Study on DNA diversity of Iranian populations of Erysiphe betae causal agent of sugar beet powdery mildew

107 samples of E. betae were collected on infected leaves from all over Iranian beet cultivation areas. Their choosing were based on geographical and host origin(sugar beet, red beet, fodder beet and wild beet). 30 isolates were single colonized and grown on sugar beet susceptible genotype 7233. 107 specimens were analyzed by restriction fragment length polymorphism (RFLP) of the ribosomal internal transcribed spacers (ITS) and 5.8s DNA which previously amplified by the polymerase chain reaction (PCR) with 2 universal primers, ITS1 and ITS4. PCR product was affected by 9 different restriction enzymes. PCR product was a 645 bp band for all of the isolates. 3 restriction enzymes; CfoI, MspI and HaeIII could cut this fragment into smaller bands, but electrophoretic patterns were identical for all of the isolates. 30 single colonized isolates were used in RAPD experiments. In RAPD-PCR experiment genetic diversity was investigated with 30 isolates from different parts of the country. 59 random primers were used and then 21 primers that displayed good consistency and reproducibility were selected. Most of the primers revealed identical patterns between 3 to 14 bands. 5 primers that showed more polymorphism were selected to analyze 30 isolates. For these 5 primers 61 distinct bands were obtained which 62% of these bands were polymorphic. Results indicated that there is no relationship between cluster grouping and geographical origin and the isolates showed a high similarity.     

Translocation and the control of photosynthesis in sugar beet

Summary Evidence is presented that the size and activity of sinks for the products of photosynthesis exert a large measure of control over carbohydrate levels in the leaves of the sugar beet plant. Further data is presented to show that a correlation exists between the level carbohydrate in the leaf and the rate of photosynthesis. The rate of photosynthesis can thus be linked directly to the sinks of the plant by their ability to control rates of translocation from leaves.     

Controlling the sugar beet fly Pegomyia mixta Vill. with entomopathogenic nematodes

Sugar beet, Beta vulgaris L. is a strategic crop of sugar industry in Egypt. It is threatened by several insect pests among most important of them is the beet fly Pegomyia mixta. This work deals with the biological control of this insect using four entomopathogenic nematodes (EPNs). The nematodes included Steinernema carpocapsae S2, Steinernema feltiae, Heterorhabditis bacteriophora (HB1-3) and Heterorhabditis bacteriophora S1. Daily mortality of larvae and pupae of P. mixta were recorded after treatment with serial concentrations (500, 1000, 2000 and 4000 infective juveniles (IJs)/ml) of each of four studied EPNs. In the laboratory all tested nematodes killed the larvae inside their mines in the sugar beet leaves and developed in their bodies in different extends. They also killed the insect pupae in the soil and developed in their bodies. Young larvae were more susceptible than old ones. New pupae were more susceptible than old ones. In the field a single spray of S. feltiae or H. bacteriophora caused 81.3 or 75.9% reduction in the larval population of the in sugar beet leaves.     

Aphids from mangold clamps and their importance as vectors of beet viruses

Mangold clamps are over-wintering sources of the aphid-transmitted beet mosaic, beet yellows and beet mild yellowing viruses, and of several species of aphid, three of the most common in clamps being Myzus persicae, Rhopalosiphoninus staphyleae tulipaellus and R. latysiphon. This study attempted to assess the relative importance of the different species in spreading viruses from clamps. Compared with M. persicae, R. s. tulipaellus and R. latysiphon are seldom trapped in flight, except near large infestations. Alatae of M. persicae and R. s. tulipaellus become common in clamps in April, but few fly below 15d? C., a temperature seldom reached in eastern England in early spring. Flight muscle autolysis, which occurs later in R. s. tulipaellus and R. latysiphon than in some aphid species, also probably prevents many alatae in clamps from flying. We confirmed the importance of clamps as sources of beet viruses, the percentage of infected plants decreasing with increasing distance from infested clamps. M. persicae is shown to be a better vector of beet viruses than the other clamp aphids, and is probably responsible for most virus spread from clamps. R. s. tulipaellus did not transmit beet mosaic virus, but it is a fairly efficient vector of beet yellows and beet mild yellowing viruses, and, although we did not find this species on sugar beet in the field, it probably spreads these viruses from clamps. R. latysiphon did not transmit any of the viruses, and the role of Macrosiphum euphorbiae, Aulacorthum solani and Myxus ascalonicus is probably small.     

