Flow cytometry-based determination of ploidy from dried leaf specimens in genomically complex collections of the tropical forage grass Urochloa s. l

Abstract

We aimed to develop an optimized approach to determine ploidy for dried leaf material in a germplasm collection of a tropical forage grass group, including approaches to collect, dry and preserve plant samples for flow cytometry analysis. Urochloa (including Brachiaria, Megathyrus and some Panicum) tropical grasses are native to Africa and are now, after selection and breeding, planted worldwide, particularly in South America, as important forages with huge potential for further sustainable improvement and conservation of grasslands. The methods enable robust identification of ploidy levels (coefficient of variation, CV, typically <5%). Ploidy of some 353 forage grass accessions (ploidy range from 2 to 9), from international genetic resource collections, showing variation in basic chromosome numbers and reproduction modes (apomixis and sexual), were determined using our defined standard protocol. Two major Urochloa agamic complexes used in the current breeding programs at CIAT and EMBRAPA: the ' brizantha' and 'humidicola' agamic complexes are variable, with multiple ploidy levels and DNA content. U. brizantha has odd level of ploidy (x=5), and the relative differences in nuclear DNA content between adjacent cytotypes is reduced, thus more precise examination of this species is required. Ploidy measurement of U. humidicola revealed some aneuploidy.

The five Urochloa spp. used in development of tropical forage cultivars originate from defined subpopulations with differentiated gene pools

“…Megathyrsus maximus ). Species identity and ploidy were previously determined using plant architecture traits and flow cytometry of fluorescently stained nuclei (Tomaszewska et al, 2021a, Tomaszewska et al, 2021b). The country of origin of 92 accessions was known and for 75 accessions we also knew the collection coordinates (Fig.…”

“…Urochloa spp. show varying ploidy levels and sub-genome compositions (Do Valle and Savidan, 1996, Keller-Grein et al, 1996, Tomaszewska et al, 2021b, Tomaszewska et al, 2021a), which likely result in a highly diverse gene pool that can be leveraged for continued improvement through breeding. Exploiting sub-genome variability among species and ploidy levels has been highly successful in the improvement of other crop tribes, such as Triticeae and Brassicaceae (Gale and Miller, 1987, Burton et al, 2004, Ali et al, 2016).…”

Variability of pollen grains quality in oat amphiploids and their parental species

“…(Guohua et al 2009) and Bothriochloa Kuntze (Ma and Huang 2007). All of these genera include species showing high ploidy levels (Higgins et al 2021; Tomaszewska et al 2021a,b). It can be concluded that formation of multiporate pollen is associated with young allopolyploids and the interaction of various genomes in the nucleus, whereas apomictic reproduction allows the population to function with a generative defect.…”

Genome size evolution in the beetle genusDiabrotica

“…The copyright holder for this preprint this version posted September 6, 2021. ; https://doi.org/10.1101/2021.09.04.458993 doi: bioRxiv preprint considered appropriate for accurate genome size estimates (Dolezel et al, 2007;Tomaszewska et al, 2021) undecimpunctata ( n = 50) were collected from maize fields near Ames, Iowa, and Monmouth, Illinois, respectively. Each sample was pooled by species, flash-frozen in liquid nitrogen and ground in liquid nitrogen, and then DNA extracted from ~3.0 mg of tissue using the Qiagen DNeasy Blood and Tissue Extraction kit, with modifications as described (Coates et al, 2014).…”