Temperature Control and Metabolic Drifts in Ageing Disks of Storage Tissue

The respiratory drifts of ageing disks of sugar-beet, red beet,carrot, swede, and potato maintained at different temperatureshave been determined mano-metrically. The general pattern ofthe respiratory time-drift exhibited by all tissues is thatof a hyperbolic curve but its exact form is largely determinedby the temperature of pretreatment, higher temperatures causinga telescoping effect. Different respiratory time-drifts obtainedby earlier workers from the same tissue are shown to be explicablein terms of the temperature of pretreatment. Except in swededisks, estimations of total and reducing sugar content of thedisks throughout the experimental period revealed a very considerableconversion of sucrose (or starch in potato) to reducing sugars.In sugar-beet, red beet, carrot, and potato the concentrationof reducing sugar is positively correlated with the rate ofrespiration. The character of the respiratory time-drift inthe disks is discussed in relation to substrate concentrationand other possible determinants.     

A Germination Inhibitor from Sugar-Beet

There is present in the water extract of sugar-beet seed ballsan unsaturated yellow oil which is capable of inhibiting germinationof various seeds. It also inhibits salt uptake and the respirationof sugar-beet tissue disks. The activity of the polyphenolaseenzyme present in beet tissue is also depressed. The role ofthe oil in inhibition of sugar-beet germination is discussed.     

Changes in the Pectin (Uronic Acid) Content of Storage Tissue 1

Changes in the pectin (uronic acid) content are reported fordisks of carrot, swede turnip, sugar-beet, red beet, and potatomaintained in aerated, running tap water at three temperaturesfor periods of up to 20 days. Under certain conditions, synthesisof uronic acids, as estimated by a micro-decarboxylation method,occurs and there are changes in the relative amounts of water-solubleand water-insoluble constituents of the tissues. The increasesin water-insoluble material and the periods when the maximumchanges occur are discussed in relation to the correspondingchanges in dry weights of the tissues.     

Synthesis of folate derivatives in aerated storage tissue disks

Microbiological assay of extracts prepared from carrot, potato, turnip and beet storage tissue disks revealed that folate derivatives were synthesized during a 48 hr aeration period in sterile distilled water. The composition of the folate pool in carrot was examined by DEAE—cellulose column chromatography, γ-glutamylcarboxypeptidase treatment and differential assay of individual derivatives using Lactobacillus casei and Streptococcus faecalis. The principal folates were polyglutamates of formyl and methyl tetrahydrofolate. Smaller quantities of the corresponding mono- and di-glutamates were also detected. The latter derivatives occurred in pools having a high degree of metabolic turnover. The specific activities of three enzymes catalyzing production of these derivatives from tetrahydrofolate increased during the first 12 hr of aeration. Amino acid analyses revealed that folate synthesis in carrot disks was accompanied by depletion of free serine and by net synthesis of free and protein methionine.     

The development of invertase activity in slices of the root of Beta vulgaris L. washed under aseptic conditions

1. When disks of root tissue from sugar or red beet (Beta vulgaris L.) are washed in running aerated tap water the sucrose contained in them disappears and glucose and fructose are formed. 2. Invertase activity in the disks has been measured by a polarimetric method. Freshly cut tissue has a very low activity, but a considerable increase occurs during the first 3–4 days of washing, the final activity being sufficient to hydrolyse the sucrose contained in the disk within a few hours. 3. Disks of red beet have been cut and shaken in water under aseptic conditions. Sucrose breakdown and invertase development still took place. Microbial contamination is therefore not responsible. 4. Trisaccharides that appear in sugar-beet disks during the washing process have been isolated and identified; their formation also suggests that a higher-plant invertase is acting. 5. The significance of these results is discussed in relation to protein synthesis in washed storage-tissue slices, and the occurrence of high invertase activity in growing plant cells.     

