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.     

Identification and mapping of random amplified polymorphic DNA markers linked to a rhizomania resistance gene in sugar beet (Beta vulgaris L.) by bulked segregant analysis

Bulked segregant analysis was employed to identify random amplified polymorphic DNA (RAPD) markers linked to a gene that confers rhizomania resistance to a sugar beet line created from a Holly Sugar Company breeding population (USA). Polymorphism revealed with 160 arbitrary 10-mer oligonucleotide primers was screened in two bulks produced by separately pooling the individual DNAs from the six most resistant and the six most susceptible plants of an F₂ population segregating for rhizomania resistance. A study of the F₂ individuals showed that 19 primers generated 44 polymorphic markers which were then grouped into nine linkage groups. By analysis of variance, 12 were shown to have a significant effect upon the level of resistance and were mapped on a segment 22.3 cM long. A quantitative trait locus (QTL) of resistance was identified and located in a 4.6cM interval between two markers. It accounted for 67.4% of the observed variation and almost all the genetic variation. These results suggest that the identified QTL corresponds to a unique major gene conditioning the Holly resistance studied, which we have named Rz-l.     

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.     

Expression in vitro of resistance to Heterodera schachtii in hairy roots of an alien monotelosomic addition plant of Beta vulgaris,transformed by Agrobacterium rhizogenes

Summary Hairy roots, induced by Agrobacterium rhizogenes, were obtained of nematode susceptible beet plants (Beta vulgaris) and of the nematode resistant alien monotelosomic addition AN5, carrying a telosome from B. patellaris. The additional telosome was found to be stably present in vitro in the roots of AN5. The hairy root cultures were inoculated with larvae of the beet cyst nematode Heterodera schachtii. On the root culture of AN5 significantly less cysts developed than on the other root cultures. These results indicate that the resistance to the beet cyst nematode is expressed in the roots after transformation and can be monitored under in vitro conditions.     

Resistance to Polymyxa betae in Beta Species of the Section Procumbentes, in Hybrids with B. vulgaris and in Monosomic Chromosome Additions of B. procumbens in B. vulgaris

Plant regeneration from callus cultures of Allium trifoliatum subsp. hirsutum fertile accession F-370, was studied as a means for clonal multiplication and germplasm storage of Allium spp. Callus was induced on in votro-cultured basal leaf explants. Best proliferation was obtained on modified BDS medium supplemented with (mg/1): 0.75 picloram, 2.0 benzyl adenine, and 900 casein hydrolysate. Shoot and root organogenesis were obtained in 3 to 5 month old subcultured calli, on BDS or MS medium supplemented with (mg/1): either 0.03 picloram or no auxin, 2 BA or 2-isopentenyladenine, and 900 casein hydrolysate. Direct bulb formation, without shoot elongation, occurred on BDS medium with 10 mg/1 IBA. Under these conditions, callus formation and organogenesis were not obtained with A. trifoliatum subsp. hirsutum var. sterile, a male-sterile genotype. Most regenerants were phenotypically normal, but some abnormal shoots were also observed, i.e. shoots with vitrified or extremely broad leaves. Isozyme polymorphism analysis of seven proteins in the latter regenerants, and in several callus cultures, revealed significant deviation from the original pattern in esterase, 6-phosphogluconate dehydrogenase and superoxide dismutase. No such deviations were detected in normal regenerated plants.     

The inheritance of resistance to beet necrotic yellow vein virus (BNYVV) in B. vulgaris subsp. maritima, accession WB42: Statistical comparisons with Holly-1-4

In this study, the inheritance of resistance to Beet necrotic yellow vein virus (BNYVV) in accessions Holly-1-4and WB42 was investigated. Crosses between both resistant sources and susceptible parents were carried out and F₁F₂ and BC₁ populations were obtained. Virus concentrations in WB42and its F₁ populations were lower than in Holly-1-4. Observed ratios of susceptible and resistant plants in segregating populations of Holly-1-4 as well as WB42 were in agreement with hypothesis of one dominant major gene. Segregation of plants in F₂ populations obtained from crosses betweenHolly-1-4 and WB42 revealed that the resistance genes in Holly-1-4 and WB42 were nonallelic and linked loci. This revised version was published online in July 2006 with corrections to the Cover Date.