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.     

Restricted host range of the weevil Aubeonymus mariaefranciscae, a new sugar-beet pest

The extent of feeding, fecundity and fertility of a new sugar beet pest, Aubeonymus mariaefranciscae Roudier (Coleoptera: Curculionidae), on a range of plants from different families was determined. We have found that the adult weevils were only able to feed and oviposit on two closely related cultivated plants, beet and sugar beet, both subspecies of Beta vulgaris L., suggesting a restricted host range for this curculionid. None of 16 secondary metabolites (widely distributed among plants, and representative of different chemical groups), nor any of 19 non-host extracts from 13 different families, deterred the adults of this curculionid from feeding on sugar beet. We found a phagostimulatory effect when beet and sugar beet homogenates from various plant tissues were supplied to adult weevils on weeds that they do not feed on. Conversely, no effect was observed when sucrose was provided. These findings suggest that host selection by A. mariaefranciscae adults is due to the presence of an undetermined phagostimulant compound(s) in beet and sugar beet, instead of the recognition of deterrent substances among the non-host plants.     

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.     

Influence of Different Intensities of Pesticide Management on the Structure of Ground Beetle Communities (Coleoptera; Carabidae) During a Crop Rotation

Investigations were lead through in the years 1992 to 1995 at Halle (Saale) on a stand 24ha in size. Aim of the survey was to record the effects of graduate intensities of pest management on ground beetles. For this purpose 6 plots were installed on the field, 72 ‐ 200m each. Two plots served as control areas, without any application of pesticides. On two other plots intensive chemical pest management was applied. On the last two plots treatments were lead through considering the economic thresholds for weeds, fungal and insect pests according to the rules of integrated pest management. Ground beetles were sampled by using pitfall traps. In 1992 complementary methods to the pitfall trap catches, pick up of beetles after pesticide applications and semi-field-tests, on all plots were lead through. The graduate pest management was carried out 1992 and 1993 in winter wheat and 1994 in sugar beet stands. The last crop in 1995 was summer barley. In this year all plots were treated conventionally. In 1992 the differences between the total catches of ground beetles on the experimental sites were not high. In the following year most species were predominant on the control sites. In 1994 in sugar beet mechanical weed control was carried out on the control plots. The intensity of pesticide management between intensive and integrated plots differs only small. The amounts of ground beetles reached similar values on all experimental sites. In contrast to the expections the trap catches of ground beetles in the final investigations in summer barley were highest in the plots which had been treated integrated in the years before. The smallest amount was sampled in the former intensively managed sites. Renunciation of pesticides often is connected with economic losses which are not tolerable. If management is conducted considering the economic thresholds corresponding to the principles of integrated pest management negative effects on the economy of nature should not be expected for the longer term.     

Insect feeding-induced differential expression of <Emphasis Type="Italic">Beta vulgaris</Emphasis> root genes and their regulation by defense-associated signals

Root responses to insect pests are an area of plant defense research that lacks much information. We have identified more than 150 sugar beet root ESTs enriched for genes responding to sugar beet root maggot feeding from both moderately resistant, F1016, and susceptible, F1010, genotypes using suppressive subtractive hybridization. The largest number of identified F1016 genes grouped into the defense/stress response (28%) and secondary metabolism (10%) categories with a polyphenol oxidase gene, from F1016, identified most often from the subtractive libraries. The differential expression of the root ESTs was confirmed with RT-PCR. The ESTs were further characterized using macroarray-generated expression profiles from F1016 sugar beet roots following mechanical wounding and treatment of roots with the signaling molecules methyl jasmonate, salicylic acid and ethylene. Of the examined root ESTs, 20, 17 and 11% were regulated by methyl jasmonate, salicylic acid and ethylene, respectively, suggesting these signaling pathways are involved in sugar beet root defense responses to insects. Identification of these sugar beet root ESTs provides knowledge in the field of plant root defense and will lead to the development of novel control strategies for control of the sugar beet root maggot.Electronic Supplementary Material Supplementary material is available in the online version of this article at and is accessible for authorized users     

In vitro and in vivo antagonism of actinomycetes isolated from Moroccan rhizospherical soils against Sclerotium rolfsii: a causal agent of root rot on sugar beet (Beta vulgaris L.)