Progress towards the understanding and control of sugar beet rhizomania disease

Rhizomania is a soil-borne disease that occurs throughout the major sugar beet growing regions of the world, causing severe yield losses in the absence of effective control measures. It is caused by Beet necrotic yellow vein virus (BNYVV), which is transmitted by the obligate root-infecting parasite Polymyxa betae . BNYVV has a multipartite RNA genome with all natural isolates containing four RNA species, although some isolates have a fifth RNA. The larger RNA1 and RNA2 contain the housekeeping genes of the virus and are always required for infection, whereas the smaller RNAs are involved in pathogenicity and vector transmission. RNA5-containing isolates are restricted to Asia and some parts of Europe, and these isolates tend to be more aggressive. With no acceptable pesticides available to restrict the vector, the control of rhizomania is now achieved almost exclusively through the use of resistant cultivars. A single dominant resistance gene, Rz1 , has been used to manage the disease worldwide in recent years, although this gene confers only partial resistance. More recently, new variants of BNYVV have evolved (both with and without RNA5) that are able to cause significant yield penalties on resistant cultivars. These isolates are not yet widespread, but their appearance has resulted in accelerated searches for new sources of resistance to both the virus and the vector. Combined virus and vector resistance, achieved either by conventional or transgenic breeding, offers the sugar beet industry a new approach in its continuing struggle against rhizomania.     

Observations on the biology of Boschniakia hookeri (Orobanchaceae)

Observations on Boschniakia hookeri Walp. (Orobanchaceae), a root parasite, have been carried out at locations on the Kitsap Peninsula, Washington State, U.S.A.; Bamfield, British Columbia, Canada; and Sand Lake, Tillamook County, Oregon State, U.S.A. The hosts of B. hookeri , all Ericaceae, identified by excavation of the host root–parasite connection, were Arbutus menziesii Pursh., Gaultheria shallon Pursh., Arctostaphylos uva–ursi (L.) Spreng., and an introduced South American species, Pernettya mucronata Gaud. Seasonal development above ground and recurrence of blooming were monitored. It was shown that the plants are autogamous. Predation plays an important role in the biology of Boschniakia hookeri , including infestation by nematodes, destruction of entire plants by rodents, and attack on the inflorescences by a fly, Pegomya sp. A life history of Boschniakia hookeri was assembled from the data of this study.     

Intraspecific variation of Myzus persicae on sugar beet (Beta vulgaris)

Differences in inherited resistance among seven sugar-beet stocks had similar effects on Myzus persicae clones representing the range of variation in aphid response to resistant and susceptible sugar beet observed in fifty-eight clones collected between 1969 and 1971. Three sugar-beet stocks were consistently resistant. Statistically significant interactions between beet stocks and aphid clones did not indicate the existence of biotypes with specific abilities to overcome resistance. M. persicae clones differed in their vigour of colonizing sugar beet, irrespective of the differences between beet stocks. The readiness of adult aphids to settle determined the size of aphid population produced and included a component related to the response of the aphid clone to sugar beet as a host, and a component related to the resistance ranking of the beet stock. Breeding sugar beet with resistance to aphids will be simplified, as the results indicate that, at present, differences between aphid biotypes need not be considered a problem.     

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

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

In vitro dual culture of Polymyxa betae in Agrobacterium rhizogenes transformed sugar beet hairy roots in liquid media

Polymyxa betae is a soil-borne protist and an obligate parasite of sugar beet that transmits the beet necrotic yellow vein virus. Sugar beet hairy roots, transformed by Agrobacterium rhizogenes, were inoculated with surface-sterilized root fragments infected by P. betae. After 10 wk in a liquid medium, typical structures of P. betae were observed in this in vitro system. This first in vitro culture of P. betae in liquid medium will contribute to a better understanding of this protist's biology through providing a way to conserve and produce purified isolates of the protist.     

A study of sugar beet growers' pest control decisions

The results of a survey of sugar beet growers are reported which provide subjective information on farmer perceptions of the hazard from pests and diseases on sugar beet, the control methods available and used, farmers' estimates of the costs and effect of controls, their objectives for pest control, and their attitudes to advice. In addition, objective information from research and field observations on losses and control methods is provided. The basis of pest control decisions and implications from comparisons of subjective and objective perceptions of the various problems and solutions are discussed.     

Distribution of violet root rot (Helicobasidium purpureum Pat.) of sugar beet and preliminary experiments on factors affecting the disease

Examination of sugar beet grown in eastern England over the period 1936-43 has shown that up to 5% of factory tarehouse samples contain roots infected with violet root rot. The results of the survey suggest that there are considerable areas where light attacks of the disease occur, as well as fields in which severe attacks develop when susceptible crops are grown. The disease occurred on roots grown in many types of soil but most frequently on those from light alkaline soils. It was found to reduce the sugar content and increase the dirt tare of sugar beet.
The causal fungus, Helicobasidium purpureum, has a wide host range and observations suggest that it persists in the field on weeds, as severe attacks on cultivated crops often occur in weed-infested fields. It also survives as sclerotia, which develop freely on the roots of susceptible crops. While the undisturbed soil conditions of leys and uncultivated land favour increase in infectivity, good cultural practices, trap cropping and application of nitrogenous fertilizers act as a check. These control measures will reduce infectivity even when applied to soil in which consecutive, susceptible crops are grown. Wet soil conditions did not favour the development of infection, and the frequent occurrence of the disease in wet places may be due to such soil conditions favouring survival of sclerotia.
Experiments with compost made from factory waste showed that although the fungus can survive the process, its virulence was so reduced that there is no likelihood that use of such compost would lead to severe violet root rot infection.     

