Natural variation within the genus Beta and its possible use for breeding sugar beet: A review

Summary Sugar beet is a relatively young crop, which supposedly has a narrow genetic base. Natural variation occurring in primitive beet varieties and in wild Beta species has been used for breeding sugar beet. This paper reviews information on desirable characteristics in Beta germplasm and the attempts made for the introgression of such characters into commercial breeding material. After an introduction on the availability of germplasm and the possibilities of hybridisation, attention is focussed on the mating system (especially male sterility), on morphological and physiological characteristics, including yield and sugar content, and on resistances to diseases and pests.     

The production of alien monosomic additions in Beta vulgaris as a source for the introgression of resistance to beet root nematode (Heterodera schachtii) from Beta species of the section Patellares

Summary Experiments were carried out for adding the chromosome carrying resistance to beet root nematode (Heterodera schachtii) from the wild Beta species of the section Patellares (B. procumbens, B. webbiana and B. patellaris) to the genome of B. vulgaris. Preliminary experiments indicated that crosses between the wild species and B. vulgaris cultivars of the mangold type yielded on average more viable F₁ hybrids than crosses with sugar and fodderbeet. However, crossability varied strongly between individual parental combinations. It was concluded that most types of B. vulgaris can be hybridized with the wild species of the section Patellares if a sufficient number of pair-crosses is made. Crosses between diploid cultivars or species of the section Vulgares and diploid wild species of the section Patellares yielded many hybrids which, however, were highly sterile. From crosses between tetraploid B. vulgaris and the wild species a great number of viable allotriploid and allotetraploid hybrids was obtained. In the backcross progenies of allotriploid hybrids 26% alien monosomic additions occurred, of which 4.1% carried the resistance bearing chromosome of B. procumbens or B. patellaris. The programme will be continued by sereening progenies of the resistant monosomic addition plants for the occurrence of resistant disomic introgression products.     

Peroxidase activity as a possible test for distinguishing s-plasm from n-plasm in sugar beet (Beta vulgaris L.)

Summary The O-type lines (N-plasm) of sugar beet (Beta vulgaris L.) proved to have a consistently lower peroxidase activity (49.2–62.7%) than their male sterile (MS) equivalents (S-plasm).Similar differences in peroxidase activity (45.4–56.3%) were found when O-type lines were compared with unrelated MS lines. They were also observed in different parts of the plant (cotyledons, hypocotyl + radicle, true leaves) and were reproducible.The fertile lines could be grouped by their level of peroxidase activity in categories of either S-plasm or N-plasm.The peroxidase activity test could be used for selection of N-plasm lines from fertile sugar beet populations and for selection of MS and O-type lines of higher stability.     

RFLP analysis of genetic variation in species of section Arachis, genus Arachis (Leguminosae)

Four A-genome species of the genus Arachis (A. cardenasii, A. correntina, A. duranensis, A. kempff-mercadoi), three B genomes species (A. batizocoi, A. ipaënsis and A. magna),the AABB allotetraploid A. hypogaea (cultivated peanut) and introgression lines resulting from a cross between A. hypogaea and A. cardenasii were analyzed by RFLP. The A genome species (cytologically characterized by the presence of a small chromosome pair ‘A’) were closely similar to each other and shared a large number of restriction fragments. In contrast, the B genome species differed more from one another and shared few fragments. The results of this study indicate that the absence of the small chromosome pair is not a good criterion for grouping species of section Arachis as B genome species, since their genome might be quite distinct from the B genome of A. hypogaea.The lowest genetic variation was detected within accessions of A. duranensis (17 accessions), followed by A. batizocoi (4 accessions) and A. cardenasii (9 plants of accession GKP 10017).The high level of genetic variation found in A. cardenasii might indicate that not all accessions of wild species of Arachis are autogamous, as reported for A. hypogaea.     

Crosses between Beta vulgaris L. and Beta lomatogona F. et M.