Cation exchange properties and pectin content of storage-tissue disks

Summary The cation-exchange capacity (C.E.C.) of disks of storage tissue of sugar beet, red beet, potato, carrot, and swede turnip kept in running tap water at constant temperature, has been measured using an acid-washing technique. The pectin content of the disks has been estimated by measuring the CO₂ evolved on decarboxylation.There is quantitative agreement between exchange capacity and pectin content of the disks provided the former is measured on a tissue volume basis, and also provided that in assessing the latter, the substances yielding CO₂ yet not participating in cation exchange are first removed from the tissues by boiling in water. The C.E.C. and pectin content of the disks increase with time and reach a maximum 3 to 4 days after the disks are cut from the parent tissue.     

Effects of increasing weed-beet density on sugar-beet yield and quality

Weed beets are an increasing problem in many sugar-beet crops in many countries. At present about one sugar-beet field in four in England is infested with weed-beet seed. Control in other crops can be achieved using selective herbicides but in sugar beet the weed beets, many of which are of annual habit, are not easily controlled and often compete with the crop. Experiments were done to quantify the yield loss caused by weed beet in sugar-beet crops. Transects were laid out across three fields in 1985 and 1986 and plots located thereon to include the range of weed-beet densities found in the field. Weed beet did not affect the concentration of sugar (sucrose), potassium, sodium, α amino nitrogen or invert sugar in the crop beets. Root and sugar yields were progressively reduced by increasing densities of weed beet. A rectangular hyperbola described the data slightly better than an asymptotic model. There was no indication of a threshold density of weed beet below which there was no yield loss, which averaged 11.7% for each weed beet plant/m². This corresponds to an average 0.6% sugar yield loss for each 1% of bolted weed beet in the root crop up to 100%, which is similar to the reported losses resulting from bolters in the root crop.     

The Net Assimilation Rates of Wild and Cultivated Beets

The net assimilation rate (E) of Kleinwanzleben sugar-beet wasthe same as that of three types of wild sea-beet (Beta vulgarissubsp. maritima) when the leaf-area index (L) was near to I.In a subsequent period, when mean L of sugar-beet and of theleafiest wild beet type was 2.5, there was an inverse relationbetween E and L of the three wild types, and E of sugar-beetwas then much greater than that of the wild type with equalL but was little different from that of the wild type with smallestL (about 1.5). It is concluded that the development of sugar-beetfrom its wild ancestors by selection and breeding has not affectedthe intrinsic photosynthetic efficiency of the leaves, but hasdiminished the effect of mutual-interference between leaves,so that E falls less rapidly as L increases, i.e. it has decreasedthe leaf-density dependence of E. This change may be relatedto the difference in form between sugar-beet and wild beet plants.     

STUDIES ON THE IMPORTANCE OF WILD BEET AS A SOURCE OF PATHOGENS FOR THE SUGAR-BEET CROP

Beet yellows virus, beet mosaic virus, rust ( Uromyces betae (Pers) Lév.), and downy mildew ( Peronospora schachtii Fuckel.) were found to be common in wild beet ( Beta vulgaris s.-sp. maritima L.) growing on the foreshores of south Wales and southern England. The virus diseases were more prevalent in southeast England than in the west, rust more in the west than in the east, and downy mildew is equally prevalent in all regions.
Beet yellows is the most commercially important disease and is more common in sugar-beet crops in East Anglia than elsewhere in Great Britain. There was no evidence that beet yellows spread in East Anglia from wild beet to nearby sugar-beet crops during the springs of 1958 or 1959, and Myzus persicae Sulz., the principal vector of yellows, was rarely found on wild beet growing on the foreshore.
In glasshouse experiments aphids colonized sugar-beet plants watered with tap water in preference to those watered with sea water. Daily watering with sea water made plants unpalatable to aphids within 14 days. Aphids also preferred leaves sprayed with distilled water to those that had been sprayed with sea water. Salt solutions gave results similar to those obtained with sea water.     

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.     

