Optimizing a pheromone lure for the sugar beet root maggot fly,Tetanops myopaeformis

We previously described a putative aggregation pheromone in adults of the sugar beet root maggot, Tetanops myopaeformis (von Röder) (Diptera: Ulidiidae), comprising nine compounds identified from males. Here, we conducted a series of experiments aimed at simplifying the blend of compounds necessary to achieve attraction as well as determining the dose that maximizes captures when formulated into an attractant lure. In all experiments, females showed stronger and more consistent evidence of attraction than males. White sticky traps baited with different blends of pheromone compounds that included the major component, (R)-(−)-2-nonanol, showed significantly higher female captures relative to those baited with blends that excluded the major component. (R)-(−)-2-nonanol alone was at least as effective as any blend that included this compound with other minor pheromone components. Lures using racemic 2-nonanol were as effective as the (R) enantiomer for both females and males, with some evidence of weak attraction to the (S) enantiomer (which is not produced by males) observed as well. Maximum capture rates using racemic 2-nonanol were estimated to occur with doses of ca. 795.5 and 621.6 mg for females and males, respectively. Addition of 2-nonanol lures to standard orange sticky stake traps currently used to monitor flies increased captures of both sexes. The pheromone lure developed here could improve trapping efficiency of current monitoring programs for T. myopaeformis and may also be used to develop other management tools for this important pest of sugar beet.     

Plant regeneration from protoplasts of sugar beet (Beta vulgaris)

Mesophyll protoplasts from two of five sugar beet lines tested were regenerated into plants. Mesophyll protoplasts of all lines showed high plating efficiencies up to 4.0% developed hard compact callus, and two of the lines also developed white, soft and friable callus consisting of starch grain-containing cells. Whereas the compact callus never regenerated into plants, the white friable ones frequently developed globular structures, which became green in the light and formed adventitious shoots after cytokinin (BAP or thidiazuron) treatment. Genetic analysis by PCR-fingerprinting and flow cytometry showed uniformity and unchanged ploidy levels in 15 independently regenerated plantlets in line NF. but altered ploidy level (from diploid to triploid) in a regenerated plantlet of clone VRB.     

Cadmium effects on leaf transpiration of sugar beet (Beta vulgaris)

Seedlings of sugar beet ( Beta vulgaris L. cv Monohill) were cultivated for 4 weeks in nutrient solution containing different concentrations of CdCl₂ (0 to 10 μ M ). The effects of Cd on appearance and function of stomata and leaf cuticle were investigated by water loss measurements and microscopy. The leaf transpiration rate increased with increasing Cd concentrations while the sum total of stomatal aperture area per unit leaf area decreased. Already at low Cd levels. an increase of defective and undeveloped stomata was found in Cd treated plants. These stomata are closed or have small apertures and probably lack a functional closing mechanism. The number of intact stomata per unit leaf area was lower in leaves of Cd treated plants than in controls, and Cd induced closure of intact stomata. The total number of stomata per leaf area slightly increases with increasing Cd concentration. as does the percentage of small stomata. Furthermore. specific leaf area increased, while the density of leaf structure was decreased by Cd. From this observation we conclude that the increase in transpiration rate caused by Cd is primarily due to effects on the permeability of the leaf cuticle to water.     

Direct and indirect effects of Cd2+ on photosynthesis in sugar beet (Beta vulgaris)

Sugar-beet plants ( Beta vulgaris L. cv. Monohill) were cultivated for 4 weeks in a complete nutrient solution. Indirect effects of cadmium were studied by adding 5, 10 or 20 μ M CdCl₂ to the culture medium while direct effects were determined by adding 1, 5, 20, 50 or 2 000 μ M CdCl₂ to the assay media. The photosynthetic properties were characterized by measurement of CO₂ fixation in intact plants, fluorescence emission by intact leaves and isolated chloroplasts, photosystem (PS) I and PSII mediated electron transport of isolated chloroplasts, and CO₂-dependent O₂ evolution by protoplasts. When directly applied to isolated leaves, protoplasts and chloroplasts. Cd²⁺ impeded CO₂ fixation without affecting the rates of electron transport of PSI or PSII or the rate of dark respiration. When Cd²⁺ was applied through the culture medium the capacity for, and the maximal quantum yield of CO₂ assimilation by intact plants both decreased. This was associated with: (1) decreased total as well as effective chlorophyll content (PSII antennae size), (2) decreased coupling of electron transport in isolated chloroplasts, (3) perturbed carbon reduction cycle as indicated by fluorescence measurements. Also, protoplasts isolated from leaves of Cd²⁺-cultivated plants showed an increased rate of dark respiration.     