Aims:  To evaluate the ability of the isolated actinomycetes to inhibit in vitro plant pathogenic fungi and the efficacy of promising antagonistic isolates to reduce in vivo the incidence of root rot induced by Sclerotium rolfsii on sugar beet.
Methods and Results:  Actinomycetes isolated from rhizosphere soil of sugar beet were screened for antagonistic activity against a number of plant pathogens, including S.   rolfsii . Ten actinomycetes out of 195 screened in vitro were strongly inhibitory to S. rolfsii . These isolates were subsequently tested for their ability to inhibit sclerotial germination and hyphal growth of S. roflsii . The most important inhibitions were obtained by the culture filtrate from the isolates J-2 and B-11, including 100% inhibition of sclerotial germination and 80% inhibition of hyphal growth. These two isolates (J-2 and B-11) were then screened for their ability to protect sugar beet against infection of S. rolfsii induced root rot in a pot trial. The treatment of S. rolfsii infested soil with a biomass and culture filtrate mixture of the selected antagonists reduced significantly ( P  ≤ 0·05) the incidence of root rot on sugar beet. Isolate J-2 was most effective and allowed a high fresh weight of sugar beet roots to be obtained. Both antagonists J-2 and B-11 were classified as belonging to the genus Streptomyces species through morphological and chemical characteristics as well as 16S rDNA analysis.
Conclusion:  Streptomyces isolates J-2 and B-11 showed a potential for controlling root rot on sugar beet and could be useful in integrated control against diverse soil borne plant pathogens.
Significance and Impact of the Study:  This investigation showed the role, which actinomycete bacteria can play to control root rot caused by S.   rolfsii , in the objective to reduce treatments with chemical fungicides.     

Olfactory response of Anagrus,nigriventrls (HYM.: Mymaridae): Effects of host plant chemical cues mediated by rearing and oviposition experience

The egg parasitoid Anagrus nigriventris Girault is an important natural enemy of the beet leafhopper, Circulifer tenellus (Baker) which has a broad host range that includes cultivated sugar beets and the weed, Russian thistle. When parasitoids were reared on leafhopper eggs deposited in sugar beets, females were attracted to sugar beet volatiles and preferred them over a blank control and over Russian thistle volatiles in Y- tube olfactometer tests. No preference was detected for either plant by female wasps that were reared on Russian thistle. Wasps reared on Russian thistle and allowed an oviposition experience on sugar beet showed a strong attraction to sugar beet volatiles; however, wasps reared on sugar beets and allowed oviposition experience on Russian thistle demonstrated no preference between the two plants. The implications of parasitoid response towards plant volatiles and their importance in biological control are discussed.     

Multi-trait association mapping in sugar beet (<Emphasis Type="Italic">Beta vulgaris</Emphasis> L.)

Association mapping promises to overcome the limitations of linkage mapping methods. The main objective of this study was to examine the applicability of multivariate association mapping with an empirical data set of sugar beet. A total of 111 diploid sugar beet inbreds was selected from the seed parent heterotic pool to represent a broad diversity with respect to sugar content (SC). The inbreds were genotyped with 26 simple sequence repeat markers chosen according to their map positions in proximity to previously identified quantitative trait loci for SC. For SC and beet yield (BY), the genotypic variances were highly significant (P < 0.01). Based on the global test of the bivariate mixed-model approach, four markers were significantly associated with SC, BY, or both at a false discovery rate of 0.025. All four markers were significantly (P < 0.05) associated with BY but only two with SC. The identification of markers associated with SC, BY, or both indicated that association mapping can be successfully applied in a sugar beet breeding context for detection of marker-phenotype associations. Furthermore, based on our results multivariate association mapping can be recommended as a promising tool to discriminate with a high mapping resolution between pleiotropy and linkage as reasons for co-localization of marker-phenotype associations for different traits.     

Molecular genetic investigation of sugar beet (Beta vulgaris L.)

Molecular genetic studies of sugar beet (Beta vulgaris L.) are reviewed as a basis for the development of genomics of this species. The methods used to study structural and functional genomics are considered. The results and their application to increase the efficiency of sugar beet breeding are discussed.     

Molecular genetic investigation of sugar beet (<Emphasis Type="Italic">Beta vulgaris</Emphasis> L.)

