Evaluation of genetic diversity and root traits of sea beet accessions of the Adriatic Sea coast

Thirty-nine sea beet [Beta vulgaris L. ssp. maritima (L.) Arcang.] accessions of the Adriatic coast were screened genetically and for their adaptive morpho-functional root traits in order to identify new sources of abiotic resistances for sugar beet breeding programs. Genetic diversity was evaluated with 21 microsatellites markers that identified 44 polymorphic alleles. Sea beets grouped into two main clusters: the West and the East Adriatic coast groups, with the latter showing higher genetic diversity. Among sea beet accessions with desirable root traits, four accessions have proved to be interesting for sugar beet [B. vulgaris (L.) ssp. vulgaris] breeding aimed to improve tolerance to nutritional stresses. Lastovo (ID 29) and Zut (ID 34) accessions were characterized by the highest values of RER, TRL, FRL and RSA still maintaining a high value of RTD, while Grado (ID 21) an Portic (ID 23) accessions were characterized by the highest RTD, but with low values of RER, TRL, FRL and RSA parameters.     

Beet mild yellowing virus resistance derived from wild and cultivated Beta germplasm

Sugar beet (Beta vulgaris ssp. vulgaris L.) has a relatively narrow genetic base and several programmes have sought to evaluate the potential for introducing novel traits from wild and cultivated Beta germplasm into the crop. In particular, resistance to important sugar beet diseases has been identified within individual Beta accessions. We report here the successful transfer of resistance to Beet mild yellowing virus (BMYV) from garden beet, fodder beet and leaf beet accessions to progeny populations in initial crosses with sugar beet. Twelve plant populations derived from different Beta accessions were inoculated with viruliferous aphids carrying BMYV and the virus content of individual plants subsequently quantified by an ELISA test. Seven populations were significantly more resistant than a control sugar beet cultivar (P ≤ 0.05). BMYV resistance was successfully inherited in BC₁ and BC₂ generations, suggesting that resistance could potentially be introgressed from these sources into elite sugar beet lines.     

Root traits and yield in sugar beet: identification of AFLP markers associated with root elongation rate

Morpho-physiological and molecular analysis were conducted to identify useful root indexes of sugar beet nutrient uptake capacity and productivity. Root architectural parameters, root elongation rate, sulfate uptake rate and glucose and fructose content in the root apex, traits involved in the plant response to sulfate stress, were evaluated in 18 sugar beet genotypes characterized by different root yield. Morpho-physiological traits, determined on 11-day-old seedlings grown in hydroponics under sulfate deprivation, showed variations from 59 to 197% and were significantly correlated (P < 0.01) with root yield. Under field conditions, the highest root yield genotype (L18), which has the highest root phenotypic values following sulfate shortage, also showed the greatest root length density and leaf relative water content, with respect to the lowest root yield genotype (L01). Bulk segregant analysis based on AFLP analysis, done on a segregating progeny obtained from the cross between the two lines L01 × L18, allowed the identification of two AFLP markers associated to the root elongation rate parameter that showed the highest variation among all the analyzed root traits. The genetic diversity of root adaptive traits and the use of marker-assisted selection aimed at increasing sugar yield under water and nutrient stress in sugar beet breeding programmes are discussed.     

Ecological aspects of transgenic sugar beet: transfer and expression of herbicide resistance in hybrids with wild beets

Summary An increasing number of genetically engineered cultivars of several crops is being experimentally released into the environment. In future, crops with new transgenic traits will probably play an important role in agricultural practice. The long-term effect of transgenes on community ecology will depend on the distribution and establishment of transgenic plants in the wild, on the sexual transfer of their new genes to the environment and on the potential ecological impact of the transgenic trait. The starting point was the use of transgenic sugar beet lines, Beta vulgaris subspec. vulgaris var. altissima DÖLL (Helm 1957), with transgenes coding for rhizomania and herbicide (BASTA^®) resistance. The first two questions to answer were: Can the transgenes be transferred via pollen to wild beets, Beta vulgaris subspec. maritima (L.) ARCANG. or cultivated relatives such as red beet or spinach beet and are they expressed in the hybrids? Can transgenes be monitored in young Beta vulgaris-hybrids? The experimental transfer of transgenes was conducted in 1993 at a field location in northern Germany. The beets were hand-pollinated with transgenic pollen. In a non destructive biotest, the hybrid seedlings were tested for herbicide resistance. Transgenic plants showed no noxious phenotypic effects whereas control plants developed leaf necroses. All herbicide resistant hybrids within the biotest were assumed to be transgenic.     

