Adjusting to Increased Temperature and Salinity Associated With Climate Change: Phenotypic Response and Genetic Variation for Seed Germination and Seedling Growth in Alfalfa

Abstract

Seed germination and seedling growth represent two vulnerable stages in a plant life cycle and it is important to determine how they will be affected by environmental changes associated with climate change. This study examines the impact of salinity levels (0, 50, 100, and 150 mM) at each of three temperatures (15, 25, and 35˚C) on seed germination and radicle growth for three dormant and three non-dormant varieties of conventional, glyphosate resistant, or reduced lignin alfalfa. The genetic basis and phenotypic plasticity for seed germination and seedling growth in response to salinity and temperature were determined. Both traits were phenotypically plastic with respect to temperature and salinity. Seed germination was 87.0% ± 1.7 at 25˚C, 0mM (no salinity), but decreased to 33.9% ± 3.9 germination at 35˚C and 150mM. Radicle length went from 36.7 ± 1.5 mm after four days at 25˚C, 0mM, to 10.5 ± 0.7 mm at 35˚C, 150mM. The phenotypic response brought seed germination and radicle length away from their optimum, but we detected standing genetic variation for both seed germination and radicle length. Selection to increase both traits at high temperature and salinity would facilitate alfalfa establishment under climate change.