Divergent Selection for Seed Ability to Germinate at Extreme Temperatures in Perennial Ryegrass (Lolium perenne L.)

Abstract

Various adaptive mechanisms can ensure that seedlings are established at the most favourable time and place. These mechanisms include seed dormancy i.e., incapacity to germinate in any environment without a specific environmental trigger and inhibition i.e., incapacity to germinate in an unfavourable environment (water availability, temperature: thermoinhibition and light). The objective of this research was to study in the temperate range for germination of forage and turf grass species perennial ryegrass, if the thermal requirements for germination are under genetic controlled and could be selectively bred. Two divergent selections of three cycles were realized on a natural population: one to select for the capacity to germinate at 10°C vs. the impossibility to germinate at 10°C, and one to select for the capacity to germinate at 32°C vs. the impossibility to germinate at 32°C. Seeds of all the lots obtained from the two divergent selections were then germinated at constant temperatures from 5 to 35°C to evaluate their germination ability. Concerning the positive selection, the first cycle of positive selection at 10°C was highly efficient with a very strong increase in the germination percentage. However, afterward no selection effect was observed during the next two cycles of positive selection. By contrast, the positive selection at 32°C was efficient during all cycles with a linear increase of the percentage of germination at 32°C. Concerning the negative selection, we observed only a large positive effect of the first cycle of selection at 10°C. These findings demonstrate that seed thermoinhibition at 10 and 32°C observed in a natural population of perennial ryegrass has a genetic basis and a single recessive gene seems to be involved at 10°C.

Unexpected Intraspecific Variability of Perennial Ryegrass (Lolium perenne L.) in Response to Constant Temperature During Germination and Initial Heterotrophic Growth

“…Germination is a complex biological process influenced by genetic and environmental factors including temperature (Shafii and Price, 2001). However, the genetic diversity of response to temperature during seed germination of pasture species has received little attention (Volaire et al, 2016;Ahmed et al, 2019;Ghaleb et al, 2021Ghaleb et al, , 2022. A similar situation is observed for the study of initial heterotrophic growth in general (Escobar-Gutiérrez et al, 1998a,b) and of pastures in particular (Ahmed, 2015).…”

“…The results presented here reveal, for the first time, high genetic variability within L. perenne germplasm for the response to temperature in the initial life phases. We have recently shown that the response of germination to temperature is at least partially controlled genetically (Ghaleb et al, 2022). Thus, the newly discovered genetic variability should serve breeders to create perennial ryegrass varieties for the future.…”

“…Thus, breeding perennial ryegrass cultivars adapted to new ranges of temperature could be necessary under most climate change scenarios. However, before any breeding effort in such a direction, an account of the intraspecific variability of responses to temperature is essential (Ghaleb et al, 2021(Ghaleb et al, , 2022. Seed germination (Ahmed et al, 2019;Ghaleb et al, 2021) and early heterotrophic growth (Escobar-Gutiérrez et al, 1998a,b;Ahmed, 2015) in response to temperature can be used as an early marker for selecting promising material.…”

Tall Fescue (Festuca arundinacea Schreb.) Shows Intraspecific Variability in Response to Temperature during Germination

“…The rates of chemical and biochemical reactions, as well as the rates of cell growth and plant functioning, all depend on the temperature [6,7]. The relationship between seed germination and temperature has been extensively studied [2,8], and several mathematical models have been proposed to describe such a relationship that can be expressed in terms of the cardinal temperatures [9][10][11][12].…”

“…The analysis of intraspecific genetic diversity is crucial for its conservation [5] and utilization [12]. However, as for many other species, published knowledge is scarce concerning the intraspecific variability of tall fescue in response to climate factors, particularly to temperature during germination and early growth [7].…”