Dry Matter Distribution between Shoot and Storage Root of Carrot, Parsnip, Radish and Red Beet

The relationship between shoot and storage root weights of carrot,parsnip, radish and red beet was examined using plants of differentsize and age. For both carrot and parsnip plants of the sameage there was a linear relationship between the logarithms ofshoot and storage root d. wts which was unaffected by plantdensity. For parsnip the parameters of the regression were unchangedby harvest time, while for carrot the slope of the regressionremained constant and the intercept progressively declined withharvest time. These observations are consistent with an hypothesisof assimilate partition based on competition between sinks.For both radish and red beet at very high densities the logarithmicrelationship between shoot and storage root weight was curvilinearwith significant effects of both harvest time and density. Itis suggested that interplant competition may affect the initiationof storage tissue development in both these species. It is concludedthat for radish and red beet, even when considering only plantsproducing normal swollen storage roots, partition of assimilateis affected by factors not incorporated into the above hypothesis. Root crop, carrot, parsnip, radish, red beet, partition of assimilated carbon, model     

The effects of yellowing viruses on yield of sugar beet in field trials, 1985 and 1987

The separate effects of beet yellows virus (BYV) and beet mild yellowing virus (BMYV) on yield of sugar-beet cultivars inoculated at different growth stages were assessed in field trials in 1985 and 1987. Early or mid-season inoculation decreased sugar yield by up to 47% for BYV, and up to 29% for BMYV. Infections after the end of July had no significant effect on yield. Both viruses caused significant increases in the juice impurities sodium, potassium and amino-nitrogen after infecting plants early in the season. Yield losses associated with infection were determined by the causative virus, the time of infection, and susceptibility of the sugar-beet cultivars.     

Some factors affecting germination of Peronospora farinosa conidia in water

The germination of conidia of Peronospora farinosa f. sp. betae, collected from sugar beet and suspended in deionized water, was inhibited by dilution with 10% solutions of glycerol, glucose or sucrose and with sap from sugar-beet leaves. Germination was stimulated by diluting with deionized water but not with tap water or biological saline. Substances that diffused from excised buds of sugar-beet plants into deionized water also stimulated germination of conidia but diffusates from leaves did not. This may partly explain why buds are more susceptible to downy mildew than leaves in sugar beet. Germination of conidia was apparently stimulated more by diffusates from buds of seedlings than by those from buds of older plants; this may help to explain why sugar-beet seedlings are more susceptible to downy mildew than older plants. Diffusates from plants of four sugar-beet stocks, that differed from each other in susceptibility to downy mildew, had very similar effects on germination of P. farinosa conidia. Stimulation of spore germination on the surfaces of buds and leaves did not seem, therefore, to be an important factor in determining resistance or susceptibility to downy mildew in these stocks.     

Indole-3-acetic acid and indole-3-butyric acid in tissues of carrot inoculated withAgrobacterium rhizogenes

The role of auxins in induction of roots byAgrobacterium rhizogenes was studied in carrot root disks. Transformed roots were produced on root disks by inoculation withA. rhizogenes, A4. Measurement of indole-3-acetic acid (IAA) by gas chromatography-mass spectrometry (GC-MS) indicated that there was a significant increase in the concentration of IAA in transformed callus and induced roots compared with initial IAA concentrations in carrot disks. Indole-3-butyric acid (IBA) was found to occur naturally in carrot roots. The presence of IBA, a potent root inducer, must be taken into account when assessing the role of auxin during transformation and induction of roots byA. rhizogenes.     

SUGAR-BEET YELLOWS: FURTHER STUDIES ON VIRUSES AND VIRUS STRAINS AND THEIR DISTRIBUTION IN EAST ANGLIA, 1958-59

Experiments have shown that, as in the years 1955-57, two yellowing viruses, beet yellows virus (SBYV) and sugar-beet mild yellowing virus (SBMYV), were present in commercial sugar-beet crops in East Anglia in 1958 and 1959. The evidence that they are not closely related viruses has been confirmed. In both years the prevalence of the two viruses was estimated by aphid transmissions from yellowed sugar-beet leaves to healthy sugar beet and Chenopodium capitatum seedlings in the glasshouse, and in 1959 additionally by examination of symptoms on field plants. SBMYV was more common than SBYV over the whole region in 1958, but in 1959 SBYV was slightly more prevalent than SBMYV. In both years SBYV was found more often in the southern than in the northern parts of the region. The results described in this paper suggest that breeding for tolerance to SBMYV may be at least as important economically in East Anglia as breeding for tolerance to SBYV. A wide range of SBYV strains was present in East Anglia in 1959, most of the strains being those which caused severe symptoms in sugar beet and C. capitatum.     

