DROUGHT STRESS: Soil Water Availability Alters the Inter‐ and Intra‐Cultivar Competition of Three Spring Wheat Cultivars Bred in Different Eras

Competition for water generates a classic aspect of the tragedy of the commons, the ‘race for fish’, where crops must allocate more resource to acquisition of the limiting resource than is optimal for crop yield allocation. A pot experiment using a simple additive (target–neighbour) design was conducted to examine the above‐ground and below‐ground growth of three spring wheat (Triticum aestivum L.) cultivars when grown alone and in mixtures at three levels of water availability. The effects of competition and water availability were compared by observing patterns of growth, biomass allocation and below‐ground outcomes. Competitive interactions were investigated among cultivars ‘HST’, ‘GY602’ and ‘LC8275’, target plant of each cultivar grown without neighbouring plants are referred to herein as control plant and one target plant of each cultivar sown surrounded either by same or another cultivar as intra‐ or inter‐cultivar competition. Competitive ability was assessed as the response ratio (lnRR) between the target plant surrounded by six other plants and the target plant in isolation. Our results showed that the cultivar ‘HST’, released over a century ago, produced a higher biomass and grain yield than the more recently released cultivars ‘LC8275’ and ‘GY602’ when grown as isolated plants with sufficient water supply. However, competition for resources from neighbours led to target plant biomass and grain yield being significantly reduced relative to controls in all three cultivars, particularly in ‘HST’. When subjected to intra‐cultivar competition, the two recently released cultivars ‘LC8275’ and ‘GY602’ had higher grain yields and water use efficiency for grain than ‘HST’ in all three water regimes. The landrace ‘HST’ had better and significantly linear relationships between biomass and biomass allocation, root length and specific root length, whereas the recent and modern cultivars had much more water‐related species‐specific changes in root morphology and allocation patterns. These results suggest that crop traits that influence competitive ability, such as biomass allocation to roots and root plasticity in response to drought have changed in modern wheat cultivars because of breeding and selection.     

Screening and Analysis of Proteins Interacting with TaPDK from Physiological Male Sterility Induced by CHA in Wheat

To further research the regulatory network of pyruvate dehydrogenase kinase (designated as TaPDK) in physiological male-sterility (PHYMS) of wheat induced by chemical hybridizing agent (CHA) SQ-1, an anther cDNA library was constructed, and the proteins interacting with TaPDK were screened via yeast two-hybrid technique. Subsequently, a few candidate proteins in nucleotide expression levels were detected by real-time quantitative PCR. Yeast-two hybrid screening was performed by mating yeast strain Y2HGold containing BD-TaPDK bait plasmid with yeast strain Y187 including anther cDNA library plasmid. Diploid yeast cells were plated on synthetic dropout nutrient medium (SD/-Ade/-His/-Leu/-Trp) (QDO), and further were incubated on QDO medium containing AbA and X-α-Gal. The interactions between TaPDK and the proteins obtained from positive colonies were further confirmed by co-transformation validation. After plasmids DNA were extracted from blue colonies and sequenced, the sequences results were analyzed by bioinformatic methods. Finally, 24 colonies were obtained, including eight genes, namely non-specific lipid-transfer protein precursor (TanLTP), polyubiquitin (TaPUbi), glyceraldehyde-3-phosphate dehydrogenase, proliferating cell nuclear antigen (TaPCNA), CBS domain containing protein (TaCBS), actin, guanine nucleotide-binding protein beta subunit, chalcone synthase, and three new genes with unknown function. The results of quantitative RT-PCR showed that the expression levels of TanLTP, TaPUbi, and TaPCNA were obviously up-regulated in PHYMS anther, and TaCBS expression was only increased at the tricellular stage in PHYMS anther compared with in fertile lines. Whereas, the expression of TaPDK was obviously down-regulated in PHYMS lines. Collectively, these datas indicated that the majority of candidate proteins might be related to pollen abortion in PHYMS lines, which further suggested that TaPDK plays multiple roles in pollen development, besides participating in regulating pyruvate dehydrogenase complex activity.     

