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.     

Sugar Beet Pectin–Protein Complexes

The physical structure of pectin extracted from fresh sugar beet has been examined by atomic force microscopy (AFM). The images obtained reveal that these extracts contain a mixture of pectin polysaccharides and protein–pectin complexes. The AFM data demonstrate, for the first time, that these protein–pectin complexes consist of pectin molecules with protein attached to one end of the pectin chain.     

Beet luteovirus coat protein sequence variation

The sequences of cDNA clones covering the coat protein genes of 29 isolates of beet mild yellowing virus from sugar beet and beet western yellows virus mainly from oilseed rape were compared. The sequences could be partitioned into seven distinct clusters falling into three main groups. Group 1 isolates were found both in oilseed rape and sugar beet mainly from north Europe; group 2 isolates were from hosts other than sugar beet in England and France; group 3 isolates were beet-specific and found from northern Italy and Iran. The factors affecting this variation and its significance in relation to coat protein-mediated protection are discussed.     

Production of Regenerants in Sugar Beet

The experimental results are presented on production of plants-regenerants of the sugar beet (Beta vulgaris L.) via callus formation or direct organogenesis from the leaf tissues. The method of aseptic treatment was developed for the seeds with strong bacterial and fungal invasion. The regenerant plants were obtained in the presence of various concentrations of synthetic hormones, such as cytokinin (6-benzaminopurine) and auxin (naphthylacetic acid), and inhibitor of auxin transport in plants (2,3,5-triiodobenzoic acid). This combination of growth regulators made it possible to avoid callus formation. The genotype of initial plants affected the capacity for callus formation and regeneration. The temperature influenced rhizogenesis in regenerants.     

Observations on Fertilization in Sugar Beet

The whole process of double fertilization in sugar beet has been observed, the main results are as follows: About 2 hours after pollination, the pollen grains germinate, the sperms in the pollen tube are long-oval. 15 hours after pollination, the pollen tube destroys a synergid and releases two sperms on one side or at the chalazal end of the egg cell. The sperms are spherical each having a cytoplasmic sheath. 17 hours after pollination, one sperm enters the egg cell, and the sperm nucleus fuses with the egg nucleus rapidly. 21 hours after pollination, the zygote is formed. In the meantime, the primary endosperm nucleus has divided into two free endosperm nuclei. 25 hours after pollination, the zygote begins to divide, forming a two-celled proembryo. The dormancy stage of the zygote is about 4 hours. In the meantime the endosperm is at the stage of four free nuclei. 17 hours after pollination, the sperm nucleus comes into contact and fuses with the secondary nucleus. The sperm nucleus fuses with the secondary nucleus, faster than the sperm with the egg. he first division of the primary endosperm nucleus is earlier than that of the zygote, it takes place about 20 hours after pollination, the dormancy stage of the primary endosperm is about 2 hours. The endosperm is free nuclear. The fertilization of sugar beet belongs to premitotic type of syngamy. From the stage of zygote to the two-celled proembryo, it can be seen that addition- al sperms enter the embryo sac, but polyspermy has not been observed yet.     

Bacterial Microflora on Disinfected Sugar Beet Seeds

Sugar beet seeds disinfected with the carbofuran-containing insecticide adifur and the fungicide tachygaren by seed-producing firms were found to be abundantly populated with bacterial microflora. The bacteria isolated from the seed surface were identified to a species level. The selection of bacteria with respect to pesticide resistance may lead to the obtaining of agronomically useful bacterial strains.     

宁夏甜菜丛根病的研究

发生在宁夏甜菜上的一种病毒病的病株叶丛主要表现为黄化、焦桔和叶脉黄化坏死。从其分离的病毒粒子呈杆状,宽约20nm,长度为65—110nm、270—300nm和390—420nm,能侵染甜菜、菠菜、昆诺阿藜、苋色藜、番杏,与甜菜坏死黄脉病毒(BNYVV)抗血清呈阳性反应。综上所述,认为该病害是由BNYVV引起的。     

Changes in Ribonuclease and Glucose-6-Phosphate Dehydrogenase Activities Induced by Beet Necrotic Yellow Vein Virus in Sugar Beet

Activities of host ribonucleases and glucose-6-phosphate dehydrogenase were studied in three cultivars (Monosvalof, Steffi and Rimini) of sugar beet differing in their resistance to beet necrotic yellow vein virus (BNYVV). No differences were found in the susceptibility of cultivars to BNYVV between mechanically inoculated and Polymyxa betae (a natural fungal vector of the virus) infected plants, but the culmination of reproduction curves of BNYVV in mechanically inoculated plants was observed one week earlier than in plants inoculated by means of P. betae. The activities of ribonucleases corresponded with virus multiplication. In roots, activities of ribonucleases reached a maximum at day 7; in leaves, maximum activity was found at day 21 in cv. Monosvalof, and at day 14 in cv. Steffi. The relatively resistant cultivar Rimini showed much lower activities. The activity of glucose-6-phosphate dehydrogenase was only slightly increased at the time of culmination of the BNYVV reproduction curve in cvs. Monosvalof and Steffi. This revised version was published online in June 2006 with corrections to the Cover Date.     

