Genetic study of a new color of the beet Beta vulgaris L.

A new genetic character of the beet Beta vulgaris L., named stem color, was described and studied genetically. This character was shown to be dominant and monogenically inherited. The first-year beet plants with the genotype Stc/_ have red leafstalks, weakly colored central rib, and colored storage root; however, the root itself is not colored. The second-year plants have a red-colored low third of the floral shoot. The plants with the genotype stc/stc are uncolored. The Stc gene was localized to the first linkage group at a distance of 17.5 ± 2.1% crossing over units from the gene B (Bolting), which controls the annual-perennial habit of beet.     

dw2, a new mutation of beet Beta vulgaris L

Twelve dwarf plants were found in the second hybrid generation of beet. The average height of mutant plants was 21.8 cm, their leaf blades and flowers were significantly smaller than normal, and the plants exhibited male and female sterility. This dwarfism was shown to be caused by a mutation differing from that previously described in beet, which is named dwarf2 (dw2). The experimental evidence suggests that this mutation appeared in one of the first-generation plants. Based on plant phenotype in the first hybrid generation and the number of mutant plants in the second one, this mutation is suggested to be under recessive monogenic control of the dw2 gene. The genotypic class segregation in the second hybrid generation indicates that the dw2 gene is inherited independently of genes m, at, and ap that control choricarpousness, gene male sterility, and pollen grain aggregation into tetrads.     

Genetic control of morphological characters of the beet (Beta vulgaris L.)

A brief review of theoretical and practical results of investigation of genetical control of a number of traits of beet, including self-incompatibility, monogerm-multigerm, cytoplasmic male sterility and some others is presented. Data concerning linkage groups of individual genes, determining morphological and biochemical traits are demonstrated.     

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

Key message

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.

Abstract

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.     

A new cytoplasmic male sterile genotype in the sugar beet Beta vulgaris L.: a molecular analysis

Summary Mitochondrial DNA (mtDNA) from fertile (N) and possibly new cytoplasmic male sterile (CMS) genotypes was studied in the sugar beet Beta vulgaris L. It was found by restriction endonuclease analysis that BMC-CMS, a cytoplasm that was derived from the wild beet Beta maritima, contained a unique type of mtDNA which is distinguishable from both the N and S-CMS, the only other CMS genotype that is currently availabe in B. vulgaris L. The organization of three genes: coxI, coxII and cob, was analyzed by hybridization with heterologous probes from maize. These genes have a similar structure in N and BMC-CMS that is different from S-CMS. It is concluded that BMC-CMS is a novel CMS genotype in the sugar beet.     

A linkage map of sugar beet (Beta vulgaris L.)

Summary We have established a first linkage map for beets based on RFLP, isozyme and morphological markers. The population studied consisted of 96 F₂ individuals derived from an intraspecific cross. As was expected for outbreeding species, a relatively high degree of polymorphism was found within sugar beet; 47% of the DNA markers were polymorphic for the chosen population. The map consists of 115 independent chromosomal loci designated by 108 genomic DNA probes, 6 isozyme and one morphological marker. The loci cover 789 cM with an average spacing of 6.9 cM. They are dispersed over nine linkage groups corresponding to the haploid chromosome number of Beta species. Eighteen markers (15.4%) showed distorted segregation which, in most instances, can be explained by gametic selection of linked lethal loci. The application of the linkage map in sugar beet breeding is discussed.     

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.     

Biolistic transformation of highly regenerative sugar beet (Beta vulgaris L.) leaves

Leaves of greenhouse-grown sugar beet (Beta vulgaris L.) plants that were first screened for high regeneration potential were transformed via particle bombardment with the uidA gene fused to the osmotin or proteinase inhibitor II gene promoter. Stably transformed calli were recovered as early as 7 weeks after bombardment and GUS-positive shoots regenerated 3 months after bombardment. The efficiency of transformation ranged from 0.9% to 3.7%, and stable integration of the uidA gene into the genome was confirmed by Southern blot analysis. The main advantages of direct bombardment of leaves to regenerate transformed sugar beet include (1) a readily available source of highly regenerative target tissue, (2) minimal tissue culture manipulation before and after bombardment, and (3) the overall rapid regeneration of transgenic shoots.     

The "crystals" in the sugar beet (Beta vulgaris L.) leaves

Crystal containing cells widely distributed in plant tissues, though the origin of the crystals and their functions are still opened to question. Membrane vesicles in beet leaves are visible in electronic microscope. They originate in cytoplasm and penetrate into vacuole by pinocytosis with participation of tonoplast. In light microscope, vesicles are luminous likewise crystals in crystal cells. Such vesicles-"crystals" fulfill crystal cells also. The content of vesicles-"crystals" are electronic transparent at every path of leaf development. It was proposed that distinct vesicles-"crystals" in cytoplasm and vacuole and mass of them in crystal cells, vein bundles, and epidermal cells--all of them are lytic compartments. Later, obviously, true crystals are formed.     

