A Greenhouse Test for Screening Sugar Beet (Beta Vulgaris) for Resistance to Rhizoctonia Solani

Rhizoctonia solani Kühn is a serious plant pathogenic fungus, causing various types of damage to sugar beet (Beta vulgaris L.). In Europe, the disease is spreading and becoming a threat for the growing of this crop. Plant resistance seems to be the most practical and economical way to control the disease. Experiments were carried out to optimise a greenhouse procedure to screen plants of sugar beet for resistance to R. solani. In the first experiment, two susceptible accessions were evaluated for root and leaf symptoms, after being grown in seven different soil mixtures and inoculated with R. solani. The fungus infected all plants. It was concluded that leaf symptoms were not reliable for the rating of disease severity. Statistically significant differences between the soil mixtures were observed, and there were no significant differences between the two accessions. The two soil mixtures, showing the most severe disease symptoms, were selected for a second experiment, including both resistant and susceptible accessions. As in the first experiment, root symptoms were recorded using a 1–7 scale, and a significant expression of resistance was observed. The average severity of the disease in the greenhouse experiment generally was comparable with the infection in field experiments, and the ranking of the accessions was the same in the two types of experiments. It was concluded that evaluation procedures in the greenhouse could be used as a rapid assay to screen sugar beet plants for resistance to R. solani.     

Major genes for resistance to beet necrotic yellow vein virus (BNYVV) in Beta vulgaris

Summary Inheritance of resistance to beet necrotic yellow vein virus (BNYVV) was studied in segregating F2 and backcross families obtained from crosses between resistant plants of the sugar beet selection Holly-1-4 or the wild beet accession Beta vulgaris subsp. maritima WB42 and susceptible parents. Greenhouse tests were carried out, in which seedlings were grown in a mixture of sand and infested soil. Virus concentrations of BNYVV in the rootlets were estimated by ELISA. To discriminate resistant and susceptible plants, mixtures of normal distributions were fitted to log₁₀ virus concentrations, estimated for segregating F1, F2 and BC populations of both accessions. The hypothesis that Holly-1-4 contained one single dominant major gene was accepted. For WB42, results fitted with the hypotheses that resistance was based on either one (or more) dominant major gene(s) showing distorted segregation, or two complementary dominant genes, which are both required for resistance. Resistance from WB42 appeared to be more effective against BNYVV than resistance from Holly-1-4.This research was carried out as part of a PhD study at the Graduate School Experimental Plant Sciences (EPS), Department of Virology, Wageningen, The Netherlands     

Chromosome localisation of genes for resistance to Heterodera schachtii, Cercospora beticola and Polymyxa betae using sets of Beta procumbens and B. patellaris derived monosomic additions in B. vulgaris

Beet cyst nematodes (BCN, Heterodera schachtii), Cercospora beticola, and rhizomania, caused by the beet necrotic yellow vein virus (BNYVV) and vectored by the soil-borne fungus Polymyxa betae, are the most serious diseases of sugar beet ( Beta vulgaris subsp. vulgaris). The wild Beta species of section Procumbentes are known to be completely resistant to H. schachtii, C. beticola and P. betae. Alien monosomic additions (2n=19), plants of cultivated beet (2n=18) carrying different individual chromosomes of B. procumbens (2n=18) or B. patellaris (2n=36), were tested in greenhouse experiments for resistance to these pathogens. Gene(s) conferring full resistance to the beet cyst nematode in B. patellaris are located on chromosome 1.1, and the other tested chromosomes of B. patellaris are not involved in the expression of resistance. Artificial inoculation under greenhouse conditions, with in vitro produced inoculum of C. beticola and spot-percentage rating of the disease intensity, showed that the high level of resistance that was observed in the wild species B. procumbens and B. patellaris was not found in any of the monosomic additions tested. It was suggested that genes on various chromosomes of the wild species are needed to express full resistance, and that the chromosomes of group 7 of B. patellaris and chromosome 7 of B. procumbens have the largest effect. The greenhouse tests for resistance to P. betae in B. patellaris derived monosomic additions showed that the addition families of group 4.1 have a strong partial resistance, while the addition families of group 8.1 appeared to be completely resistant to the pathogen. Resistance to P. betae in the two wild species as well as in the two resistant addition types did not exclude infection with BNYVV, but resulted in a considerable reduction of the virus concentration. It was concluded that resistance to the vector would complement virus resistance, and may provide a more effective and durable control of rhizomania. This revised version was published online in July 2006 with corrections to the Cover Date.     

