Resistant Sugar Beet Research Articles

Gas Chromatography-Mass Spectrometry (GC-MS) Analysis of Sugar Beet Leaf Extracts in Response to Exogenous Application of Resistance Inducers to Manage Sugar Beet Powdery Mildew

The effect of foliar application of some chemical resistance inducers i.e., chitosan, ascorbic acid, salicylic acid and tap water as a control were tested to evaluate their efficacy to induce systemic resistance against Erysiphe betae, the causal agent of sugar beet powdery mildew (Herkl cv.) versus the traditional fungicide Opera under greenhouse and field conditions at Gemmeiza Agric. Res. Sta., Agric. Res. Cent. (ARC), Egypt during two successive winter seasons (2014/2015 and 2015/2016). Under greenhouse conditions, results revealed that spraying plants with all the tested IRCs reduced the disease severity of powdery mildew. The fungicide Opera was the most effective treatment in reducing disease severity and increasing the efficacy followed by chitosan and salicylic acid. Also, all treatments significantly increased total phenols and orthodihydric (OD) phenol content of the leaves compared to the control at 15, 30 and 45 days after inoculation. The GC-MS analysis of methanol extracts of 60 days old leaves of sugar beet plants under the greenhouse conditions, which have been treated with chitosan, ascorbic acid, salicylic acid as inducers to the systemic resistance of sugar beet against Erysiphe betae recorded the highest concentration (peak area %) for all bioactive phytochemical compounds such as flavonoids, alcohols, aldehydes, aromatic compounds, fatty acid methyl esters, terpenoids, phenolics and steroids that can be postulated for antimicrobial activity compared to control (tap water). Under field conditions, results indicated that the fungicide Opera was the most effective treatment for controlling powdery mildew followed by ascorbic acid. Meanwhile, all treatments showed lower effect than the fungicide Opera in this regard but higher than control. All treatments increased root yield per feddan compared to the control. The fungicide Opera and salicylic acid gave the highest root yield per feddan followed by ascorbic acid then chitosan. Moreover, salicylic acid and the fungicide Opera gave the highest percentages of total soluble solids (T.S.S.) and sucrose percentages, whereas salicylic acid, ascorbic acid and fungicide Opera gave the highest percentages of purity in sugar beet roots.

POLYMORPHISM IN SUGAR BEET VARIETIES AND HYBRIDS IN CELL SELECTION FOR RESISTANCE TO ABIOTIC FACTORS

In the article, the results on the development of cell selection scheme for sugar beet genotypes resistant to high temperature are presented. In terms of increase in the callus diameter and the ability to regenerate plants, lines of high-temperature resistant genotypes Yaltushkivskyi MS 72, Ukrainian MS 70, Ukrainian MS 72 and Katiusha found to be promising for breeding. Experiments confirmed that 5-7 times increased proline content is typical of the temperature resistant lines. We investigated the molecular and genetic polymorphism in sugar beet genotypes using RAPD and SSR analyses. Fourteen alleles were identified and analyzed by four RAPD markers and five alleles by GZM 086 marker. Cluster analysis using DNA markers shows that Ukrainian MS 72 and Ivanivskyi MS 33 are the most similar genotypes, and they are found in the same cluster. It was determined that the temperature resistant sugar beet genotypes Yaltushkivskyi MS 72, Ukrainian MS 70, Ukrainian MS 72 and Katiusha are genetically distant and therefore can be used to create heterotic hybrids.

New Generation of Resistant Sugar Beet Varieties for Advanced Integrated Management of Cercospora Leaf Spot in Central Europe.