Foliar uptake of Cd by pea (Pisum sativum) and sugar beet (Beta vulgaris)

Pea ( Pisum sativum L. cv. Fenomen) and sugar beet ( Beta vulgaris L. cv. Monohill) were cultivated in nutrient media without or with 10 μM CdCl₂. Leaves of the same size and stage of development, detached or still attached to the intact plants, were submerged into redistilled water containing 1 to 250 μM CdCl₂. The uptake experiments were run for 1 to 8 h at pH 3.6 and 5.1. Cuticular transpiration rate, density of leaf and density of stomata were also measured. Percentage of open stomata was studied at different pH.
Foliar uptake of Cd into the leaf is evident since Cd is transported from the exposed part of the pea leaves, through the petioles and into the stipules, and since the Cd concentration of the leaves increases with time and external Cd concentration. The foliar uptake depends on the permeability of the cuticular membrane, which is increased by a high intrinsic Cd level, which in turn enhances the foliar uptake of Cd in sugar beet. Higher cuticular permeability in pea than in sugar beet is shown by a 2.5 times higher cuticular transpiration rate and a 4 times lower density of leaf for pea, which causes a 7 times higher foliar uptake in pea than in sugar beet. Low pH decreases the net uptake of Cd, probably by an exchange reaction in the cutin and pectin of the cuticular membrane. Stomata are not directly involved in the Cd uptake, and the differences in the sum total of stomatal aperture area per unit leaf area is not related to differences in foliar uptake of Cd. Percentage of open stomata, calculated as average of both sides of the leaves, was not affected by changes in pH: but especially at high pH. proportionally more stomata were open on the adaxial than on the abaxial side.     

An analysis of genetic variation in sugar beet (Beta vulgaris L. using an augmented biparental (ABIP) mating design

An augmented biparental (ABIP) mating design was used to investigate the quantitative variation, particularly the dominance variation, for morphological and chemical characters in sugar beet. Diploid O-type plants were both crossed and selfed and the progeny were grown in a single-plant randomised field trial. A comparison of the two kinds of family provided tests for both dominance variation and directional dominance effects. Estimates of the narrow heritability were also obtained for each character. Germination problems reduced the size of the final analysis but evidence was obtained of dominance variation and positive directional dominance effects for leaf length, root weight and potassium concentration and, to a lesser extent, sugar concentration. Genetic control of sodium and alpha-amino nitrogen concentrations appeared to be mostly additive. Hybrid varieties of sugar beet should exploit these directional dominance effects and the more closely varieties approach true F, hybrids the more they will capitalise on these advantages. It is possible that other factors such as epistasis, contamination, competition and seed effects may cause us to under- or overestimate the importance of dominance.     

Genetic approaches to sustainable pest management in sugar beet (Beta vulgaris)

Sugar beet (Beta vulgaris) is an important arable crop, traditionally used for sugar extraction, but more recently, for biofuel production. A wide range of pests, including beet cyst nematode (Heterodera schachtii), root‐knot nematodes (Meloidogyne spp.), green peach aphids (Myzus persicae) and beet root maggot (Tetanops myopaeformis), infest the roots or leaves of sugar beet, which leads to yield loss directly or through transmission of beet pathogens such as viruses. Conventional pest control approaches based on chemical application have led to high economic costs. Development of pest‐resistant sugar beet varieties could play an important role towards sustainable crop production while minimising environmental impact. Intensive Beta germplasm screening has been fruitful, and genetic lines resistant to nematodes, aphids and root maggot have been identified and integrated into sugar beet breeding programmes. A small number of genes responding to pest attack have been cloned from sugar beet and wild Beta species. This trend will continue towards a detailed understanding of the molecular mechanism of insect–host plant interactions and host resistance. Molecular biotechnological techniques have shown promise in developing transgenic pest resistance varieties at an accelerated speed with high accuracy. The use of transgenic technology is discussed with regard to biodiversity and food safety.     