Molecular genetic studies of sugar beet (Beta vulgaris L.) are reviewed as a basis for the development of genomics of this species. The methods used to study structural and functional genomics are considered. The results and their application to increase the efficiency of sugar beet breeding are discussed.     

Comparison of the growth and development of beet armyworm,Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae) on two different diets

Beet armyworm (Spodoptera exigua (Hübner)) (Lepidoptera: Noctuidae) is the most economically important sugar beet (Beta vulgaris) pest worldwide. In this study, a comparison was made between two different diets: one was based on Merkx diet (Holidic diet) and the other was based on sugar beet leaf (Oligidic diet). Results showed that the whole development time from larvae to adult between two diets (Merkx and leaf) was not significantly different. For example, developmental time from first instar larvae to adult in Merkx diet was 11.33?days, whilst developmental time of larvae to adult when larvae fed with sugar beet leaf was 10.33?days. However, analysis of variance showed that in some cases like development time of the first instar, third instar and fifth instar larvae and pupae was significantly different between two treatments (p?<?0.05). Larval weight showed differences when larvae fed on Merkx diet and sugar beet leaves. For example, significant differences were shown between first, third and fourth instar larvae weight when larvae fed on Merkx diet and sugar beet leaves (p?<?0.05). However, significant differences were not observed between weight of second and fifth instar as well as pupae weight when larvae fed on Merkx diet and sugar beet leaves (p?>?0.05).     

Multiplexed,linkage group-specific SNP marker sets for rapid genetic mapping and fingerprinting of sugar beet (<Emphasis Type="Italic">Beta vulgaris</Emphasis> L.)

A set of single nucleotide polymorphism (SNP) markers has been developed for each of the nine linkage groups of sugar beet. Each set can monitor the polymorphic state at five to six linked marker loci. In each set, the loci selected for marker development are first amplified in a multiplexed reaction. These amplification products are the basis for sequence-specific elongation of primers adjacent to SNP positions. The extension step revealing SNP loci is based on fluorescently labelled nucleotides. In each set, primers developed to reveal SNP alleles differ in length to allow clear peak resolution in capillary electrophoresis. The nine linkage group (LG) –specific sets provide information on the polymorphism at a total of 52 SNP marker loci. Using the SNP-based tool, groups of concerned loci have been anchored to three different linkage maps of sugar beet. In a second experiment, sugar beet breeding lines have been fingerprinted. The use of the nine sets of LG-specific markers in sugar beet genetics and breeding is discussed. The information necessary to specify the 52 marker loci, as well as their map location, and all details concerning SNP assays, including allele type and nature of mutation, are reported.     

Biotechnology Applications for Sugar Beet

Sugar beet (Beta vulgaris L.) is an important industrial crop, being one of only two plant sources from which sucrose (i.e., sugar) can be economically produced. Despite its relatively short period of cultivation (ca. 200 years), its yield and quality parameters have been significantly improved by conventional breeding methods. However, during the last two decades or so, advanced in vitro culture and genetic transformation technologies have been incorporated with classical breeding programs, the main aim being the production of herbicide-and salt-tolerant, disease- and pest-resistant cultivars. Among the many applications of in vitro culture techniques, sugar beet has benefited the most from haploid plant production, protoplast culture, and somaclonal variation and in vitro cell selection. Several genetic transformation technologies have been developed, such as Agrobacterium-meditated, PEG-mediated, particle bombardment, electroporation, sonication and somatic hybridization, the first two being the most successful. Development of herbicide- and salt-tolerant, virus-, pest/nematode-, fungus/Cercospora- and insect-resistant sugar beet has been demonstrated. However, only herbicide-tolerant varieties have been approved for commercialization but not yet available in the marketplace; rhizomania-resistant varieties are being evaluated in field trials. Transgenic plants that convert sucrose into fructan, a polymer of fructose, were also developed. Initial attempts to increase sucrose yields produced promising results, but it still requires additional work. Despite marked progress in improving regeneration and transformation of sugar beet, genotype dependence and low regeneration and transformation frequencies are still serious restrictions for routine application of in vitro culture and, more importantly, transformation technologies. Selected food safety and environmental impact, as well as regulatory and public acceptance issues relating to transgenic sugar beet are also discussed.     

