Sugar Beet Chromosomes Research Articles

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

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.

Nematode Resistance Derived from Wild Beet and its Meiotic Stability in Sugar Beet

AbstractThree different karyotypes of sugar beet with resistance against the beet cyst nematode (Heterodera schachtii) have been investigated. These comprised monosomic addition lines (2n = 19) with one complete chromosome from B. patellarris or B. procumbens, one line with a chromosomal fragment added to the normal sugar beet chromosome complement (2n =18 + fragment) and one diploid line (2n = 18). The fragment originated from a B. procumbens chromosome since during meiosis it formed a univalem. It carries the gene for nematode resistance. Meiotic disturbances like univalems. laggards, anaphase I bridges, fragments and micronuclei were observed in all resistant genotypes. These may result in an exclusion of the chromosome fragment carrying the resistance from the rest of the genome. In the diploid resistant line, a chromosome with a translocation could be distinguished from the other B. vulgaris chromosomes. Meiotic irregularities also appeared in diploid resistant types and are one main reason for low transmission of the resistance. Tin‐relationship between meiotic stability and the transmission rate of the resistance gene is discussed.

Production and Reproductive Behavior of Monoploid Sugarbeet1

The rarity of sugarbeet (Beta vulgaris L.) monoploids has limited the usefulness of monoploids sugarbeet breeding. This study was conducted to evaluate the production and cytogenetical behavior of monoploid sugarbeets. The rate of occurrence of monoploids in three sugarbeet lines was 0.017%. Meiotic pairing in the monoploids indicated the presence of three or more duplications that involved at least six of the nine chromosomes in the basic genome. Chromosomes of monoploid sugarbeet usually were condense and seldom congregated at metaphase plates. Chromatid bridges and a centric fragments occurred in > 2% of microsporocytes. Only those gametes that developed from restitution nuclei and contained a complete set of sugarbeet chromosomes did not abort. Seed setting was rare, and not every monoploid sugarbeet produce viable seed. Sugarbeet monoploids gave rise to monoploid progeny through pollination with diploids at a rate of 1.49%, which was > 80 times higher than that from pollinating diploids. The progeny plants also contained 18, 19, 27, 36, and 18/36 chromosomes when monoploids were pollinated with diploids. A great majority (92.3%) of these progenies were diploids. The 19‐chromosome (trisomic) progeny was the only aneuploidy class recovered. It may not be possible to establish monosomic series of sugarbeet genotypes through conventiona pollination techniques because unbalance gametes (without an intact genome) do not survive. Although the monoploids exhibited morphologic dailvergence from diploid parents, the monoploid progeny resembled their respective maternal monoploids. This is the first reports howing the feasibility of recovering monoploid sugarbeet from monoploids.

Acetocarmine squash method for observing sugar beet chromosomes

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.

HYBRIDIZATION BETWEEN BETA VULGARIS AND B. PROCUMBENS AND TRANSMISSION OF NEMATODE (HETERODERA SCHACHTII) RESISTANCE TO SUGARBEET

Triploid hybrids between tetraploid Beta vulgaris (4x = 36) and diploid B. procumbens (2x = 18) were used to transmit nematode resistance into sugarbeet. In meiosis of triploid hybrids, nine B. vulgaris bivalents and nine B. procumbens univalents were usually observed. In some pollen mother cells (PMC's) trivalent associations (8II + 8I + 1III) were formed. The second anaphase varied from near regular to very irregular. The regular anaphase produced normal quartets and viable gametes.The B1 plants and the plants of all succeeding backcross generations were tested for nematode resistance. From 6,750 B1 plants, four nematode-resistant trisomics were selected that had 18 B. vulgaris chromosomes and one B. procumbens chromosome responsible for resistance. The B. procumbens chromosome and nematode resistance were transferred to the eighth backcross generation with an average transmission rate of 12%. In meiosis of trisomies, trivalent associations of two B. vulgaris and one B. procumbens chromosomes were formed in a few PMC's. Two diploid nematode-resistant plants were selected from 8,834 backcross plants in the progenies of trisomies, and resistance was transferred from both of these plants to F1 hybrids. The segment of the B. procumbens chromosome bearing the gene for nematode resistance has been transferred to a sugarbeet chromosome.