Some remarks on carrot breeding (Daucus carota sativus Hoffm.)

Carrot breeding in the past 150 years has resulted in varieties with high yield, a short growing period, and excellent root colour. Recently, hybrid varieties have demonstrated good uniformity of roots, a quality accepted by most consumers. By contrast, only a few resistant varieties (mainly open-pollinated varieties) are offered by seed companies, most being resistant to Alternaria. Hybrid breeding offers a chance of combining good uniformity and different sources of resistance. Efforts in future breeding should concentrate on the improvement of health and the development of genotypes suitable for cultivation in suboptimal climates and regions, as well as for special applications.     

Evaluation of genetic resources in the genus <Emphasis Type="Italic">Asparagus</Emphasis> for resistance to <Emphasis Type="Italic">Asparagus virus 1</Emphasis> (AV-1)

Forty-four Asparagus officinalis cultivars, gene bank accessions and breeding lines as well as thirty-four accessions of wild relatives of Asparagus were evaluated for resistance to Asparagus virus 1. Three different test strategies were developed for the assessment of individual plants: (1) natural infection under field conditions, or two vector-mediated infection assays using the green peach aphid Myzus persicae (2) in an insect-proof gauze cage or (3) in a climate chamber. The AV-1 infections were verified by DAS-ELISA and RT-PCR approaches. All tested 660 individual plants of A. officinalis germplasm were susceptible to AV-1 infection. In contrast, in 276 plants of 29 Asparagus wild accessions no virus infection could be detected. These resistant accessions comprised of nineteen diploid, tetraploid and hexaploid species of both the Eurasian clade and the African clade of the asparagus germplasm. Data of the AV-1 resistance evaluation are discussed in relation to the genetic distance of the resistance carrier and potential application in breeding.     

Genetic diversity of carrot (<Emphasis Type="Italic">Daucus carota</Emphasis> L.) cultivars revealed by analysis of SSR loci

Polymorphism of simple sequence repeat (SSR) loci was assessed in a collection of 88 carrot (Daucus carota L. subsp. sativus Hoffm.) accessions. The collection comprised cultivars and landraces mainly from Asia, Europe, and North America. Plants were grown in the glasshouse and characterized for root color and shape. Thirty SSR loci were fully characterized using parameters derived from allele frequencies, i.e. the number of total, effective and rare alleles, the observed and expected heterozygosity, and fixation index. Using a Bayesian approach, two clusters of 17 and 61 accessions were distinguished, which comprised the Asian and Western type accessions, respectively. Genetic diversity of the Asian gene pool was higher than that of the Western gene pool. The results of SSR analysis were supported by morphological characterization, and are congruent with current knowledge on the history of carrot domestication and breeding.     

Morphology, inheritance and mapping of a compressed lamina mutant of carrot

A compressed lamina mutant at a locus named COLA was selected in an inbred population of the cultivated carrot Daucus carota sativus Hoffm. Whereas segregation analyses of F₂ progenies, as well as corresponding F₃ families, indicated a monogenic recessive inheritance, detailed morphological and histological analyses revealed pleiotropic effects of the COLA gene. The mutant plants exhibited a semi‐dwarf phenotype, shortened epidermal and leaf parenchyma cells and significantly reduced lamina dimensions. Furthermore, the mutant developed stipules and hypogynous flowers, contrary to the stipule‐less leaves and epigynous flowers of the wild type. Using bulked segregant analyses, thirty‐nine marker candidates were detected using 180 RAPD primer and 56 AFLP primer pairs. Twelve primers were linked to the COLA locus and mapped in a linkage group with a total length of 44.2 cM. Potential application of the compressed lamina mutant in carrot research is discussed.     

In situ simultaneous analysis of polyacetylenes, carotenoids and polysaccharides in carrot roots

This paper presents an approach to simultaneously analyze polyacetylenes, carotenoids, and polysaccharides in carrot (Daucus carota L.) roots by means of Raman spectroscopy. The components were measured in situ in the plant tissue without any preliminary sample preparation. The analysis is based on the intensive and characteristic key bands observed in the Raman spectrum of carrot root. The molecular structures of the main carrot polyacetylenes, falcarinol and falcarindiol, are similar, but their Raman spectra exhibit specific differences demonstrated by the shift of their -C[triple bond]C- mode from 2258 to 2252 cm(-)(1), respectively. Carotenoids can be identified by -C=C- stretching vibrations (about 1520 and 1155 cm(-)(1)) of the conjugated system of their polyene chain, whereas the characteristic Raman band at 478 cm(-)(1) indicates the skeletal vibration mode of starch molecule. The other polysaccharide, pectin, can be identified by the characteristic band at 854 cm(-)(1), which is due to the -C-O-C- skeletal mode of alpha-anomer carbohydrates. The Raman mapping technique applied here has revealed detailed information regarding the relative distribution of polyacetylenes, carotenoids, starch, and pectin in the investigated plant tissues. The distribution of these components varies among various carrot cultivars, and especially a significant difference can be seen between cultivated carrot and the wild relative D. carota ssp. maritimus.     

