Assessment of the natural endophytic association between Rhizobium and wheat and its ability to increase wheat production in the Nile delta

Aim of the research This study examined whether rhizobia naturally associate with wheat ( Triticum aestivum ) and can enhance its production. Methods Field-grown, surface-sterilized, macerated wheat roots were inoculated on legume roots to isolate rhizobial endophytes. Nodule occupants were purified, genotypically differentiated, and tested gnotobiotically for legume symbiotic effectiveness and wheat growth-promotion. Biofertilizer performance of 13 selected strains was evaluated on 8 wheat varieties in 24 field experiments in 10 counties of the Kafr El-Sheikh governorate in the Egypt Nile delta. Results Only inoculated clover ( Trifolium alexandrinum ) produced root nodules hosting Rhizobium leguminosarum bv. trifolii. Some were symbiotically effective on clover and promoted wheat growth under gnotobiotic conditions. Inoculation significantly increased wheat grain yield in 21, 23, and 20 field experiments under N-application of 60, 120, and 180 kg N/ha, respectively, with corresponding increases of 9.2, 18.9, and 22.5 % higher grain yield over the mean of farmers’ yields using the same varieties in adjacent fields. Unlike the harvest indices, straw yield and agronomic fertilizer N-use efficiency benefitted from inoculation. Rhizobial mixed-strain inocula frequently outperformed single-strain inocula. Inoculation did not adversely affect endomycorrhizal infection of field-grown wheat roots. Conclusion Rhizobium naturally develops an endophytic association with wheat. Selected biofertilizer strains can enhance wheat production with acceptable input/output economy.