The taxonomic characterisation of annual Beta germplasm in a genetic resources collection using RAPD markers

Summary Annual beets in the genus Beta section Beta represent an important genetic resource. Representative accessions of annual beets from a beet germplasm collection were analysed using RAPD to assess the patterns of variation and relationships among them. Using arbitrary primers, markers showing variation across accessions were identified. A dendrogram of similarity was produced using these molecular markers. All the accessions analysed were classified into three major groups corresponding to species or subspecies macrocarpa, adanensis and maritima. Macrocarpa was shown to be the most divergent group in this section. Using RAPD molecular markers, it was possible to ascribe an accession to one of three taxonomic groups and overcome much of the confusion encountered when morphological traits are used for identification. The group of maritima was found to be more polymorphic than either the group of macrocarpa or adanensis at both accession and subspecies levels.     

Variation in some agronomically important characters in a germplasm collection of beet (Beta vulgaris L.)

Summary A geographically representative selection of germplasm of Beta vulgaris, section Beta has been assessed for characteristics important in sugarbeet breeding, including downy mildew resistance, resistance to aphid colonisation and infection by the beet virus yellow complex. The occurrence of maintainer lines for cytoplasmic male-steriles was also investigated. Desirable qualities were found in some accessions, including nothern European wild vulgaris ssp. maritima and some old multigerm cultivars of fodder beets.     

Assessing fitness parameters of hybrids between weed beets and transgenic sugar beets

Herbicide resistance is a desired trait for sugar beet (Beta vulgaris L.) production because it is a low‐competitor crop that requires careful weed management. However, gene flow to weed beet (also B. vulgaris) could jeopardize the weed control strategy by causing the emergence of resistant weed beets; it could also lead to further adaptation of weed beet as a troublesome weed for other crops by selecting more competitive plants. To evaluate the hazard that such a selection process represents, apart the herbicide resistance, we investigated the morphology and reproduction of progeny of weed beets having inherited a herbicide resistance gene. First‐generation resistant weed beet exhibited traits likely counter‐selected. But such crop traits rapidly disappeared with backcrossing to weedy relatives: no biologically relevant difference was noted between resistant and susceptible near‐isogenic siblings in the various experiments. In the absence of resistance selection, our data indicate low chances for weed beet to evolve more competitive forms than present weed beet populations. However, they also suggest that there is no fitness cost limiting transgenes spread.     

Wild Oryza species as potential sources of drought-adaptive traits

Wild species of Oryza may serve as sources of superior drought tolerance alleles for cultivated rice. In a series of three screenhouse experiments, we compared traits associated with leaf water status, stomatal conductance, membrane stability, and root development in several wild Oryza accessions and O. sativa cultivars, when grown under well-watered or water-deficient conditions. One accession of O. longistaminata had greater stomatal conductance under stress and maintained leaf elongation better under stress than most other genotypes. Several upland-rice cultivars from the japonica subspecies also maintained greater conductance and leaf expansion than an indica cultivar or O. rufipogon accessions. Leaves of an accession of O. latifolia were particularly sensitive to water deficit. Oryza longistaminata and several O. rufipogon accessions had greater membrane stability, measured as electrolyte leakage from leaf disks after heat treatment, than cultivated rice. Drought treatments tended to reduce the levels of electrolyte leakage observed. Wild species had levels of osmotic adjustment under stress that were similar to O. sativa. Entries differed in the growth of roots with water deficit:O. longistaminata accessions and some japonica cultivars showed either an increase in total root mass or an increase in the proportion of root mass in deeper soil levels when water deficit was imposed, whereas indica cultivars and O. rufipogon accessions did not. Changes in root mass and distribution were correlated with values of stomatal conductance and leaf elongation; this suggests that leaf measurements made at key times in the drying cycle may reveal possible genetic differences in rooting behavior, which are otherwise difficult to measure. These studies indicate that O. longistaminata and O. rufipogon may serve as sources of novel alleles for improved leaf traits under drought stress–specifically, for maintenance of leaf elongation, stomatal conductance, and membrane stability. Alleles for improved root growth and distribution under water deficit exist in some japonica rice cultivars.     

