Introgression of Allium fistulosum L. into Allium cepa L.: cytogenetic evidence

Summary A diploid Allium cepa plant was recovered from the backcross of an interspecific triploid (2 x A. cepa + 1 x A. fistulosum) to an A. cepa diploid which exhibited both A. cepa and A. fistulosum Adh-1 alleles. Cytogenetic analyses revealed a recombinant sub-telocentric chromosome. The ADH-1 locus is believed to be on the long arm of the sub-telocentric A. fistulosum chromosome 5. Meiosis of the triploid progenitor gives strong evidence that recombination occurred. A. fistulosum chromosome 8 has been substituted for A. cepa chromosome 1.Contribution of the College of Agricultural Sciences, Texas Tech University, Journal No. T-4-275     

Microtubule Cycle in Root Tip Cells of Allium fistulosum L.

Using immunofluorescent localization techniques and TEM methods, the organization of microtubule arrays during the cell cycle of root tip cells of Allium fistulosum L. was studied. There are four basic types of microtubule organization, namely, interphase cortical microtubule, pre-prophase band microtubule, spindle microtubule and phragmoplast microtubule, which constitute the typical microtubule cycle in dividing cells of higher plants. The fluorescent figures of microtubules observed under fluorescent microscope were explained and analysed by the ultrastractural informations of microtubules obtained from TEM.     

Three Forms of α-Glucosidase from Welsh Onion (Allium fistulosum L.)

Tremerogen A-10 is an S-polyisoprenyl peptide mating pheromone secreted by the AB cells of the heterobasidiomycetous yeast Tremella mesenterica. We investigated the feasbility of the use of compactin (ML 236-B), a potent inhibitor of mevalonate synthesis in mammalian cells, for the study of the mating pheromone production. Compactin specifically inhibited mevalonate synthesis of the yeast cells without affecting protein synthesis. The secretion of tremerogen A-10 was effectively blocked by the drug. Accumulation of a large precursor polypeptide (M.W. 28,000) for the mature pheromone (M.W. 1,480) in the membrane fraction of compactin-treated cells was demonstrated by immunoprecipitation of ³⁵-S-labeled proteins. The results suggested that the addition of the nonpolar residue to a polypeptide precursor is important for the production of tremerogen A-10 especially in the intracellular transport and processing of the precursor molecules.     

葱卵细胞的分离

将大葱(Allium fistulosum)胚珠置于酶液中30分钟可将其外珠被去掉。可清楚地看到由内珠被包裹的胚珠中胚囊的轮廓。将胚珠转移至不含酶的相同溶液中, 用解剖针从胚珠中部切割, 然后挤压胚珠的珠孔部位, 卵器细胞从胚珠的切口处逸出。再用显微操作仪将卵细胞和2个助细胞分开, 达到葱卵细胞分离的目的。酶对分离卵细胞具有重要的作用, 经0.2%果胶酶Y23、0.8%果胶酶、0.8%纤维素酶和0.5%半纤维素酶的处理, 可在2小时内从30 个胚珠中分离出18个卵细胞。随着胚囊的发育, 2个助细胞的体积出现明显差异。生活的葱卵细胞的成功分离, 为建立葱离体受精体系创造了条件。     

Bulb-type onion introgressants posessing Allium fistulosum L. genes recovered from interspecific hybrid backcrosses between A. cepa L. and A. fistulosum L.

