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.     

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.     

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.     

A comparative study of the effects of NaCl salinity on respiration, photosynthesis, and leaf extension growth in Beta vulgaris L. (sugar beet)

Abstract. Three parameters influencing the capacity for carbon accumulation, i.e. photosynthesis, respiration, and leaf extension growth, were studied in Beta vulgaris L. (sugar beet) cultured in nutrient solution containing 0.5 to 500 mol m⁻³ NaCl. Leaf extension growth was the parameter most sensitive to salinity: the initial rate of leaf extension and final leaf length each declined linearly with increase in external NaCl concentration. Photosynthetic O₂ evolution of thin leaf slices did not decline until salinity levels reached 350 to 500 mol m⁻³ NaCl, while respiratory O₂ consumption was not affected by salinity throughout the range. The results suggest that the influence of salinity on the capacity for carbon accumulation in B. vulgaris occurs primarily through reduction in the area of photosynthetic surface.     

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.     

Transcriptome analysis of sugar beet root maggot (Tetanops myopaeformis) genes modulated by the Beta vulgaris host

Sugar beet root maggot (SBRM, Tetanops myopaeformis von Röder) is a major but poorly understood insect pest of sugar beet (Beta vulgaris L.). The molecular mechanisms underlying plant defense responses are well documented, however, little information is available about complementary mechanisms for insect adaptive responses to overcome host resistance. To date, no studies have been published on SBRM gene expression profiling. Suppressive subtractive hybridization (SSH) generated more than 300 SBRM ESTs differentially expressed in the interaction of the pest with a moderately resistant (F1016) and a susceptible (F1010) sugar beet line. Blast2GO v. 3.2 search indicated that over 40% of the differentially expressed genes had known functions, primarily driven by fruit fly D. melanogaster genes. Expression patterns of 18 selected EST clones were confirmed by RT‐PCR analysis. Gene Ontology (GO) analysis predicted a dominance of metabolic and catalytic genes involved in the interaction of SBRM with its host. SBRM genes functioning during development, regulation, cellular process, signaling and under stress conditions were annotated. SBRM genes that were common or unique in response to resistant or susceptible interactions with the host were identified and their possible roles in insect responses to the host are discussed.     

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.     

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     

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.     

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.     

Selection in vitro for UV-tolerant sugar beet (Beta vulgaris) somaclones

With a reduced stratospheric ozone concentration, the generation of UV-tolerant plants may be of particular importance. Among different crop plants there is large variation in sensitivity to UV-B radiation. This study was undertaken to investigate the possibilities of using somaclonal variation and selection in vitro for improving UV-B tolerance in sugar beet (Beta vulgaris L.). Sugar beet callus was exposed to UV radiation (280–320 nm, 0.863–5.28 kJ m^-2 day^-1, unweighted) and resultant shoots were selected from surviving cells. After establishment of the plants, they were grown under either visible radiation (114 μmol m^-2 s^-1 PAR) or with the addition of UV radiation (6.3 kJ m^-2 day^-1 biologically effective UV-B). Screening of regenerants in vivo for tolerance to UV radiation was undertaken 10 months after termination of the UV selection pressure. Screening was done visually and by using a number of physiological parameters, including chlorophyll fluorescence induction, ultraweak luminescence, pigment analysis and total content of UV-screening pigments. A clear difference between the unselected and the UV-selected somaclones was observed when visually studying the UV damage and other leaf injury. The observations were supported by the ultraweak luminescence measurements. Unselected plants showed significantly greater damage when subjected to subsequent UV radiation as compared to the selected plants. The clones subjected to UV selection pressure displayed a significantly higher concentration of UV-screening pigments under subsequent UV radiation. The unselected plants under subsequent UV treatment showed a lower carotenoid concentration when compared to selected plants. However, no significant difference between treatments was found for chlorophyll a/b, or F/F_max, a measure of photosynthetic quantum yield.     

