Changes in plant morphological expression in 12 perennial ryegrass cultivars following frequent and infrequent cutting management

Abstract

SUMMARYPerennial ryegrass (Lolium perenne L.) cultivars are out-breeding populations of differing phenotypes, potentially allowing for directional selection to occur after sowing. To investigate this, the morphology of individual space plants (i.e. isolated plants sown at 0·75 m row spaces) grown from tillers extracted from single-cultivar swards subjected to frequent cutting (FC) or infrequent cutting (IC) for 5 years (aged accessions) were compared with plants grown from seed (seed accessions). The study examined 12 cultivars, creating 36 ‘accessions’ of 80 plants in each. These plants were examined for 23 morphological measurements to test for and classify directional selection in perennial ryegrass swards. A high degree of separation was achieved between the 12 seed accessions, validating the discriminating power of the experiment. Changes in morphological expression of plants taken from swards indicated selection in favour of particular morphological ideotypes. This directional selection was identified in 10 of the accessions subjected to FC and eight subjected to IC management. Emergence natural height (plant undisturbed height at inflorescence emergence) and plant volume (emergence width × emergence natural height) were the characters modified most between seed and aged accessions. The magnitude of these morphological changes varied between cultivars. Glencar had the greatest number of morphological characters exhibiting directional selection under frequent cutting, whereas Greengold had the greatest number exhibiting directional selection under infrequent cutting. The plants grown from aged swards were also smaller than the seed accessions in all characters, raising the possibility that they may also be less productive. The present study showed that sward management can cause and influence directional selection of plants from within the morphological range of expression within perennial ryegrass cultivars.

Effects of pasture age on the genotype and phenotype of perennial ryegrass

“…The shorter lamina lengths in the field survivors compared with plants freshly grown from remnant seed that was observed in the first controlled experiment were not unexpected. Cashman, Gilliland, McEvoy, Watson, and O'Donovan (2016) reported that ryegrass cultivars grown from aged swards were smaller than the same cultivar grown from seed. The leaves on ryegrass ecotypes from New Zealand hill pastures were on average 20% shorter than on six ryegrass cultivar controls grown from seed (Wedderburn et al, 1989).…”

Identifying morphological traits associated with vegetative persistence in the perennial ryegrass (Lolium perenne L.) cultivar 'Grasslands Samson'

“…Whether this difference was due to a genetic shift has been studied. Cashman (2014) was not able to distinguish between 'aged' and 'seed' accessions of any plants sampled directly from the 12 cultivars at the Poukawa site assessed in a spaced plant trial in Hamilton. Conversely, O'Connor et al (2020) did identify additive genetic differences associated with grazing avoidance traits between half-sib families generated from plants of 'Grasslands Samson' sourced from Poukawa and their commercially bought seed counterparts in a grazed row field trial undertaken in Palmerston North.…”

“…The study found 'Grasslands Samson' was more subject to directional selection. Cashman et al (2016) assessed phenotypic characters of 'aged' and 'seed' accessions of European and New Zealand ('Alto', 'Arrow', and 'Bealey') cultivars in a sown plot field trial in Fermoy, Ireland. They also found the direction and magnitude of change between 'aged' and 'seed' accessions was cultivar dependant.…”

Evaluation of the Relationship between Cultivar, Endophyte and Environment on the Expression of Persistence in Perennial Ryegrass Populations Using High-Throughput Phenotyping

“…Over time, the selected population may have undergone selection pressure, leading to the development of stronger genotypes that exhibit higher dry matter yields, greater ground cover, increased plant survival, and taller plant height. Adaption of the selected population explains its superior performance in terms of these phenotypic traits [55]. Additionally, the harvesting year was identified as a short-term environmental influence on the expression of plant phenotypic traits.…”

“…The occurrence and performance of endophytes can be influenced by plant genotype and environmental factors, and the genomic information of endophytes can undergo changes through natural selection [55]. Thus, the observed persistence of perennial ryegrass can be influenced by the interaction between endophytes and the environment and between cultivars and the environment.…”