Allium fistulosum possesses a number of traits which would be desirable in A. cepa. Thus far, no commercial A. cepa cultivars have been released which harbor Allium fistulosum traits. F₁BC₃ populations were generated for this study by backcrossing A. cepa to A. cepa×A. fistulosum hybrids. The F₁BC₃ plants were evaluated for plant morphology, floral characters, male- sterile cytoplasm, soluble solids and pungency, and isozymes. Overall growth habit and floral characters of the F₁BC₃ plants were much like A. cepa. We report here the recovery of recombinant, bulbing, and fertile A. cepa-type onions that exhibit A. fistulosum isozyme alleles and morphological markers. Recombination between A. cepa and A. fistulosum genomes was achieved using the introgression strategy of backcrossing A. fistulosum into A. cepa, thereby ameliorating the nuclear cytoplasmic barriers that occurred in previous less successful introgression attempts when plants were not in A. cepa cytoplasm. We believe this report to be the first demonstration of onion introgressants that are like A. cepa in appearance, are male- and female-fertile, and possess A. fistulosum genes. Received: 29 May 1999 / Accepted 22 June 1999     

葱卵细胞的分离

将大葱（Allium fistulosum）胚珠置于酶液中30分钟可将其外珠被去掉。可清楚地看到由内珠被包裹的胚珠中胚囊的轮廓。将胚珠转移至不含酶的相同溶液中,用解剖针从胚珠中部切割,然后挤压胚珠的珠孔部位,卵器细胞从胚珠的切口处逸出。再用显微操作仪将卵细胞和2个助细胞分开,达到葱卵细胞分离的目的。酶对分离卵细胞具有重要的作用,经0．2％果胶酶Y23、0．8％果胶酶、0．8％纤维素酶和0．5％半纤维素酶的处理,可在2小时内从30个胚珠中分离出18个卵细胞。随着胚囊的发育,2个助细胞的体积出现明显差异。生活的葱卵细胞的成功分离,为建立葱离体受精体系创造了条件。     

胡葱与洋葱、葱过氧化物酶同工酶研究及聚类分析

本文对胡葱与洋葱、葱的功能叶过氧化物酶同工酶电泳图谱分析和聚类分析表明：这三个种及葱的3个交种闻的亲缘关系被区分开来;胡葱与洋葱的亲缘关系比胡葱与大葱的亲缘关系更近。     

GISH study of advanced generation of the interspecific hybrids between Allium cepa L. and Allium fistulosum L. with relative resistance to downy mildew

Genomic in situ hybridization (GISH) was used for a chromosomal composition study of the later generations of interspecific hybrids between A. cepa L. and A. fistulosum L., which are relatively resistant to downy mildew (peronosporosis). GISH revealed that F₂ hybrids, which did not produce seeds, were triploids (2n = 3x = 24) with 24 chromosomes and possessed in their complements 16 chromosomes of A. fistulosum L. and eight chromosomes of A. cepa L. or eight chromosomes of A. fistulosum L. and 16 chromosomes of A. cepa L. The advanced F₅ hybrid, which produced few seeds, was amphidiploid with 32 chromosomes. BC₁F₅ hybrid was triploid with eight chromosomes of A. fistulosum L. and 16 chromosomes of A. cepa L., which did not produce seeds. BC₂ (BC₁F₅) plant was amphidiploid that possessed 4 recombinant chromosomes and produced few seeds. GISH results point to 2n-gametes formation in macro- and microsporogenesis of the hybrids. The mechanism of 2n-gametes formation and the possibility of apomixes events in the backcrossing progeny are discussed.     

Waterlogging tolerance of Welsh onion (Allium fistulosum L.) enhanced by exogenous spermidine and spermine

Soil flooding is a seasonal factor that negatively affects plant performance and crop yields. In order to investigate the effects of spermidine (Spd) and spermine (Spm) on the waterlogging stress, it was checked that the content of relative water content (RWC), proline, chlorophyll and malondialdehyde (MDA), net photosynthesis, the rate of hydrogen peroxide (H₂O₂) and superoxide radicals (O₂^?) generation and the antioxidant enzyme activities of superoxide dismutase (SOD) (EC 1.15.1.1), catalase (CAT) (EC 1.11.1.6), ascorbate peroxidase (APX) (EC 1.11.1.11) and glutathione reductase (GR) (EC 1.6.4.2) in Welsh onion (Allium fistulosum L) plants. Pretreatment with 2 mM of Spd and Spm effectively maintained the balance of water content in plant leaves and roots under flooding stress. In addition, the data indicate that the protective role of proline should be considered minimal, as its accumulation was found to be inversely correlated with tolerance to stress; it also significantly retarded the loss of chlorophyll, enhanced photosynthesis, decreased the rate of O₂^? generation and H₂O₂ content, and prevented flooding-induced lipid peroxidation. Spd and Spm helped to maintain antioxidant enzyme activities under flooding; however, APX activity was found to increase slightly in response to Spm. The antioxidant system, an important component of the water-stress-protective mechanism, can be changed by PAs, which are able to moderate the radical scavenging system and to lessen in this way the oxidative stress. The results suggest that pretreatment with Spd and Spm prevents oxidative damage, and the protective effect of Spd was found to be greater than that of Spm.     