Fibrous root turnover and growth in sugar beet (Beta vulgaris var. saccharifera) as affected by nitrogen shortage

The root system of plants is subject to fast cycles of renewal and decay within the growing season. In water and/or nutrient stress conditions, this turnover may become strategic for plant survival and productivity, but knowledge about its mechanisms is still insufficient. In order to investigate the effects of nitrogen fertilization on growth and turnover of sugar beet roots, an experiment was carried out over two growing seasons in northern Italy with two levels of N supply (0, 100 kg ha^–1). Biomass production and partitioning were followed during growth, and fibrous root dynamics were inspected by means of computer-aided procedures applied to minirhizotron images.In conditions of N shortage, lower yields (storage roots) were associated with greater allocation of biomass to tap roots (final tap-root/shoot ratio = 5.6 vs. 4.1) and shallower distribution of fibrous root length density. The maximum depth of roots was not affected by N, but unfertilized plants reached it more slowly.The ratio of cumulative root dead length to produced length at the end of the growing period (TDL _max/TPL _max) was used as the most suitable approach for assessing overall root turnover. This ratio was greater in controls (0.73 vs. 0.50), which showed lower root longevity (–34% life-span on average), indicating that a greater proportion of root growth was renewed by unfertilized plants over the season.     

The design and analysis of breeders' trials of sugar beet (Beta vulgaris) using two-dimensional blocking structures

A method for generating two-dimensional blocking designs to fit any shape and size of experimental area is presented. The method takes an alpha design appropriate to the experimental area and imposes additional blocking perpendicular to the alpha blocks. Improvements to the design are then made by repositioning entries within the alpha blocks. Although this method of construction is less sophisticated than for other two-dimensional designs, the designs are particularly suited to large scale breeders trials where no alternative two-dimensional design may exist. The designs have been used for 3 yr in a sugar beet breeding programme, and have given improvements in efficiency over one-dimensional alpha designs.     

In vitro culture of petioles and intact leaves of sugar beet (Beta vulgaris)

Methods are described for obtaining explants which produce adventitious shoots, for subsequent stimulation of rooting and then transplanting using six commercial sugar-beet cultivars. The rate of adventitious shoot regeneration from petioles or intact leaf explants was affected by the source of donor plants, cytokinin type (BAP or Kin) and concentration and cultivar. Increasing the sucrose concentration of the medium from 3% to 5% or 8% had no apparent effect. Adventitious shoots could be produced directly from callus formed on the base of the petioles. In general adventitious shoots were produced on either the concave surface of the petiole or from the callus, occasionally simultaneously on both, and on the convex surface of the petiole in intact leaf explants. The highest rooting rate with 3% sucrose and 1.0 mg l^–1 NAA was obtained using half-strength MS medium. There was considerable variation in the propagules from petioles or callus indicating that this system may provide valuable somaclonal variation.Abbreviations BAP benzylaminopurine - IBA indole-3-butyric acid - GA₃ gibberellic acid - MS Murashige and Skoog medium - NAA naphthaleneacetic acid Author for correspondence     

Response of sugar beet (Beta vulgaris L.) yield and biochemical composition to elevated CO2 and temperature at two nitrogen applications

