Sustainable Management of Soil-Borne Bacterium Ralstonia solanacearum In Vitro and In Vivo through Fungal Metabolites of Different Trichoderma spp.

Abstract

The efficacy of traditional control measures for the management of plant pathogens is decreasing, and the resistance of these pathogens to pesticides is increasing, which poses a serious threat to global food security. The exploration of novel and efficient management measures to combat plant disease is an urgent need at this time. In this study, fungal metabolites from three Trichoderma spp. (T. harzianum, T. virens and T. koningii) were prepared on three different growth media (STP, MOF and supermalt (SuM)). The fungal metabolites were tested in vitro and in vivo from March–April 2020 under greenhouse conditions in a pot experiment utilizing completely randomized design to test their management of the bacterial wilt disease caused by R. solanacearum in tomato plants. The effect of the fungal metabolites on bacterial cell morphology was also investigated through scanning electron microscopy (SEM) analysis. In vitro investigation showed that the fungal metabolites of T. harzianum obtained on the STP medium were the most effective in inhibiting in vitro bacterial growth and produced a 17.6 mm growth inhibition zone. SEM analysis confirms the rupture of the cell walls and cell membranes of the bacterium, along with the leakage of its cell contents. Generally, fungal metabolites obtained on an STP medium showed higher activity than those obtained on the other two media, and these metabolites were then evaluated in vivo according to three application times (0 days before transplantation (DBT), 4 DBT and 8 DBT) in a greenhouse trial to examine their ability to manage R. solanacearum in tomato plants. Consistent with in vitro results, the results from the greenhouse studies showed a level of higher anti-bacterial activity of T. harzianum metabolites than they did for the metabolites of other fungi, while among the three application times, the longest time (8 DBT) was more effective in controlling bacterial wilt disease in tomato plants. Metabolites of T. harzianum applied at 8 DBT caused the maximum decrease in soil bacterial population (1.526 log cfu/g), resulting in the lowest level of disease severity (area under disease progressive curve (AUDPC) value: 400), and maximum plant freshness (with a resulting biomass of 36.7 g, a root length of 18.3 cm and a plant height of 33.0 cm). It can be concluded that T. harzianum metabolites obtained on an STP medium, when applied after 8 DBT, can suppress soil bacterial population and enhance plant growth, and thus can be used as a safe, environmentally-conscious and consumer-friendly approach to managing bacterial wilt disease in tomato plants and possibly other crops.

Antifungal activity of Lysinibacillus macroides against toxigenic Aspergillus flavus and Fusarium proliferatum and analysis of its mycotoxin minimization potential

“…Lysinibacillus macroides Bac6, the highest antagonistic bacteria, were selected for assay of the reduction of toxigenic fungal growth. Well-grown bacterial colonies which were incubated at 35 º C for 48 h were picked and further purified by streaking [ 93 , 94 ]. The isolates were maintained on nutrient agar (NA) slants and stored at 4 ºC.…”

Expression of EPL1 from Trichoderma atroviride in Arabidopsis Confers Resistance to Bacterial and Fungal Pathogens

“…The genus Trichoderma comprises many rhizocompetent filamentous fungi found in different ecosystems [1]. Trichoderma species are fast-growing, opportunistic invaders and prolific producers of secondary metabolites with antibiotic activity that suppresses diverse phytopathogens such as bacteria, fungi, and nematodes [2][3][4]. These properties make these fungi an ecologically dominant species.…”

Trichoderma atroviride LZ42 releases volatile organic compounds promoting plant growth and suppressing Fusarium wilt disease in tomato seedlings

“…Trichoderma spp. have been reported to exhibit antagonistic activity against a broad spectrum of plant pathogenic fungi and oomycetes, such as Fusarium oxysporum [ 6 , 7 ], Phytophthora colocasiae [ 8 ], and Pythium graminicola [ 9 ], as well as plant pathogenic bacteria [ 10 ] and nematodes [ 11 ]. The many secondary metabolites produced by Trichoderma species are responsible for their highly antagonistic effects, contributing to the success of their application [ 12 ].…”