Abstract
Tomato bacterial wilt caused by Ralstonia solanacearum (RS) is one of the most devastating soil-borne diseases, and compost is to be considered as a resource-saving and environment-friendly measure to control the disease. Herein, a pot experiment was implemented to explore the effects of vinegar residue matrix amendments on the growth performances of tomato seedlings and to examine the suppression ability against bacterial wilt under vinegar residue substrate (VRS), and peat substrate (Peat) with RS inoculation. The results revealed that VRS effectively suppressed the disease incidence of bacterial wilt, increased the number of bacteria and actinomycetes, decreased fungi populations, promoted soil microbial populations and microbial activities, enhanced the growths of tomato seedlings, and modulated defense mechanism. In addition, VRS efficiently inhibited the oxidative damage in RS inoculated leaves via the regulation of excess reactive oxide species (O2•− and H2O2) production, lessening of malondialdehyde (MDA) content, and causing less membrane injury; resulting in enhancements of antioxidants enzymes activities accompanying with modulating their encoding gene expression. The transcription levels of NPR1, PIN2, PR1b, ACO1, EDS1, PR1B, MAPK3, PIN2, and RRS1 were also modulated with the pathogens inoculated in tomato leaves both in VRS and Peat treatments, which indicated that systemic-acquired resistance possesses cross-talk between salicylic acid, jasmonic acid, and the ethylene-dependent signaling pathway. Besides, the RS inoculation significantly inhibited the growth of tomato seedlings, and all growth indices of plants grown in VRS were considerably higher than those produced in Peat. Taken together, VRS represents a new strategy to control tomato bacterial wilt through boosting the soil microbial populations and microbial activities. Furthermore, VRS promotes the plant immune response to provide a better growth environment for plants surviving in disease conditions.
Highlights
Tomato (Solanum lycopersicum L.) is an important and generally cultivated vegetable crop all over the world [1]
We found that the application of vinegar residue substrate (VRS) could promote plant growth, transform soil microbial populations and microbial enzyme activities, enhance defense-related enzyme activities and induce stress-related genes expression, which resulted in increased tolerance to Ralstonia solanacearum (RS) in tomato
We found that pathogen attack significantly induced higher levels of ROS in terms of O2 − and H2 O2 production (Figure 4), which resulted in higher electrolyte leakages (ELs) and MDA contents (Figure 5); similar results were obtained in other studies [31,32]
Summary
Tomato (Solanum lycopersicum L.) is an important and generally cultivated vegetable crop all over the world [1]. Pathogens 2020, 9, 227 resulting in severe quality deterioration and economic losses [2]. The disease reduced the fresh fruit yield of hybrid tomatoes by about 26% and total yield losses around 90.62% under severe disease incidence [3]. The management of bacterial wilt is primarily dependent on crop rotation, grafting, growing disease-resistant cultivars, and the use of bactericides. These tactics have their shortcomings due to the high survivability of pathogens in complex environmental conditions and instability in disease-resistance breeding [4]. Adding compost to the soil or substrates is beneficial as it promotes plant development, improves soil quality and structure, and inhibits some soil-borne pathogens [5]. Compost mainly utilizes the effects of various microorganisms to mineralize, humus and harmless plant organic residues, so that various complex organic nutrients can be converted into soluble nutrients and humus
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