Flavin excretion from roots of iron-deficient sugar beet (Beta vulgaris L.)

The characteristics of flavin excretion from iron-deficient sugar-beet roots have been studied. Roots from iron-deficient sugar beet excreted flavins when plants were allowed to decrease the pH of the nutrient solution, but not when plants were grown in nutrient solutions buffered at high pH. As shown by reversed-phase high-performance liquid chromatography, the two major flavins whose excretion was induced by iron deficiency were different from riboflavin, FMN and FAD. These flavins have been identified as riboflavin 3′-sulfate and riboflavin 5′-sulfate by electrospray-mass spectrometry, inductively coupled plasma emission spectroscopy, infrared spectrometry and¹H-nuclear magnetic resonance. We have characterized the time courses of accumulation of the different flavins in the nutrient solution and considered several possible roles for flavin excretion in iron acquisition.     

Production of betacyanins by a cell suspension culture of table beet (Beta vulgaris L.)

A cell suspension culture of table beet (Beta vulgaris L.) was established for efficient betacyanin production from violet callus induced from the hypocotyls of aseptic seedlings. This suspension culture produced large amounts of betacyanins. The betacyanin content increased with increasing cell growth during the log phase. Reducing the total nitrogen concentration (30 mM) and modifying the ratio of ammonium to nitrate (1:14) resulted in an increased betacyanin content. Supplementation of Fe2+ to the LS medium also promoted betacyanin production. The maximal betacyanin yield was achieved with a 2 mM Fe2+ concentration. Combining these conditions, we established a revised LS medium to improve betacyanin productivity (250 mg/l for a 14-day culture).     

Thidiazuron-induced organogenesis and somatic embryogenesis in sugar beet (Beta vulgaris L.)

Summary Improved in vitro tissue culture systems are needed to facilitate the application of recombinant DNA technology to the improvement of sugar beet germplasm. The effects of N ⁶-benzyladenine (BA) and thidiazuron (TDZ) pretreatment on adventitious shoot and somatic embryogenesis regeneration were evaluated in a range of sugar beet breeding lines and commercial varieties. Petiole explants showed higher frequencies of direct adventitious shoot formation and produced more shoots per explant than leaf lamina explants. TDZ was more effective than BA for the promotion of shoot formation. The optimal TDZ concentrations were 2.3–4.6 μM for the induction of adventitious shoot regeneration. Direct somatic embryogenesis from intact seedlings could be induced by either BA or TDZ. TDZ-induced somatic embryogenesis occurred on the lower surface of cotyledons at concentrations of 0.5–2μM and was less genotype-dependent than with Ba. A high frequency of callus induction could be obtained from seedlings and leaf explants, but only a few of the calluses derived from leaf explants could regenerate to plants via indirect somatic embryogenesis. These results demonstrated that TDZ could prove to be a more effective cytokinin for in vitro culture of sugar beet than BA. Rapid and efficient regeneration of plants using TDZ may provide a route for the production of transgenic sugar beet following Agrobacterium-mediated transformation.     

Expression of CMS in zygotic and apozygotic progenies of sugar beet Beta vulgaris L

Zygotic and apozygotic progenies of sugar beet exhibit high phenotypic variation with respect to cytoplasmic male sterility (CMS). There are progenies with completely sterile, semisterile, semifertile, and fertile pollen. The proportions of semifertile and fertile plants in zygotic and apozygotic progenies varied from zero to 28% and from zero to 17.8%, respectively. Comparison of the phenotypic distributions in zygotic and apozygotic progenies did not reveal significant differences in the CMS expression, although the latter is determined by the maternal S-plasmotype and both maternal and paternal (pollinator) genotypes in zygotic progenies and only by the maternal S-plasmotype and genotype in apozygotic progenies. It has been hypothesized that the instability of the CMS expression in apozygotic progenies is determined by epigenetic variation in the activities of the genes that control the maintenance of the pollen-grain sterility. Inactivated dominant alleles Rf1(0) and Rf2(0) in homozygous state may function as sterility maintenance genes, whereas activation of these alleles during ontogeny results in a partial or complete restoration of pollen-grain fertility. It was demonstrated that pollen fertility of mother plants with S cytoplasm did not affect the CMS expression in two sib progenies. Conversely, in two other progenies, the proportion of fertile plants was significantly higher in the sib progenies of mother plants with fertile pollen and S cytoplasm (inheritance of epigenetic variation).     