Competition and interactions among stripe rust pathotypes in wheat-cultivar mixtures

A series of experiments was conducted with wheat stripe rust to analyse competition between simple and complex pathotypes in host mixtures. Two different pathotype combinations were tested, with different host components. Each combination included a complex (able to infect two host components) and two simple pathotypes. For one of the combinations, induced resistance was tested in a separate experiment as a possible interaction among pathotypes. Disease severity and pathotype frequencies were measured three times during the epidemic, on each host component grown in pure stands and in mixtures. In one of the experiments, pathotype frequencies were also measured within secondary foci. One of the complex pathotypes appeared to have a low fitness on one of the host components and did not significantly increase in frequency in host mixtures relative to pure stands. The average frequency of the other complex pathotype increased during the first epidemic cycles, but remained stable afterwards, below expected values. The results suggest that the development of complex pathotypes in host mixtures may be influenced by differential aggressiveness on the host components, by induced resistance and by random effects resulting from the formation of disease foci, and depends on pathogen autoinfection rate and dispersal mechanisms.     

Metabolism of [ring-2,6-14]parathion in plant cell suspension cultures of carrot (Daucus carota), purple foxglove (Digitalis purpurea), soybean,thorn apple (Datura stramonium) and wheat (Triticum aestivum)

By means of standardized procedures, the metabolism of [ring-2,6-¹⁴C]-parathion was investigated in carrot (Daucus carota L.), purple foxglove (Digitalis purpurea L.), soybean (Glycine max Merrill cv. ?Mandarin’?, and Glycine max Merrill cv. ?Harosoy 63’? cultivated on B5 and Miller media, respectively), thorn apple (Datura stramonium L.), and wheat (Triticum aestivum L.) cell suspension cultures. In the wheat and soybean (Mandarin) cells only 2.9 and 8.9%, respectively, of the applied parthion remained unmetabolized after 48 h of incubation, while 51.2, 57.9, 60.3, and 62.4% of the unchanged parent were detected in the D. purpurea, D. Stramonium, carrot and soybean (Harosoy) cultures, respectively. In all suspensions, paraoxon and 4-nitrophenol were found as phase I metabolites, thus demonstrating that plant tissues can catalyse oxidative desulfuration and dearylation of parathion. 4-Nitrophenol was also glycosylated with glucose and possibly galactose. Further, as yet unidentified, metabolites indicated that bio-transformations had also occurred at the aromatic moiety. Large amounts of non-extractable residues were detected in the wheat suspension (38.3%), while the other cultures showed a lower incorporation of ¹⁴C into insoluble cell material (0.9-9.4%). For a prospective ecotoxicological evaluation of the metabolic fate of pesticides and xenobiotics in plants in general, the differential metabolic capacity of plant cell cultures and plants should be taken into account.     

小麦品种在低温下膜功能变化的生物物理学分析

本文以冬性及春小麦品种为试材，用示踪，液闪计数及测定电解质泄漏的方法，测定低温胁迫下膜脂的代谢和电解质渗透的变化，并根据热力学的原理，分析其生物膜上的化学反应和扩散过程及膜上物质通量Ｊｊ与跨膜电势Ｅｍ的函数关系。     

Identification of Alternaria spp. on wheat by pathogenicity assays and sequencing

The pathogenicity of Alternaria spp. isolated from wheat leaves collected in regions where alternaria leaf blight has been reported was compared with that of IMI reference isolates of A. triticina and A. alternata using two durum and two bread wheat genotypes. To identify isolates putatively corresponding to A. triticina , morphological and DNA sequence analyses based on ribosomal DNA from the internal transcribed spacer (ITS) region (ITS1, 5·8S rRNA gene, ITS2) and toxicity bioassays of culture filtrate were combined. Glasshouse inoculations provided reliable information to assess the pathogenicity of A. triticina isolates on wheat. Alternaria leaf blight symptoms were produced by the A. triticina isolates only on durum wheat cv. Bansi, while A. alternata , A. tenuissima and A. arborescens isolates were found to be nonpathogenic on the wheat cultivars tested. Alternaria triticina isolates were distinguished from other Alternaria species by Simmons and Roberts' sporulation pattern 6 and two to three conidia per sporulation unit associated with primary conidia bearing long (> 7  µ m) apical secondary conidiophores. Phylogenetic analysis also proved effective at discriminating wheat-pathogenic A. triticina from other nonpathogenic Alternaria species. Alternaria triticina isolates yielded longer ITS sequences than A. alternata , A. tenuissima and A. arborescens isolates, leading to clear-cut differences as visualized with agarose gel electrophoresis. Additionally, only culture filtrates of A. triticina isolates caused nonspecific necrotic lesions on leaves of 3-week-old wheat plants.     