Variation in annual and regional damage to sugar beet by pygmy beetle (Atomaria linearis)

SUMMARY
The reported amount of damage done by pygmy beetle to the sugar-beet crop varies greatly with year and with region. Annual variation in damage is most strongly correlated with soil temperatures of the previous August, implying improved breeding success in warm summers. The value of predicting damage using this relationship is discussed. Damage is most severe in areas of intensive beet growing, particularly on low-lying areas around The Wash.
There was no relationship between damage and the numbers caught in a 12.2 m suction trap in the spring. It is suggested that much of the damage is done by beetles which are present in the beet fields at or shortly after sowing, having arrived there before the great majority fly in May-July.     

Breeding for resistance to infection with yellowing viruses in sugar beet

Differences in resistance to infection with beet yellows virus (BYV) and beet mild yellowing virus (BMYV) have been observed in virus-tolerant sugar-beet breeding material. The results of glasshouse virus-susceptibility tests usually agreed well with those of field experiments in which plants were exposed to artificial, or natural, infestation with viruliferous aphids. Breeding lines and varieties, which showed resistance to BYV when Myzus persicae Sulz, was used as vector, generally showed a similar resistance to this virus when Aphis fabae Scop. was used. Varieties which were resistant to infection with one virus were not necessarily resistant to the other, although some showed resistance to both BYV and BMYV. Preliminary results suggest that resistance to infection may be controlled by recessive genes which occur widely in sugar-beet cultivars. The mechanism of this form of resistance is not understood, but it does not appear to be closely associated with resistance to the aphid vectors of the viruses. The observed differences in resistance to infection demonstrate the possibility of breeding a sugar-beet variety in which two forms of resistance to virus yellows, tolerance and resistance to infection, are combined.     

Some factors affecting the concentrations of sugars in leaves of inbred sugar-beet lines

In the glasshouse, large differences in concentrations of glucose and sucrose were observed between leaves of inbred sugar-beet lines that are known to differ from each other in resistance to pests and diseases. Differences between these lines in concentrations of fructose, glucose and sucrose were more pronounced in the petiole than in the lamina. The concentrations of glucose and fructose were lower in the first two leaves (primary leaves) than in those produced subsequently (secondary leaves); both types of leaf contained similar concentrations of sucrose. Secondary leaves from plants that had been kept in darkness for 17 h contained less fructose, glucose and sucrose than those of plants kept in sunlight for 5 h. Longer period of darkness lowered the concentrations of monosaccharides in the leaves further but did not affect the sucrose content. Primary and secondary leaves from the same sugar-beet plant often differ in non-race-specific resistance to pests and diseases; and darkness can affect suscetibility of beet to downy mildew and to the aphid Myzus persicae. The results of the sugar determinations therefore support the hypothesis that the concentrations of certain carbohydrates in sugar-beet leaves are important in non-race-specific resistance to pests and diseases.     

The occurrence of beet mild yellowing virus in Czechoslovakia

The occurrence of beet mild yellowing virus (BMYV) on feeding- and sugar-beet in Czechoslovakia has been proved. The virus was transmitted by aphidMyzus persicae (Sulz.) on indicator plantsSinapis alba L.,Capsella bursa-pastoris Medik, andClaytonia perfoliata Donn and from these plants back to sugar-beet cv. ‘Dobrovická A.’ A weed plantRaphanus raphanistrum L. was identified as a new natural host plant of BMYV. The virus was identified in ten of twelve biologically examined samples of beet with BMYV-like symptoms, which were collected at various places in Czechoslovakia