Functional Diversity and Rational Selection of PGPR Rhizobacteria from Durum Wheat: Comparative Performance of a Multi-Strain Consortium (Biostim) and Individual Isolates Against Fusarium culmorum and F. pseudograminearum

Abstract

Fusarium crown rot, caused by F. culmorum and F. pseudograminearum, seriously constrains durum wheat production in semi-arid regions, and chemical control remains limited. Plant growth-promoting rhizobacteria (PGPR) offer a sustainable alternative, but whether multi-strain consortia outperform single isolates is unclear. Thirty-five fluorescent rhizobacteria from durum wheat rhizosphere were screened for seven growth-promotion and biocontrol traits. Multivariate analysis showed weak trait correlations and identified four functional groups, guiding selection of six multifunctional isolates (BNJ2, BNJ22, BNJ24, BNJ26, BNJ27, BNJ35). Applied alone or as a thirty-five-strain consortium on durum wheat under healthy and pathogen-inoculated conditions, treatments showed significant main and interaction effects. with pathogen-specific responses (BNJ2 vs. F. culmorum; BNJ27/BNJ35 vs. F. pseudograminearum). The Biostim consortium consistently outperformed the control, the isolate average, and the best single isolate, indicating functional complementarity. These results support combining functional screening with multivariate analysis to rationally select robust PGPR consortia for biocontrol of Fusarium crown rot. This work highlights the potential of natural-based biostimulants to promote sustainable wheat production, reduce reliance on chemical inputs, and contribute to human health by supporting the production of safer and healthier food.