Root imaging showing comparisons in root distribution and ontogeny in novel <i>Festulolium</i> populations and closely related perennial ryegrass varieties

Abstract

The incorporation of new sophisticated phenotyping technologies within a crop improvement program allows for a plant breeding strategy that can include selections for major root traits previously inaccessible due to the challenges in their phenotype assessment. High-throughput precision phenotyping technology is employed to evaluate root ontogeny and progressive changes to root architecture of both novel amphiploid and introgression lines of <i>Festulolium</i> over four consecutive months of the growing season and these compared under the same time frame to that of closely related perennial ryegrass (<i>L. perenne</i>) varieties. Root imaging using conventional photography and assembled multiple merged images was used to compare frequencies in root number, their distribution within 0-20 and 20-40 cm depths within soil columns, and progressive changes over time. The <i>Festulolium</i> hybrids had more extensive root systems in comparison with <i>L. perenne</i>, and this was especially evident at depth. It was shown that the acquisition of extensive root systems in <i>Festulolium</i> hybrids was not dependent on the presence of an entire <i>Festuca</i> genome. On the contrary, the most pronounced effect on root development within the four <i>Festulolium</i> populations studied was observed in the introgression line Bx509, where a single small genome sequence from <i>F. arundinacea</i> had been previously transferred onto its homoeologous site on the long arm of chromosome 3 of an otherwise complete <i>L. perenne</i> genome. This demonstrates that a targeted introgression-breeding approach may be sufficient to confer a significant improvement in the root morphology in <i>Lolium</i> without a significant compromise to its genome integrity. The forage production of Bx509 was either higher (months 1-3) or equivalent to (month 4) that of its <i>L. perenne</i> parent control demonstrating that the enhanced root development achieved by the introgression line was without compromise to its agronomic performance.