Summary A population of 2x^ms sugar beets was crossed with 4x Beta lomatogona F. et M. The 3x F₁-plants were male sterile and were backcrossed with 2x and 4x sugar beets and multiplied without pollination as well. After the 1st backcross mainly 3x apomict types arose again and, among others, a small number of successful 4x backcrosses. After pollination by 4x sugar beets this 4x F₁ B₁ produced. besides predominatly apomictically multiplied 4x plants, also about 7% haploid 2x hybrids. The latter probably possess 1 genome from B. vulgaris and 1 genome from B. lomatogona. In the meiosis of the PMC's a certain amount of homeology between a number of chromosomes of both species could be established. The amphihaploid hybrids can be used as breeding parents for the creation of types in which introgession can occur. During hybridization in addition to 2x and 4x B. vulgaris types a number of 2x-, 3x-, 5x- and 6x-hybrids arose. This is presumably caused by the presence of gametes with the somatic number of chromosomes and the occurrence sometimes of haploid apomictic multiplication.The presence of large numbers of bolters in the F₁ and F₁ B₁ suggests that the bolting tendency of both species is based on different genes.     

Sugar beets homozygous for resistance to beet cyst nematode (Heterodera schachtii Schm.), developed from monosomic additions of Beta procumbens to B. vulgaris

Summary Monosomic additions of Beta vulgaris x B. procumbens with resistance to beet cyst nematode (Heterodera schachtii Schm.) were used for the production of resistant diploids through incorporation of the B. procumbens chromosome fragment bearing the resistance gene(s) into one of the sugar beet chromosomes. The heterozygotes obtained accordingly were selfed for producing homozygotes. These homozygotes differed morphologically from commercial sugar beet varieties, but produced reasonable amounts of pollen. Female transmission of resistance was 100%, whereas male transmission, apart from some exceptions, was more than 90%. The number of hypersensitivity reactions to penetrated larvae was related to the degree of susceptibility. Larval development was severely retarded in the resistant plants, preventing most of them to produce cysts. If cysts were formed, their content was considerably less as compared to those in the susceptible plants.     

An evaluation of single plant randomised field trials of sugar beet (Beta vulgaris L.)

Summary Diploid, monogerm families of sugar beet were grown in transplanted field trials randomised on a single-plant basis. Individual roots were weighed and a range of chemical characters were assessed. There was no significant difference in performance between plants that had members of their own family as nearest neighbours within the row and plants that had randomly assigned neighbours. Good correlations were found between the performance of families in single-plant trials and their performance in conventional plot trials. We conclude that single-plant randomisation could prove useful for genetical studies and for breeding trials particularly when seed or facilities are limited.     

Major genes for resistance to beet necrotic yellow vein virus (BNYVV) in Beta vulgaris

Summary Inheritance of resistance to beet necrotic yellow vein virus (BNYVV) was studied in segregating F2 and backcross families obtained from crosses between resistant plants of the sugar beet selection Holly-1-4 or the wild beet accession Beta vulgaris subsp. maritima WB42 and susceptible parents. Greenhouse tests were carried out, in which seedlings were grown in a mixture of sand and infested soil. Virus concentrations of BNYVV in the rootlets were estimated by ELISA. To discriminate resistant and susceptible plants, mixtures of normal distributions were fitted to log₁₀ virus concentrations, estimated for segregating F1, F2 and BC populations of both accessions. The hypothesis that Holly-1-4 contained one single dominant major gene was accepted. For WB42, results fitted with the hypotheses that resistance was based on either one (or more) dominant major gene(s) showing distorted segregation, or two complementary dominant genes, which are both required for resistance. Resistance from WB42 appeared to be more effective against BNYVV than resistance from Holly-1-4.This research was carried out as part of a PhD study at the Graduate School Experimental Plant Sciences (EPS), Department of Virology, Wageningen, The Netherlands     

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.     