Cercospora leaf spot (CLS) epidemics in sugar beet have been increasing in recent years causing higher use of fungicides. Concomitantly, the availability of effective fungicides is at risk because of resistance development in the fungus, the lack of new active ingredients as well as restrictive approval practices. A key option for an integrated management of CLS is cultivation of resistant varieties. Because of the yield penalty in resistant varieties, acceptance in commercial practice so far has been low. The aim of our study was to characterize recent sugar beet varieties registered in Germany in terms of resistance and tolerance to CLS and their value for integrated pest management. The genetic basis of CLS resistance in varieties is protected by intellectual property rights even after variety registration and not open to the public due to economic competition. To gain reliable data for cultivation, varieties have to be tested for their resistance traits under field conditions at varying levels of infection with Cercospora beticola. In collaboration with variety related stakeholders, 15 sugar beet varieties were tested in 49 field trials in Germany from 2014 to 2016 for their yield response to CLS. The trials were set up in a split-plot design with and without infection (i.e., with and without fungicide). The classification of varietal reaction to CLS is based on symptomatic leaf area (susceptibility) and the resulting relative yield loss (tolerance). Since the relation between both parameters varied among varieties, it was used as an additional parameter to describe tolerance. On this basis, three groups of varieties were identified. They can be characterized as a susceptible, a resistant and a presumably tolerant cluster. A comparison of the data with an older dataset originating from 2009 to 2011 revealed that yield performance of recent varieties with resistance to C. beticola caught up with susceptible varieties due to breeding progress. They showed no yield penalty in the absence of the disease and better economic performance than susceptible varieties. It is assumed that these varieties will allow a substantial reduction of fungicide use for an advanced integrated pest management under central European conditions.

Distribution of resistance-breaking isolates of beet necrotic yellow vein virus differing in virulence in sugar beet fields in Turkey

ABSTRACTRhizomania, caused by Beet necrotic yellow vein virus (BNYVV), is one of the most devastating diseases on sugar beet throughout the world. A total of 235 BNYVV-infested soil samples taken from 29 provinces during the growing seasons of 2004–2005 and 2010–2011 were investigated for resistance-breaking properties of BNYVV isolates. BNYVV resistant (Rz1, Rz1 + R2, Rz1 + C48 + minor genes) and susceptible (rz1) sugar beet cultivars were grown in the BNYVV-infested soils by the bait plant technique, and virus infection was evaluated based on disease symptom and DAS-ELISA. Of the soil samples tested, 57.4% produced infection in the roots of sugar beet cultivar (cv.) containing the Rz1 gene, 51.9% in cv. carrying the Rz1 + Rz2 and 18.9% in cv. carrying the Rz1 + C48 + minor genes. Also, the presence of Beet soil-borne virus (BSBV) was evaluated by TAS-ELISA. Additionally, the presence of BNYVV RNA-5 component was investigated by RT–PCR using the primers specific for p26 coding region. Our results revealed that BNYVV isolates compromising resistance genes are highly common and widespread in sugar beet production areas in Turkey, and it seems unlikely that BSBV and/or RNA-5 were directly involved in RB-event.

Resistance assessment and biochemical responses of sugar beet lines against Pythium aphanidermatum, causing root rot

Root rot, caused by Pythium aphanidermatum, is a major disease of sugar beet in warm regions with high levels of soil moisture. Use of resistant cultivars is an effective strategy to control this destructive disease. However, the mechanisms involved in resistance of sugar beet to the pathogen is still unknown. In this research, 10 sugar beet lines were evaluated in greenhouse for resistance to P. aphanidermatum at 6 and 12 weeks growth stages. Our results revealed higher level of resistance in the mature plants. Also, there is no interaction between growth stages and sugar beet lines to P. aphanidermatum suggested the possibility of evaluating resistance of sugar beet genotypes to this oomycetous pathogen at earlier growth stages, which leads to save time and expenses. Activity of defense-related enzymes, including peroxidase (POX), catalase (CAT), polyphenol oxidase (PPO), and ascorbate peroxidase (APX) in the resistant (S2–24-P.107) and susceptible (SB-191) lines inoculated with the pathogen at two different growth stages viz. 6 and 12 week, was evaluated. Obtained results revealed that the activity of POX, CAT, and PPO enzymes was enhanced earlier and to the higher extent in the resistant compared to the susceptible line at both growth stages. The activity of APX was not significantly affected by plant inoculation. Phenolic content of the resistant line was higher than that of the susceptible line at both growth stages investigated. Therefore, our results indicated the prominence of POX, CAT, PPO, and phenolics in sugar beet resistance against P. aphanidermatum.

