A Multi-parent Advanced Generation Intercross (MAGIC) tomato population was developed by crossing eight founder lines chosen to include a wide range of variability. The lines were previously genotyped by a genotyping by sequencing approach. The MAGIC population was used to develop genotypes with important agronomic traits and to perform the Participatory Plant Breeding (PPB). Among the 400 plants of generation 4 (G4) of the MAGIC population cultivated in an organic field experiment, 22 individuals were phenotypically selected and a molecular analysis was done for both presence of resistance genes and fruit shape (marker assisted selection) on G5 seedlings. Three selected plants showed both the pyramiding gene of resistance to the main diseases and the ovate gene for pear shape typology. The 400 G10 stable lines that obtained from single seed descent will represent an important genetic resource for the tomato scientific community. The MAGIC population G4 was also cultivated in three organic farms located in North, Central and South Italy to carry out the PPB. The plants showed significant phenotypic differences in development, productivity and fruit color. This variability was used to select families of tomato adapted to low input crop management, different environments, agricultural practices and market conditions.

Integrating cover crops into vegetable cropping systems can provide a wide range of ecological services, of which weed management is a key component. Cover crop effects on weed control, however, are dependent on termination methods and weed species present in specific cropping seasons. A 2-year weed management experiment with two cultivars of organic zucchini (Cucurbita pepo L.) in central Italy was carried out to compare the effect of a barley (Hordeum distichum L.) cover crop terminated with a modified roller-crimper (RC) to incorporated barley as green manure (GM) and a tilled control left fallow (FA) in the off-season. The effects of cover-crop management on crop competitiveness, yields and weed populations were evaluated by direct measurement, visual estimation and competition index methods. Results showed a significant reduction in weed biomass (>80%) and weed abundance with the RC compared to the GM and FA treatments. Moreover, the RC barley mulch maintained weed control in zucchini plots even under high weed pressure, as determined by the agronomic tolerance to competition (ATC) value of 67% in the RC treatment compared to 40 and 34% in the FA and GM treatments, respectively, averaged over both years of the experiment. The competitive balance (C_b), which quantified the ability of the zucchini crop to compete with weed populations, was also greater (+0.37) in the RC treatment compared to FA (−0.87) and GM (−0.69) treatments over the same period. Zucchini crop biomass was greatest in the RC treatment in 2011. Zucchini fruit yields varied from an average over both years of 1.4 Mg ha⁻¹ in the RC treatment to 0.7 Mg ha⁻¹ in the GM treatment, but yields in the FA treatment, 1.2 Mg ha⁻¹, did not differ from the RC treatment. No differences in yield between ‘Dietary’ and ‘Every’ zucchini, or any significant interactions between cultivar and cover management related to fruit biomass, were observed. Our findings suggested the viability of the modified RC in creating a barley cover-crop mulch to effectively manage weeds and enhance yields in transplanted zucchini.