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  • 1
    Electronic Resource
    Electronic Resource
    An isozyme marker for resistance to race 3 of Fusarium oxysporum f. sp. lycopersici in tomato (1989)
    Springer
    Theoretical and applied genetics 78 (1989), S. 489-494 
    Details
    ISSN: 1432-2242
    Keywords: Fusarium wilt ; Lycopersicon pennellii ; Isozyme marker ; Tomato ; Disease resistance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The inheritance and the linkage relationship of resistance to race 3 of Fusarium oxysporum f. sp. lycopersici derived from Lycopersicon pennellii (LA 716) were analyzed in an interspecific backcross to L. esculentum. Progeny from each backcross (BC1) individual were in-oculated with race 3 and their response was measured according to a visual rating system; progeny responses were used to calculate a mean disease rating for each BC1 individual. The frequency distribution of the disease ratings was bimodal, indicating that resistance to race 3 was controlled by one major locus. Linkage analysis of this locus proceeded in two steps. Initially, disease ratings were compared between homozygotes and heterozygotes at each of 17 segregating marker enzyme loci. Highly significant differences were detected for the chromosome segment marked by the Got-2 locus on chromosome 7. This indicated that Got-2 was linked to the race 3 resistance gene, designated I-3; this gene accounted for the observed bimodal distribution of BC1 disease ratings. In the second step, the genotype of each BC1 individual at the I-3 locus was determined using cluster analysis of the disease ratings; a test for independent assortment between I-3 and Got-2 revealed strong linkage, with an estimated map distance of 2.5 centiMorgans. Additional evidence for this linkage was obtained from the analysis of five breeding lines previously selected for resistance to race 3 solely on the basis of inoculations; all five showed co-selection for Got-2. The Got-2 locus is proposed as a selectable marker to expedite the transfer of race 3 resistance to commercial tomato cultivars.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00290832
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  • 2
    Electronic Resource
    Electronic Resource
    Genetic analysis of resistances to races 1 and 2 of Fusarium oxysporum f. sp. lycopersici from the wild tomato Lycopersicon pennellii (1990)
    Springer
    Theoretical and applied genetics 79 (1990), S. 641-645 
    Details
    ISSN: 1432-2242
    Keywords: Fusarium wilt ; Tomato ; Disease resistance ; Isozyme ; Linkage
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Resistance to race 3 of Fusarium wilt in the wild tomato Lycopersicon pennellii (LA 716) was previously found to be controlled by one major locus, I-3, tightly linked to Got-2 on chromosome 7. This accession was also found to carry resistance to races 1 and 2; a genetic analysis of these resistances is reported in this paper. This analysis proceeded in two steps. First, allelism tests demonstrated that race 1 and 2 resistances carried by L. pennellii were not allelic to the I and I-2 genes originally incorporated into L. esculentum from L. pimpinellifolium. Second, an interspecific backcross with L. pennellii (BC1) was used to determine the mode of inheritance of these new resistances and their chromosomal location by segregation and linkage analysis. BC1 responses to each of the races were determined using progeny tests (BC1S1). BC1S1 plants were inoculated with race 1 or 2 and evaluated after 1 month using a visual disease rating system; mean disease ratings were calculated for each BC1 individual for each race based on the progeny scores. A bimodal frequency distribution of the BC1 mean disease ratings was observed for both races, indicating that one major locus controlled resistance in each case. Statistical comparisons of the mean disease ratings of homozygous versus heterozygous individuals at each of 17 segregating enzyme loci were used to map the resistances to races 1 and 2. Tight linkage was detected between the enzyme locus Got-2 and resistances to both races, as was previously reported for the I-3 locus. Therefore, the Got-2 locus can be used as a selectable marker for resistances to all three races. The relationship of these resistances is discussed in the paper. In addition, as previously reported for race 3, significance was also detected for the chromosome segment marked by Aps-2 on chromosome 8 for both races. Currently many cultivars carry I and I-2 resistances to races 1 and 2. Incorporation of the LA 716 resistances to these two races into cultivars may reduce the likelihood of new race development.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00226877
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  • 3
    Electronic Resource
    Electronic Resource
    Ultrastructure of cell division in the marine red algaLomentaria baileyana (1986)
    Springer
    Protoplasma 131 (1986), S. 1-10 
    Details
    ISSN: 1615-6102
