Identification of superior parents in a potato breeding programme

Summary An incomplete diallel cross was used to study components of genetic variation in potatoes for a range of characters after early and late harvest. The progenies were also used to evaluate five predictors of progeny performance, namely the mean seedling performance, the mid-parent value and the means of the selfed progenies, of the diploid progenies and of the test-cross progenies. For almost all characters, the general combining ability effects were predominant, although the specific combining ability effects present were greater at late than at early harvests. The seedling performance for tuber yield, number of tubers and average tuber weight did not show any relevant relationship to the field performance. The midparent value provided, in general, satisfactory predictions of the mean progeny performance obtained in the diallel, except for ware tuber yield. The selfed and the diploid progenies did not improve the prediction of progeny means compared to the mid-parent value. The predictions based on the test-crosses surpassed those of the mid-parent value, particularly for tuber yield at ware potato harvest. Methods to identify superior parents are discussed.     

Transfer of Hessian fly resistance from rye to wheat via radiation-induced terminal and intercalary chromosomal translocations

Summary A new Hessian fly (Mayetiola destructor) resistance gene derived from Balbo rye and its transfer to hexaploid wheat via radiation-induced terminal and intercalary chromosomal translocations are described. Crosses between resistant Balbo rye and susceptible Suwon 92 wheat and between the F₁ amphidiploids and susceptible TAM 106 and Amigo wheats produced resistant BC₂F₃ lines that were identified by C-banding analysis as being 6RL telocentric addition lines. Comparative chromosomal analyses and resistance tests revealed that the resistance gene is located on the 6RL telocentric chromosome. X-irradiated pollen of 6RL addition plants was used to fertilize plants of susceptible wheats TAM 106, TAM 101, and Vona. After several generations of selection for resistance, new sublines were obtained that were homogeneous for resistance. Thirteen of these lines were analyzed by C-banding, and three different wheat-6RL chromosomal translocations (T) were identified. Wheat chromosomes involved in the translocations were 6B, 4B, and 4A. Almost the complete 6RL arm is present in T6BS · 6BL-6RL. Only the distal half of 6RL is present in T4BS · 4BL-6RL, which locates the resistance gene in the distal half of 6RL. Only a very small segment (ca 1.0 m) of the distal region of 6RL is present in an intercalary translocation (Ti) Ti4AS · 4AL-6RL-4AL. The 6RL segment is inserted in the intercalary region between the centromere of chromosome 4A and the large proximal C-band of 4AL. The break-points of the translocations are outside the region of the centromere, indicating that they were induced by the X-ray treatment. All three translocations are cytologically stable and can be used directly in wheat breeding programs.Cooperative investigations of the Kansas Agricultural Experiment Station, Departments of Entomology and Plant Pathology, the Wheat Genetics Resource Center, Kansas State University, and the US Department of Agriculture, Agricultural Research Service. Contribution No. 91-117-JDeceased     

Acid phosphatase-11, a tightly linked molecular marker for root-knot nematode resistance in tomato: from protein to gene,using PCR and degenerate primers containing deoxyinosine

With a view to cloning the root-knot nematode resistance gene Mi in tomato by chromosome walking, we have developed a molecular probe for the tightly linked acid phosphatase-1 (Aps-1) locus. The acid phosphatase-1 allozyme (APS-1¹), encoded by the Aps-1 ¹ allele originating from Lycopersicon peruvianum, was purified to apparent homogeneity from tomato roots and suspension cells. Microsequencing of CNBr and tryptic peptides generated from APS-1¹ provided a partial amino acid sequence, which accounted for approximately 23% of the protein and revealed two stretches of homology with soybean proteins KSH3 and VSP27, comprising 22 matches within 26 amino acid residues. The partial amino acid sequence information enabled us to isolate a 2.4 kb genomic Aps-1 ¹ sequence by means of the polymerase chain reaction (PCR), primed by degenerate pools of oligodeoxyribonucleotides, synthesized on the basis of the amino acid sequences. Synthesis of the 2.4 kb PCR product was specific for genomic templates carrying the L. peruvianum Aps-1 ¹ allele. Crucial to the priming specificity and the synthesis of the 2.4 kb genomic sequence was the use of degenerate primer pools in which the number of different primer species was limited by incorporating deoxyinosine phosphate residues at three and four base ambiguities. In using cDNA as a template, a 490 bp sequence was obtained, indicating a high proportion of intron sequences in the 2.4 kb genomic Aps-1 ¹ sequence. The Aps-1 ¹ origin of the PCR product was confirmed by RFLP (restriction fragment length polymorphism) analysis, using both a chromosome 6 substitution line and a pair of nearly isogenic lines, differing for a small chromosomal region around the Aps-1/Mi loci.     

