Trichoderma harzianum strain T22 enhances direct and indirect defenses in tomato plants against the stink bug Halyomorpha halys

This dataset describes the effect of plant growth-promoting fungus Trichoderma harzianum T22 on direct and indirect tomato plant defenses against the invasive stink bug, Halyomorpha halys.Insect performance bioassays To investigate the effects of T. harzianum T22 on direct plant defenses, 3rd instar H. halys nymphs were allowed to feed on tomato plants previously inoculated with T. harzianum T22 or on non-inoculated control plants. Plants were enclosed individually with five 3rd instar nymphs in nylon mesh bags for one week under controlled conditions. Initial and final weights of nymphs were recorded to calculate relative growth rate and mortality was assessed at the end of the experiment. For each treatment, 10 replicates were carried out.Olfactometer bioassays To investigate whether T. harzianum T22 affects indirect plant defenses and egg parasitoid attraction, olfactory responses of T. japonicus females towards differently treated tomato plants were evaluated using a Y-tube olfactometer. Tomato plants received the following treatments: 1) non-inoculated and uninfested control plants (CTRL); 2) non-inoculated plants exposed to H. halys feeding and oviposition (FO); 3) T. harzianum T22-inoculated plants exposed to H. halys feeding and oviposition (T22-FO). For treatments, gravid H. halys females were allowed to feed and oviposit on tomato leaves enclosed in mesh bags for 24 h under controlled environmental conditions. After insect removal, plants were used in olfactometer bioassays. Parasitoid preference was assessed in terms of residence time spent in each olfactometer arm during a 600s observation period. Each choice bioassay was replicated with four 4-plant pairs and 10 female wasps per plant pairwise combination (≈40 wasps in total number). Volatile organic compound (VOC) analysis To investigate whether T. harzianum T22 inoculation alters plant volatile emissions, headspace VOCs were collected from differently treated tomato plants. Plants were subjected to the following treatments: 1) non-inoculated and uninfested control plants (CTRL); 2) non-inoculated plants exposed to H. halys feeding and oviposition (FO); 3) T. harzianum T22-inoculated plants exposed to H. halys feeding and oviposition (T22-FO). Volatile collections were performed using cylindrical glass chambers connected to Porapak Q adsorbent traps. VOCs were collected for 24h and subsequently analyzed using gas chromatography–mass spectrometry (GC–MS). Compounds were tentatively identified using mass spectral libraries, retention indices and synthetic standards. The dataset contains raw and processed peak-area measurements of volatile compounds detected across treatments. Five biological replicates were replicated for each treatment.