Azospirillum brasilense and cytidine as combination treatment to enhance drought resilience of peas

Aims: This study tested the efficacy of two combination treatments on drought resistance of peas; Azospirillum brasilense Sp7 together with either the chemoattractant seedling exudate compound cytidine or total pea seedling exudate. Methods and Results: Phenotypic characterization revealed that the treatment with cytidine (ACyt) was more efficient than that with seedling exudate (AEx). Drought tolerance of peas treated with ACyt was 68.9% higher than that of peas treated with the inoculant alone (A). Dry shoot weight of ACyt Drought plants was 30.7% higher than that of plants from the untreated control group NB Drought, drought recovery of ACyt plants was 21.6% better. 16S rDNA analysis revealed that increase in drought tolerance/recovery was accompanied by modulation of the rhizosphere. The abundance of the inoculant was 163% higher in ACyt plants when comparing drought treated to watered groups. Abundance of Azospirillum sp. was 954% higher in plants from the ACyt Drought group than those from NB Drought. The possibility arises that the ACyt treatment may contribute to protecting pea plants from drought by increasing the abundance of Azospirillum. Within the complete analysis of the 16S rDNA data set, both ACyt Drought and AEx Drought groups had similar increases in Shannon and Pielou alpha-diversity indices, relative to the NB Drought group. These two test groups also exhibited high abundances of Rhizobium and lower abundance of Massilia. Conclusion: The ACyt treatment enhanced drought tolerance and recovery. Both treatments enhanced alpha-diversity and modulated the rhizosphere.