The chromosomal locations of enzyme-coding genes Adh-1 and Pgm-1 in Allium fistulosum L.

Summary The chromosomal locations of two enzymecoding genes were investigated using allele dosage effects in two Allium cepa alien addition lines possessing different A. fistulosum chromosomes as the trisomes. Adh-1 has been assigned to the A. fistulosum sub-telocentric chromosome 5, while Pgm-1 is on the A. fistulosum submetacentric chromosome 4. Karyotype data of a shortday cultivar of A. cepa, Temprana, A. fistulosum Ishikura Long White, and the relevant chromosomes of the two trisomies are presented.Contribution of the College of Agricultural Sciences, Texas Tech University, Journal No. T-4-224     

Production of interspecific hybrids between Allium fistulosum L. and A. macrostemon Bunge through ovary culture

Interspecific hybridization is an effective method to generate a new crop in a short time that exhibits available traits. Nine interspecific hybrids between Allium fistulosum and A. macrostemon were produced through reciprocal crossings by ovary culture. This is the first report of hybrid development in the cross-combination. When A. macrostemon, a vegetative propagated plant, was used as the mother plant, no hybrid was obtained, but it was obtained by removal of bulbils and separation of the flower stalk, as with cut flowers. Ovary culture was performed on phytohormone-free B5 medium modified by Dunstan and Short (BDS) medium containing 30 g l⁻¹ sucrose 7 days after pollination. Germinated embryos were transferred to BDS medium containing 1 mg l⁻¹ 6-benzylaminopurine and 15 g l⁻¹ sucrose for 21 days. The plantlets were subcultured on phytohormone-free B5 medium for subsequent rooting. Hybridity was confirmed using cleaved amplified polymorphic sequence analysis of the rDNA internal transcribed spacer region and chromosome observation. In addition, the hybrids showed intermediate traits: they had fistulous leaves like those of A. fistulosum and bulbs like those of A. macrostemon. They displayed vigorous growth and propagated vegetatively by tillering. These results show the important discovery that vegetatively propagated plants are useful for cross breeding.     

Synaptonemal complex spreading in Allium cepa and A. fistulosum

The general features and fine structure of homologous chromosome alignment and pairing have been investigated in two species of Allium (A. fistulosum and A. cepa), which have similar karyotypes but very different patterns of chiasma distribution. Although there is no support for the occurrence of a general pre-meiotic alignment of homologous chromosomes, both species show some alignment of homologues as an immediate prelude to synaptonemal complex (SC) formation. In both species pairing usually commences at sub-terminal sites and is succeeded by numerous separate intercalary initiations of pairing in interstitial and distal regions and then in proximal regions. The last parts to pair, in both species, are pericentromeric and telomeric regions. There is, therefore, no evident relationship between the sequence of pairing and chiasma distribution in these species. Regularly alternating convergences and divergences of aligned axial cores (ACs), termed multiple association sites, are frequently observed. It is proposed that these represent potential pairing initiation sites and from observations on their spatial distribution it is argued that they may be evenly distributed through most of the genome. Small spherical or ellipsoid nodules are found at association sites and between closely aligned ACs which persist in the SC segments present during zygotene, but most of them disappear abruptly at the end of zygotene. These are termed zygotene nodules (ZN) and it is proposed that they are involved in matching corresponding sites on homologous chromosomes as well as possibly having a recombinational role. Their composition, structure, mode of action and relationship to pachytene recombination nodules are at present unknown.     