Iron deficiency-induced changes in carbon fixation and leaf elemental composition of sugar beet (Beta vulgaris) plants

In this experiment we (i) tested the hypothesis that, besides decreasing leaf C fixation, lime induced iron (Fe) deficiency increases root C fixation via PEP carboxylase and (ii) assessed the Fe-induced modifications in the elemental composition of plant tissues. Sugar beet plants were grown in nutrient solutions with Fe (45 M Fe-EDTA; +Fe control) or in a similar nutrient solution without Fe (–Fe) and in presence of CaCO₃ (1.0 gL^–1), either labelled with ¹³C (20 at. %) or unlabelled. After 7 and 17 days from treatment imposition, plants were harvested and single organs analysed for total O, C, H, macro and micronutrients. ¹³C abundance was also assessed in control, unlabelled and labelled –Fe plants. Iron deficiency caused significant growth reductions; chlorophyll and net photosynthesis decreased markedly in Fe-deficient plants when compared to the controls, whereas leaf transpiration rates and stomatal conductance were not affected by Fe deficiency. Iron deficient plants had leaf biomass with lower C (2 to 4%) and higher O (3 to 5%) concentrations than +Fe plants. The ¹³C was higher (less negative) in +Fe than in –Fe unlabelled plants. Iron deficient plants grown in the nutrient solution enriched with labelled CaCO₃ absorbed a relatively small amount of labelled C, which was mainly recovered in the fine roots and accounted for less than 2% of total C gain in the 10 d treatment period. Evidences suggest that iron deficient sugar beets grown in the presence of CaCO₃ do not markedly shift their C fixation from leaf RuBP to root PEPC.     

Volatile components of sugar beet leaves

Extracts of both young and old sugar beet plants were obtained using a modified Likens and Nickerson apparatus. Constituents were identified by GC/MS, and using selected ion monitoring it was shown that the previously determined phenylacetonitrile was probably not of glucosinolate origin. Some unsaturated aldehydes, alcohols and derivatives (enzymic lipid degradation products) were formed to greater extents by the younger leaves, but otherwise such quantitative differences were relatively few and generally random. An interesting range of chlorinated compounds was obtained only from the older plants; a pesticide origin is suggested.     

Ploidy levels in Beta vulgaris (red beet) plant organs and in vitro systems

The ploidy levels of the cells in different organs (leaves, petioles and roots) of red beet (Beta vulgaris L.) plants of different ages, as well as of different in vitro systems (transformed hairy roots, calli derived from leaves and rhizogenic calli), were investigated using flow cytometry. Two callus lines with red and yellow phenotypes, derived by mechanical separation of the morphologically heterogeneous rhizogenic callus, were also examined. All investigated samples experienced several cycles of endoreduplication. The older organs exhibited higher levels of polysomaty than the young ones. The highest degree of endoreduplication was found in old petiole tissue and the lowest in the red callus line (cycle values of 1.81 and 0.55, respectively). Interestingly, the callus derived from leaves did not exhibit a 2Cx peak, but was tetraploid, probably due to genetic instability, which may have been caused by prolonged cultivation under in vitro conditions. Red and yellow calli showed significantly lower polysomaty (cycle values of 0.55 and 0.59, respectively) than the primary rhizogenic callus (cycle value of 1.09). The DNA profiles of the two phenotypes differed, possibly reflecting differences in their metabolism.     

A linkage map of sugar beet (Beta vulgaris L.)

Summary We have established a first linkage map for beets based on RFLP, isozyme and morphological markers. The population studied consisted of 96 F₂ individuals derived from an intraspecific cross. As was expected for outbreeding species, a relatively high degree of polymorphism was found within sugar beet; 47% of the DNA markers were polymorphic for the chosen population. The map consists of 115 independent chromosomal loci designated by 108 genomic DNA probes, 6 isozyme and one morphological marker. The loci cover 789 cM with an average spacing of 6.9 cM. They are dispersed over nine linkage groups corresponding to the haploid chromosome number of Beta species. Eighteen markers (15.4%) showed distorted segregation which, in most instances, can be explained by gametic selection of linked lethal loci. The application of the linkage map in sugar beet breeding is discussed.     

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.