Open field inoculation with PGPR as a strategy to manage fertilization of ancient Triticum genotypes

Ancient wheats are characterized by high nutritional value, low nitrogen requirements, and good adaptability which make them particularly suitable for marginal areas or low-input agricultural systems. Among environmental-friendly fertilizers, plant growthpromoting rhizobacteria represent a promising tool thanks to their ability to colonize soil and plant roots. In this study, a consortium of plant growth-promoting rhizobacteria was applied on three ancient wheat varieties (durum wheat: Senatore Cappelli, Saragolla; emmer: Molisano). Colonization and survival of bacteria in wheat seedling roots were investigated on in vitro cultures. The effects of the bacteria on crop growth, yield, and grain protein accumulation were studied in a 2-year open field experiment (split-plot arranged on a randomized block). Three different fertilization strategies were compared: (i) one bacterial application at sowing, (ii) two bacterial applications at sowing and tillering stages, (iii) zero bacterial application. Scanning electron microscope imaging revealed the ability of the bacteria to colonize effectively seedling roots thanks to biofilm formation on root surfaces. In both years, double bacterial application positively affected plant physiology, growth, and yield. Plants with double bacterial application showed highest physiological traits, and resulting enhanced yield and grain protein contents. The applied bacterial consortium positively performs on ancient wheats, even if the magnitude of its success depends on timing and rate of application