Sources of resistance to diseases of sugar beet in related Beta germplasm: II. Soil-borne diseases

Between 580 and 700 accessions of related cultivated and wild species of the genus Beta were assessed for resistance to four soil-borne diseases of sugar beet: two seedling damping-off diseases caused by the fungi Aphanomyces cochlioides and Pythium ultimum and two diseases of more mature plants, Rhizoctonia root and crown rot, caused by the fungus R. solani, and Rhizomania, caused by Beet necrotic yellow vein virus (BNYVV), a furovirus transmitted by the plasmodiophorid Polymyxa betae. Analysis of resistance data (assessed on an international standardised 1–9 scale of Resistance Scores) indicated that the highest levels of resistance ({RS} 2) to A. cochlioides and P. ultimum were to be found amongst accessions of the more distantly related sections Corollinae (93% of accessions tested) and Procumbentes (10%), respectively; although useful levels could also be found in the more closely related, and sexually compatible, section Beta (1–6%). Resistance to Rhizoctonia was also found in section Beta (5–7%), depending on whether field or glasshouse tests were used, but there was little evidence of generally high levels of resistance to Rhizomania among accessions of this section. None of the accessions of sections Corollinae and Procumbentes exhibited any notable resistance to Rhizoctonia. However, all sections Procumbentes and some sections Corollinae (4%) accessions were highly resistant to Rhizomania. Individuals with high levels of resistance to Rhizomania were identified from within some section Beta and Corollinae accessions, in which there was evidence of segregation.     

Acetocarmine squash method for observing sugar beet chromosomes

Summary Based on successful results of an acetocarmine squash method for staining chromosomes of many plant species, the method was applied to chromosomes of sugar beet (Beta vulgaris L.). This simple method proved to be applicable to the relatively small chromosomes of sugar beet. Several known disadvantages of acetocarmine staining techniques are overcome by applying acid hydrolysis and maceration. Squashing the stained specimens in 45% acetic acid increases the contrast between stained chromosomes and destained cytoplasm. The advantages of this method are its simple procedure and applicability to both somatic and meiotic chromosomes. Uniform and high quality preparations make detailed analysis possible even with the relatively small chromosomes of sugar beet.Contribution from the Department of Agronomy and published with the approval of the Colorado State University Experiment Station as Scientific Series Paper No. 2334.Supported in part by a Research Grant from the Great Western Sugar Company, Longmont, Colorado.     

RFLP variation and genetic relationships in cultivated cucumber

Summary Two sets of cucumber (Cucumis sativus L.) germplasm were used to determine the potential use of restriction fragment length polymorphisms (RFLPs) for estimating genetic relationships. Sixteen accessions [15 domesticated variety sativus and one feral variety hardwickii (PI 183967)] of diverse origin were used to assess RFLP variation in cucumber, and to determine if genetic relationships based on RFLPs were similar to those obtained by isozyme analysis. Additionally, 35 commercial lines or cultivars were surveyed to determine genetic relationships among and within common cucumber types (narrow genetic base). The 16 accessions were surveyed with 440 low copy clones from two libraries (Pst I partial genomic and cDNA) using two restriction enzymes. Data from a subset of 104 random (mapped and unmapped) and a set of 30 mapped RFLPs were used to estimate genetic relationships among the 16 cultigens. Variability was low among RFLPs (33% of all probes) and putative alleles ( 2.2 polymorphic fragments/probe). RFLP variation between sativus lines and hardwickii (21±4%) was greater than among sativus lines (12±2%). RFLPs among the 16 accessions revealed genetic relationships which agree with those obtained using isozymes. Genetic relationships estimated using mapped and unmapped RFLPs were similar. The 35 elite lines were surveyed using a set of 40 RFLPs from 3 libraries (Pst I and EcoR I partial genomic and cDNA) to evaluate the discriminatory value of RFLPs among and between commercial cucumber types. The RFLP-derived genetic relationships among this germplasm were in agreement with predictions based on fruit type and pedigree information. Thus, RFLPs are a useful addition to the morphological characters and isozyme loci currently used for taxonomic classification and plant variety protection of cucumber.     

