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  1. Article: Hermaphroditism in Meloidogyne hapla.

    Triantaphyllou, A C

    Journal of nematology

    2009  Volume 25, Issue 1, Page(s) 15–26

    Abstract: Hermaphrodites were detected in diploid and polyploid isolates of population 86-Va of Meloidogyne hapla. Young hermaphrodites are indistinguishable from normal females. Initially, hermaphrodite ovaries are filled with oocytes at various stages of ... ...

    Abstract Hermaphrodites were detected in diploid and polyploid isolates of population 86-Va of Meloidogyne hapla. Young hermaphrodites are indistinguishable from normal females. Initially, hermaphrodite ovaries are filled with oocytes at various stages of development. Hermaphroditism is expressed later when young oocytes in the early pachytene region of the growth zone suddenly advance to diakinesis and proceed with maturation divisions, resulting in spermatid production. Spermatogenesis may be initiated shortly after the fourth molt, or later, after a female has produced some eggs. Spermatogenesis may occur in one or both gonads, and it may be initiated in one gonad before the other. Once initiated, spermatogenesis continues for the entire reproductive life of the hermaphrodite. Several thousand spermatozoa accumulate in the ovotestis. Because they do not pass through the oviduct into the spermatotheca, they do not take part in reproduction (nonfunctional hermaphroditism). Among the progeny of hermaphrodites, ca. 50% are hermaphroditic, and the remainder are apparently normal females which, however, produce about 50% hermaphroditic progeny. Two temperature regimes (20-23 C and 27-30 C) did not influence the percentage of hermaphrodites among the progeny. Hermaphroditism could not be transmitted to nonhermaphroditic isolates following attempted crosses between males of hermaphroditic and females of nonhermaphroditic isolates. Although this result suggests cytoplasmic rather than nuclear inheritance, this conclusion is not definitive.
    Language English
    Publishing date 2009-03-11
    Publishing country United States
    Document type Journal Article
    ZDB-ID 410426-2
    ISSN 0022-300X
    ISSN 0022-300X
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article: Oogenesis and the chromosomes of twelve bisexual species of heterodera (nematoda: heteroderidae).

    Triantaphyllou, A C

    Journal of nematology

    2009  Volume 7, Issue 1, Page(s) 34–39

    Abstract: Twelve bisexual species of Heterodera reproduced by amphimixis and had the same number of n=9 (2n=18) chromosomes in maturing oocytes. H. schachtii had slightly larger chromosomes than all other species. Only sperm nuclei with n=9 chromosomes were ... ...

    Abstract Twelve bisexual species of Heterodera reproduced by amphimixis and had the same number of n=9 (2n=18) chromosomes in maturing oocytes. H. schachtii had slightly larger chromosomes than all other species. Only sperm nuclei with n=9 chromosomes were observed inside maturing oocytes and no specialized sex chromosomes were detected in any case. A "supernumerary" chromosome was observed occasionally in oocytes of H. schachtii and H. weissi and was transmitted regularly to one-half of the progeny of the nematodes that possessed it. Cytological characteristics were not very instructive in differentiating amphimictic tleterodera species. Such karyotypic uniformity indicates cytogenetic stability of the genus and close interrelationship among its members.
    Language English
    Publishing date 2009-03-24
    Publishing country United States
    Document type Journal Article
    ZDB-ID 410426-2
    ISSN 0022-300X
    ISSN 0022-300X
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  3. Article: Gametogenesis and Reproduction of Meloidogyne graminis and M. ottersoni (Nematoda: Heteroderidae).

    Triantaphyllou, A C

    Journal of nematology

    2009  Volume 5, Issue 2, Page(s) 84–87

    Abstract: Oogenesis and spermatogenesis of seven populations of Meloidogyne graminis and one population of M. ottersoni (formerly Hypsoperine spp.) were of the meiotic type. When males were abundant, reproduction was by amphirnixis. In most greenhouse cultures, ... ...

    Abstract Oogenesis and spermatogenesis of seven populations of Meloidogyne graminis and one population of M. ottersoni (formerly Hypsoperine spp.) were of the meiotic type. When males were abundant, reproduction was by amphirnixis. In most greenhouse cultures, however, males were rare and reproduction was by meiotic parthenogenesis. M. graminis and M. ottersoni are closely related to each other and to M. graminicola and M. naasi, but differ in some respect from other Meloidogyne species. It is suggested that these four species be treated together as a group of species, either in the genus Meloidogyne or in the genus Hypsoperine.
    Language English
    Publishing date 2009-03-19
    Publishing country United States
    Document type Journal Article
    ZDB-ID 410426-2
    ISSN 0022-300X
    ISSN 0022-300X
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  4. Article: Genetic structure of races of Heterodera glycines and inheritance of ability to reproduce on resistant soybeans.