P-glycoprotein as multidrug transporter: a critical review of current multidrug resistant cell lines

MDR has been studied extensively in mammalian cell lines. According to usual practice, the MDR phenotype is characterized by the following features: cross resistance to multiple chemotherapeutic agents (lipophilic cations), defective intracellular drug accumulation and retention, overexpression of P-gp (often accompanied by gene amplification), and reversal of the phenotype by addition of calcium channel blockers. An hypothesis for the function of P-gp has been proposed in which P-gp acts as a carrier protein that actively extrudes MDR compounds out of the cells. However, basic questions, such as what defines the specificity of the pump and how is energy for active efflux transduced, remain to be answered. Furthermore, assuming that P-gp acts as a drug transporter, one will expect a relationship between P-gp expression and accumulation defects in MDR cell lines. A review of papers reporting 97 cell lines selected for resistance to the classical MDR compounds has revealed that a connection exists in most of the reported cell lines. However, several exceptions can be pointed out. Furthermore, only a limited number of well characterized series of sublines with different degrees of resistance to a single agent have been reported. In many of these, a correlation between P-gp expresson and transport properties can not be established. Co-amplification of genes adjacent to the mdr1 gene, mutations [122], splicing of mdr1 RNA [123], modulation of P-gp by phosphorylation [124] or glycosylation [127], or experimental conditions [26,78] could account for some of the complexity of the phenotype and the absence of correlation in some of the cell lines. However, both cell lines with overexpression of P-gp without increased efflux [i.e., 67,75] and cell lines without P-gp expression and accumulation defects/increased efflux [i.e., 25,107] have been reported. Thus, current results from MDR cell lines contradict - but do not exclude - that P-gp acts as multidrug transporter. Other models for the mechanism of resistance have been proposed: (1) An energy-dependent permeability barrier working with greater efficacy in resistant cells. This hypothesis is supported by studies of influx which, although few, all except one demonstrate decreased influx in resistant cells; (2) Resistant cells have a greater endosomal volume, and a greater exocytotic activity accounts for the efflux. Furthermore, large amounts of P-gp in the plasma membrane altering the ultrastructure and generalized changes, such as increases or decreases in membrane fluidity, alterations in lipid composition, changes in transmembrane pH gradient and membrane potential have been described in MDR cell lines and could account for some of the findings.     

Non‐pathogenic association of L‐form bacteria (pseudomonas syringae pv. phaseolicola) with bean plants (Phaseolus vulgaris L.) and its potential for biocontrol of halo blight disease

L‐forms of the halo blight pathogen, Pseudomonas syringae phaseolicola, were maintained in a medium which suppressed cell wall synthesis. These L‐forms, unlike revertants (walled forms derived from unstable L‐forms) and cell walled (parent) organisms, did not elicit a hypersensitive response in tobacco leaves. Association of L‐forms with Phaseolus vulgaris was established by seed imbibition in L‐form suspensions compared with appropriate control treatments (5% mannitol or heat‐killed cells). Seedling emergence and plant growth was not affected by L‐form imbibition. The association was detected by agglutination assays using polyclonal antibody. The L‐form association was localized to the lower shoot tissue and was progressively lost with age of plants. Plants with associated L‐forms had vigour and shoot weights equivalent to controls and showed no disease symptoms. The cell walled form could not be isolated from plants showing positive agglutination. On challenge with the pathogen, plants associated with L‐forms showed significantly less disease symptoms than controls. Stem extracts, from associated plants, were inhibitory to in vitro cultures of both L‐forms and parent forms of Ps. syr. phaseolicola. These results indicate that L‐form associations confer induced systemic resistance to bean plants and might be developed as novel biocontrol systems.     

