Temperature Differentially Influences the Capacity of Trichoderma Species to Induce Plant Defense Responses in Tomato Against Insect Pests

Abstract

Species of the ecological opportunistic, avirulent fungus, Trichoderma are widely used in agriculture for their ability to protect crops from the attack of pathogenic fungi and for plant growth promotion activity. Recently, it has been shown that they may also have complementary properties that enhance plant defense barriers against insects. However, the use of these fungi is somewhat undermined by their variable level of biocontrol activity, which is influenced by environmental conditions. Understanding the source of this variability is essential for its profitable and wide use in plant protection. Here, we focus on the impact of temperature on Trichoderma afroharzianum T22, Trichoderma atroviride P1, and the defense response induced in tomato by insects. The in vitro development of these two strains was differentially influenced by temperature, and the observed pattern was consistent with temperature-dependent levels of resistance induced by them in tomato plants against the aphid, Macrosiphum euphorbiae, and the noctuid moth, Spodoptera littoralis. Tomato plants treated with T. afroharzianum T22 exhibited enhanced resistance toward both insect pests at 25°C, while T. atroviride P1 proved to be more effective at 20°C. The comparison of plant transcriptomic profiles generated by the two Trichoderma species allowed the identification of specific defense genes involved in the observed response, and a selected group was used to assess, by real-time quantitative reverse transcription PCR (qRT-PCR), the differential gene expression in Trichoderma-treated tomato plants subjected to the two temperature regimens that significantly affected fungal biological performance. These results will help pave the way toward a rational selection of the most suitable Trichoderma isolates for field applications, in order to best face the challenges imposed by local environmental conditions and by extreme climatic shifts due to global warming.

Selection of Endophytic Beauveria bassiana as a Dual Biocontrol Agent of Tomato Pathogens and Pests

“…However, it should be mentioned that the biocontrol efficacy of pathogens and/or pests plus the plant benefits observed in this study may be influenced by the controlled conditions imposed in the experimental design. In fact, abiotic factors, such as temperature, have been noted to significantly affect the important favorable characteristics of diverse strains of Trichoderma tested as the biological control agents as well as their culturability [86]. The next phase in the present BM selection process should involve testing in the field, in the "real-world" cultivation environment to determine if the selected isolates maintain their capacity as useful agricultural products.…”

“…On the other hand, another mechanism that several authors reported is once again ISR in which the endophyte induces the activation of plant defenses that suppress insects [14,40]. As evidenced by a recent study, the resistance of tomato plants root-colonized by Trichoderma against M. euphorbiae is related to an increase of plant endogenous defense processes attested by the up-regulation of the transcripts coding for ET, JA, SA, and PR proteins that are likely responsible for a primed state of the plants, as described for ISR and SAR [86]. It can be hypothesized that a similar mechanism underlies the biocontrol effect that was observed in B. bassiana-colonized plants, but further investigation need to be undertaken to shed light on this important aspect.…”

“…This insect pest was chosen since it has been successfully utilized in previous studies in which it was found to readily feed on the tomato cv. Dwarf San Marzano, and the protocol of infestation and monitoring was already well defined [86,109].…”

Ecological and Molecular Interactions between Insects and Fungi

“…Colonization by Trichoderma spp. (Sordariomycetes, Hypocreaceae) induces the systemic defense response of plants against aphids [30,32,33] and Lepidoptera [32,34], and attracts both parasitoids [35] and predators [36]. Endophytic B. bassiana can control different species of aphids on a series of crops [37][38][39] and negatively affects the fitness of several Lepidoptera species [40][41][42][43][44], even if further investigations are required for more thoroughly understanding the mechanism of action.…”

The Influence of Temperature on the Growth, Sporulation, Colonization, and Survival of Trichoderma spp. in Grapevine Pruning Wounds

“…Moreover, another experiment showed that temperature and moisture levels could be used to make good predictions for effective biocontrol using Trichoderma among other BCAs against Botrytis cinerea in grape berries [33]. Moreover, an increase of 5 • C can significantly influence the response of Trichoderma in relation to the induction of the plant response in tomato plants [34]. All these environmental factors and the alteration in temperatures due to climate change [35] represent major challenges in wine production.…”