Effects on sugar beet ( Beta vulgaris L.) of current and elevated CO₂ and temperature alone and in combination and their interactions with abundant and deficient nitrogen supply (HN and LN, respectively) have been studied in three experiments in 1993, 1994 and 1995. Averaged over all experiments, elevated CO₂ (600 μ mol mol^–1 in 1993 and 700 μ mol mol^–1 in 1994 and 1995) increased total dry mass at final harvest by 21% (95% confidence interval (CI) = 21, 22) and 11% (CI = 6, 15) and root dry mass by 26% (CI = 19, 32) and 12% (CI = 6, 18) for HN and LN plants, respectively. Warmer temperature decreased total dry mass by 11% (CI = – 15, – 7) and 9% (CI = – 15, – 5) and root dry mass by 7% (CI = – 12, – 2) and 7% (CI = – 10, 0) for HN and LN plants, respectively. There was no significant interaction between temperature and CO₂ on total or root dry mass. Neither elevated CO₂ nor temperature significantly affected sucrose concentration per unit root dry mass. Concentrations of glycinebetaine and of amino acids, measured as α -amino-N, decreased in elevated CO₂ in both N applications; glycinebetaine by 13% (CI = – 21, – 5) and 16% (CI = – 24, – 8) and α -amino-N by 24% (CI = – 36, – 11) and 16% (CI = – 26, – 5) for HN and LN, respectively. Warmer temperature increased α -amino-N, by 76% (CI = 50, 107) for HN and 21% (CI = 7, 36) for LN plants, but not glycinebetaine.     

Evaluation of nematode-resistant sugar beet (Beta vulgaris L.) lines by molecular analysis

 Thirty sugar beet (Beta vulgaris) lines conferring complete resistance to the beet cyst nematode (BCN, Heterodera schachtii) originating from interspecific crosses with wild beets of the section Procumbentes (B. procumbens, B. webbiana and B. patellaris) were investigated by morphology and wild beet-specific molecular markers. The beet lines carrying chromosome mutations consisted of monosomic additions (2n=18+1), fragment additions (2n=18+fragment) and translocations (2n=18) from the wild beets. Genome-specific single-copy, satellite and repetitive probes were applied to study the origin, chromosomal assignment and presence of nematode resistance genes. Within the wild beet species at least three different resistance genes located on different chromosomes were distinguished: Hs1 on the homoelogous chromosomes I of each species, Hs2 on the homoelogous chromosomes VII of B. procumbens and B. webbiana and Hs3 on chromosome VIII of B. webbiana. A clear distinction between the three chromosomes was possible by morphological and molecular means. The translocation lines were separated into two different groups: one containing the resistance gene Hs1 from chromosome I and the other carrying a different nematode resistance gene. The molecular data combined with sequence analyses of Hs1 of the three wild beet species revealed a clear distinction between B. procumbens and B. webbiana. The evolutionary and taxonomical relationship of these species supporting the idea of three different species originating from a common ancestor is discussed. Received: 6 April 1998 / Accepted: 22 April 1998     

DNA methylation of retrotransposons,DNA transposons and genes in sugar beet (Beta vulgaris L.)

The methylation of cytosines shapes the epigenetic landscape of plant genomes, coordinates transgenerational epigenetic inheritance, represses the activity of transposable elements (TEs), affects gene expression and, hence, can influence the phenotype. Sugar beet (Beta vulgaris ssp. vulgaris), an important crop that accounts for 30% of worldwide sugar needs, has a relatively small genome size (758 Mbp) consisting of approximately 485 Mbp repetitive DNA (64%), in particular satellite DNA, retrotransposons and DNA transposons. Genome‐wide cytosine methylation in the sugar beet genome was studied in leaves and leaf‐derived callus with a focus on repetitive sequences, including retrotransposons and DNA transposons, the major groups of repetitive DNA sequences, and compared with gene methylation. Genes showed a specific methylation pattern for CG, CHG (H = A, C, and T) and CHH sites, whereas the TE pattern differed, depending on the TE class (class 1, retrotransposons and class 2, DNA transposons). Along genes and TEs, CG and CHG methylation was higher than that of adjacent genomic regions. In contrast to the relatively low CHH methylation in retrotransposons and genes, the level of CHH methylation in DNA transposons was strongly increased, pointing to a functional role of asymmetric methylation in DNA transposon silencing. Comparison of genome‐wide DNA methylation between sugar beet leaves and callus revealed a differential methylation upon tissue culture. Potential epialleles were hypomethylated (lower methylation) at CG and CHG sites in retrotransposons and genes and hypermethylated (higher methylation) at CHH sites in DNA transposons of callus when compared with leaves.     