The emergence of transgenic potatoes as commercial products and tools for basic science

The potato has tremendous potential as a transgenic crop and is a good model system by which to analyse metabolic regulation and gene expression. The potato’s difficult genetics, but ease of genetic transformation and its clonal means of propagation make it ideal for applied agricultural molecular genetics. Thus, the next 4 years promise to put the potato (with a diversity of transgenic constructs expressed) in the limelight as many of the first transgenic agricultural products enter the marketplace.     

八种针阔叶幼树清晨叶水势与土壤含水量的关系及其抗旱性研究

一、前言土壤是植物根系的生活环境,是供给植物赖以生存的水分和养分的源泉。干旱区的植物尤其是树木常常由于土壤供水不足而限制其自然分布和生长。根据土壤-植物-大气连续体系     

Activation of antifreeze proteins from larvae of the beetle Dendroides canadensis

Summary Purified antifreeze proteins (AFPs) from the larvae of the beetle Dendroides canadensis do not produce the high levels of antifreeze activity seen in the hemolymph of overwintering larvae, even when the purified AFPs are assayed at very high concentrations. However, addition of certain proteins or agar (at concentrations sufficiently low that the gel state does not result) to the Dendroides AFP resulted in a 2–3-fold increase in activity. A 70-kDa protein with AFP-activating capabilities was purified from Dendroides larvae. Addition of this endogenous activator protein to a 4 mg·ml^-1 solution of AFP increased the activity of the AFPs to values comparable to those of the hemolymph of overwintering larvae. Data derived from a modified immunoblot technique demonstrate that the activators bind to the AFP, or vice versa. Formation of this association must allow the AFP to block ice crystal growth by binding to the surface of potential seed crystals in the normal fashion. However, because the AFP-activator complex is much larger than the AFP alone, the complex probably blocks a greater surface area of the crystal and is thus a more efficient antifreeze.Abbreviations AFP antifreeze protein - BSA bovine serum albumine - DEAE diethylaminoethyl - Ig immunoglubolin - LPIN lipoprotein ice nucleator - PIN protein ice nucleator - SDS sodium dodecyl sulfate - PAGE polyacrylamide gel electrophoresis - TH thermal hysteresis     

Structures of the α(1-3)-galactose-containing asparagine-linked glycans of a Lewis lung carcinoma cell subline resistant toAleuria aurantia agglutinin: elucidation by1H-NMR spectroscopy

Four bi-antennary glycan fractions of theN-acetyllactosamine-type, derived from a Lewis lung carcinoma (LL₂) cell subline resistant to theAleuria aurantia agglutinin were studied by 400 MHz¹H-NMR spectroscopy. By this method, their antennae were found to be terminated either by (2-3 or 6)-linkedN-acetylneuraminic acid or (1-3)-linked galactose residues. The primary structure of glycans of these four glycopeptide or derived oligosaccharide-alditols has been determined in full detail.Abbreviations NAc N-acetyl group - NGc N-glycolyl group - GlcNAc N-acetylglucosamine - NeuAc N-acetylneuraminic acid - NeuGc N-glycolylneuraminic acid - Man mannose - Gal galactose - Fuc fucose - Con A concanavalin A - LCA Lens culinaris agglutinin - AAA Aleuria aurantia agglutinin - WGA Wheat germ agglutinin - RCA II Ricinus communis agglutinin II - PBS phosphate buffered saline, 0.01m Na₂HPO₄/0.14m NaCl, pH 7.2 - HPLC high performance liquid chromatography - EMEM Eagle's Minimal Essential Medium - Lec^R lectin resistant - MG -methylglycoside