    Keywords: Cell division ; Lomentaria ; mitosis ; Red algae ; Rhodophyta ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Mitosis in the marine red algaLomentaria baileyana (Rhodymeniales, Rhodophyta) was studied with the electron microscope. Nucleus associated organelles known as polar rings (PRs) migrate to establish the division poles at prophase. At prometaphase, shallow invaginations in the nuclear envelope (NE) form on two sides of each PR and soon rupture. The gaps that are consequently formed contain several small fragments of NE. A larger region of NE remains intact between the two gaps. By metaphase several cisternae of perinuclear endoplasmic reticulum (PER) have enclosed most of the nucleus but remain absent from the polar regions. The nucleolus disperses partially and a typical metaphase plate of chromosomes is formed. Each PR has disjoined into separate proximal and distal portions. MTs converge widely on all regions of the polar area, but do not extend into the cytoplasm. Some MTs end near or at the chromosomes while others extend slightly farther past the chromosomes or diagonally to the NE. As chromosomes move to opposite poles at anaphase, they are accompanied by nucleolar material. An interzonal midpiece (IZM) is created as the pole to pole distance increases and the NE remains intact except for the polar gaps. Following detachment from the IZM, the daughter nuclei are separated by a large central vacuole as a cleavage furrow develops and eventually constricts to form two cells following pit connection formation. It is suggested that mitosis inLomentaria represents an evolutionary intermediate between that seen in the higher and lower groups of red algae. This conclusion is in agreement with conventional morphological and light microscopic criteria used to placeLomentaria in theRhodymeniales, which is considered to be the next to most advanced order in theRhodophyta.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01281682
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  • 4
    Electronic Resource
    Electronic Resource
    Mitosis in the freshwater red algaBatrachospermum ectocarpum (1983)
    Springer
    Protoplasma 118 (1983), S. 56-70 
    Details
    ISSN: 1615-6102
    Keywords: Carposporophyte ; Cell division ; Mitosis ; Rhodophyta ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Mitotic ultrastructure was observed in meristematic cells of carposporophyte generations of the freshwater red algaBatrachospermum ectocarpum. Prior to nuclear division, cell elongation occurs resulting in the nucleus being located at the proximal end of the cell and separated by a large central vacuole from a distal “empty region” which the daughter nucleus eventually occupies. In late prophase, nuclear envelope-attached polar rings are situated adjacent to shallow nuclear invaginations. At prometaphase the nuclear invaginations extend deeply into the nucleus forming continuous cytoplasmic channels containing microtubules. Perinuclear ER and a typical equatorial chromosomal plate are formed by metaphase at which time the nuclear envelope lining the cytoplasmic channels has dispersed. Chromosomal and non-chromosomal microtubules converge at the poles where a single, large gap is seen in the otherwise intact nuclear envelope. Polar rings were not detected in the few mitotic cells observed beyond prometaphase but are thought to be present. During anaphase an interzonal midpiece is formed and the distal-most incipient daughter nucleus moves laterally past the central vacuole into the apical “empty region”. Features of mitosis inBatrachospermum are believed to be intermediate between those exhibited by the lower and higher orders of red algae, this being consistent with the taxonomic placement of the genus in theNemaliales, the least advanced order of the classFlorideophyceae.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01284747
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  • 5
    Electronic Resource
    Electronic Resource
    Ultrastructure of cell division and reproductive differentiation of male plants in theFlorideophyceae (Rhodophyta). Mitosis inDasya baillouviana (1981)
    Springer
    Protoplasma 106 (1981), S. 329-341 
    Details
    ISSN: 1615-6102
    Keywords: Dasya ; Mitosis ; Rhodophyta ; Spermatangia ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Mitosis in the marine red algaDasya baillouviana (Ceramiales, Florideophyceae) was observed with the electron microscope. Most details of the process are quite similar to those observed in the other macroscopic red algae studied to date. However, some minor variations were noted. At late prophase a very small nuclear envelope protrusion (NEP) is formed at each division pole subjacent to the “nucleus associated organelle” known as the polar ring (PR) and 2–3 cisternae of perinuclear endoplasmic reticulum (PER) are commonly present during metaphase-anaphase. In contrast, in the other florideophycean algae where mitosis has been reported, a prominent NEP is present at late prophase (McDonald personal communication,Scott et al. 1980) and only a single cisterna of PER is observed. Additionally, during mid-late interphase and in mitotically-quiescent cells ofDasya, a single cisterna of smooth-surfaced ER is always juxtaposed with each PR. The possible significance of PER in theFlorideophyceae and other multinucleate organisms is discussed as well as the likely functions of spindle-associated smooth ER. It is suggested that ultrastructural features of mitosis should be useful as criteria to aid in the interpretation of the phylogeny of red algae.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01275563
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