Studies on beet western yellows virus in oilseed rape (Brassica napus ssp. oleifera) and sugar beet (Beta vulgaris)

Oilseed rape (Brassica napus L. ssp. oleifera) was studied as a potential overwintering host for the sugar-beet yellowing viruses, beet yellows virus (BYV) and beet mild yellowing virus (BMYV), and their principal vector, Myzus persicae. In spring 1982, plants infected with a virus which reacted positively in enzyme-linked immunosorbent assay (ELISA) with BMYV antibody globulin were found in oilseed-rape crops; none of the plants contained virus which reacted with BYV antibody globulin. This virus was subsequently identified as beet western yellows virus (BWYV). No leaf symptoms could be consistently associated with infection of oilseed rape, but the virus was reliably detected by sampling any leaf on an infected oilseed-rape plant. Some isolates from oilseed rape did infect sugar beet in glasshouse tests, but the proportions of inoculated plants which became infected were low. Apparently there is therefore little danger of much direct transmission of BWYV by M. persicae from oilseed rape to sugar beet in spring. BWYV was introduced to and spread within oilseed-rape crops in autumn by M. persicae, and autumn-sown oilseed rape proved to be a potentially important overwintering host for M. persicae. In a survey of 80 autumn-sown crops of oilseed rape in East Anglia, northern England and Scotland in spring 1983, 78 were shown to be extensively infected with BWYV. Experimental plots of oilseed rape with 100% BWYV-infection yielded approximately 13.4% less oil than plots with 18% virus infection, the result of a decrease in both seed yield and oil content.     

Phenotypic polymorphism and allele differentiation of isozymes in fodder beet,multigerm sugar beet and monogerm sugar beet

Summary Thirteen enzymes (MDH, SDH, LAP, PGM, PX, IDH, GPI, 6PGD, APH, GOT, GDH, ME and SOD) of 3 cultivated beet (B. vulgaris L.) gene pools, comprising 12 accessions of fodder beet, 11 of old multigerm sugar beet and 10 of modern monogerm sugar beet, were investigated using horizontal starch gel electrophoresis. Eleven accessions of primitive or wild B. vulgaris were also included for the comparison of isozymes. Variation in isozyme phenotypes was investigated to detect diversity in the three cultivated forms of beet. Phenotypic variation was observed in all except ME and SOD, which were monomorphic. A high degree of phenotypic polymorphism (Pj) was found in GDH, PGM, IDH, APH and MDH. Differences in phenotypic polymorphism in MDH, GPI and PX were recognized between fodder beet and both sugar beet groups. Average polymorphism for 13 enzymes in both sugar beets was significantly higher than that in fodder beet. For 13 enzymes, the existence of high isozyme diversity in both sugar beet gene pools was revealed. Allele frequencies in 13 alleles of five enzyme-coding loci, Lap, Px-1, Aph-1, Got-2 and Gdh-2, were investigated. New alleles, Px-1 ¹ and Got-2 ¹, were found in fodder beet accessions. No significant differences of average allele frequencies of five loci between fodder beet and both sugar beets were recognized. Several unique alleles and different isozyme phenotypes were observed in the accessions of B. vulgaris ssp. macrocarpa and ssp. adanensis. Future utilization of cultivated beet gene pools for sugar beet breeding is discussed from the viewpoint of genetic resources.     

Detection of beet yellows virus in sugar beet leaves and roots by enzyme-linked immunosorbent assay (ELISA)

Using the enzyme-linked immunosorbent assay (ELISA) beet yellows virus (BYV) could be detected reliably in the leaves of sugar beet andTetragonia expansa Pall. and in the roots of sugar beet. Specifio γ-globulin of BYV antiserum was coupled to horse radish peroxidase by periodate oxidation. Optimum dilutions of antigen (extract from infected leaves) were1: 50 to 1: 200 for BYV detection in sugar beet andT. expansa leaves and1: 2 to 1: 5 for detection in sugar beet roots. Extracts from beet roots are not to be purified by ultracentrifugation, however, by the described method virus can be demonstrated only in 80–90% of naturally infected sugar beet roots. The method is specific, no increase of extinction values was found in healthy or beet western yellows virus infected plants. Presence of virus can be demonstrated by visual as well as photometric evaluation. Results confirmed the suitability of peroxidase application for detection of plant viruses by ELISA.