Microbial communities investigation and biocontrol activity in saffron cultures

Crocus sativus L., commonly known as saffron, is recognized as one of the most valuable spices in the world for the flavouring, nutritional and bioactive properties of its dried stigmas. As underground organs, saffron corms are exposed to infections caused by fungi, bacteria, viruses and nematodes. Among the latter, the genus Fusarium includes fungal pathogens that destroy these cultures, affecting also the composition of the microbial communities associated with the plant. The corms are typically chemically disinfested before sowing to control diseases. However, most fungal pathogens, such as Fusarium spp., are resistant to this treatment. The aim of this work was to i) investigate the microbial communities associated with the rhizosphere of saffron in presence of fusariosis; ii) isolate and characterize the Fusarium pathogen strains; iii) evaluate the biocontrol potential of selected beneficial bacterial strains against the isolated phytopathogens. Soil and plant samples of the saffron cultures were sampled in L’Aquila territory (Italy) and analysed with microbiological approaches, including culture–independent and – dependent methods. The 16S rRNA metabarcoding ITS barcoding was performed to investigate microbial communities composition and identify fungal pathogen isolated strains respectively. Four beneficial bacteria were tested against phytopathogen strains by dual culture method and microscope observations. The metabarcoding analysis revealed the presence of taxa related to the Proteobacteria phylum. The three isolated fungal strains were identified as Fusarium oxysporum ff. spp. and two of the four selected beneficial strains (Bacillus pumilus and WG6) showed an inhibition percentage greater than 50% with disgregation and vacuolization of the hyphae. These preliminary findings serve as the basis for future studies about the possibility of asses more sustainable agricultural practices and eco-friendly strategies to avoid or mitigate Fusarium disease in saffron cultivation and protect a such valuable and precious plant.

Keywords: Fusarium, pathogens, biocontrol