    Triantaphyllou, A C

    Journal of nematology

    2009  Volume 7, Issue 4, Page(s) 356–364

    Abstract: Four field populations of Heterodera glycines tested for ability to reproduce on three host differentials were each classified into one of the recognized races. A fifth population represented a new race. Genetic analysis indicated that the designated ... ...

    Abstract Four field populations of Heterodera glycines tested for ability to reproduce on three host differentials were each classified into one of the recognized races. A fifth population represented a new race. Genetic analysis indicated that the designated races are actually field populations that differ from each other primarily in the frequencies of three groups of genes (genes for parasitism) that act quantitatively and control the ability of the nematode to reproduce on resistant P.I. 88788, Pickett, and P.I. 90763 soybeans. Populations of race-3 have none of these genes for parasitism, or they have some in low frequency that results in an index of parasitism of less than 10 on any one of the resistant soybeans. Race-1 has a high frequency of one group of genes that enable it to reproduce on P.I. 88788. Race-2 has two groups of genes for parasitism in high frequency; one for P.I. 88788, and one for Pickett. Based on these findings, it was assumed that race-4 has three groups of genes for parasitism; one for P.I. 88788, one for Pickett, and one for P.I. 90763. Additional races may be recognized when new genes are identified, or when new gene combinations are discovered. The ability to reproduce on P. I. 88788 is inherited independently from the ability to reproduce on Pickett. Although the genetic structure of field populations does not provide a solid foundation for race designation, recognizing races under the present system may be useful when it clearly characterizes the behavior of field populations. Race designations, however, should be regarded as provisional since gene frequencies change with time in response to selection forces and, therefore, the race status of a population may change accordingly.
    Language English
    Publishing date 2009-03-24
    Publishing country United States
    Document type Journal Article
    ZDB-ID 410426-2
    ISSN 0022-300X
    ISSN 0022-300X
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  5. Article: Further studies on the role of polyploidy in the evolution of meloidogyne.

    Triantaphyllou, A C

    Journal of nematology

    2009  Volume 23, Issue 2, Page(s) 249–253

    Abstract: Two tetraploid isolates of Meloidogyne hapla, 86P and E289P, with haploid chromosome numbers of 34 and 28, respectively, were studied cytogenetically and biologically in relation to the diploid populations, 86-Va (n = 17) and E289-Taiwan (n = 14), from ... ...

    Abstract Two tetraploid isolates of Meloidogyne hapla, 86P and E289P, with haploid chromosome numbers of 34 and 28, respectively, were studied cytogenetically and biologically in relation to the diploid populations, 86-Va (n = 17) and E289-Taiwan (n = 14), from which they had been originally isolated. Both isolates were quite stable, converting to diploidy at the low rate of about 2.5%. The tetraploid isolate 86P maintained itself in competition with its diploid counterpart in mixed cultures, although an initial frequency of 50% polyploidy was reduced to about 9% at the end of the sixth generation. Both tetraploid isolates could maintain themselves in greenhouse cultures without artificial selection for at least 2 years. Crosses between diploid females and tetraploid males resulted in a few triploid females that produced mostly nonviable eggs, suggesting partial reproductive isolation between the two ploidy forms. Ten generations of propagation of only polyploid females of isolate 86P that were associated with males failed to yield an obligatorily amphimictic isolate that would not convert at all to diploidy. If one accepts a previous assumption that the present day amphimictic root-knot nematodes are tetraploids derived from diploid ancestors, results of the present study are not inconsistent with an evolutionary trend toward an even higher level of ploidy in Meloidogyne, presumably octaploidy.
    Language English
    Publishing date 2009-03-06
    Publishing country United States
    Document type Journal Article
    ZDB-ID 410426-2
    ISSN 0022-300X
    ISSN 0022-300X
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  6. Article: Cytogenetic Status of Meloidogyne (Hypsoperine) spartinae in Relation to Other Meloidogyne Species.

    Triantaphyllou, A C

    Journal of nematology

    2009  Volume 19, Issue 1, Page(s) 1–7

    Abstract: Four populations of Meloidogyne spartinae from the coast of North and South Carolina were identical cytogenetically. Fourteen rod-shaped chromosomes were present in oogonia and spermatogonia, whereas seven bivalents were observed in oocytes and ... ...

    Abstract Four populations of Meloidogyne spartinae from the coast of North and South Carolina were identical cytogenetically. Fourteen rod-shaped chromosomes were present in oogonia and spermatogonia, whereas seven bivalents were observed in oocytes and spermatocytes. There were no distinguishable sex chromosomes. Chromosome behavior was similar to that of other Meloidogyne species. A slight deviation in morphology of prometaphase bivalents was attributed to an increase in frequency of chiasmata that may be associated with the obligatorily amphimictic reproduction of this nematode. The anatomy of the oviduct-spermatotheca region and most cytogenetic features studied suggested that M. spartinae can be regarded as a root-knot nematode. Its position in the genus Meloidogyne or Hypsoperine can be decided by taxonomists. Its small chromosome number (n = 7) compared to the larger number (n = 13-19) of other Meloidogyne species suggests that, cytologically, M. spartinae stands closer to the ancestral form from which the prescent day root-knot nematodes have evolved.
    Language English
    Publishing date 2009-03-12
    Publishing country United States
    Document type Journal Article
    ZDB-ID 410426-2
    ISSN 0022-300X
    ISSN 0022-300X
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  7. Article: Cytogentic aspects of evolution of the family heteroderidae.