Chromosomal interchanges and phylogeny of some accessions of Triticum aestivum subsp. spelta

Summary The occurrence of chromosomal interchanges was studied in F1 hyrids in two diallel schemes, including nine accessions of Triticum aestivum subsp. spelta, originating from Iran, Europe and North Africa, and the common wheat variety Chinese Spring as a reference. Seven accessions of subsp. spelta differed in one translocation from Chinese Spring. The European accession Grey differed in one or perhaps two interchanges from the reference variety, and Iran 417a showed a difference of three interchanges with Chinese Spring. In total six or perhaps seven interchanges were observed. Thus the number of translocation events in subsp. spelta appeared to be low. One translocation was unique and occurred only in the accession from North Africa. Also one accession from Europe, the landrace Schwarzwald, possibly carried a unique translocation. In both diallels an interchange with a relatively low coefficient of multivalent realisation at first meiotic metaphase was observed in most accessions. The two extra translocations in Iran 417a are considered to be the result of more recent translocation events, whereas the possible second translocation in accession Grey showed such a low coefficient of multivalent realisation that its existence could be doubted.     

Effects of different management practices on the soil–water balance and crop yield for improved dryland farming in the Chinese Loess Plateau

Field experiments were carried out to study the effects of different soil management practices on the water balance, precipitation use efficiency (PUE), and crop yield (i.e. winter wheat and peanut) on a loess soil near Luoyang (east edge of the Chinese Loess Plateau, Henan Province, China). Field plots were set up in 1999 including following soil management practices: subsoiling with mulch (SS), no-till with mulch (NT), reduced tillage (RT), two crops per year (i.e. winter wheat and peanut, TC), and a conventional tillage control (CT). The field plots were equipped to monitor all components of the soil–water balance except evapotranspiration, which was computed by solving the water balance equation. The results showed that although soil management had smaller influence on the magnitude of the water balance components than did precipitation variations, small influences of the applied soil management practices on water conservation during the fallow period can greatly affect winter wheat yield. SS increased consistently precipitation storage efficiency (PSE) and PUE over the 5 years compared to CT except during the wettest year. NT also had a noticeable effect on postharvest water storage during the fallow period; however, the influence on yield of NT depended on the amount of precipitation. TC lowered the winter wheat yield mainly due to the unfavorable soil moisture conditions after growing peanut in summer; however, the harvested peanut gained an extra profit for the local farmer. No matter which kind of soil management practices was adapted, PSE never exceeded 41.6%, which was primarily attributed to high evapotranspiration. From data of five consecutive agricultural years between 2000 and 2005, it could be concluded that SS resulted in the highest PSE, PUE and crop yield. TC also showed promising results considering the economic value of the second crop. NT performed slightly less as SS. CT gave intermediate results, whereas RT was the worst alternative.     

Evidence for the involvement of arabinoxylan and xylanases in refrigerated dough syruping

The relationship between syruping in refrigerated doughs upon prolonged storage and different aspects of arabinoxylan (AX) hydrolysis was investigated using Triticum aestivum xylanase inhibitor (TAXI) and different xylanases in the dough formula. Dough characteristics were evaluated with strong emphasis on the AX population and its fate as a function of storage time. Selective reduction of part of the flour endogenous xylanase activity in dough by added TAXI reduced dough syruping after 12 and 20 days of storage by 50%, providing straightforward evidence for the involvement of xylanases and, thus, AX in the syruping phenomenon. Addition of xylanases with different inhibitor sensitivities [an inhibition-sensitive Bacillus subtilis xylanase (XBS(i)) as well as a noninhibited mutant (XBS(ni)) thereof] to dough confirmed the importance of xylanases in dough syruping, on one hand, and the power of wheat flour TAXI to constitute a significant barrier against xylanase-mediated dough syruping, on the other hand. Use of xylanases with different substrate selectivities [an Aspergillus aculeatusxylanase (XAA) versus XBS(ni)] showed degradation of water-extractable AX (WE-AX) and solubilized AX to low molecular weight molecules rather than the conversion of water-unextractable AX (WU-AX) to high molecular weight water extractable components to be the main factor influencing dough syruping.     

