Effects of Autotoxicity on Alfalfa (Medicago sativa): Seed Germination, Oxidative Damage and Lipid Peroxidation of Seedlings

Xiao-Yan Zhang,Chang-Ning Li,Shang-Li Shi,Wen-Juan Kang,Yun A,Guo-Li Yin,Xiao-Long Li,Cui-Mei Zhang

doi:10.3390/agronomy11061027

Abstract

Alfalfa (Medicago sativa) is a highly valuable perennial forage legume that suffers from autotoxicity, which decreases plant resistance, reduces soil fertility, causes serious soil-borne diseases, and promotes ecological imbalance. We evaluated the effects of autotoxicity on the seed germination of 22 alfalfa varieties, and then elucidated the oxidative damage and lipid peroxidation in two alfalfa varieties with contrasting autotoxicity tolerances. The technique for order of preference by similarity to ideal solution (TOPSIS) method was used to rank the germination of the 22 alfalfa varieties when exposed to six autotoxic concentrations (0, 0.025, 0.075, 0.125, 0.175, and 0.225 g∙mL−1). We found WL656HQ and 3105C to be autotoxicity-tolerant and autotoxicity-sensitive varieties, respectively. The germination index mainly affects the comprehensive allelopathic index of WL656HQ and 3105C, which were the simple vigor index and radicle length according to the random forest model, respectively. 3105C eliminates reactive oxygen species (ROS) via antioxidant enzymes and antioxidants under T1 (0.025 g∙mL−1), but the oxidative stress system and the oxidative scavenging system cannot maintain the balance under T2 (0.125 g∙mL−1), causing oxidative bursts. In comparison, WL656HQ used its oxidative scavenging system (peroxidase (POD), ascorbate peroxidase (APX), and glutathione reductase (GR)) to maintain its redox dynamic balance by removing excess ROS at all concentrations. In conclusion, the positive and negative indicators of autotoxicity for the two varieties were ascorbate (ASA) and hydroxyl free radicals (OH•), and proline (Pro) and dehydroascrobate (DHA), respectively. The most sensitive autotoxic concentrations of 3105C and WL656HQ were T2 (0.125 g∙mL−1) and T1 (0.025 g∙mL−1), respectively.

Highlights

Legumes comprise one of the largest plant families on Earth [1]
We found that the autotoxicity of 22 alfalfa varieties had significantly different effects on seed germination
More long-term research is needed to evaluate the autotoxicity of different varieties of alfalfa in field conditions In Stage 1, we determined that autotoxicity has three main effects

Summary

Introduction

Legumes comprise one of the largest plant families on Earth [1]. Alfalfa (Medicago sativa) is a perennial forage legume with high nutritive values, high yield, and strong adaptability and is widely used as a high-quality livestock feed. As the quality of life in China has improved with rapid economic development, the demand for high-protein foods has increased in recent years. This has promoted the rapid development of high-quality forage, and a sharp increase in alfalfa demand [3]. The primary method to cultivate alfalfa is via single, intensive production. This large-scale continuous cropping method has led to increasingly difficult production obstacles. The greatest of these are autotoxic effects, which is a major problem in sustainable animal husbandry development [5]

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