The influence of size and duration of aphid infestation on host plant quality, and its effect on sugar beet yellowing virus epidemiology

This paper studies the influence of previous infestation on the host quality of sugar beet (Beta vulgaris L.) for aphids and the influence of previous infestation on sugar beet yellowing virus epidemiology. Sugar beet previously infested with Myzus persicae (Sulzer) or Aphis fabae Scopoli (Homoptera: Aphididae) had an improved host quality for subsequently infesting aphids of the same species. There was a significant negative relationship between the number of M. persicae infesting a plant and the proportion of those that died with a dark deposit in their stomachs, and a significant positive relationship between the number that settled on a plant and the number that infested it previously. Nymphs feeding on previously infested plants grew more rapidly than those on control plants. The beneficial effect of previous infestation persisted for at least 2 weeks and prolongation of the infestation beyond 2 weeks was of no further benefit to the aphids. Field grown sugar beet, previously colonised by M. persicae, was more susceptible to natural infestation by M. persicae up to 5 days after exposure. Previously infested plants were also more susceptible to infection with beet mild yellowing virus (BMYV) but not beet yellows virus (BYV), suggesting that the aphids on the previously infested sugar beet settled more readily and were more inclined to feed (and thus transmit BMYV) than aphids on the previously uninfested plants. The consequences for the control of sugar beet yellowing virus vectors are discussed.     

Spatio-temporal pattern of Pentastiridius leporinus migration in an ephemeral cropping system

• 1 Cixiid planthoppers (Hemiptera: Fulgoromorpha: Cixiidae) are considered to be important economic pests because of their ability to transmit phloem‐restricted prokaryotes causing emerging plant diseases worldwide. However, little information is available on the biology and ecology of such species. This is the case for Pentastiridius leporinus (Linnaeus), a cixiid planthopper reported to live on common reed across Countries of Central and Northern Europe. However, in the east of France, the same planthopper species appears to complete its life cycle in the sugar beet‐wheat cropping system and has been repeatedly shown to transmit prokaryotic plant pathogens that are associated with an emerging disease of sugar beet called syndrome ‘basses richesses'.
• 2 To gather evidence on the biology of the planthopper in the cropping rotation, we analysed the flight activity of adults. We used transparent sticky traps for sampling migrating adults and quantified nymphs as well as emerging adults on the roots of wheat plants.
• 3 Results showed a significant correlation between disappearance of nymphs and emerging adults from wheat roots and the occurrence of migrant adults in nearby sugar beet fields. Planthoppers migrated more abundantly and colonized sugar beet for longer periods than any other crop available. Flight activity was very pronounced during the migratory phase that was extended from the middle of June to the middle of July. A geographic information system and geostatical analysis revealed that planthoppers flew and colonized the centre of the sugar beet field rather than the borders.
• 4 Overall, results obtained in the present study suggest that the ecology and biology of the planthopper vector in the cropping rotation is a primary factor that leads to the emergence of the syndrome ‘basses richesses' disease of sugar beet.

     

Yield of glyphosate-resistant sugar beets and efficiency of weed management systems with glyphosate and conventional herbicides under German and Polish crop production

In sugar beet production, weed control is one of the most important and most expensive practices to ensure yield. Since glyphosate-resistant sugar beets are not yet approved for cultivation in the EU, little commercial experience exists with these sugar beets in Europe. Experimental field trials were conducted at five environments (Germany, Poland, 2010, 2011) to compare the effects of glyphosate with the effects of conventional weed control programs on the development of weeds, weed control efficiency and yield. The results show that the glyphosate weed control programs compared to the conventional methods decreased not only the number of herbicide applications but equally in magnitude decreased the dosage of active ingredients. The results also showed effective weed control with glyphosate when the weed covering was greater and sugar beets had a later growth stage of four true leaves. Glyphosate-resistant sugar beets applied with the glyphosate herbicide two or three times had an increase in white sugar yield from 4 to 18 % in comparison to the high dosage conventional herbicide systems. In summary, under glyphosate management sugar beets can positively contribute to the increasingly demanding requirements regarding efficient sugar beet cultivation and to the demands by society and politics to reduce the use of chemical plant protection products in the environment.     