In vitro protein synthesis of sugar beet (Beta vulgaris) and maize (Zea mays) is differentially inhibited when potassium is substituted by sodium

The substitution of potassium ions (K+) by sodium ions (Na+) in the nutrition of plants is restricted. It was shown earlier that net protein synthesis is the process which is most sensitive to the substitution of K+ by Na+ in young sugar beet. We hypothesized that the activity of ribosomes is inhibited by the substitution. This hypothesis was tested in an in vitro approach. Cytosolic polysomes were isolated from growing leaves of sugar beet and maize by means of differential centrifugation. In vitro systems of both plant species were tested for functionality and comparability. Translation was quantified by the 35S-methionine incorporation in TCA-precipitable products. The effect of different substitution levels (0%, 20%, 40%, 60%, and 80% substitution of K+ by Na+) on in vitro translation was measured. Translation by polysomes of both plant species was significantly inhibited by the substitution. However, the translation by maize polysomes was more negatively affected by the substitution. A significant decrease in the translation by maize polysomes was observed already when 20% of K+ were replaced by Na+, whereas in the case of sugar beet, the translation was inhibited firstly at the substitution level of 40%. The in vitro results show that the process of translation itself is disturbed by the substitution and indicate a higher tolerance of sugar beet polysomes to increased Na+ concentrations and Na+/K+ ratios compared to polysomes of maize. We propose that this tolerance contributes to the salt resistance of sugar beet.

Irrigation and nitrogen managements affect nitrogen leaching and root yield of sugar beet

Irrigation water and nitrogen (N) are the limiting factors for crop production in arid and semi-arid areas. However, excess irrigation and N application rate is a source of groundwater contamination. Partial root drying irrigation (PRD) is the water-saving technique and would perform as a controlling measure of groundwater N contamination as it reduces irrigation amount. Sugar beet is an industrial crop that is widely grown in arid and semi-arid area where N and water are highly required for high sugar beet yield production. The objectives of this study were to evaluate the interaction effect of ordinary furrow irrigation (OFI), and PRD irrigation as variable alternate furrow irrigation (VAFI) and fixed alternate furrow irrigation (FAFI) with different N application rates (0, 80, 160, and 240 kg ha−1) on sugar beet root and sugar yield, yield quality, drainage water, N leaching, N uptake, and N efficiency indices. Results indicated that the alternate furrow irrigation (AFI) used 24% less irrigation water compared with the OFI in the study region, whereas its sugar yield was reduced just by 9%. However, it resulted in higher water productivity by 12 and 17% for root and sugar yields, respectively. In different N application rates nitrate leaching reduced by 46 and 52% in the VAFI and FAFI irrigation treatments compared with the OFI, respectively. Physiologic nitrogen efficiency enhanced in VAFI with 160 kg N ha−1 that implied higher production of uptake N in plants. Therefore, considering the nitrogen use economics and environmental impacts, the VAFI and 160 kg N ha−1 were preferred to the other irrigation treatments and N application rates in the study region. Higher nitrogen saving occurred because of less leaching and higher soil residual in the AFI treatment compared with the OFI. Furthermore, leaf level stress sensitivity index indicated that VAFI increased the sugar beet resistance to water stress. Overall, in order to avoid N losses in sugar beet production, the amount of N fertilizer should be reduced in proportion to the amount of soil water available under VAFI water-saving irrigation.

