Tetraploid races of Paspalum notatum show polysomic inheritance and preferential chromosome pairing around the apospory-controlling locus

Abstract

The objective of this work was to determine the type of inheritance (disomic/polysomic) in tetraploid (2 n=4 x=40) Paspalum notatum and investigate the transmission pattern of the chromosome region associated with apospory. An F(1) family segregating for the reproductive mode (aposporous vs non-aposporous) was generated by crossing a tetraploid sexual plant as female parent with an apomictic individual as pollen donor. Pollen mother cells from both parental plants were examined to ascertain chromosome-pairing behavior at meiosis. The high rate of quadrivalent chromosome associations indicated an autotetraploid origin of the species, although bivalent pairing and occasional univalents were detected. The observation of a lagging bivalent, a bridge of chromatin, or two aligned laggards in the aposporous parent suggested a chromosome inversion in this strain. Segregation ratios of AFLP markers and the proportion of linkages in repulsion versus coupling phase denoted tetrasomic inheritance, but markers displaying disomic ratios were also observed. Preferential chromosome pairing (disomic inheritance) in the chromosome segment related to apospory was detected. The possible relationship between a chromosome rearrangement and the inheritance of apospory is discussed.

Cytoembryological evaluation, meiotic behavior and pollen viability of Paspalum notatum tetraploidized plants

“…In telophase I, both apomictic and sexual accessions presented chromosomes clustered in the poles of the cells, as well as small size micronuclei, suggesting they were composed of chromosome fragments. It can be inferred that meiotic behavior is characteristic of each genotype, as previously reported by Stein et al (2004) for the species. Pessim et al (2010) observed high meiotic stability in hybrid genotypes and parents of P. maximum, with abnormalities ranging from 6.7 to 14.2%, such as irregular chromosome segregation, chromosome stickiness, and absence of cytokinesis.…”

Determination of the mode of reproduction of bahiagrass hybrids using cytoembryological analysis and molecular markers

“…Contrary to that found in this study, Fortes et al (2004) mentioned that this distortion had been found responsible for values of 4.3:1 (sexual:apomictic), differing from the expected 1:1. Martínez et al (2001) found values of 2.8:1 (sexual: apomictic), while the work of Stein et al (2004) found 6.5:1 (sexual:apomictic). All these studies were conducted with Paspalum notatum genotypes.…”

Molecular cytogenetics and DNA sequence analysis of an apomixis-linked BAC in Paspalum simplex reveal a non pericentromere location and partial microcolinearity with rice

“…This core region underwent intense rearrangement that in the species P. notatum was indentified as a translocation that locally interrupted synteny of rice markers. On a cytological study of the same species, a meiotic abnormality typical of an inversion was detected (Stein et al 2004). Although translocation and a subsequent inversion might have occurred simultaneously or even at different times, a common feature in the apomictic Paspalum species analysed is that the ACL has been inherited as an alien and highly rearranged chromosome region.…”