Enhancing resistance of transgenic carrot to fungal pathogens by the expression of Pseudomonas fluorescence microbial factor 3 (MF3) gene

Microbial factor 3 (MF3) gene from a plant-growth promoting rhizobacteria Pseudomonas fluorescence was introduced into carrot genome using Agrobacterium-mediated transformation. The obtained transgenic plants expressing MF3 protein were grown in a glasshouse and evaluated for their resistance to phytopathogens. The assays were performed by the assessment of disease symptoms developing on the detached leaflets and petioles inoculated by three fungal pathogens. The results showed that transgenic plants had significantly enhanced resistance to Alternaria dauci, Alternaria radicina and Botrytis cinerea, on average, by 20–40% in comparison to the non-transformed control plants. This is the first report of enhancing plant resistance by expressing the bacterial protein homologous to the family of FK506-binding proteins.     

Successful backcrosses of somatic hybrids between Sinapis alba and Brassica oleracea with the Brassica oleracea parent

Somatic hybrids between Sinapis alba (2n= 24) and Brassica oleracea (2n= 18) have been backcrossed with the B. oleracea parent. Whereas backcrosses with the diploid B. oleracea parent were unsuccessful, 344 BC₁ seeds could be obtained from inter-valence crosses with tetraploid B. oleracea (2n= 4x= 36). The investigated 96 BC₁ plants segregated for morphological traits and for fertility. They were backcrossed with diploid B. oleracea or self-pollinated, depending on their male fertility. The BC₁F₂ and BC₂ progenies segregated well for the morphological traits. Disturbances were observed especially in the generative phase (flower development and pollen fertility). Both male fertile and male sterile BC₁F₂ and BC₂ plants were obtained and backcrossed or self-pollinated with the B. oleracea parent. The presence of either one of the parental or the cybrid organelle genomes was detected. In the progenies, a stable maternal inheritance of the organelle genome patterns was observed. Isozyme analyses revealed polymorphism for the leucine aminopeptidase (LAP) which was used for the identification of S. alba genes in the progenies. Cytological investigations showed a clear differentiation between the BC₁F₂ and BC₂ plants. Whereas the BC₁F₂ plants possess large numbers of chromosomes ranging from 34 to 40, the BC₂ material was strongly reduced to chromosome numbers ranging from 20 to 22. Preliminary investigation of the meiosis suggests the possibility of introgressions of S. alba-DNA into the B. oleracea genome.     

Inheritance and mapping of a yellow leaf mutant of carrot (Daucus carota)

A yellow leaf mutant at a locus named YEL was selected in a population of the cultivated carrot. Genetic analysis of segregating F₂ progenies and corresponding F₃ families, indicates that the phenotype expressed is controlled by a single recessive nuclear gene. The mutant is stably inherited and is associated with a reduced leaf‐biomass of approximately 30% compared with the wild‐type. Amplified fragment length polymorphism markers were developed and used in bulked segregant analysis. Seventeen marker candidates were detected by using 45 primer pairs. Ten of these could be linked with the YEL locus and mapped in a linkage group with a total length of 33.2 cM. Application of the yellow leaf mutant in carrot research is discussed.     

Morphological characterization of modified flower morphology of three novel alloplasmic male sterile carrot sources

Three novel sources of cytoplasmic male sterility (CMS) in carrot are characterized by altered flower phenotypes. Flowers were classified into subtypes, according to stamen (and petal) modification. Flower anatomy was investigated by light microscopy to describe organ modification and to specify the timing when morphology begins to deviate. Early stages of floral development were defined in fertile male flowers of the cultivated carrot according to model plants such as Antirrhinum and Arabidopsis and compared with corresponding stages of the novel cytoplasmic male-sterile flower types. Early organogenesis was identical in the different CMS types and comparable to corresponding stages of unmodified flowers. The morphology of stamens, and in some cases petals, became different in CMS flowers during early organ differentiation. For each CMS type, the cytoplasm appears to influence organogenesis in a specific way. Although homoeosis is usually considered to be controlled exclusively by specific nuclear genes, a role of cytoplasmic factors is suggested     

Cold agglutinin activity in 2 dogs

A 5‐year‐old neutered male Mastiff and an 8‐year‐old spayed female Labrador Retriever were presented to the University of Minnesota Veterinary Medical Center. The Mastiff was presented for evaluation of lameness and pyoderma one month prior in Missouri, where he tested positive for Ehrlichia canis by serum ELISA test, treated with doxycycline. PCR for Ehrlichia sp, Anaplasma sp, Babesia sp, and Bartonella sp, and PCR for antigen receptor rearrangement were negative, serum protein electrophoresis (SPE) revealed polyclonal gammopathy, and mildly reactive lymphoid cells were seen cytologically. The Labrador presented with a proliferative rostral mandibular gingival mass and lipomas for further presurgical evaluation of cold agglutinin activity documented by a commercial laboratory 2 years earlier prior to removal of a grade II mast cell tumor. This dog had a negative SNAP4Dx, normal SPE, and persistently increased serum ALP activity and polyuria/polydipsia suggestive for hyperadrenocorticism. Both dogs had markedly agglutinated RBC in the EDTA samples that dispersed with warming, and normal plasma color. Cold agglutinin activity was demonstrated by direct saline agglutination testing using whole blood and washed erythrocytes demonstrating agglutination at 30°C, 25°C, 15°C, and 4°C, but not at 37°C . CBC results (ADVIA 2120i) from the Mastiff revealed no significant differences in the RBC results obtained at room temperature (RT) and at 37°C; however, the RT run demonstrated negative bias in neutrophil and platelet concentrations attributed to rapid RBC settling. This uncommon hematologic condition may cause artifacts on the automated leukogram and platelet count, and may be subclinical for long periods.