Structural karyotypic variability and polyploidy in natural populations of the South American Lathyrus nervosus Lam. (Fabaceae)

Abstract

Knowledge of the chromosome variation in wild populations is essential to understand the pathways and restrictions of karyotype evolution in plants. The aim of this study is to conduct an intraspecific analysis of the karyotypes by fluorochrome banding and ribosomal DNA (rDNA) loci detection by fluorescent in situ hybridization (FISH) and of the meiotic behaviour in natural populations of Lathyrus nervosus, sect. Notolathyrus. Chromosome banding showed that, despite the high constancy in the karyotype formula and in the rDNA loci among populations, there is intraspecific variation in the amount and distribution pattern of 4',6-diamidino-2-phenylindole (DAPI ? ) heterochromatin. However, those changes were not related to the total chromosome length of the haploid complements. This fact demonstrates that structural chromosome changes may be one of the most important mechanisms for karyotype variation among natural populations of L. nervosus. The chromosome number surveyed at the population level revealed the first case of polyploidy in South American species and the first case of uneven polyploidy of the genus. All the chromosome markers analysed indicated that the polyploids found originated by autopolyploidy. The meiotic analysis showed different chromosome abnormalities that may be generating numerical and structural changes in the sporads. The finding of unreduced gametes that are alive at anthesis suggests sexual polyploidization as the most probable mechanism involved in the origin of these 3x and 4x autopolyploid cytotypes in L. nervosus.

Inferring the mode of origin of polyploid species from next‐generation sequence data

“…Lines represent Loess regression lines for the correct inference of heterosomic inheritance (P(hetero | hetero); solid black line), an inference of tetrasomic inheritance when the correct model was heterosomic (P(tetra | hetero); solid grey line) and an inference of disomic inheritance when the correct model was heterosomic (P(diso | hetero); dashed grey line). each of the homeologous chromosomes group together as expected under autopolyploidy) (Chalup et al 2012). The mode of inheritance discerned by cytogenetic analysis is still frequently used to infer polyploid origin directly (Hardy et al 2000); even though this relationship may be misleading (Le Comber et al 2010).…”

“…Distinguishing between a history of auto‐ vs. allopolyploidy has hitherto required detailed cytogenetic analysis, such as the extraction and staining of metaphasic chromosomes (in order to characterize chromosomal configuration), or cluster analysis (to test whether each of the homeologous chromosomes group together as expected under autopolyploidy) (Chalup et al . ). The mode of inheritance discerned by cytogenetic analysis is still frequently used to infer polyploid origin directly (Hardy et al .…”

Ribosomal DNA localization on Lathyrus species chromosomes by FISH

“…Such divergences have been also detected at the infraspecific level, especially in the extensively studied L. odoratus L. and L. sativus L. [ 53 , 63 , 64 ]. Many cytological studies have been performed to find out the chromosome banding patterns and karyotypes and /or ideograms of some Lathyrus species including L. odoratus , L. articulatus and L. incospicuus L. [ 49 – 52 , 56 ], in previous investigation, the chromosome measurements, karyotype and chromosome banding patterns of six out of the nine studied species ( L. gorgoni Parl, L. hirsutus L., L. amphicarpos L., L. sphaericus Retz, L. paranensis Burkart, and L. nissolia L.) have been studied by [ 52 ]. At the cytogenetical level, FISH was very useful to localize 45S and 5S rRNA genes on other Lathyrus species as well [ 51 , 53 – 58 ].…”

Contributions to cytogenetics of Plectranthus barbatus Andr. (Lamiaceae): a medicinal plant

“…In Lathyrus nervosus Lam. ( Fabaceae ), for example, it was observed karyotypic variations in different populations although the individuals showed the same chromosome number ( Chalup et al 2012 ).…”