancy-associated mRNAs, represented by polypeptides D₁ and D₂, were differentially overexpressed in dormant embryos after 3 h of imbibition. mRNA levels for D₁ and D₂ were about 8- and 3-fold higher, respectively, in dormant embryos than in nondormant embryos after 3 h of imbibition. Overexpression of D₁ continued through 12 h of imbibition, while expression of both mRNAs fell to low and equivalent amounts in dormant and nondormant embryos after 24 h. Similar dormancy-associated changes in two soluble proteins were observed during imbibition. The results demonstrate that steady-state levels of specific mRNAs and proteins change during early imbibition of dormant and nondormant A. fatua embryos and indicate that these changes may be associated with differential gene expression responsible for the maintenance of dormancy.     

Pigments in mesocotyls of corn (Zea mays) and oats (Avena sativa) in darkness, and after irradiation and treatment with 5-aminolevulinic acid

The aim of the study was to clarify the pigment content and light-induced pigment formation in the grass mesocotyl (oats, Avena sativa L. cv. Seger I, and corn, Zea mays L. cv. Seneca). This organ, localized between root and coleoptile, only develops in darkness. To date, there are no data on its pigment content in the literature. The data found indicate a close relationship with conditions in roots, particularly with respect to the importance of yellow pigments as bleaching-preventing agents and response to red and blue light. The mesocotyl contained small amounts of both Pchl_628–632 and Pchl_636–642 with a dominance of the former. Occasionally minute amounts of Pchl_650–652 were present, particularly in corn. The highest pigment concentration was found in the zone around the primordia of the pair of roots, which after several days in darkness protruded from the upper part of the mesocotyl close to the attachment to the coleoptile. Carotenoids were not detectable with absorption spectrophotometry. All pigments present in darkness were rapidly bleached in daylight and in strong red and blue light, and no more were synthesized under continuous irradiation. In continuous weak red and blue light small amounts of chlorophyll were formed at the same time as the protochlorophylls disappeared. Red light seemed to be somewhat more effective than blue, at least in corn. This chlorophyll biosynthesis stopped at very low values. The mesocotyls never became visibly green. Normal chloroplasts with grana did not develop. Mesocotyls, which had been irradiated for a short time, with no additional pigment formed, synthesized small amounts of Pchl when placed in darkness. ALA treatment of dark-grown mesocotyls yielded Pchl_628–632 to a higher degree than did irradiation.     

Filipin-sterol complexes in bean rust- and oat crown rust-fungal/plant interactions: Freeze-etch electron microscopy

Summary Treatment with the polyene antibiotic filipin resulted in the formation of granular protuberances of the plasmamembranes of the mesophyll cells of bean (Phaseolus vulgaris) and oat (Avena sativa) plants, and of intercellular hyphal cells of the rust fungiUromyces appendiculatus var.appendiculatus andPuccinia coronata var.avenae, as seen by freeze-etch electron microscopy. The granules were also occasionally seen in intracellular vesicles ofU. appendiculatus. None were found in any intracellular organelles of plant or fungal tissue. The granules ranged in size from about 20–25 nm in the plant tissue and 21–27 nm in the fungal tissue. They were concluded to be filipin-sterol (FS) complexes. The extrahaustorial membranes of either bean or oat rustinfected tissue were generally devoid of FS complexes. The extrahaustorial membrane is continuous with the host plasmamembrane but appeared to have a lower sterol content as compared to the non-invaginated plasmamembrane. The results are discussed in relation to membrane associations at the host-parasite interface.Contribution No. 1011. Winnipeg Research Stn.