Occurrence and detection of chimeral sectors in leaf tissue of novel Lolium multiflorum x L. arundinaceum hybrids

Authors: Kindiger, Bryan

Submitted to: Journal of Horticulture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/9/2021
Publication Date: 12/15/2021
Citation: Kindiger, B.K. 2021. Occurrence and detection of chimeral sectors in leaf tissue of novel Lolium multiflorum x L. arundinaceum hybrids. Journal of Horticulture. 8(7). Article 299.

Interpretive Summary: A novel diploid, annual ryegrass line has been previously observed to induce genome instability and genome loss following its hybridization with tall fescue. This genome loss behavior results in sectoring within the leaf tissue of the hybrid plants. The early visual observation of sectors in these hybrids has suggested that a form of mitotic chromosome or genome loss was responsible for the recovery of the annual ryegrass and tall fescue homozygous, inbred lines from these hybrids. Flow cytometry, a technology that can be used to estimate the genome size and the genome constitution at a cell nuclei level, was applied to examine the occurrence of sectors in these hybrids. The evaluation of leaf nuclei from twenty-one F1 hybrids were submitted to flow cytometry and the results indicate the generation of numerous sectors which correspond to a high level of mitotic genome instability. The flow cytometry examination of the hybrid leaf tissue also provided information regarding the type and degree of genome loss in these hybrids. These examinations provide additional evidence that mitotic instability represents the definitive cause for genome loss and subsequent homozygous, inbred line generation in these materials. A comparison regarding the frequency of sectoring across the various tall fescue germplasm, as well as a comparison of greenhouse vs field nursery growing conditions, did not suggest any positive or negative influences on levels of leaf sectoring.

Technical Abstract: A novel diploid, Lolium multiflorum line has previously been observed to induce genome loss and dihaploid generation following hybridization with hexaploid, L. arundinaceum. The early observation of chimeral sectors in these F1 has suggested a form of mitotic chromosome or genome loss was one behavior responsible for the recovery of the L. multiflorum or L. arundinaceum dihaploids. Flow cytometry represents a methodology that can be applied to estimate genome size, but also ongoing genome loss or instability. An evaluation extracted leaf nuclei from twenty-one F1 hybrids were submitted to flow cytometry to obtain ploidy estimations and observe the occurrence of plant sectoring. Results of the analysis suggest a high degree of mitotic genome instability in the leaf tissue sections, providing additional evidence that mitotic instability represents the definitive cause for genome loss and subsequent dihaploid generation in these materials. A comparison on the frequency of sectoring across the various L. arundinaceum genotypes, among greenhouse and field grown plants and their respective growing conditions did not indicate any obvious differences.