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.     

Resistance to Heterodera schachtii in patellares section of the genus Beta

Summary Fifty-two accessions of the section Patellares wild beet (including 26 Beta patellaris Moq., 13 B. procumbens Chr. Sm and 13 B. webbiana Moq.) and 14 progeny families were selected and tested against sugarbeet cyst nematode, Heterodera schachtii Schm. All Patellares species tested were highly resistant, but not immune, to the development of H. schachtii, after infection. This is the first report that mature female nematodes developed in the roots of B. webbiana plants. The occasional development of nematode cysts in roots of juvenile wild beets was, however, not a heritable genetic factor.Mention of a trademark, vendor, or proprietary product does not constitute a guarantee or warranty of the product by the USDA and does not imply its approval to the exclusion of other products or vendors that may also be suitable.     

Genotypic variation in the in vitro morphogenesis from leaf explants ofBeta vulgaris L. andB. maritima L.

Summary Leaf discs from sixBeta vulgaris lines and threeB. maritima accessions were tested for their morphogenic responses in Murashige and Skoog medium supplemented with 0.25 mg/l benzyladenine (BA). Direct shoot formation took place in two genotypes:B. vulgaris line TA33-MS andB. maritima acc. France. Rooting of differentiated shoots was achieved by culturing the shoots on a medium containing 0.2 mg/l indolebutyric acid (IBA). Our results indicate that genotypes differ in the morphogenic potential of leaf explants.     

Use of haploids of Beta vulgaris L. for the study of orcein and giemsa stained chromosomes

Summary Some haploids isolated among the progeny from crosses involving several genotypically different motherplants of Beta vulgaris L., were used for an investigation on chromosome morphology of the genus Beta.The length of both the long and short arms proved to vary considerably for each chromosome, so that a representative idiogram of the 9 chromosomes could not be made. Staining the chromosomes according to the BSG-technique revealed only bands in the centromere regions. However, one chromosome with a narrow band in the short arm could be identified, which was supposed to be the nucleolar chromosome. The C-bands presumably correlate with the heterochromatic blocks as observed in mitotic and meiotic (pachytene) prophase.This study was part of a project on cytogenetics of interspecific hybrids resistent to beet cyst eelworm, supported by the Institute of Rational Sugar Production,Bergen op Zoom, the Netherlands.     

Induction of cytoplasmic male sterility and fertility reversion by mutagenesis; negative evidence from a study on sugar beet

Summary Attempts have been made to induce cytoplasmic male sterility (cms) and cytoplasmically inherited fertility reversion in sugar beet using various mutagenic agents by repeating techniques previously described. Despite the previous report of successful induction of cms and reversion at very high frequency it was not possible to repeat this success. Analysis of M₂ plants at the DNA level demonstrated no major rearrangements in chloroplast or mitochondrial DNA.     

Partial resistance of sugarbeet to beet cyst eelworm (Heterodera schachtii Schm.)

Summary Within Beta vulgaris and B. maritima origins some partial resistance to beet cyst eelworm was found which could be raised to a very limited extent by selection. However after the second backcross to commercial sugar beet varieties and successive selection of the inbreds this resistance was lost. It was demonstrated that in the rootsystem of resistant plants as much nematodes penetrate and develop as in susceptible ones but the ratio between males and females is different. It was therefore quite probable that this resistance is polyfactorial and merely recessive.     

Vegetative propagation of Beta vulgaris by leaf cuttings with axillary buds

Summary In leaf cuttings with a short piece of hypocotyl tissue axillary bud development was poor. Most cuttings with a long piece of hypocotyl tissue developed into plants. The latter type enabled vegetative propagation of various genotypes.