Molecular, morphological, and cytological analysis of diverse Brachypodium distachyon inbred lines

Abstract

Brachypodium distachyon (brachypodium) is a small grass with the biological and genomic attributes necessary to serve as a model system for all grasses including small grains and grasses being developed as energy crops (e.g., switchgrass and Miscanthus). To add natural variation to the toolkit available to plant biologists using brachypodium as a model system, it is imperative to establish extensive, well-characterized germplasm collections. The objectives of this study were to collect brachypodium accessions from throughout Turkey and then characterize the molecular (nuclear and organelle genome), morphological, and cytological variation within the collection. We collected 164 lines from 45 diverse geographic regions of Turkey and created 146 inbred lines. The majority of this material (116 of 146 inbred lines) was diploid. The similarity matrix for the diploid lines based on AFLP analysis indicated extensive diversity, with genetic distances ranging from 0.05 to 0.78. Organelle genome diversity, on the other hand, was low both among and within the lines used in this study. The geographic distribution of genotypes was not significantly correlated with either nuclear or organelle genome variation for the genotypes studied. Phenotypic characterization of the lines showed extensive variation in flowering time (7-22 weeks), seed production (4-193 seeds/plant), and biomass (15-77 g). Chromosome morphology of the collected brachypodium accessions varied from submetacentric to metacentric, except for chromosome 5, which was acrocentric. The diverse brachypodium lines developed in this study will allow experimental approaches dependent upon natural variation to be applied to this new model grass. These results will also help efforts to have a better understanding of complex large genomes (i.e., wheat, barley, and switchgrass).