The Effects of Aqueous Extracts of Red Beet Root on Salt Accumulation and Respiration of Discs of Red Beet Root

An account is given of the preparation of aqueous extracts ofred beet root which are shown to stimulate potassium uptakein beet discs washed for a short period, but inhibit potassiumuptake in discs washed for four days or more. Analysis of extractsshowed them to contain organic anions (especially citrate andmalate) which affect both the metabolic phase of potassium uptakeand respiration of the tissue. The effects of extracts and organicacids on uptake of manganese by beet discs is described andcompared with effects on potassium absorption. The results arediscussed with respect to current theories of salt accumulationand in relation to the hypothesis relating an inhibitor of saltaccumulation to the lag phase of ion uptake by beet discs.     

高效诱导甜菜再生植株的研究

研究了栽培甜菜(Beta vulgaris L.)4倍体品系405叶柄外植体的离体培养。成功地建立了一套高频率诱导再生芽的程序。外植体取自生长在改良MS(MSB)附加BA和NAA或者单加BA的培养基中。经过30d以上预培养后的幼苗叶柄,在MS附加BA 1．0mg／L或NAA0．3mg／L,Bal．0mg／L培养基上直接诱导再生芽,并发育成苗．诱导频率最高可达51．3％。在1／2MS(MS培养基大量元素减半)附加NAA0．5～1．0mg／L的培养基上诱导生根．这一程序为甜菜扩大繁殖和遗传转化提供了一个良好的试验系统。     

Exchangeable Ions in Beet Disks at Low Temperature

The relatively rapid passage of ions into the ‘Free Space’of disks of beetroot has been studied using radioactive tracerswhile active accumulation was reduced to a negligible proportionby using ‘salt saturated’ tissue at 20°C. The experiments confirm the suggestion made previously thatthe free space can be treated as if made up of two main components,the ‘Water Free Space’ (W.F.S.), where the concentrationsof anion and cation quickly become equal to those of the externalsolution, and the ‘Donnan Free Space’ (D.F.S.),containing a high concentration of non-diffusible anions. In disks pretreated with solutions of RbI to remove all othermobile ions from the free space the amount of exchangeable Iand Rb was measured by the uptake of I¹³¹ and Rb⁸⁶ at variousexternal concentrations. The excess of cations over anions (the‘extra exchangeable Rb‘) was used as an estimateof the amount of non-diffusible anions in the D.F.S. This wasapproximately constant at 10–13 m.equiv./kg. A gradualrise in the extra exchangeable Rb as the external concentrationrose from 1 to 20 m.equiv./l. has been explained as consistentwith the Donnan anions having arisen from weak acids with apK of about 3. The volume of the D.F.S. was estimated from the amount of extraexchangeable Rb in disks which had previously been treated sothat the counterions in the D.F.S. were exclusively Ca, andwhich were subsequently brought to equilibrium with variousconcentrations of RbBr. The mean volume from four experimentswas 2·1 percent. so that the concentration of non-diffusibleanions in the D.F.S. was 560 m.equiv./l. In consequence thefraction of the exchangeable anion in the Donnan part of thefree space is negligible and so the amount in the free spacedivided by the external concentration gives an estimate of thevolume of W.F.S. as 200 ml./kg. The results are compared with earlier estimates of the non-diffusibleanions concentration made by different means. In consideringthe location of the D.F.S. in the tissue, account must be takenof the fact that the area of the cell protoplasts consideredas smooth spheres is much too small to contain the number ofimmobile anions present (c. 12 m.equiv./kg) since there wouldbe less than 1 A{ring}² for each ion. For reasons given, theD.F.S. is thought to be mainly in the cell cytoplasm, a layer1 micron thick in cells of diameter 120 microns contributingthe required volume.     

Effect of Photoperiod on Growth of Sugar Beet

Sugar beet grown in controlled environments were given similardaily amounts of visible radiation during three different photoperiodtreatments. Plants were given (a) 115 W m^–2 visible irradiancefrom fluorescent and tungsten lamps for 12 h; (b) 88 W m^–2of the same light for 16 h or (c) 115 W m^–2 from fluorescentand tungsten lamps for 12 h extended to 16 h with low intensity(3 W m^–2) incandescent light from the tungsten lamps only.Plant growth was increased similarly in both long day treatments[(b) and (c)] and dry weights were 25 per cent greater thanin the 12 h photoperiod (a) after 6 weeks. Leaf area was increasedby 18 per cent and net assimilation rate by 10 per cent in the16 h photoperiod at 88 W ^m–2 (b). By contrast, extendingthe photoperiod with 4 h of incandescent light (c) triggereda photomorphogenic increase in leaf expansion which increasedleaf area per plant by 47 per cent and leaf-area ratio by 12per cent.