Anatomical, Physiological and Transcriptomic Insights into Salt Tolerance in Two Peanut Lines with Different Oil Contents

Soil salinization is a significant global challenge that severely impacts agricultural productivity, particularly through its negative effects on crop growth and yield. Peanuts (Arachis hypogaea L.) are an important oil crop. One of the major goals in peanut breeding programs is to develop varieties with both high oil content and salt tolerance. Previously, we obtained a peanut line (HO) with high oil content through mutagenesis, which showed higher salt tolerance than its parental line (HY20). In this study, we employed multiple approaches including anatomical, physiological, and transcriptomic analyses to elucidate salt tolerance mechanisms of the HO peanut line. Under salt stress, the HO line exhibited better-developed vascular structures, with increased root vessel diameter and higher crystal idioblast density in leaves compared to HY20. HO also showed enhanced antioxidant enzyme activities, with POD and SOD activities higher than HY20. Photosynthetic efficiency was substantially improved in HO, with Fv/Fm decreasing under severe salt stress. Additionally, HO maintained a lower Na+/K+ ratio and higher linolenic acid content under salt stress. Transcriptomic analysis revealed up-regulated lignin biosynthesis genes in HO. This study established potential connections between salt stress tolerance and oil biosynthesis in peanuts, providing insights that could be leveraged for the development of high-yield and salt-resistant varieties.