Growth analysis of autumn and spring sown sugar beet

Slow leaf formation in spring is regarded as the main factor limiting sugar beet yield. It is therefore expected that yield can be enhanced when plants develop leaves earlier resulting in an extended growing period. The aim of this study was to analyse leaf and storage root growth of sugar beet plants sown in autumn or very early in spring with regard to possible yield increases. In 2005/06 and 2006/07, field trials were conducted at 4 sites with 6 sowing dates: August, beginning and mid of September, and in February, March and April. Sequential harvests were conducted to follow yield formation.Field emergence of autumn sown sugar beets was fast and reached 90% whereas in early spring it was severely restricted due to low temperature. Leaf and root yield formation of autumn and spring sown sugar beets could well be described with thermal time confirming that sugar beet growth is temperature driven and day length insensitive. Despite longer growing periods autumn sown beets did not form more cambium rings in the storage root than spring sown beets. That might be partly due to the bolting process after winter. However, early spring sown beets as well did not achieve more cambium rings than plants sown in April pointing to a presumably limited ability to adapt cambium ring formation. Because of the shift to reproductive growth, autumn sown beets formed high amounts of shoot dry matter, but not much root dry matter. Furthermore, the root dry matter consisted of a lower sugar and a higher marc content and would therefore not be suitable for sugar recovery. Earlier sowing in spring did not result in a significant yield increase because the benefit from early sowing diminished throughout the season as also obvious from the distance between the cambium rings.For bolting resistant sugar beet varieties, which are expected to be available in near future, the presented data form a basis to predict yield with models. However, it has to be investigated to what extent sugar beet growth and yield formation benefits from early sowing and extended growing periods.     

Sources of resistance to diseases of sugar beet in related <Emphasis Type="Italic">Beta</Emphasis> germplasm: I. Foliar diseases

Resistance to four foliar diseases of sugar beet (Beta vulgaris ssp. vulgaris), virus yellows caused by Beet mild yellowing virus (BMYV) and Beet yellows virus (BYV), powdery mildew (Erysiphe betae) and Cercospora leaf spot (Cercospora beticola), was assessed in up to 600 accessions of closely related wild and cultivated Beta species. Most accessions were from the Section Beta, a taxon containing types most closely related to, and sexually compatible with, sugar beet and therefore most valuable for use in crop improvement. Between 1–12% of accessions were highly resistant (resistance scores of 2 on an international standardised resistance scale of 1–9) to these diseases. These levels, however, underestimate the potential number of resistant sources available from this section as some accessions with intermediate mean resistance scores contained a significant proportion of highly resistant plants within segregating populations. Variation in resistance to all diseases except BYV was observed within the Section Beta. Much higher levels of resistance were observed, and more frequently, in more distantly related sections of the genus Beta. Accessions of the Section Corollinae were highly resistant to both viruses (>62% of accessions tested), but less so to Cercospora (15%) and they were very susceptible to powdery mildew. Section Procumbentes accessions were highly resistant to BMYV and Cercospora (100%) but less so to powdery mildew (50%) and BYV (20%). However, sexual incompatibility between these sections and sugar beet make utilisation of these sources impractical using conventional breeding methods.     

Sucrose Accumulation in Sugar Beet Under Drought Stress

Drought stress may affect sucrose accumulation of sugar beet by restricting leaf development and storage root growth. The objective of this study was to identify changes occurring in the storage root of Beta beets in growth characteristics and ions and compatible solutes accumulation under drought with regard to sucrose accumulation. Two pot experiments were conducted: (1) sugar beet well supplied with water (100 % water capacity), under continuous moderate (50 %) and severe drought stress (30 %), (2) sugar beet and fodder beet well supplied with water (100 %) and under continuous severe drought stress (30 %). Under drought stress, the ratio of storage root to leaf dry matter of sugar beet decreased indicating a different partitioning of the assimilates. The sucrose concentration of the storage root was reduced. In the root, the number of cambium rings was only slightly affected, although drought stress was implemented already 6 weeks after sowing. In contrast, the distance between adjacent rings and the cell size was considerably restricted, which points to a reduced expansion of existing sink tissues. The daily rate of sucrose accumulation in the root showed a maximum between 16 and 20 weeks after sowing in well‐watered plants, but it was considerably reduced under drought stress. The concentration of compatible solutes (K, Na, amino acids, glycine betaine, glucose and fructose) decreased during growth, while it was enhanced because of drought. However, when sucrose concentration was added, a constant sum of all examined solutes was found throughout the vegetation period. It was similar in sugar beet and in fodder beet despite different concentrations of single solutes, and the total sum was not affected by water supply. A close negative relationship between the concentration of compatible solutes and sucrose occurred. It is therefore concluded that the accumulation of compatible solutes in the storage root of Beta beets under drought might be a physiological constraint limiting sucrose accumulation.     

