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

Abstract

Perennial ryegrass (Lolium perenne L.) vegetative persistence (maintained herbage growth and survival without reseeding) is an important economic trait for farmers in New Zealand as it decreases the frequency of reseeding pastures. Vegetative persistence is difficult to breed for due to a lack of long-term trials to observe the complex interactions between plant genotype and the environment. In a long-term trial a genetic shift in the sown cultivar population could occur as individual plants with advantageous traits outcompete other plants and survive. The objectives of our study were to investigate the occurrence of a potential genetic shift in a sample (30 plants) of a persistent population of ‘Grasslands Samson’ perennial ryegrass. Persistent plants were collected from a nine-year-old trial at Poukawa, Hawke's Bay. To identify a genetic shift, these plants were compared to a sample of 30 plants sourced from commercial seed of ‘Grasslands Samson’ representing the original population. This study estimated genotypic variation within and between the populations for eight morphological traits after 10 weeks' growth under glasshouse conditions. Phenotypic and genotypic correlations between the traits were estimated. Results showed that the persistent population had significantly (P<0.05) greater means for tiller number, reproductive tiller number, lamina sheath length, and dry weight. Future research studying these traits across farm environments would further understanding of their roles in vegetative persistence of ryegrass.

Plant-Mediated Behavioural Avoidance of a Weevil Towards Its Biological Control Agent

“…Lolium perenne pastures such as Samson are distributed across New Zealand and are favoured by farmers due to their persistence arising from their continuous production of secondary tillers ( O’Connor et al, 2020 ). As mentioned above, in the 1990s, parasitism levels were often around 75% ( Barker, 2013 ; Goldson and Tomasetto, 2016 ); however, these have now reduced to as little as ca.…”

Persistence of the yield advantage of perennial ryegrass cultivars: concept, evidence and implications

“…Plants such as ryegrass may exhibit differences in growth strategy during the life cycle of a pasture. Parsons et al (2011) proposed that in the early stages post-sowing, plants may be released to some degree from the C and N costs of 'infrastructure' such as tillers, roots and storage organs necessary to survive under fluctuating and often sub-optimal conditions for growth (including grazing). Ryegrass plants in old pastures develop a complex morphological structure including significant basal stem and internode tissue on both vegetative and reproductive tillers (Brock & Fletcher 1993), all of which carries associated maintenance energy costs.…”

“…Yield decline post-sowing is often equated to loss of pasture 'persistence' which Parsons et al (2011) noted may be due to i) depletion of the physical population of plants that established when the new pasture was sown (i.e., plant mortality rates exceed plant recruitment rates, e.g., Lee et al 2017a) or ii) a decline over time within the surviving population in the expression of the initial yield advantage trait. In the latter case, the initial yield advantage could be the result of soil disturbance during cultivation releasing nitrogen (N) through mineralisation.…”

“…In the latter case, the initial yield advantage could be the result of soil disturbance during cultivation releasing nitrogen (N) through mineralisation. The release of plants from the need to build infrastructure such as an extensive root system or storage capacity for carbon (C) and N to optimise their long-term 'fitness' under fluctuating environmental conditions has also been implicated (Parsons et al 2011). Both of these are transient effects.…”