T. Tsuchiya

Acrotrisomic analysis in linkage mapping in barley (Hordeum vulgare L.).

SummaryThree acrotrisomic lines, Triplo IL1S, 3L3S, and 4L4S, each carrying an extra acrocentric chromosome, were used for cytogenetic linkage mapping of barley chromosomes. The cytological structures of the acrocentric chromosome of the three acrotrisomic lines were studied with an improved Giemsa N-banding technique. The long (1L) and short arm (1S) of chromosome 1 had deficiencies of approximately 38% and 65%, respectively. The percentages of deficiencies were 0 and 77.8% for 3L and 3S, and 31.7 and 59.3% for 4L and 4S, respectively. All three genes tested (br, fc, gs3) in 1S and all three genes tested, f8, n and 1k2 in 1L showed a disomic ratio indicating that they are located in the deficient segments. Two genes (ac, yst2) located in the middle segment of 3S in linkage map showed a trisomic ratio, and two others an, xs showed a disomic ratio. The only gene(f9) tested in 4L showed a trisomic ratio. Two genes (1g4, g1) located in the proximal segment of 4S in the linkage map showed a trisomic ratio, whereas two genes (br2, g13) located distally in 4S showed a disomic ratio, indicating that the breakage occurred between g1 and br2. This experiment demonstrates a new method for physical localization of genes on chromosome segments in material such as barley in which pachytene analysis can not be effectively used for accurate determination of break points in structural changes. Problems associated with this new technique are discussed.

Cytogenetic studies in barley chromosome 1 by means of telotrisomic, acrotrisomic and conventional analysis

SummaryGenetic and cytogenetic techniques were applied to linkage analysis of chromosome 1. Eight marker genes, including five on the short arm and three on the long arm, were analyzed with two telotrisomic lines, Triplo 1S and 1L, and one acrotrisomic line, Triplo 1L1S. Telotrisomic analysis confirmed the position of ac2, gs3, f3, br, f5, and f8 on the short arm, and 1k2 and n on the long arm of the linkage map of chromosome 1. Conventional three-point tests with two triple genetic marker stocks showed that fcis located between br and gs3, and n is located in the middle of f8 and 1k2. Acrotrisomic for 1L1S was used for cytogenetic linkage mapping. Giemsa N-banding technique showed that the long (1L) and short (1S) arm had deficiencies of 37.5% and 73%, respectively. Genes f5, br, fc, gs3 and f8 in 1S and 1k2 in 1L were located in the deficient segments of 1L1S. A trisomic ratio obtained with n indicated an association of this gene with the long arm of the acrocentric chromosome. Cytological behavior, morphological characteristics, fertility, and transmission in the acrotrisomic 1L1S are also reported.

Cytogenetics of four telotrisomics in barley (Hordeum vulgare L.)

SummaryFour barley telotrisomics (Triplo 3S, 5S, 6S, and 7S) were studied. No major qualitative differences in morphology between the telotrisomics and their diploid sibs were found. The pollen and seed fertility of these telotrisomics was comparable to their diploid sibs. The meiotic study showed that the average frequency of 6II + 1III at diakinesis and metaphase I was 84.2% and 71.7%, respectively. The normal chromosome separation ranged from 77.2% to 89.4% at anaphase I through telophase II. The transmission rate of the extra telocentric chromosomes averaged 28.4% upon selfing and 28.7% through the female. All four telotrisomics showed various degrees of pollen transmission, the average being 3.6%. Ditelotetrasomic plants (2n = 14 + 2 homologous telocentrics) were obtained in the progenies of selfed monotelotrisomic plants of all four types. These ditelotetrasomic plants were viable and showed various degrees of seed fertility.

Cytogenetics of ditelotetrasomics for short arms of four chromosomes of barley (Hordeum vulgare L.)

SummaryPlants with a pair of extra homologous telocentric chromosomes in addition to the normal chromosome complement are called ditelotetrasomics. Six types of ditelotetrasomics of barley have been obtained. Four types obtained in the selfed progenies of telotrisomics (Triplo 2S, Triplo 5S, Triplo 6S, and Triplo 7S) are reported in this paper. The ditelotetra 2S showed a stronger expression of the diagnostic characteristics of Triplo 2S. It was weak and small, with narrow, short, dark-green leaves, and was almost completely pollen and seed sterile. However, three other ditelotetrasomics (ditelotetra 5S, 6S, and 7S) did not show specific diagnostic characteristics and were similar to normal diploid plants, with the exception of ditelotetrasomic 5S, which showed some effects. At meiotic diakinesis and metaphase I, these ditelotetrasomic plants showed chromosome configurations of 6II+1IV, 7II+1 teloII, 6II+1III+1teloI, or 7II+2 teloI. Most of the sporocytes at anaphase and telophase in the first and second meiotic divisions showed almost normal chromosome behavior. Quartets were mostly normal with no micronuclei. Approximately 30% of the selfed progenies of these three ditelotetrasomics were ditelotetrasomics and almost 50% were telotrisomics, indicating a high percentage of male and female transmission of the extra telocentric chromosomes.