Population dynamics of Anarsia lineatella in relation to crop damage and the development of economic injury levels

Developing a relationship between pest abundance and damage to crops is essential for the calculation of economic injury levels (EILs) and to anticipate informed management decisions. Field studies were conducted for three successive years (2005, 2006 and 2007) in peach orchards of northern Greece to examine relationships between densities of Anarsia lineatella Zeller (Lepidoptera: Gelechiidae) populations and peach (Prunus persica) yields. According to a linear regression model, the increase in moth’s densities during the 1st flight resulted in a significant reduction in yield (y = 0.436x + 10.22, R² = 0.635, d.f. = 2,11, P < 0.05). Correlation of male moths captured during the 2nd flight and observed yield loss was significant (y = 0.5231x + 17.204, R² = 0.792, d.f. = 2,11, P < 0.05). Moreover, according to a linear model by counting the number of shoot strikes, during the first observation period, a forthcoming yield loss can be estimated (y = 27.389x?6.304, R² = 0.711, d.f. 2,11, F = 22.09, P < 0.05). A significant relationship was observed between the numbers of the 2nd generation larvae and yield loss (y = 163x, R² = 0.890). Regression coefficient of the above function represents yield loss per pest and was applied in the calculation of EIL’s and fixed Economic thresholds (ET’s). In addition, parameter of the price commodity was estimated for 2009 by applying stochastic autoregressive moving average model. By integrating above information, EIL and fixed ET estimated as 112 larvae and 84 larvae per sampling unit for a mean value (€4/0.1 ha) of cost management tactics and a 90% efficacy.     

Proteomics and systems biology to tackle biological complexity: Yeast as a case study

In this note we discuss how, by using budding yeast as model organism (as has been done in the past for biochemical, genetics and genomic studies), the integration of "omics" sciences and more specifically of proteomics with systems biology offers a very profitable approach to elucidating regulatory circuits of complex biological functions.     

Bayesian Methods for Examining Hardy–Weinberg Equilibrium

Summary .  Testing for Hardy–Weinberg equilibrium is ubiquitous and has traditionally been carried out via frequentist approaches. However, the discreteness of the sample space means that uniformity of  p -values under the null cannot be assumed, with enumeration of all possible counts, conditional on the minor allele count, offering a computationally expensive way of  p -value calibration. In addition, the interpretation of the subsequent  p -values, and choice of significance threshold depends critically on sample size, because equilibrium will always be rejected at conventional levels with large sample sizes. We argue for a Bayesian approach using both Bayes factors, and the examination of posterior distributions. We describe simple conjugate approaches, and methods based on importance sampling Monte Carlo. The former are convenient because they yield closed-form expressions for Bayes factors, which allow their application to a large number of single nucleotide polymorphisms (SNPs), in particular in genome-wide contexts. We also describe straightforward direct sampling methods for examining posterior distributions of parameters of interest. For large numbers of alleles at a locus we resort to Markov chain Monte Carlo. We discuss a number of possibilities for prior specification, and apply the suggested methods to a number of real datasets.     

<Emphasis Type="Italic">Bacillus megaterium</Emphasis>—from simple soil bacterium to industrial protein production host

Bacillus megaterium has been industrially employed for more than 50 years, as it possesses some very useful and unusual enzymes and a high capacity for the production of exoenzymes. It is also a desirable cloning host for the production of intact proteins, as it does not possess external alkaline proteases and can stably maintain a variety of plasmid vectors. Genetic tools for this species include transducing phages and several hundred mutants covering the processes of biosynthesis, catabolism, division, sporulation, germination, antibiotic resistance, and recombination. The seven plasmids of B. megaterium strain QM B1551 contain several unusual metabolic genes that may be useful in bioremediation. Recently, several recombinant shuttle vectors carrying different strong inducible promoters and various combinations of affinity tags for simple protein purification have been constructed. Leader sequences-mediated export of affinity-tagged proteins into the growth medium was made possible. These plasmids are commercially available. For a broader application of B. megaterium in industry, sporulation and protease-deficient as well as UV-sensitive mutants were constructed. The genome sequence of two different strains, plasmidless DSM319 and QM B1551 carrying seven natural plasmids, is now available. These sequences allow for a systems biotechnology optimization of the production host B. megaterium. Altogether, a “toolbox” of hundreds of genetically characterized strains, genetic methods, vectors, hosts, and genomic sequences make B. megaterium an ideal organism for industrial, environmental, and experimental applications.     