The flavonol quercetin-3-glucoside inhibits cyanidin-3-glucoside absorption in vitro

At present, little is known about the mechanisms responsible for intestinal absorption of anthocyanins (ACNs). For example, it has not yet been established if ACNs are absorbed through an active transport mechanism, such as the sodium-dependent glucose transporter (SGLT1), or by passive diffusion. Previously, we found that the absorption of ACNs differs between regions of the digestive tract and is maximal in the jejunum, suggesting that an active transport mechanism is involved. In the present study, we examined the effect of d-glucose (main substrate of SGLT1), phloridzin (inhibitor of SGLT1), and quercetin-3-glucose (Q3G, a flavonol) on the absorption of cyanidin-3-glucoside (C3G; approximately 5 micromol/L) by mouse jejunum mounted in Ussing chambers. We found that the presence of either D-glucose (10, 20, and 40 mmol/L) or phloridzin (50, 100, and 200 micromol/L) resulted in a small but insignificant inhibition of C3G disappearance from the mucosal solution (decrease of disappearance with glucose, 33%; with phloridzin, 18%; NS). However, when the flavonol Q3G (50 micromol/L) was added to the mucosal solution together with the C3G, the disappearance of C3G was significantly decreased (74%; p < 0.001), and Q3G disappeared instead. In addition, we found phloretin and quercetin, the aglycones of phloridzin and Q3G, respectively, present in the mucosal solution and tissue extracts, indicating hydrolysis of these compounds by the enterocytes of the jejunum. In contrast, the aglycone cyanidin was not detected at all. Our results show that in the mouse small intestine, ACN absorption is not solely dependent on the activity of the SGLT1 transporter, as d-glucose and phloridzin had only a slight effect on uptake. Q3G, however, clearly inhibited C3G disappearance. These results suggest that there might be a competitive inhibition between C3G and Q3G absorption. It is possible that an absorption mechanism other than the SGLT1 is involved, which has a structural preference toward flavonols.     

Highly conserved protective epitopes on influenza B viruses

Identification of broadly neutralizing antibodies against influenza A viruses has raised hopes for the development of monoclonal antibody-based immunotherapy and "universal" vaccines for influenza. However, a substantial part of the annual flu burden is caused by two cocirculating, antigenically distinct lineages of influenza B viruses. Here, we report human monoclonal antibodies, CR8033, CR8071, and CR9114, that protect mice against lethal challenge from both lineages. Antibodies CR8033 and CR8071 recognize distinct conserved epitopes in the head region of the influenza B hemagglutinin (HA), whereas CR9114 binds a conserved epitope in the HA stem and protects against lethal challenge with influenza A and B viruses. These antibodies may inform on development of monoclonal antibody-based treatments and a universal flu vaccine for all influenza A and B viruses.     

Serotype- and serogroup-specific detection of African horsesickness virus using phage displayed chicken scFvs for indirect double antibody sandwich ELISAs

There is an ongoing need for standardized, easily renewable immunoreagents for detecting African horsesickness virus (AHSV). Two phage displayed single-chain variable fragment (scFv) antibodies, selected from a semi-synthetic chicken antibody library, were used to develop double antibody sandwich enzyme-linked immunosorbent assays (DAS-ELISAs) to detect AHSV. In the DAS-ELISAs, the scFv previously selected with directly immobilized AHSV-3 functioned as a serotype-specific reagent that recognized only AHSV-3. In contrast, the one selected with AHSV-8 captured by IgG against AHSV-3 recognized all nine AHSV serotypes but not the Bryanston strain of equine encephalosis virus. Serving as evidence for its serogroup-specificity. These two scFvs can help to rapidly confirm the presence of AHSV while additional serotype-specific scFvs may simplify AHSV serotyping.     

Towards an objective evaluation of persistency of <Emphasis Type="Italic">Lolium perenne</Emphasis> swards using UAV imagery

Perennial ryegrass (Lolium perenne) is a perennial crop used in temperate regions as forage. In L. perenne breeding programs, persistency is an important trait. Poor persistency results in sward degradation and associated yield and nutritive value losses. Breeders assess persistency of accessions using visual scoring in field plots during the 2nd or 3rd growing season. This evaluation system is easy and cheap but is not free from human bias. In this study, the correlation between the scoring done by different breeders was only 0.243. As an alternative we have developed a methodology to assess persistency of L. perenne breeding materials based on vegetation indices (VIs) derived from Unmanned Aerial Vehicle (UAV) imagery. The VIs Excess green (ExG2), Green Leaf Index and Normalized green intensity (GCC) were found to provide consistent results for flights carried out under different light conditions and were validated by ground reference information. The correlation between the VIs and the percentage of ground cover extracted from on-ground imagery was 0.885. To test the implementation of the method we compared the ExG2 value based approach to selection with a visual score based selection methodology as applied by two breeders. The breeding decisions of Breeder A agreed well with decisions based on ExG2 values (74.6%), but those of Breeder B displayed a lower agreement (54.0%). In contrast, agreement between decisions based on different flights was very high (91.6%). The methodology was validated for general applicability. In summary, the results demonstrate that basing persistency selection in L. perenne breeding programs on ExG2 values from UAV imagery is likely to be more objective in comparison to the currently-used visual scoring method.