The indiscriminate use of chemical fertilizers and pesticides has caused considerable environmental damage over the years. However, the growing demand for food in the coming years and decades requires the use of increasingly productive and efficient agriculture. Several studies carried out in recent years have shown how the application of plant growth-promoting microbes (PGPMs) can be a valid substitute for chemical industry products and represent a valid eco-friendly alternative. However, because of the complexity of interactions created with the numerous biotic and abiotic factors (i.e., environment, soil, interactions between microorganisms, etc.), the different formulates often show variable effects. In this review, we analyze the main factors that influence the effectiveness of PGPM applications and some of the applications that make them a useful tool for agroecological transition.

Several Allium cepa L. varieties, representing a versatile set of vegetables widely utilized by consumers, are appreciated for their bioactive properties, including antimicrobial, anticarcinogenic, and antioxidant capacities. The aim of this study is to compare the morphometric characteristics and biochemical profiles of four cultivars of A. cepa, two of them represented by the perennial Sicilian landrace “Cipudda agghiarola” (Allium × proliferum (Moench) Schrader), widely known as the Egyptian walking onion (WO), and by the landrace “Cipudduzza” belonging to the variety known as aggregatum (ON), which were compared with two commercial cultivars of A. cepa var. cepa (onion), Stoccarda (OS) and Rossa Carmen (OR). The experimental trial was conducted in Catania (Sicily), following organic growing practices. The randomized complete block experimental design was adopted with one experimental factor, the genotype (GE) effect. The harvested plants were characterized for their main morphometric parameters, according to the International Plant Genetic Resources (IGPR) descriptors. The biochemical activity was assessed by analyzing the total phenolic content (TPC) and the total flavonoid content (TFC). The antioxidant capacity was determined by 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging, ferric reducing antioxidant power (FRAP), and oxygen radical absorbance capacity (ORAC). The sugar profile (total sugars, sucrose, glucose, fructose, and fructooligosaccharides—FOS) and the volatile compounds by headspace-gas chromatography/mass spectrometry (HS-GC/MS) were also determined. The OR bulb exhibited the highest TPC (16.3 mg GAE/g d.w., p < 0.01) and TFC (8.5 mg QE/g d.w., p < 0.01), with the highest antioxidant capacity measured by the FRAP (27.1 µmol TE/g d.w., p < 0.01) and DPPH assays (46.2 µmol TE/g d.w., p < 0.01). The ON bulb showed the highest ORAC value (209 µmol TE/g d.w., p < 0.01). Generally, the bulbs were richer in sugars (584 mg/g d.w., p < 0.01) than the leaf blade (239 mg/g d.w., p < 0.01), except for OR. Significant interaction between the genotype and plant organ was noted in the volatile compound profiles (p < 0.05) except for total ketones and carboxylic acids, where higher content was observed in the leaf blade compared to the bulb, regardless of the genotype. These findings highlight WO’s potential for use in ready-to-eat products, enhancing its market value.

The use of beneficial microorganisms, such as plant growth promoting rhizobacteria (PGPR) and mycorrhizal fungi, for organic farming could improve the productivity and the resilience of vegetable crops. Both PGPR and PGPF are allowed for organic farming, and they represent new important tools for regenerating poor and marginal soils in transition to environmentally friendly farming. In the experiment, the effects of PGPM-based products were evaluated on snap bean in combination with two irrigation regimes. The experimental design adopted was split-plot, with the main plot represented by the irrigation regime (reintegration of 100 and 60% of the ETc), the sub-plot by the microbial consortia, and finally the sub-sub-plot by genotype (‘Domino’ and ‘Maxi’). Seeds were sown in a cold greenhouse and the growing cycle finished after 86 days from sowing. The results showed a significant increase of the yield due to the application of PGPM compared to the control. The deficit irrigation applied (ETc 60%) affected plants growth in the two genotypes and their related production differently (in average 2.20 kg m⁻² for Domino and 3.63 kg m⁻² for Maxi), showing a positive effect of PGPM on yield (in average 2.47 kg m⁻² without PGPM and 3.36 kg m⁻² with PGPM) and product quality. Furthermore, an interesting negative correlation between the number of nodules and the yield was also observed, as a consequence of their early outcome which increased plant productivity in relation to the experimental factors.

Grafting techniques have been intricately associated with the optimization of water use efficiency (WUE). In this study, various eggplant (Solanum melongena L.) rootstock–scion combinations were compared under three irrigation regimes (IR): 50% deficit in water volume (IR50), a doubling of irrigation volume (IR200), and normal watering (IR100). The cultivar Black Bell (Bb) was employed as a scion, while the rootstock adopted included the F1 hybrids Energy (En) and Beaufort (Be) and one accession of S. torvum (To). The trial encompassed the evaluation of no- and self-grafted plants_. Plants grown in a cold greenhouse in Sicily were assessed for their morphological parameters, as well as their fruit production and quality. The leaf analysis encompassed the evaluation of chromatic parameters and water potential. Significant variation was observed for plant height, exhibiting the lowest values in self-grafted combinations. The leaf water potential varied significantly in relation to the rootstock–scion combination employed and to the irrigation regime. Fruit quality traits displayed significant variations for chromatic parameters L* and a*, as well as for the fruit’s longitudinal and transversal diameters and the soluble solid content. The number of fruits and fruit production per plant varied significantly in relation to the rootstock–scion combination; the highest fruit production was recorded for Black Bell grafted onto S. torvum grown by IR50. The fruit weight displayed a significant interaction between the experimental factors under study. Notably, for the WUE calculated in relation to fruit production, a significant interaction between the experimental factors studied was ascertained. The highest WUE was registered for IR50, specifically for To/Bb. This research aims to develop a comprehensive water-efficient organic farming protocol for sustainable agriculture.