Changes in root endogenous hormone levels and rhizosphere fungi diversity in alfalfa under drought stress

Abstract

To explain the relationship between rhizosphere fungal diversity and community composition of alfalfa under drought stress and endogenous hormones in alfalfa, we used sand culture to investigate the performance of Medicago sativa 'Qingshui' (or QS), M. sativa 'Longdong' (or LD), and M. varia 'Gongnong No. 4' (or GN) with contrasting different degrees of drought tolerance. After 7 days of drought stress treatment, we found Ascomycota and Basidiomycota were the dominant fungal groups in all treatments. Drought affected the alpha diversity, Chao1, Pielou-e, Shannon, and Simpson indices in LD were the highest under severe stress, Chao1 index in QS and in GN was highest under moderate stress, whereas Pielou-e, Shannon, and Simpson indices were the highest under their respective controls. With increasing drought stress, gibberellin (GA 3 ) and zeatin (ZA) contents and GA 3 /abscisic acid (ABA) increased rst and then decreased in the roots and were the highest under moderate stress, indole-3-acetic acid (IAA), IAA/ABA, and (IAA + GA 3 + ZA)/ABA were decreased and were the lowest under severe stress, while ABA content was increased in the roots and was the highest under severe stress. The results suggested that GA 3 (12.8%) and GA 3 /ABA (12.7%) were important driving factors for fungal composition.

Metabolomics reveal root differential metabolites of different root-type alfalfa under drought stress

“…After 7 days of stress treatment (July 26, 2021) ( Wang et al., 2023a ), there was a significant change in leaf morphology, with leaf edges wrinkled and some leaves turning yellow and falling off. Then, to start sample collection, first separate the alfalfa roots from the sand and rinse them with distilled water to absorb the surface moisture.…”

“…Many alfalfa varieties are tap-rooted and the gene sources come from Medicago sativa L. Rhizomatous-rooted, branch-rooted, and creeping-rooted alfalfa own the genes of wild M. falcata L. to varying degrees, with have strong resistance to drought and severe cold. Previously, numerous studies have focused on crown characteristics ( Nan et al., 2012 ), root development ability ( Nan et al., 2014 ), stress resistance ( Nan et al., 2011 ), root types, and yield ( Nan et al., 2012 ), and rhizosphere microorganisms of different root-type alfalfa ( Wang et al., 2023a ). However, there were few reports on the root metabolites and phytohormones of different root-type alfalfa under drought stress.…”