    Triantaphyllou, A C

    Journal of nematology

    2009  Volume 2, Issue 1, Page(s) 26–32

    Language English
    Publishing date 2009-03-26
    Publishing country United States
    Document type Journal Article
    ZDB-ID 410426-2
    ISSN 0022-300X
    ISSN 0022-300X
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  8. Article: Oogenesis and Reproduction of the Birch Cyst Nematode, Heterodera betulae.

    Triantaphyllou, A C

    Journal of nematology

    2009  Volume 2, Issue 4, Page(s) 399–403

    Abstract: Cytological study revealed that maturation of oocytes of Heterodera betulae is by regular meiosis and reproduction is by parthenogenesis. Restoration of the somatic chromosome number occurs after telophase II and before egg pronucleus formation, in the ... ...

    Abstract Cytological study revealed that maturation of oocytes of Heterodera betulae is by regular meiosis and reproduction is by parthenogenesis. Restoration of the somatic chromosome number occurs after telophase II and before egg pronucleus formation, in the absence of a mitotic apparatus through a type of endomitotic division. The haploid chromosome number is 12 (2n = 24) in 95% of the female nematodes studied and 13 in the remaining 5%. The phylogenetic relationship of H. betulae with most other Heterodera species having n = 9 is not clear.
    Language English
    Publishing date 2009-03-26
    Publishing country United States
    Document type Journal Article
    ZDB-ID 410426-2
    ISSN 0022-300X
    ISSN 0022-300X
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  9. Article: Oogenesis and the Chromosomes of the Cystoid Nematode, Meloidodera floridensis.

    Triantaphyllou, A C

    Journal of nematology

    2009  Volume 3, Issue 2, Page(s) 183–188

    Abstract: Three Meloidodera floridensis populations of different geographic or host origin all reproduced by mitotic parthenogenesis. One of them from pine had a somatic chromosome number of 26, whereas, another population from pine and one from azalea had 2n = 27 ...

    Abstract Three Meloidodera floridensis populations of different geographic or host origin all reproduced by mitotic parthenogenesis. One of them from pine had a somatic chromosome number of 26, whereas, another population from pine and one from azalea had 2n = 27 chromosomes. All are considered to be triploid forms derived from an amphimictic ancestor with n = 9 chromosomes, the basic number in the closely related genus Heterodera. Evidence is presented which suggests that during division the chromosomes of the germ-line cells of the developing embryo behave differently than the chromosomes of all other blastomeres.
    Language English
    Publishing date 2009-03-26
    Publishing country United States
    Document type Journal Article
    ZDB-ID 410426-2
    ISSN 0022-300X
    ISSN 0022-300X
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  10. Article: Gametogenesis and the Chromosomes of Two Root-knot Nematodes, Meloidogyne graminicola and M. naasi.

    Triantaphyllou, A C

    Journal of nematology

    2009  Volume 1, Issue 1, Page(s) 62–71

    Abstract: Oogenesis and spermatogenesis were studied in populations of M. graminicola and M. naasi from which the species were originally described. Maturation of oocytes and spermatocytes in both species was by normal meiosis. The haploid chromosome number ... ...

    Abstract Oogenesis and spermatogenesis were studied in populations of M. graminicola and M. naasi from which the species were originally described. Maturation of oocytes and spermatocytes in both species was by normal meiosis. The haploid chromosome number determined during the first and second maturation divisions was n = 18 with no variation. The somatic chromosome number determined in early cleavage divisions and, to a limited extent, in oogonial divisions was 2n = 36. Reproduction was regularly by meiotic parthenogenesis in both species. Re-establishment of the somatic chromosome number in mature oocytes, apparently took place through fusion of the second polar nucleus with the egg pronucleus. Occasional reproduction by cross-fertilization was demonstrated in M. graminicola and it is suspected in M. naasi in cultures with abundant males. Phylogenetic relationships in the family Heteroderidae are discussed in the light of the new cytological information. The peculiar behavior of nucleoli persisting during metaphase, anaphase and telophase of cleavage divisions is reported.
    Language English
    Publishing date 2009-03-27
    Publishing country United States
    Document type Journal Article
    ZDB-ID 410426-2
    ISSN 0022-300X
    ISSN 0022-300X
    Database MEDical Literature Analysis and Retrieval System OnLINE

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