Flow Cytometry-Based Determination of Ploidy from Dried Leaf Specimens in Genomically Complex Collections of the Tropical Forage Grass Urochloa s. l.

Abstract

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. We aimed to develop an optimized approach to determine ploidy of germplasm collection of this tropical forage grass group using dried leaf material, including approaches to collect, dry and preserve plant samples for flow cytometry analysis. Our methods enable robust identification of ploidy levels (coefficient of variation of G0/G1 peaks, CV, typically x to 9 x ), 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 are used in the current breeding programs at CIAT and EMBRAPA: the ' brizantha ' and ' humidicola ' agamic complexes are variable, with multiple ploidy levels. Some U. brizantha accessions have odd level of ploidy (5 x ), and the relative differences in fluorescence values of the peak positions between adjacent cytotypes is reduced, thus more precise examination of this species is required. Ploidy measurement of U. humidicola revealed aneuploidy.

Plant phenotyping relevance

乾燥葉を用いたフローサイトメトリーによる植物の倍数性測定法を最適化し、標準プロトコルとして確立することが研究の中心であるため、植物表現型測定法として採用する。

Code and data availability

The paper's Supplementary Data Table S1 (hosted at the MDPI supplementary URL) contains the paper-specific phenotype measurements: the list of 348 Urochloa accessions with their flow cytometry fluorescence peak positions and G0/G1 CVs. This is a public, directly actionable dataset reproducing the paper's ploidy/phenoty