Assessment of the degree of genetic variation in beet based on RFLP analysis and the taxonomy of Beta

Summary Clones derived from Beta vulgaris and Beta maritima were assayed for their ability to detect restriction fragment length polymorphisms (RFLPs) in different beet accessions. The clones able to detect polymorphism were used as genetic markers to assess the degree of genetic variation existing between and within different species of the genus Beta. The data support the current taxonomy of the Beta vulgaris section, while the great genetic similarity found between Beta webbiana and Beta procumbens indicates that they could belong to the same species.Enough variation was found between Beta vulgaris cultivars, allowing the isolation of a sufficient number of genetic markers for the construction of detailed genetic maps.     

Origin of the ‘Weisse Schlesische Rübe’ (white Silesian beet) and resynthesis of sugar beet

Summary Sugar beet-besides fodder beet, red beet, and chard-belongs to Beta vulgaris L. After it had been confirmed that the sugar of Beta beet is chemically identical with cane sugar, ACHARD started experiments on the production of sugar from fodder beet. He noticed that conical white beets seemed to have the highest sugar content. This first sugar beet, the Weiße Schlesische Rübe, is considered the ancestor of all sugar beets of today. It has been, and continues to be supposed that it had originated from crossings between typical fodder beet and chard. Hints in the literature about possibilities to resynthesize sugar beet by crossing fodder beet with chard were confirmed in the author's own trials; the F₂ from the crossing fodder beet Rote Walze x chard Lukullus segregated forms and colour variants largely corresponding to sugar beet. Such new sugar beets are not only important from a theoretical point of view; breeders are interested in new types, too. The synthesis of sugar beet is interpreted from a genetic point of view.     

Differential occurrence of beet cryptic viruses—A new tool for germplasm characterization and evolutionary studies in beets?

Summary Beet cryptic viruses occur differentially in cultivars of chard (only BCV 1) and red beet (only BCV 2). As landraces of these crops and wild beets can contain both of the viruses, the differential occurrence in cultivars should indicate founder effects in the course of evolution of chard and red beet. Consequently, the genetic base of those crops should be considered as narrow. On the basis of the presence or absence of the viruses in beet plants within the populations conclusions can be drawn concerning the uniformity of cultivars maintained in the collections, the characterization of chard and beet landraces and some evolutionary tendencies within the variable Beta vulgaris-complex.     

Effect of Extending the Growing Period on Yield Formation of Sugar Beet

Autumn sown sugar beets (winter beets) are expected to yield markedly higher than spring sown beets. This requires a continuous growth during an extended growing period. So far, bolting‐resistant sugar beet varieties are not available to test winter beets under field conditions in Central Europe. The objective of this study was therefore to analyse yield formation and sugar storage of sugar beet plants during an extended growing period to estimate whether sugar beet has the potential to generate the theoretically expected yield increase. From 2008 to 2012, pot experiments were carried out in the glasshouse with 11 sowing dates spread over the years with sequential harvests. The oldest plants were grown for 859 days (14 242 °Cd). Root fresh matter yield continuously increased till the latest harvest. In contrast, the sugar concentration reached an optimum value between 3400 and 5000 °Cd and then decreased with time. Despite longer growing periods, the number of cambium rings, which are regarded as essential for sugar storage, did not change. This points to an early and genetically fixed determination of the formation of cambium rings. Additionally, the rate of photosynthesis decreased concomitantly with the sugar concentration. In conclusion, there is some evidence that the sugar concentration of the storage root is limited by the sink capacity, which in turn controls the source activity by a feedback regulation of photosynthesis and leaf formation. The dry matter composition of the storage root changed towards lower sugar concentration and concurrent higher concentration of cell wall compounds (marc). The sugar yield still increased beyond a thermal time at which winter beets will probably be harvested in practice. Hence, the theoretical yield increase in autumn sown sugar beets can be realized, provided that the plants show sufficient winter hardiness and bolting resistance.     