Mutants in wheat showing multipathogen resistance to biotrophic fungal pathogens

Five fast-neutron-derived mutants were isolated from the wheat line Hobbit 'sib' that show enhanced field resistance towards Puccinia striiformis f.sp. tritici , the causal agent of yellow rust. Subsequent testing showed the yellow rust resistance phenotypes to differ between mutants, to be expressed at different growth stages and, in some cases, to show an isolate interaction. Three mutants, I3-48, I3-49 and I3-54, exhibited an enhanced yellow rust resistance phenotype from the third seedling leaf onwards, while mutants I3-27 and I3-30 did not show an altered yellow rust phenotype until later growth stages. Additional resistance for brown rust (causal agent Puccinia triticina ) was identified in mutants I3-27, I3-30, I3-48 and I3-49, and for powdery mildew caused by Blumeria graminis f.sp. tritici in mutants I3-27, I3-30, I3-48 and I3-54, although in some cases the resistance was isolate-specific.     

小麦小分子RNA TaMIR1129介导植株抵御低氮逆境功能研究

本研究针对迄今有关小麦小分子RNA(miRNA)家族成员介导植株氮素吸收和利用机理尚少见报道的现状,对TaMIR1129的表达特征和介导植株抵御低氮逆境功能进行了研究。结果表明,TaMIR1129呈低氮胁迫诱导表达,表现为随氮浓度降低(0.02~6mmol/L)和处理时间延长(0~48h)表达水平不断增高特征。此外,低氮诱导的高表达水平在恢复供氮后表达下调。表明该miRNA对介质中氮素应答呈典型的时间及浓度依赖特征。TaMIR1129作用2个靶基因,包括Molybdenum cofactor sulfurase(TaMCS)和Major facilitator family transporter(TaMFFT),上述基因应答低氮特征与TaMIR1129相反。遗传转化结果表明,超表达TaMIR1129具有显著增强植株抵御低氮逆境的能力。表现为与野生型对照相比,转基因系Sen 1和Sen 2低氮处理后植株形态增大,干质量增加,氮累积量增多。表明TaMIR1129与作用靶基因构建miRNA/target模块在介导植株抵御低氮逆境中发挥重要作用。     

Construction of Genetic Linkage Map of Bread Wheat （Triticum aestivum L.） Using an Intervarietal Cross and QTL Map for Spike Related Traits

Most often a genetic linkage map is prepared using populations obtained from two highly diverse genotypes. However, the markers from such a map may not be useful in a breeding program as these markers may not be polymorphic among the varieties used in breeding. For the past nine years, intraspecific maps have been gaining importance and such maps based on Swiss （PaiUard et al., 2003）, Japanese （Suenaga et al., 2005）, Australian （Chaimcrs et al., 2001） wheat varieties arc available. A map based on Indian wheat varieties however has not been reported. We constructed a genetic linkage map based on a cross between two Indian bread wheat （Triticum aestivum L.） varieties, Sonalika and Kalyansona. One hundred and fifty F2 individuals were analyzed for arbitrarilyprimed polymerase Chain reaction （AP-PCR）, random amplified polymorphic DNA （RAPD）, inter simple sequence repeats （ISSR）, Sequence Tagged Microsatelhte Sites （STMS）, Amplified Fragment Length Polymorphism （AFLP） markers, seed storage proteins and known genes. A linkage map was constructed consisting of 236 markers and spanning a distance of 3 639 cM with 1 211.2 cM for A genome, 1 669.2 cM for B genome, 192.4 cM for D genome and 566.2 cM for unassigned groups,     

小麦不育材料幼胚培养植株再生性研究

本试验对小麦两类不育材料幼胚愈伤诱导及分化进行了研究,结果表明:①N6培养基愈伤组织诱导率最高95%～100%;不同材料平均出愈率由高到低依次为雄性不育1号、雄性不育2号、雌性不育1号;②接种18～30dMS培养基最早产生不定芽分化。最早可见不定芽分化的材料为雄性不育1号,分化进程较雌性不育幼胚提早7～10d;雄性不育1号和雌性不育1号幼胚愈伤组织分别培养45,52d分化率达峰值均为100%,雄性不育2号材料在培养112d分化率达峰值67.4%;③单独加入2,4 D并随2,4 D浓度降低不定芽分化率有增加的趋势。2,4 D与KT配合使用不定芽分化率最高,达100%,以低浓度2,4 D(0.25～0.50mg·L-1)与KT(0.1～0.2mg·L-1)配合为宜。④分化不定芽在不同培养基中生长增殖不同,以C17为最佳同时附加KT0.2mg·L-1 2,4 D0.1mg·L-1分化苗可增殖6倍;再生植株移栽成活率80%以上;接种至移栽历时4个月。