Comparison of aerobic heterotrophic taxa isolated from four root domains of mature sugar beet (Beta vulgaris)

Abstract: The distribution of bacteria in the rhizosphere, rhizoplane, interior root tissues (core) and lower root (all tissues) of mature sugar beet roots ( Beta vulgaris ) was compared. Of 556 isolates, 102 species from 40 genera were identified by fatty acid methyl ester gas-chromatographic (FAME-GC) analysis. The ten most common genera ( Bacillus , 14%; Arthrobacter , 12%; Pseudomonas , 11%; Aureobacterium , 9%; Micrococcus , 6%; Xanthomonas , 5%; Alcaligenes , 4%; Flavobacterium , 3%; Agrobacterium , 3%; Microbacterium , 3%) accounted for 70% of isolates, and were found in each of three root domains (rhizosphere, rhizoplane and interior root tissues) on the two principal sampling occasions. Gram-positive strains were more abundant in the rhizosphere than the rhizoplane. Compared to the rhizoplane, rhizosphere bacterial communities were represented by a less diverse, more hierarchical distribution of species where twice as many isolates formed late developing colonies on isolation plates. Between October and January, the bacteria isolated from root interior tissues acquired a distinct change in taxonomic pattern, with decreased diversity and increased hierarchy. A bacterial continuum of similar taxa was observed which extended from the rhizosphere to interior root tissues.     

Polymorphic microsatellite markers for inferring diversity in wild and domesticated sugar beet (Beta vulgaris)

Eight microsatellite loci were characterized within two cultivated beet (Beta vulgaris ssp. vulgaris) accessions and one accession of the wild progenitor of domesticated sugar beet, Beta vulgaris ssp. maritima. Allele diversity was high, yielding two to 11 alleles per locus. Polymorphism information content (PIC) values obtained for these eight loci where also high and indicate the highly informative nature of the microsatellites presented here. These described markers add to a small set of publicly available microsatellite markers for beet and will be instrumental in identifying patterns of genetic diversity and origins of domestication.     

Restriction fragment map of sugar beet (Beta vulgaris L.) chloroplast DNA

Summary A restriction endonuclease fragment map of sugar beet chloroplast DNA (ctDNA) has been constructed with the enzymes SmaI, PstI and PvuII. The ctDNA was found to be contained in a circular molecule of 148.5 kbp. In common with many other higher plant ctDNAs, sugar beet ctDNA consists of two inverted repeat sequences of about 20.5 kbp separated by two single-copy regions of different sizes (about 23.2 and 84.3 kbp). Southern hybridization analyses indicated that the genes for rRNAs (23S+16S) and the large subunit of ribulose 1,5-bisphosphate carboxylase were located in the inverted repeats and the large single-copy regions, respectively.     

Improvement of protoplast culture protocols for Beta vulgaris L. (sugar beet)

Summary The effects of NaCl, feeder cells and the embedding of protoplasts in calcium alginate have been investigated in an attempt to improve culture conditions of recalcitrant sugar beet (Beta vulgaris L.) mesophyll protoplasts. While the use of NaCl in all instances proved detrimental to protoplast development, the other two treatments had clear beneficial effects. Minimum plating densities, necessary to sustain cell division, could be reduced to <5% (<4000 protoplasts / ml) of the control levels and plating efficiencies could be significantly enhanced by approx. 10 fold. Plants could still be regenerated from soft calli derived from mesophyll protoplasts cultured under the modified conditions at a frequency of 20–30 %. In particular, the use of alginate is considered of potentially great importance for the further application of beet protoplasts for other aims e.g. asymmetric hybridization.