Morpho-physiological responses of sugar beet (Beta vulgaris L.) genotypes to drought stress

The identification of morpho-physiological traits related to drought tolerance and high yield potential is a challenge when selecting sugar beet genotypes with greater tolerance to water stress. In this paper, root morphological parameters, antioxidant systems, leaf relative water content (RWC) and H⁺-ATPase activity as key morpho-physiological traits involved in drought tolerance/susceptibility of sugar beet were studied. Genotypes showing a different drought tolerance index (DTI) but a similar yield potential, under moderate (?0.6 Mpa) and severe (?1.2 MPa) water stress, were selected and their morpho-physiological traits were investigated. The results showed a wide genetic variation in morpho-physiological parameters which demonstrated the different adaptive strategies under moderate and severe drought conditions in sugar beet. In particular, an efficient antioxidant system and redox signalling made some sugar beet genotypes more tolerant to drought stress. The alternative strategy of other genotypes was the reduction of root tissue density, which produced a less dense root system improving the axial hydraulic conductivity. These results could be considered as interesting challenge for a better understanding of the drought tolerance mechanisms in sugar beet.     

Ultrastructural expression of cytoplasmic male sterility in sugar beet (Beta vulgaris L.)

Summary The development of microspore mother cells (MMC) and tapetum in male-fertile and male-sterile anthers of Beta vulgaris L. was compared at the electron microscope level. These studies were complemented by morphometric analyses of mitochondria in both tissues through successive stages of microsporogenesis. The earliest irregularities in the ultrastructure of male-sterile anthers were noted within the tapetum at the tetrad stage. These disturbances were initially expressed by a slight reduction in mitochondrial size and the appearance of concentric configurations of endoplasmic reticulum. As development proceeded, a further decrease in mitochondrial size become more conspicuous and was accompanied by a reduction in ribosome population and a failure of the tapetum to produce Ubisch bodies. This failure to produce Ubisch bodies is reflected in the underdevelopment of sterile microspore exine.     

Evaluation of nematode-resistant sugar beet (Beta vulgaris L.) lines by molecular analysis

 Thirty sugar beet (Beta vulgaris) lines conferring complete resistance to the beet cyst nematode (BCN, Heterodera schachtii) originating from interspecific crosses with wild beets of the section Procumbentes (B. procumbens, B. webbiana and B. patellaris) were investigated by morphology and wild beet-specific molecular markers. The beet lines carrying chromosome mutations consisted of monosomic additions (2n=18+1), fragment additions (2n=18+fragment) and translocations (2n=18) from the wild beets. Genome-specific single-copy, satellite and repetitive probes were applied to study the origin, chromosomal assignment and presence of nematode resistance genes. Within the wild beet species at least three different resistance genes located on different chromosomes were distinguished: Hs1 on the homoelogous chromosomes I of each species, Hs2 on the homoelogous chromosomes VII of B. procumbens and B. webbiana and Hs3 on chromosome VIII of B. webbiana. A clear distinction between the three chromosomes was possible by morphological and molecular means. The translocation lines were separated into two different groups: one containing the resistance gene Hs1 from chromosome I and the other carrying a different nematode resistance gene. The molecular data combined with sequence analyses of Hs1 of the three wild beet species revealed a clear distinction between B. procumbens and B. webbiana. The evolutionary and taxonomical relationship of these species supporting the idea of three different species originating from a common ancestor is discussed. Received: 6 April 1998 / Accepted: 22 April 1998     

Improvement of protoplast culture protocols for Beta vulgaris L. (sugar beet)

Summary The effects of NaCl, feeder cells and the embedding of protoplasts in calcium alginate have been investigated in an attempt to improve culture conditions of recalcitrant sugar beet (Beta vulgaris L.) mesophyll protoplasts. While the use of NaCl in all instances proved detrimental to protoplast development, the other two treatments had clear beneficial effects. Minimum plating densities, necessary to sustain cell division, could be reduced to <5% (<4000 protoplasts / ml) of the control levels and plating efficiencies could be significantly enhanced by approx. 10 fold. Plants could still be regenerated from soft calli derived from mesophyll protoplasts cultured under the modified conditions at a frequency of 20–30 %. In particular, the use of alginate is considered of potentially great importance for the further application of beet protoplasts for other aims e.g. asymmetric hybridization.     

Multiple-line cross quantitative trait locus mapping in sugar beet (Beta vulgaris L.)

Linkage mapping based on multiple-line crosses is a promising strategy for mapping quantitative trait loci (QTL) underlying important agronomic traits. The main goal of this survey was to study the advantages of QTL mapping across versus within biparental populations using experimental data from three connected sugar beet (Beta vulgaris L.) populations evaluated for beet yield and potassium and sodium content. For the combined analysis across populations, we used two approaches for cofactor selection. In Model A, we assumed identical cofactors for every segregating population. In contrast, in Model B we selected cofactors specific for every segregating population. Model A performed better than Model B with respect to the number of QTL detected and the total proportion of phenotypic variance explained. The QTL analyses across populations revealed a substantially higher number of QTL compared to the analyses of single biparental populations. This clearly emphasizes the potential to increase QTL detection power with a joint analysis across biparental populations.