Comparison of Methods for Assessing Resistance to Meloidogyne arenaria in Peanut

Use of resistant cultivars is a desirable approach to manage the peanut root-knot nematode (Meloidogyne arenaria). To incorporate resistance into commercially acceptable cultivars requires reliable, efficient screening methods. To optimize the resistance screening protocol, a series of greenhouse tests were done using seven genotypes with three levels of resistance to M. arenaria. The three resistance levels could be separated based on gall indices as early as two weeks after inoculation (WAI) using 8,000 eggs of M. arenaria per plant, while four or more weeks were needed when 1,000–6,000 eggs/plant were used. High inoculum densities (over 8,000 eggs/plant) were needed to separate the three resistance levels based on eggs per gram of root within eight WAI. A gall index based on percentage of galled roots could separate the three resistance levels at lower inoculum levels and earlier harvest dates than other assessment methods. The use of eggs vs. second-stage juveniles (J2) as inoculum provided similar results; however, it took three to five more days to collect J2 than to collect eggs from roots. Plant age affected gall index and nematode reproduction on peanut, especially on the susceptible genotypes AT201 and D098. The genotypes were separated into their correct resistance classes when inoculated 10 to 30 days after planting, but were not separated correctly when inoculated on day 40.     

Expression level of heterologous tat genes is crucial for in vivo reconstitution of a functional Tat translocase in Escherichia coli

The Tat system has the remarkable capacity of exporting proteins in folded conformation across the cytoplasmic membrane. The functional Tat translocase from Gram-negative bacteria consists of TatA, TatB and TatC proteins. To gain information about the species specificity of the Tat translocase, we cloned tat genes from Gram-negative pathogens Shigella flexneri 2a str. 301, Vibrio cholerae El Tor N16961, Pseudomonas aeruginosa PAO1, thermophilic Sulfolobus solfataricus P2, Thermus thermophilus HB8 and from three Magnetospirillum species (AMB-1, MS-1 and MSR-1), and assessed the capacity of these Tat systems to restore the Tat-dependent growth defect of Escherichia coli tat mutants. We found that whereas the tat genes from the thermophilic bacterial and archaeal species were not functional in E. coli, other tat genes could all complement the phenotype of the E. coli tat mutants. In addition, a chimera composed of the N-terminus of V. cholerae TatE and C-terminus of M. magneticum TatA was functional. Whereas the expression of the tatABC genes from P. aeruginosa and Magnetospirillum strains must be induced to obtain a functional Tat system, overproduction of the V. cholerae TatABC proteins abolished the complementation. The complementation impairment seemed to be correlated with increasing level of slow-migrating TatC isoforms. In vitro studies showed that slow-migrating TatC isoforms in the purified V. cholerae TatABC complex increased with storage time. Together these results showed that the Tat translocases from the Gram-negative bacteria are generally functional in E. coli and the expression level is crucial for in vivo reconstitution of a functional Tat translocase.     

