Resistance of Multiple Diploid and Tetraploid Perennial Ryegrass (Lolium perenne L.) Varieties to Three Projected Drought Scenarios for the UK in 2080

Mark Lee,Michael Chester,Victoria Howard-Andrews

doi:10.3390/agronomy9030159

Mark Lee, Michael Chester + Show 1 more

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https://doi.org/10.3390/agronomy9030159

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Abstract

Forage plants underpin the livestock industry. Selective breeding, including polyploidization, where genome size is increased by whole genome duplication, changes the productivity and stress tolerance of new varieties. We conducted a growth chamber experiment to investigate the likely responses of Lolium perenne L. to drought, testing four diploid and four tetraploid varieties. We simulated projected spring and summer temperatures for the South-West of England in 2080, applying three projected rainfall scenarios, which varied in drought severity. Drought caused a reduction in productivity, but there was substantial variation between varieties (up to 82%), with the optimal variety changing depending on drought severity. Across three harvests, productivity declined by 43% and 27% (dry biomass) for the severe and likely drought scenarios, respectively. In the final harvest, tetraploids exhibited a greater biomass under severe drought, whereas diploids had a greater biomass under the current rainfall and likely drought scenarios. Longer stomata were observed in tetraploids; however, stomatal conductance was not significantly different between ploidy levels. Trait selection will be important for future drought adaptation. Local climate projections will need to be consulted when selecting L. perenne varieties to tolerate the spatially variable reductions in future rainfall.

Highlights

IntroductionPlant breeding, including polyploidization (whole genome duplication), has sought to increase forage plant yields, nutritive values, and seed set
Plant breeding, including polyploidization, has sought to increase forage plant yields, nutritive values, and seed set
Mean fresh biomass (−39%), dry biomass (−27%), and plant water content (−9%) declined under the likely drought scenario across all three harvests when compared with the current rainfall control (Table 1)

Summary

Introduction

Plant breeding, including polyploidization (whole genome duplication), has sought to increase forage plant yields, nutritive values, and seed set. Forage plants are very likely to be growing in different conditions than they are today. Droughts may lead to a decline in forage productivity (defined as the rate of production of new biomass over a defined time period) and different varieties may be better adapted to future growing conditions [2]. Tetraploid perennial ryegrass varieties have been marketed as offering superior characteristics, including being more tolerant of drought; experiments comparing diploid and tetraploid varieties have provided mixed results. Total plant biomass was compared for different ploidy levels of the same variety of L. perenne and no significant differences in response to reduced soil moisture or severe defoliation were detected [3]. There are several other traits which may modulate drought resistance, including leaf size, crown diameter, plant height, leaf:stem ratio, and root architecture [5]

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