Identification of Differential Drought Response Mechanisms in Medicago sativa subsp. sativa and falcata through Comparative Assessments at the Physiological, Biochemical, and Transcriptional Levels.

Stacy D Singer,Abdelali Hannoufa,Surya Acharya,Biruk A Feyissa,Madeline Lehmann,Gaganpreet Kaur Dhariwal,Kazi Kader,Rodrigo Ortega Polo,Kimberley Burton Hughes,Guanqun Chen,Timothy Schwinghamer,Bin Shan,Udaya Subedi

doi:10.3390/plants10102107

Stacy D Singer, Abdelali Hannoufa + Show 11 more

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https://doi.org/10.3390/plants10102107

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Abstract

Alfalfa (Medicago sativa L.) is an extensively grown perennial forage legume, and although it is relatively drought tolerant, it consumes high amounts of water and depends upon irrigation in many regions. Given the progressive decline in water available for irrigation, as well as an escalation in climate change-related droughts, there is a critical need to develop alfalfa cultivars with improved drought resilience. M. sativa subsp. falcata is a close relative of the predominantly cultivated M. sativa subsp. sativa, and certain accessions have been demonstrated to exhibit superior performance under drought. As such, we endeavoured to carry out comparative physiological, biochemical, and transcriptomic evaluations of an as of yet unstudied drought-tolerant M. sativa subsp. falcata accession (PI 641381) and a relatively drought-susceptible M. sativa subsp. sativa cultivar (Beaver) to increase our understanding of the molecular mechanisms behind the enhanced ability of falcata to withstand water deficiency. Our findings indicate that unlike the small number of falcata genotypes assessed previously, falcata PI 641381 may exploit smaller, thicker leaves, as well as an increase in the baseline transcriptional levels of genes encoding particular transcription factors, protective proteins, and enzymes involved in the biosynthesis of stress-related compounds. These findings imply that different falcata accessions/genotypes may employ distinct drought response mechanisms, and the study provides a suite of candidate genes to facilitate the breeding of alfalfa with enhanced drought resilience in the future.

Highlights

Alfalfa (Medicago sativa L.) is one of the most widely grown and valuable perennial forage legumes, with an estimated global cropping area of over 30 million hectares
To assess the extent of differential drought responses between M. sativa subsp. falcata accession PI 641381 and sativa cultivar Beaver, water was withheld from plants, volumetric soil moisture contents were measured daily, and symptoms of stress were monitored
‘Sativa’ plants typically began to wilt when volumetric soil moisture levels reached between 7–9%, while ‘falcata’

Summary

Introduction

Alfalfa (Medicago sativa L.) is one of the most widely grown and valuable perennial forage legumes, with an estimated global cropping area of over 30 million hectares. This popularity stems from the high nutritional value, palatability, environmental adaptability, and biomass yield of alfalfa, as well as its low fertilizer requirements due to its ability to fix nitrogen through symbiosis with rhizobia [1]. While alfalfa is relatively drought tolerant compared to many other crop species as a result of the typical presence of a deep tap root, its production depends upon irrigation in many growing regions, and it consumes a high amount of water due to its long growing season and dense canopy [3]. There is a vital need to develop alfalfa cultivars that use water more efficiently and/or exhibit improved drought resilience compared to current varieties in a timely manner [7,8]

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