Flow Cytometry and a Thioredoxin-like Gene: Useful Tools to Identify Poa Arachnifera x Poa Pratensis Interspecific Hybrids.

Phenotypic assessment of Poa arachnifera x Poa pratensis hybrids can be time consuming and sometimes unreliable. Here we demonstrate the utility of flow cytometry and the trx gene as useful tools in the identification of P. arachnifera x P. pratensis hybrids.  Flow cytometry results show that interspecific hybrids have an intermediate nuclear DNA content to each of their polyploid parents. Furthermore, a wide range of 2C nuclear DNA content was observed among 19 different ecotypes of P. arachnifera collected from northern, central, and southeastern Texas. Statistical analysis suggests at least 3 distinct groups of ploidy within P. arachnifera.  Phylogenetic analyses of the trx sequences from P. arachnifera x P. pratensis hybrids demonstrate their sequence similarity and clustering with trx sequences from both parents. In particular, a unique 851 bp allele was found to be uniformly present among 38 P. arachnifera ecotypes and 25 hybrids from 9 different pedigrees. Amplification of this band in cultivars of P. pratensis from different morphological classes will be presented.  This allele is characterized by a 163 bp insertion within the intron region that folds to form a hairpin loop. Results of the miRBase search show sequence similarity of the stem loop structure of the insertion region with micro RNA from sorghum, wheat, rice, and barley suggesting a potential role as a precursor to a micro RNA.