Molecular markers for improving control of soil-borne pathogen Fusarium oxysporum in sugar beet

Fusarium spp. cause severe damage in many agricultural crops, including sugar beet, with Fusarium oxysporum historically being considered as the most damaging of all species. Sugar beet needs to be protected from this class of soil-borne pathogens in order to ensure an optimal sugar yield in the field. Genetic control of the disease is crucial in managing these pathogens. Identification of single nucleotide polymorphism (SNP) markers linked to resistance can be a powerful tool for the introgression of valuable genes needed to develop Fusarium-resistant varieties. A candidate gene approach was carried out to identify SNP markers linked to putative Fusarium resistance sources in sugar beet. Five resistant analogue genes (RGAs) were screened by means of high resolution melting (HRM) analysis in a set of sugar beet lines, considered as resistant and susceptible to Fusarium oxysporum. HRM polymorphisms were observed in 80% of amplicons. Two HRM polymorphisms were significantly associated with Fusarium resistance (P < 0.05). The amplicons that showed association were sequenced and two SNPs were identified. The association was further validated on 96 susceptible and 96 resistant plants using competitive allele-specific PCR (KASPar) technology. The selected SNPs could be used for marker-assisted breeding of Fusarium resistance in sugar beet.

Hyperspectral imaging reveals the effect of sugar beet quantitative trait loci on Cercospora leaf spot resistance.

The quantitative resistance of sugar beet (Beta vulgaris L.) against Cercospora leaf spot (CLS) caused by Cercospora beticola (Sacc.) was characterised by hyperspectral imaging. Two closely related inbred lines, differing in two quantitative trait loci (QTL), which made a difference in disease severity of 1.1-1.7 on the standard scoring scale (1-9), were investigated under controlled conditions. The temporal and spatial development of CLS lesions on the two genotypes were monitored using a hyperspectral microscope. The lesion development on the QTL-carrying, resistant genotype was characterised by a fast and abrupt change in spectral reflectance, whereas it was slower and ultimately more severe on the genotype lacking the QTL. An efficient approach for clustering of hyperspectral signatures was adapted in order to reveal resistance characteristics automatically. The presented method allowed a fast and reliable differentiation of CLS dynamics and lesion composition providing a promising tool to improve resistance breeding by objective and precise plant phenotyping.

Effect of Sugar Beet Variety and Nonhost Plant on Rhizoctonia solani AG2-2IIIB Soil Inoculum Potential Measured in Soil DNA Extracts

A direct soil DNA extraction method from soil samples (250 g) was applied for detection of the soilborne sugar-beet-infecting pathogen Rhizoctonia solani anastomosis group (AG) 2-2IIIB using a newly developed real-time polymerase chain reaction assay that showed specificity to AG2-2IIIB when tested against various R. solani AG. The assay showed a good relation between cycle threshold and amount of AG2-2IIIB sclerotia detected in three spiked field soils and was also able to detect the pathogen in naturally infested field soil samples. A field trial was conducted to quantify R. solani AG2-2IIIB soil inoculum potential (IP) before and after growing a susceptible and a resistant sugar beet variety as well as after subsequent growth of an expected nonhost winter rye. Plants of the susceptible sugar beet variety displayed a higher disease severity. A more than sixfold increase of the R. solani AG2-2IIIB soil IP was observed in contrast to the resistant variety that resulted in a constant IP. Growing winter rye significantly reduced soil IP to the initial level at sowing. Further research is required to better understand the interaction between disease occurrence and soil IP as well as the environmental influence on IP development.