甜菜直接再生体系的建立及优化

探究东北地区栽培甜菜直接再生体系的建立，以期为基因工程手段培育甜菜品种奠定基础。本研究以甜菜子叶节和叶柄为外植体，研究不同消毒方法、不同激素水平对诱导甜菜不定芽和不定根再生的影响。结果表明，最佳消毒方法为：剥除种球外壳获取种胚，并使用75%酒精30 s+0.1% HgCl2消毒10 min；诱导不定芽的最佳激素配比为：MS+6-BA 0.5 mg/L+NAA 0.05 mg/L，在此培养条件下子叶节和叶柄的不定芽诱导率均达最大值，分别为14.44%、11.67%；（3）诱导不定根的最佳激素配比为：1/2MS+NAA 0.05 mg/L，诱导率达到93.33%。本研究初步建立了东北甜菜直接再生体系，为下一步建立遗传转化体系及甜菜遗传改良奠定基础。     

New Genetic Markers in a Wild Species of Beet (Beta nana Boiss. et Heldr.): Prospects for Utilization

In a study of variation in 13 enzymes occurring in B. nana, unique and invariant phenotypes were found for five of these enzymes, when compared with a range of other wild and cultivated beets. In similar comparisons unique alleles were found in B. nana for two other enzyme loci. For the remaining six enzymes B. nana was found to have variation and alleles which were common to other forms of beet. It is concluded that reliable markers for B. nana exist, and that this species represents a source of novel genes for sugar beet breeding.     

Adaptability and variation in <Emphasis Type="Italic">Isatis tinctoria</Emphasis> L.: a new crop for Europe

Isatis tinctoria L. was cultivated until the 19th century to produce indigo, a natural blue pigment used principally for dyestuffs. The current search for alternative crops and interest in natural products has led to reconsidering I. tinctoria as a crop to be grown in marginal areas to produce natural indigo. To reintroduce I. tinctoria into cultivation, its behaviour under different climatic conditions as well as its morpho-physiological and genetic diversity must be assessed in order to evaluate the possibilities of future breeding work. To do this, a Eurasian collection of 15 accessions was studied in a 2-year experiment. The study was carried out in four locations in order to assess plant performance at altitudes ranging from 380 to 1,700 m a.s.l. A second experiment evaluated the morpho-physiological diversity of several traits (some related to agronomic performances) of the collection. In a third experiment the genetic traits of the collection were characterised by using eight AFLP and eight SAMPL markers. The species showed a wide adaptability to different mountainous conditions and the populations showed high morphologic and genetic variability and differed according to their origins. Both morpho-physiological and molecular characterisation allowed the accessions to be distinguished into groups of European and Asian origin. Future breeding work is recommended because some accessions have good agronomic potential.

甜菜种质资源品质性状鉴定与评价

旨在更加科学真实地评价甜菜种质资源的品质性状,有针对性地对种质资源优异品质性状进一步挖掘利用。引用甜菜块根蔗糖可回收率、杂质指数、可回收蔗糖量3 个综合指标,排除甜菜块根中有害性非糖分钾、钠、α-氮的影响,对参试的162 份甜菜种质资源2 年试验鉴定结果的有关品质性状进行分析。结果表明：甜菜块根中影响蔗糖提取的有害性非糖分钾、钠、α-氮在不同的种质资源材料间差异较大,其中钠含量在参试种质资源材料中极差达到4.763 mmol/100 g,为平均数的1.84 倍,变异系数34.43%;α-氮含量和钾含量在不同参试种质资源材料间也表现出较大差异,变异系数分别为16.90%和19.03%。通过对参试种质资源材料的评价,筛选出蔗糖含量高、有害性非糖分含量低的高糖组种质资源材料10份、中高糖组48份材料,2组平均蔗糖可回收率分别为15.88%和14.95%;筛选出杂质指数低于4.0、块根产量在45.00 t/hm2以上的丰产型种质资源材料7份,杂质指数4.0~4.5、块根产量在45.00 t/hm2以上丰产性较好的种质资源材料14 份。甜菜块根中可回收蔗糖量指标综合了蔗糖可回收率和块根产量2个性状指标,利用该项指标评价种质资源材料,可以挖掘出丰产优质的种质资源。用可回收蔗糖量指标评价甜菜品种,筛选丰产、高工艺品质的品种,兼顾甜菜种植者和制糖企业双方利益,有利于甜菜制糖产业可持续发展。