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 Festulolium over four consecutive months of the growing season and these compared under the same time frame to that of closely related perennial ryegrass (L. perenne) 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 Festulolium hybrids had more extensive root systems in comparison with L. perenne, and this was especially evident at depth. It was shown that the acquisition of extensive root systems in Festulolium hybrids was not dependent on the presence of an entire Festuca genome. On the contrary, the most pronounced effect on root development within the four Festulolium populations studied was observed in the introgression line Bx509, where a single small genome sequence from F. arundinacea had been previously transferred onto its homoeologous site on the long arm of chromosome 3 of an otherwise complete L. perenne genome. This demonstrates that a targeted introgression‐breeding approach may be sufficient to confer a significant improvement in the root morphology in Lolium 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 L. perenne parent control demonstrating that the enhanced root development achieved by the introgression line was without compromise to its agronomic performance.
Highlights
Grass varieties developed and marketed for agricultural use within Europe have hitherto been selected solely on their forage quality, yield, and persistence with little or no regard given to their root growth or architecture
Relevant to the new plant breeding approach has been the emergence of novel Festulolium hybrids that combine the good agronomic attributes of Lolium species with the deep rooting and stress resistance found in various close relatives of the broad-leaved fescue (Festuca) subgenus Schedonorus (Humphreys et al 2014; Kopecky et al, 2016) and as hybrids provide novel opportunities for additional ecosystem service (MacLeod et al, 2013; Humphreys et al, 2014)
Whilst Festulolium hybrids are considered generally to have deeper root systems than Lolium varieties, which may confer them some selective advantage when exposed to water-limiting conditions (Durand et al, 2007), comparisons undertaken have been limited to small experimental genotype numbers and have not incorporated comparisons in root development throughout the growing season
Summary
Grass varieties developed and marketed for agricultural use within Europe have hitherto been selected solely on their forage quality, yield, and persistence with little or no regard given to their root growth or architecture. Grasslands have a fundamental role in ecosystem provision due to their significant land cover, biodiversity, perpetuity over many consecutive years, and location in upland and marginal areas Through their root-soil interactions, grasslands play a major role in river catchments, regulating both rainwater capture and its subsequent release (Humphreys et al 2014; Macleod et al, 2013). Relevant to the new plant breeding approach has been the emergence of novel Festulolium hybrids that combine the good agronomic attributes of Lolium species with the deep rooting and stress resistance found in various close relatives of the broad-leaved fescue (Festuca) subgenus Schedonorus (Humphreys et al 2014; Kopecky et al, 2016) and as hybrids provide novel opportunities for additional ecosystem service (MacLeod et al, 2013; Humphreys et al, 2014). Populations of diploid and tetraploid L. perenne varieties were grown under the same growth conditions and time-frame as representative populations of two diploid Festulolium introgression lines selected for their drought resistance and two amphiploid Festulolium hybrid populations
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