Integrated control of Heterodera schachtii Schmidt in Central Europe by trap crop cultivation, sugar beet variety choice and nematicide application

An integrated strategy is required to control the sugar beet cyst nematode Heterodera schachtii which causes severe yield losses in sugar beet. This study aimed at evaluating the effect of trap crop cultivation (nematode resistant mustard, crop mixture (Trifolium alexandrinum L., Lupinus angustifolius L., Pisum sativum L., Phacelia tanacetifolia Benth., Guizotia abyssinica (L.F.) Cass., Avena strigosa Schreb., Vicia sativa L.), straw mulch as control), nematicide application before sugar beet sowing and sugar beet variety (susceptible, tolerant or resistant to H. schachtii) on population dynamics of H. schachtii and sugar yield. Field experiments were conducted in eight environments (site×year) located in Northern Germany in 2012–2013 and 2013–2014. An insufficient trap crop dry matter yield (1.1–2.5tha−1) mostly led to non-significant trap crop effects on the nematode population whereas in one environment a high dry matter yield of mustard (3.3tha−1) resulted in a nematode reduction of 40%. However, there were no significant differences to the straw mulch control. The nematicide application had no effect on nematode reproduction. In contrast, population dynamics of H. schachtii were strongly influenced by the sugar beet variety and the initial nematode population (PiSB). The highest reduction of 70% was achieved when a resistant sugar beet variety was grown, while the tolerant and susceptible varieties increased the nematode population in most environments. There was evidence that the sugar beet harvest date can highly influence population dynamics of H. schachtii. Sugar yield was influenced by variety and PiSB, but not by trap crop cultivation or nematicide application. Sugar yield decreased with increasing PiSB for all varieties. The resistant and tolerant varieties did not differ in sugar yield and response to H. schachtii, while the susceptible showed the steepest decline in sugar yield with increasing PiSB. The cultivation of the resistant sugar beet variety can be clearly suggested with respect to sugar yield and nematode control because all other tested factors failed to control the nematode population.

Breeding and usage of sugar beet cultivars and hybrids resistant to sugar beet nematode Heterodera schachtii

Heterodera schachtii Schmidt, 1871 is one of the most economically important pests of sugar beet (Beta vulgaris L.) worldwide. It is also widespread in most sugar beet growing regions in Ukraine causing serious yield reduction and decreasing sugar content of sugar beet in infested fi elds. An advanced parasitic strategy of H. schachtii is employed to support nematode growth, reproduction and harmfulness. In intensive agriculture systems the nematode control measures heavily rely on nematicides and good agricultural practice (crop rota- tion in the fi rst place). But alternative strategies based on nematode resistant sugar beet cultivars and hybrids are required as none of nematicides approved for the open fi eld application are registered in Ukraine. Here we review the achievements and problems of breeding process for H. schachtii resistance and provide the results of national traditional breeding program. Since the beginning of 1980s fi ve sugar beet cultivars (Verchnyatskyi 103, Yaltuschkivska 30, Bilotcerkivska 45, BTs-40 and Yuvileynyi) and seventeen lines partly resistant or toler- ant to H. schachtii have been obtained throughout targeted crossing and progenies assessment in the infested fi elds. The further directions for better utilization of genetic sources for nematode resistance presented in na- tional gene bank collection are emphasized. There is a need for more accurate identifi cation of resistance genes, broader application of reliable molecular markers (suitable for marker-assisted selection of nematode resistant plants in the breeding process) and methods for genetic transformation of plants. Crop cash value and national production capacity should drive the cooperation in this fi eld. Knowledge as well as germplasm exchange are thereby welcomed that can benefi t breeding progress at national and international level.

Genetic analysis of bolting after winter in sugar beet (Beta vulgaris L.).