Cytotoxic effect of chlorophenols on cells of the root meristem of welsh onion (Allium fistulosum L.) seeds

Chlorophenols are precursors to more dangerous environmental toxicants, which are characterized by mutagenic and carcinogenic properties. The methods of bioassay on plant test objects to study the influence of different pollutants allow one to connect the mutagenicity and cytotoxicity of investigated substances. The genotoxic and cytotoxic effects of pentachlorophenol and trichlorophenol solutions on root meristem cells of the Welsh onion Allium fistulosum L. shoots have been studied. Doze-dependent inhibition of seed germination of Welsh onions as a consequence of the influence of pentachlorophenol and trichlorophenol solutions with different concentrations shows a significantly greater toxic effect of pentachlorophenol, dependending on the doze, on seed germination than trichlorophenol.     

Evidence for nuclear-cytoplasmic incompatibility between Allium fistulosum and A. cepa

An F₂ population (Allium fistulosum x A. cepa) of 20plants, 10 BC₁,[(A. fistulosum x A. cepa) x A. cepa], and 50 BC₂ plants, [(A. fistulosum x A. cepa) x A. cepa] x A. cepa were studied cytogenetically and characterized for four isozyme alleles plus various morphological characteristics. All of the progenies were in A. fistulosum (the bunching onion) cytoplasm. In the F₂ population we observed non-random chromosomal and allelic segregation, suppression of bulb onion allelic expression, and abnormalities in mitosis and meiosis. Most BC₂ plants resembled A. cepa (the bulbing onion) morphologically, but anthers, filaments, pistils, and petals were abnormal. Only 3 plants, and these were most nearly like the F₁ hybrid morphologically, produced any seeds.The data and observations support the hypothesis of nuclear-cytoplasmic incompatibility interactions between the bunching and bulb onion species.Use of trade names does not imply endorsement of the products named nor criticism of similar ones not named. This research was supported by the New Mexico Agricultural Experiment Station.     

Recombinant chromosomes of advanced backcross plants between Allium cepa L. and A. fistulosum L. revealed by in situ hybridization

Cytological analysis of (Allium cepa L.×Allium fistulosum L.)×A. cepa L. F₁BC₃ plants revealed most plants were diploid with 16 chromosomes. Karyotypes of these plants showed recombinant chromosomes. Fluorescence and genomic in situ hybridization patterns of interspecific F₁ hybrid and F₁BC₃ plants revealed A. fistulosum chromosomes or chromosomal segments. A highly repetitive 376-bp DNA sequence and genomic DNA of A. fistulosum revealed similar telomeric hybridization sites when hybridized onto A. fistulosum chromosomes. Cytogenetic evidence showed that A. fistulosum DNA has recombined into the A. cepa genome. Received: 20 October 1999 / Accepted: 11 November 1999     

Dynamics of chromosomal instability in Welsh onion (Allium fistulosum L.): Influence of seed storage temperature

The age-related dynamics of chromosomal instability in cells of the root meristem of seedlings and germination capacity of seeds of Welsh onion (Allium fistulosum L.) in two storage temperature regimes in the course of six years following collection of the seeds are investigated. Seeds that had been stored at room temperature (14–28°C) lost germination capacity after six years of storage. The frequency of aberrant anaphases in these seeds grew from 2% in the first month of storage of the seeds to 80% in the 75th month. The germination capacity of seeds that had been stored at reduced temperatures (4–9°C) amounted to 73–77% in the sixth year, while the frequency of aberrant anaphases in these seeds remained within the range 2–4% throughout the six years. Thus, storage of Welsh onion seeds for six years at reduced temperatures tends to preserve the germination capacity of the seeds and prevents the development of chromosomal instability in the root meristem cells of the seedlings over this period.