The mitigating effect of Rhodotorula mucilaginosa on Fusarium wilt-induced stress in tomato plants under different irrigation levels

This study was carried out to investigate the effect of Rhodotorula mucilaginosa in mitigating the effects of Fusarium wilt on tomato plant growth under water stress conditions. The pot experiment was conducted in a shade net house using a randomized complete block design with 12 treatments and 3 replicates. Tomato seedlings were inoculated with/without R. mucilaginosa and Fusarium oxysporum f. sp. lycopersici (the causative agent of Fusarium wilt) under three water stress levels: I100 = 100% of field capacity (FC), I80 = 80% of FC, and I60 = 60% of FC. Disease severity and tomato plant growth were assessed. All treatments reduced disease incidence and severity compared with the untreated plants, and the highest reduction was achieved by yeast strain with water I80. In addition, the treatments enhanced the total phenol, polyphenol oxidase, and peroxidase contents in treated plants, which is a promising result. Severe stress (I60) significantly decreased tomato plant growth (plant height, number of leaves, number of branches, and fresh and dry matter of tomatoes plants) compared with the control plants that received full irrigation (I100). Under all irrigation treatments, tomato plants treated with yeast produced the highest values of these parameters. The interaction between water stress, yeast strain, and Fusarium had a significant effect on tomato plant growth. The highest values of tomato plant growth were recorded in plants irrigated with mild stress (I80) and treated with yeast under Fusarium-infected tomatoes. By contrast, the lowest parameter values were obtained from plants irrigated with I60 and treated with yeast under Fusarium-infected tomatoes. Therefore, in the case of Fusarium infection, it is recommended to add yeast and apply a decreasing irrigation system I80.