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Woodland strawberry (Fragaria vesca L.) is an underutilized plant species that could benefit from the use of biostimulants to improve crop productivity and fruit quality. The scope of the present study was to appraise the influence of two biostimulants (Trichoderma atroviride and plant protein hydrolysate)—used either alone or combined—on the plant performance and economic profitability of two woodland strawberry genotypes (‘Alpine’ and ‘Regina delle Valli’). Overall, data showed that ‘Alpine’ had the highest productive performances, whereas ‘Regina delle Valli’ revealed the highest fruit qualitative traits. T. atroviride inoculation and V-PH application significantly boosted plant marketable yield (+20.5% for T. atroviride and +12.9% for V-PH), total sugars (+1.9% for Trichoderma and +1.4% for V-PH) and anthocyanins (+14.1% for T. atroviride and +9.8% for V-PH) compared to non-treated plants. Plants supplied with both biostimulants had a higher marketable yield (+34.8%), mean fruit weight (+6.0%), fruit dry matter (+13.8%), total sugars (+3.5%), ascorbic acid (+12.7%), flavonoid (+26.3%) and anthocyanins (+29.9%) compared to non-treated plants. Furthermore, our study revealed that the highest fruit polyphenol concentration was recorded in both genotypes treated with the combination of biostimulants and in ‘Regina delle Valli’ sprayed with V-PH, whereas the highest antioxidant activity was found in ‘Regina delle Valli’ fruit when plants were supplied with both biostimulants. Our study pointed out that the application of microbial and non-microbial biostimulants, especially in combination, might be a useful strategy for improving the performances of underutilized species and, therefore, encouraging their cultivation, valorization and economic profitability (+6208.3 EUR /ha when plants were exposed to both biostimulants).

The grafting of vegetable crops is considered a valuable mean for ensuring the yield and quality under different cultivation conditions. Simultaneously, there are increasing research efforts in exploiting underutilised plants as potential rootstocks for vegetables to increase the sustainability of horticultural systems. In accordance with the European Green Deal, the application of biostimulants is a fashionable and ecological agronomic practice to enhance the production and quality of vegetables. Thus, the current research appraised the synergistic effect of grafting eggplant onto various allied potential rootstocks (Solanum torvum, S. aethiopicum and S. macrocarpon) and of applying a plant growth-promoting bacteria (Azospirillum brasilense DSM 2298) on eggplant growth, production, fruit quality traits (nutritional and functional features) and nitrogen use efficiency (NUE). The findings showed that ‘Gloria’ F1 plants grafted onto S. torvum or S. aethiopicum had a significant increase in plant height 50 DAT by 11.6% and 9%, respectively, compared with not grafted plants. Simultaneously, plants inoculated with A. brasilense DSM 2298 acquired a significant upsurge of plant height 50 DAT by 6% compared with the control. Our results revealed that S. torvum and S. aethiopicum-grafted plants improved their marketable yield by 31.4% and 20%, respectively, compared with not grafted ones. Furthermore, A. brasilense DSM 2298 significantly boosted the yield compared with the control plants. Plant type had no effect on fruit dry matter and firmness, whereas plants grafted onto S. macrocarpon showed a significant increase in the soluble solids content (SSC) and fruit K concentration compared with not grafted plants. Plants grafted onto S. torvum rootstock and inoculated with A. brasilense DSM 2298 had a significant increase in fruit protein concentrations compared with the combination not grafted × control. Moreover, S. torvum-grafted plants and those inoculated with the microbial biostimulant revealed the highest NUE values. The results evidenced that S. torvum and S. macrocarpon-grafted plants, inoculated with A. brasilense DSM 2298, had the highest ascorbic acid (average 7.33 and 7.32 mg 100 g−1 fw, respectively). Interestingly, S. torvum rootstock increased the chlorogenic acid concentration and reduced the glycoalkaloids concentration compared with not grafted plants. Our data also showed that A. brasilense DSM 2298 significantly increased SSC by 4.5%, NUE by 5.5%, chlorogenic acid concentration by 2.0% and the total anthocyanins by 0.2% compared to the control. Thus, our study underlined that S. aethiopicum rootstocks inoculated with A. brasilense DSM 2298 could represent a valid substitute to the common S. torvum rootstock.