This study reveals for the first time a major QTL for post-winter bolting resistance in sugar beet ( Beta vulgaris L.). The knowledge of this QTL is a major contribution towards the development of a winter sugar beet with controlled bolting behavior. In cool temperate climates, sugar beets are currently grown as a spring crop. They are sown in spring and harvested in autumn. Growing sugar beet as a winter crop with an extended vegetation period fails due to bolting after winter. Bolting after winter might be controlled by accumulating genes for post-winter bolting resistance. Previously, we had observed in field experiments a low post-winter bolting rate of 0.5 for sugar beet accession BETA 1773. This accession was crossed with a biennial sugar beet with regular bolting behavior to develop a F3 mapping population. The population was grown in the greenhouse, exposed to artificial cold treatment for 16 weeks and transplanted to the field. Bolting was recorded twice a week from May until October. Post-winter bolting behavior was assessed by two different factors, bolting delay (determined as days to bolt after cold treatment) and post-winter bolting resistance (bolting rate after winter). For days to bolt, means of F3 families ranged from 25 to 164 days while for bolting rate F3 families ranged from 0 to 1. For each factor one QTL explaining about 65% of the phenotypic variation was mapped to the same region on linkage group 9 with a partially recessive allele increasing bolting delay and post-winter bolting resistance. The results are discussed in relation to the potential use of marker-assisted breeding of winter sugar beets with controlled bolting.

Identification and Validation of a SNP Marker Linked to the Gene HsBvm-1 for Nematode Resistance in Sugar Beet

The beet-cyst nematode (Heterodera schachtii Schmidt) is one of the major pests of sugar beet. The identification of molecular markers associated with nematode tolerance would be helpful for developing tolerant varieties. The aim of this study was to identify single nucleotide polymorphism (SNP) markers linked to nematode tolerance from the Beta vulgaris ssp. maritima source WB242. A WB242-derived F2 population was phenotyped for host-plant nematode reaction revealing a 3:1 segregation ratio of the tolerant and susceptible phenotypes and suggesting the action of a gene designated as HsBvm-1. Bulked segregant analysis (BSA) was used. The most tolerant and susceptible individuals were pooled and subjected to restriction site associated DNA sequencing (RAD-Seq) analysis, which identified 7,241 SNPs. A subset of 384 candidate SNPs segregating between bulks were genotyped on the 20 most-tolerant and most-susceptible individuals, identifying a single marker (SNP192) showing complete association with nematode tolerance. Segregation of SNP192 confirmed the inheritance of tolerance by a single gene. This association was further validated on a set of 26 commercial tolerant and susceptible varieties, showing the presence of the SNP192 WB242-type allele only in the tolerant varieties. We identified and mapped on chromosome 5 the first nematode tolerance gene (HsBvm-1) from Beta vulgaris ssp. maritima and released information on SNP192, a linked marker valuable for high-throughput, marker-assisted breeding of nematode tolerance in sugar beet.

Non-Invasive Spectral Phenotyping Methods can Improve and Accelerate Cercospora Disease Scoring in Sugar Beet Breeding

Breeding for Cercospora resistant sugar beet cultivars requires field experiments for testing resistance levels of candidate genotypes in conditions that are close to agricultural cultivation. Non-invasive spectral phenotyping methods can support and accelerate resistance rating and thereby speed up breeding process. In a case study, experimental field plots with strongly infected beet genotypes of different resistance levels were measured with two different spectrometers. Vegetation indices were calculated from measured wavelength signature to determine leaf physiological status, e.g., greenness with the Normalized Differenced Vegetation Index (NDVI), leaf water content with the Leaf Water Index (LWI) and Cercospora disease severity with the Cercospora Leaf Spot Index (CLSI). Indices values correlated significantly with visually scored disease severity, thus connecting the classical breeders’ scoring approach with advanced non-invasive technology.

Impact of New Natural Biostimulants on Increasing Synthesis in Plant Cells of Small Regulatory si/miRNA With High Anti-Nematodic Activity