Distribution of flower morphs, ploidy level and sexual reproduction of the invasive weed Oxalis pes-caprae in the western area of the Mediterranean region

Background and Aims: Oxalis pes-caprae is a widespread invasive weed in regions witha Mediterranean climate. In its native habitat (southern Africa)this species has been reported as heterostylous with trimorphicflowers and a self- and morph-incompatible reproductive system.In most of the areas invaded, only a pentaploid short-styledmorphotype that reproduces mainly asexually by bulbils is reported,but this has only been confirmed empirically. This study aimsto analyse the floral morph proportions in a wide distributionarea, test the sexual female success, and explain the causesof low sexual reproduction of this species in the western areaof the Mediterranean Basin. Methods: Fifty-five populations of O. pes-caprae were sampled in theIberian Peninsula and Morocco to evaluate the floral morph ratioand individual fruit set. In plants from a dimorphic population,hand-pollination experiments were performed to evaluate theeffect of the pollen source on pollen tube growth through thestyle. The ploidy level and genome size of individuals of eachfloral morph were analysed using flow cytometry. Key Results: From the populations studied 89·1 % were monomorphic,with most of them containing the short-styled (SS) floral morph,and 10·9 % were dimorphic containing long-styled(LS) and SS morphs. In some of these, isoplethy was verifiedbut no fruit production was observed in any population. A sterileform was also recorded in several populations. Hand-pollinationexperiments revealed that pollen grains germinated over recipientstigmas. In intermorph crossings, pollen tubes were able todevelop and fruit initiation was observed in some cases, whilein intramorph pollinations, pollen tube development was sporadicand no fruit initiation was observed. All individuals withineach floral form presented the same DNA ploidy level: SS plantswere pentaploid and LS and the sterile form were tetraploid. Conclusions: The low or null sexual reproduction success of this speciesin the area of invasion studied seems related with the highfrequency of monomorphic populations, the unequal proportionof floral morphs in dimorphic populations and the presence ofdifferent ploidy levels between SS and LS morphs. The discoveryof the occurrence of an LS floral morph and a sterile form,whose invading capacity in these areas is as yet unknown, willbe valuable information for management programmes.     

氮素水平对小麦幼苗叶绿体色素蛋白复合体含量的影响

在水培条件下,研究了不同氮素水平对小麦幼苗叶绿体色素、色素蛋白复合体含量及其光谱特征的影响。结果显示:(1)氮素水平较低时PSⅡ捕光色素蛋白复合体LHCⅡ在24~30 kD范围内的蛋白含量降低,不供氮时,色素蛋白复合体含量最低,而高分子量区域的蛋白组分相对较为稳定,说明氮素水平影响PSⅡ的多肽组分,而对PSⅠ多肽组分的影响相对较小。(2)室温吸收光谱分析表明,氮素水平较低时结合态色素的含量及比例发生改变,影响植物对光的吸收能力;荧光激发及发射光谱的峰值均随氮素浓度的升高而升高,说明增加施氮量时,叶绿体类囊体中受激发的色素分子数目增加,荧光强度也随之增大;叶绿体蛋白含量在16.86 mg.L-1氮素浓度时最大。     

Dominance Relationship between Two Self-Incompatible<Emphasis Type="Italic">Brassica campestris</Emphasis> Haplotypes in Response to CO<Subscript>2</Subscript> Gas

InBrassica, self-incompatibility (SI) can be overcome by CO₂ application, an effective method for obtaining numerous inbred lines for F, commercial seed. We previously reported two different S-alleles ofBrassica campestris, S⁷³³ and S⁷³⁴, with extremely different degrees of susceptibility to this gas. In the current study, we raised a cross-population between those two genetic lines, and analyzed their reaction level of self-incompatibility to CO₂ (RLSICO₂). Here, all 40 of our progeny from the F₁ cross-population were susceptible, maintaining high values of RLSICO₂. This suggests that the susceptible line, S⁷³⁴, is dominant to the insusceptible line, S⁷³³. We also generated an F₂ selfing-population of each crossed progeny, S⁷³³♀ S⁷³⁴♂ and S⁷³³♂ S⁷³⁴♀, to assess the RLSICO₂ of each individual. PCR-RFLP analysis was performed to determine the S-genotype of the F₂ population. The S⁷³⁴ allele segregated in a theoretical ratio of the dominant trait, and the RLSICO₂ was consistent with the dominance relationship. Therefore, we have now demonstrated that high RLSICO₂ in β.campestris is controlled by a dominant gene. Both authors contributed equally to this work