Cytogenetics is complementary to genetic and molecular analysis of plant genome structure and function. Since its beginning it has been mainly used for identification of chromosomes in plant genomes and karyotype construction (karyotyping). The cytological techniques applied to karyotyping should be easy, reproducible, and should be able to identify major structural rearrangements that can occur between chromosomes. Most significant for the progress in plant cytogenetics was the development of the squash method for chromosome preparation (Darlington, 1937), chromosome banding techniques (Caspersson et al., 1968) and in situ hybridization (ISH) techniques (Pardue and Gall, 1969), especially fluorescent in situ hybridization (FISH) (Pinkel et al., 1986). These methods have had a major impact on investigation and understanding of plant genome organisation.

Recent advances in cytology

In Situ Hybridization in Plants — Methods and Application

Haplopappus gracilis (n=2),Haplopappus revenil (n=4), andHaplopappus wigginsii (n=4) are isolated by F1 hybrid sterility due mainly to translocation heterozygosity. There is no evidence that this can be overcome at the diploid level so that introgression can occur among them. They are also separated geographically, but occasional populations ofH. gracilis andH. ravenil may be brought together along roadways to form sterile hybrids. There were no statistically significant differences in nuclear DNA content among the same or structurally different aneuploidn=2 andn=3 chromosome races or ecotypes ofH. gracilis. Some of theH. gracilis races were not significantly different from one race of the ancestralH. ravenii, and these samples of both species were from plants growing on poor soils in contrast to accessions from normal habitats. How much and which classes of DNA in these species are subject to changes induced by environmental effects is not known. There were no correlations between DNA amounts and altitude, latitude, and longitude.H. wigginsii had a greater amount of DNA per nucleus than eitherH. ravenii orH. gracilis, and its increased DNA content may reflect a more rapid accumulation of noncoding sequences due to facultative self-compatibility not found in the other two species.

background

Aneuploidy, structural chromosome changes, and DNA amounts in the annual taxa of theHaplopappus spinulosus complex

https://www.tandfonline.com/doi/pdf/10.1080/11250005109436852

Corredo cromosomico e spermatogenesi aberrante in Allolohophora caliginosa trapezaides

1.

In einer durch die Kriegsumstande sich selbst uberlassenen Kultur vonVeronica-Arten verschiedener Polyploidiestufen erwiesen sich die hoher Polyploiden gegenuber den Diploiden bzw. niedriger Polyploiden im Konkurrenzkampf uberlegen.




2.

Die gleichchromosomigen Arten und Unterarten der Gruppe sind genetisch gesehen wahrscheinlich nur mendelnde Rassen.




3.

Positiv ausgefallene Kreuzungen zwischen 4x- und 8x-Arten sprechen dafur, das auch die in der Natur vorkommenden hexaploiden Unterarten derV. austriaca durch Kreuzung zwischen der tetraploidenV. prostrata und der octoploidenV. Teucrium hervorgegangen sind.




4.

7x-Pflanzen konnten sowohl durch Kreuzung von 6x- mit 8x-Arten wie auch durch anormale Befruchtung unreduzierter 6x-Eizellen mit x-Pollen erhalten werden.

Recent advances in cytology

Citations

In Situ Hybridization in Plants — Methods and Application

Aneuploidy, structural chromosome changes, and DNA amounts in the annual taxa of theHaplopappus spinulosus complex

Corredo cromosomico e spermatogenesi aberrante in Allolohophora caliginosa trapezaides

Zur Polyploidie und Genetik der Veronica-Gruppe Pentasepala

Experimentelle Untersuchungen in der Sektion Beecabunga Griseb. der Gattung Veronica

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