Plant endoparasitic cyst nematode Heterodera schachtii Schmidt, gallic nematode Meloidogyne incognita and stem nematode Ditylenchus destructor damage various agricultural crops. The application of ecologically safe natural biostimulants with bioprotective properties is a newer approach for increasing plant resistance to parasitic nematodes. The molecular-genetic analysis of biostimulants action on plant genome is necessary for creation of new effective bioregulators for plant protection against phytopathogenic organisms. In our field and greenhouse experiments, we investigated the influence of new natural biostimulants Avercom and its derivatives on plant protection against nematodes Meloidogyne incognita and Ditylenchus destructor. Considerable increase of resistance to nematodes and productivity of cucumber and potato were observed for plants treated by biostimulant Avercom and its derivatives. Impact of biostimulants Radostim-super and Avercom on increase of resistance of sugar beet and cucumber sprouts to nematodes Heterodera schachtii and Meloidogyne incognita was studied in the laboratory conditions. Comparative analysis of morpho-physiological signs of control and experimental plants showed that plants treated by Radostim-super and Avercom were more viable and resistant to these nematodes as compared to control sprouts. In the molecular-genetic experiments, we studied the impact of these biostimulants on inducing synthesis of small regulatory si/miRNA, which plays key role in plant immune protection. Using method Dot-blot hybridization we studied degree of homology between si/miRNA with mRNA populations, isolated from plants untreated and treated with new natural biostimulants. We found considerable difference in the degree of homology (6-28%) between populations of mRNA and si/miRNA from nematode-infected plants that were either untreated or treated with biostimulants. We have also investigated silencing of translation of mRNA activity of si/miRNA in the wheat embryo cell-free system of protein synthesis. In these experiments, we found high inhibitory activity (38-65%) of si/miRNA from plants treated by biostimulants as compared to low inhibitory activity (15-20%) of si/miRNA from untreated plants. Obtained differences in the degree of homology between populations of mRNA and si/miRNA from untreated and treated with biostimulants plants, which were infected by nematode, and also the high inhibitory activity of si/miRNA from plants treated by biostimulants confirm that these biostimulants induce synthesis of anti-nematodic si/miRNA in plants, resulting in considerable increase of their resistance to these phytopathogens.

Using a selective fast turn-around bioassay for population density determination of Heterodera schachtii

In Central Europe, Heterodera schachtii is kept below threshold levels by cover-cropping with resistant crucifers and crop rotation with non-hosts. Determining population densities of H. schachtii in soil is critical when implementing resistant and tolerant sugar beet cultivars in integrated pest management (IPM) programmes. Soil extraction of the cysts followed by egg counts or extraction of the second-stage juveniles (J2) facilitated by the chemical stimulant acetox can be unsatisfactory in mixed field populations of cyst nematodes. In contrast to H. schachtii, nematodes typically present in sugar beet soils, e.g., Globodera pallida, G. rostochiensis, H. avenae, H. filipjevi, Meloidogyne hapla, M. incognita and Pratylenchus penetrans, rarely penetrated radish roots. In this bioassay, equivalents of 50 g of soil dry weight were adjusted to 10-20% moisture, seeded with Raphanus sativus cv. Saxa 3, and incubated at a day-night (16:8 h) cycle of 28/23°C for 4 days before J2 in radish roots were enumerated. In different soil types, penetration by H. schachtii reflected the inoculation levels. When inoculated with mixes of H. schachtii with H. avenae or H. filipjevi, counts of H. schachtii were similar to those in soils with H. schachtii only. When comparing three methods in three soils spiked with H. schachtii cysts, the bioassay and the extraction method were lightly impacted by the soil texture but results of the acetox method varied with texture. When implemented for field samples from Franconia, the radish bioassay and the acetox method provided results related to cyst and egg extraction data. The radish bioassay provided a quick and easy method for quantifying H. schachtii in the presence of other nematode species in a wide range of soil types. Including this assay in IPM programmes may serve as an alternative to standard methods and will improve the decision making in sustainable production systems.

Systemic resistance induced by Bacillus lipopeptides in Beta vulgaris reduces infection by the rhizomania disease vector Polymyxa betae.

