Karyotype asymmetry in Cynodon Rich. (Poaceae) accessions

Abstract

Cynodon is a genus of plants with forage potential that has attracted the interest of breeders. These species have high morphological variability in a large number of varieties and cytotypes, hampering identification. This study aimed to determine the karyotype asymmetry index among accessions of Cynodon to discriminate between them. Karyotype symmetry was based on three estimates, which were compared. The basic number for the genus is x = 9. The results of the chromosome count and DNA quantification, respectively, were as follows: two diploid accessions (2n = 2x = 18 and 1.08 ± 0.094 to 1.17 ± 0.036 pg DNA and ± standard deviation), one triploid accession (2n = 3x = 27 and 1.63 ± 0.017 pg DNA), four tetraploid accessions (2n = 4x = 36 and 1.88 ± 0.069 to 2.10 ± 0.07 pg DNA), and one pentaploid accession (2n = 5x = 45 and 2.55 ± 0.098 pg DNA). C. incompletus var. hirsutus had the longest total length of the haploid lot (29.05 µm), with chromosomes that ranged from 1.7 to 6.2 µm in length. On the basis of the karyotype asymmetry indices, the accessions were divided into two groups: 1) C. dactylon var. dactylon, C. transvaalensis, C. dactylon var. polevansii, three accessions of Cynodon sp, and C. nlemfuensis; and 2) C. incompletus var. hirsutus. This is the first description of tetraploidy in C. transvaalensis. The karyotypic data facilitated a determination of the degree of proximity between the accessions.

Sequence-based genetic mapping of Cynodon dactylon Pers. reveals new insights into genome evolution in Poaceae

“…The base chromosome number of Cynodon species is x = 9 8 . A series of euploidies including diploid (2x = 18), triploid (3x = 27), tetraploid (4x = 36), pentaploid (5x = 45), and hexaploid (6x = 54) have been reported in the genus with samples collected worldwide over the past century 8 – 16 . Nevertheless, tetraploid is the predominant ploidy in C. dactylon var.…”

Molecular Cytogenetic Characterization of the Native Forage GrassTrichloris crinita

“…These values are comparable with those reported in Cynodon dactylon (L.) Pers., a close relative of T. crinita , with ranges of 1 to 2 (Christopher and Abraham, 1974) and 2 to 3 μm (Thomas and Murray, 1978). A broader range of 1.7 to 6.2 μm was found when other Cynodon species were analyzed (Chiavegatto et al, 2016). In Eleusine , a closely related genus of Trichloris , karyotypes in wild and cultivated species were described, reporting chromosome sizes similar to T. crinita (in the present work) in E. coracana and E. indica (Hiremath and Chennaveeraiah, 1982).…”

“…According to Stebbins (1971), symmetric karyotypes are primitive and typical of species phylogenetically "more basal," whereas a reduced number of metacentric chromosomes and increasing asymmetry can be in general regarded as an evolutionarily derived state (Levin, 2002). Symmetric karyotypes are also found in other Chloridoideae genera like Munroa (Amarilla et al, 2015), Cynodon (Chiavegatto et al, 2016), and Muhlenbergia (Carrillo et al, 2013).…”

Evaluation of bermudagrass [Cynodon (L.) Rich] accessions with different ploidy levels

“…also divided Cynodon into two groups, one involving C. dactylon and C. transvaalensis, and the other C. incompletus (Chiavegatto et al, 2016). For confirmation, iPBS fragments representing four different primer products were cloned and sequenced (Table 2).…”