Industrial tomato cultivar response to different bioinoculants in tunnel-greenhouse conditions

Tomato is one of the most economically important crops worldwide, mainly cultivated in the Mediterranean Basin. Soil beneficial microorganisms (SBM) as arbuscular mycorrhizal (AM) or Trichoderma fungi and plant growth-promoting bacteria (PGPB), are known to improve plant physiology, nutrition and fruit quality, allowing a consistent reduction of chemical fertilizer supply. Since the outcome of plant-SBM interactions can be variable in relation to the involved species, different bioinoculants were tested on tomato plants to evaluate their effects on growth and productivity in semi-controlled conditions, within the framework of the project ASTER_PRIMA_2021. The following SBM were tested: two AM inocula, a pure culture of Funneliformis mosseae (Fm) and a mix of AM fungi (AMFMIX); two different T. asperellum isolates, T1 from Italian soil and T4 from Algerian one; a mix of previously selected PGPB. Each of these inocula was administered alone or in combination for a total of 12 treatments (10 plants each); ten uninoculated plants were used as control. Tomato plantlets were grown in a tunnel-greenhouse, irrigated three times a week (twice with tap water and once with Long Ashton solution at 32µM of P). During the experiment, the number of flowers and fruits were weekly counted, while at two different sampling times (45 and 100 days of culture-DOC) the following parameters were analyzed: mycorrhization level, fresh and dry weight of plant organs, photosynthetic activity and pigment concentration. The fruit number, weight, size and quality (pH, total acidity, sugar content) were recorded only at 100DOC. At 45DOC, the two AM inocula differently affect the root colonization, with Fm showing a low rate of M% independently on the presence of the two Trichoderma isolates, while AMFMIX alone or in combination with T1 reached higher values. In general, plants inoculated with Fm alone or coinoculated with T4 presented an increased root and shoot biomass compared to the other treatments. The coinoculation of T4 with the two different AM inocula increased the photosynthetic pigment concentration. At 100DOC, regardless of the different Trichoderma isolates, plants inoculated with AMFMIX showed an increase of M% from 25% (45DOC) to 40% (100DOC), with significant differences compared to Fm plants, in which a strong reduction was observed. Overall, the various SBM had a different impact on plant biomass production with a good performance for Fm. The coinoculation of AMFMIX with T1 or T4 significantly increased the photosynthetic pigment concentration compared to controls, besides T1 and MIXTOT plants (a mixed inoculum in which were included all the above-mentioned used SBM). Plants inoculated with FM alone or coinoculated with T1 showed the highest number of flowers toward the end of the cultivation period, whereas T1 exhibited the lowest flower production. A similar trend was observed for the number of fruits. Regarding the fruit quality, no significant differences for the considered parameters were recorded between the various treatments.