The control of rhizomania, one of the most important diseases of sugar beet caused by the Beet necrotic yellow vein virus, remains limited to varietal resistance. In this study, we investigated the putative action of Bacillus amylolequifaciens lipopeptides in achieving rhizomania biocontrol through the control of the virus vector Polymyxa betae. Some lipopeptides that are produced by bacteria, especially by plant growth-promoting rhizobacteria, have been found to induce systemic resistance in plants. We tested the impact of the elicitation of systemic resistance in sugar beet through lipopeptides on infection by P. betae. Lipopeptides were shown to effectively induce systemic resistance in both the roots and leaves of sugar beet, resulting in a significant reduction in P. betae infection. This article provides the first evidence that induced systemic resistance can reduce infection of sugar beet by P. betae.

Beta vulgaris L. serine proteinase inhibitor gene expression in insect resistant sugar beet

Expression pattern of a sugar beet serine proteinase inhibitor gene, BvSTI, was characterized in response to mechanical and fall armyworm (FAW; Spodoptera frugiperda J.E. Smith) induced wounding. BvSTI expression was analyzed in three breeding lines moderately resistant to sugar beet root maggot (Tetanops myopaeformis Roder) and in a susceptible line, F1010. Increased mechanical wound induced levels of BvSTI expression were observed in all resistant lines as compared to F1010 during the first 24 h. The most intensive response to wounding was observed in one of the resistant lines, F1016, with a maximum 5- and 2.5-fold increase of BvSTI transcript levels over non-wounded roots and leaves, respectively. In contrast, slight increase of BvSTI transcript levels in leaves and even an initial decrease in roots were observed in F1010. BvSTI transcript accumulation in F1016 and F1010 tissues wounded by FAW showed a similar gene expression pattern, but it was delayed and less intense than the response incited by abiotic wounding. On the protein level, BvSTI specific antibody confirmed increased accumulation of the 30 kDa BvSTI protein in wounded leaves but not in roots of F1016 and F1010. Using trypsin inhibition assays, the activity of BvSTI was confirmed in F1016 roots and leaves and F1010 leaves. In F1010 roots BvSTI activity was completely lacking. We conclude that BvSTI gene expression was wound induced in the insect resistant germplasm suggesting that BvSTI can be used in biotechnological approaches or in breeding programs for improving insect resistance.

Identification and Precise Mapping of Resistant QTLs of Cercospora Leaf Spot Resistance in Sugar Beet (Beta vulgaris L.).

The complex inheritance of resistance to Cercospora leaf spot (CLS), the most severe fungal foliar disease in sugar beet, was investigated by means of quantitative trait loci (QTL) analysis. Over a three year period, recombinant inbred lines (RILs) of sugar beet (Beta vulgaris L.), generated through a cross between lines resistant (‘NK-310mm-O’) and susceptible (‘NK-184mm-O’) to CLS, were field-tested for their resistance to the pathogen. Composite interval mapping (CIM) showed four QTL involved in CLS resistance to be consistently detected. Two resistant QTL (qcr1 on chromosome III, qcr4 on chromosome IX) bearing ‘NK-310mm-O’ derived alleles promoted resistance. Across 11 investigations, the qcr1 and qcr4 QTL explained approximately 10% and over 20%, respectively, of the variance in the resistance index. Two further QTL (qcr2 on chromosome IV, qcr3 on chromosome VI) bearing ‘NK-184mm-O’ derived alleles each explained about 10% of the variance. To identify the monogenic effect of the resistance, two QTL derived from ‘NK-310mm-O’ against the genetic background of ‘NK-184mm-O’, using molecular markers. The qcr1 and qcr4 were precisely mapped as single QTL, using progenies BC5F1 and BC2F1, respectively. The qcr1 that was located near e11m36-8 had CLS disease severity indices (DSI) about 15% lower than plants homozygous for the ‘NK-184mm-O’ genotype. As with qcr1, heterozygosis of the qcr4 that was located near e17m47-81 reduced DSI by about 45% compared to homozygosis. These two resistant QTL might be of particular value in marker-assisted selection (MAS) programs in CLS resistance progression.