Influence of phloem transport, N-fertilization and ion accumulation on sucrose storage in the taproots of fodder beet and sugar beet

To investigate the factors governing the accumulation of sucroseand amino acids in the taproots of sugar beet, their contentswere measured in the leaves, phloem sap and the taproots ofsugar beet, fodder beet and a hybrid between both, grown oneither 3.0 or 0.5 mM nitrate. In the taproots the contents ofmalate, citrate and inorganic ions were also determined. Forthe high sucrose accumulation in sugar beet as compared to theother varieties three factors were found. (a) In sugar beet,less amino acids and more sucrose are taken up into the phloemthan in fodder beet. (b) In sugar beet, the sucrose and aminoacid syntheses are less sensitive to the nitrate concentrationsthat are required for optimal plant growth than in other varieties.In fodder beet, upon raising the nitrate concentration from0.5 mM to 3 mM, the synthesis and storage of sucrose is decreasedand that of amino acids increased. The corresponding valuesin sugar beet (0.5 mM) are similar to those in fodder beet andare not much affected by an increase of nitrate. (c) The sucroseaccumulation is limited by the accumulation of inorganic ionsin the taproots. The sucrose content in the taproots is negativelycorrelated to the total ion content. Whereas sucrose representstwo-third of all solutes in the taproots of sugar beet, it amountsto only one-third of the solutes in fodder beet taproots. Key words: Amino acids, Beta vulgans L, phloem sap, potassium, sucrose storage, sugar beet, taproots, transport     

Bruising of sugar beet roots and consequential sugar loss: current understanding and research needs

Bruising of sugar beet roots and the consequential sugar loss do not receive the attention they deserve within the sugar beet industry. Recent harvester tests have indicated that current levels of bruising damage could be decreased with existing technology. There is, however, little understanding of biological factors affecting susceptibility to bruising of sugar beet roots. This paper examines the available information on causes of bruising, the significance of some tissue characteristics, the processes of sugar loss following bruising and agronomic, physiological and biochemical considerations relevant to bruising and the sugar loss that follows. Some research needs are identified in conclusion.     

The effect of GNA lectin on the α-amylase activity of the beet armyworm,Spodoptera exigua Hb. (Lepidoptera: Noctuidae)

Beet armyworm (Spodoptera exigua Hb.) (Lepidoptera: Noctuidae) is the major pest of sugar beet (Beta vulgaris). Pesticide applications are the main method of the insect control. So, alternative method/s is/are needed to control this insect species. So, in the current study, the effect of Galanthus nivalis agglutinin (GNA) (snowdrop lectin) on beet armyworm α-amylase was studied. Measurement of the amylase activity of the larval midgut fed on artificial diet and sugar beet leaves showed that the enzyme activity was higher when the larvae fed on artificial diet. However, in both cases, the fourth instar larvae had the greatest amylase activity. Thus, fourth instar larvae were offered artificial diet containing 1 and 2% GNA. Both treatments of the lectin significantly reduced the α-amylase activity of the insect. For example, amylase activity of the fourth instar larvae in the control (fed only on artificial diet) was 2.62 Uml^?1 whilst the activity of the enzyme in the two treatments including diet containing 2 and 1% lectin was 1.45 and 1.75 Uml^?1, respectively. The achieved data showed that lectin, in addition to have toxic effect on the larval growth and development, affects the α-amylase activity of the insect gut.     

Control of the larvae ofConorhynchus mendicus (Col.: curculionidae) bySteinernema carpocapsae andSteinernema feltiae (nematoda,steinernematidae) in the gharb area (Morocco)

Two entomopathogenic nematodes,Steirnernema carpocapsae andS. feltiae were evaluated in the laboratory and under field conditions against larvae ofConorhynchus mendicus, a pest of sugar beet in the Gharb area of Morocco. Nematodes were applied in an artificially infested field using a knapsack sprayer either during the day or in the evening after sunset. The number of insect cadavers recovered from both soil and sugar beet plants was greater in the treated plots compared with the untreated ones. The percent reduction in live larvae was significantly greater in theS. carpocapsae treated plots (89.5% and 59.5% for night an day application respectively) compared with those treated withS. feltiae (68.5% and 28% respectively). The efficacy of entomopathogenic nematodes was therefore increased by application at night particularly in the case ofS. carpocapsae where control was maintained for 45 days.