Azospirillum lipoferum strain AL-3 reduces early blight disease of potato and enhance yield

Abstract

In sustainable agricultural systems, plant disease management with biological agents is a cost-effective and eco-friendly strategy. This study was performed to screen the biocontrol efficacy of rhizobacterial strains against early blight disease of potatoes (Solanum tuberosum). Rhizobacterial antagonists that are capable of suppressing the growth of Alternaria solani up to 50% under in-vitro conditions were selected. Next, early blight susceptible potato cultivar Sadaf plants were pre-treated with a foliar application of selected antagonist rhizobacteria and challenged 1 d later with Alternaria solani. The results showed that foliar treatment with Azospirillum lipoferum AL-3 significantly reduced early blight disease severity by 68.1%. The results of 2-year studies revealed 52.7 and 39.23% reductions in disease index of A. lipoferum AL-3 -treated plants compared with the control group along with the significant increase of 11.3–17.9% and 16.1–22.7% in tuber yield both in the presence and absence of early blight pathogen, respectively. Azospirillum lipoferum AL-3 also helped potato plants fight early blight disease through induced systemic resistance. The quantity of total phenolics, defense-related enzyme (peroxidase, polyphenol oxidase, and phenylalanine ammonia lyase) activities, and PR-gene transcriptomic levels were significantly increased by Azospirillum lipoferum AL-3. Furthermore, application of Azospirillum lipoferum AL-3 followed by pathogen challenge increased salicylic acid and H2O2 levels up to 1.9 and 3.1 fold, respectively and reduced cell death up to 1.73-fold in potato plants to fight the early blight pathogen. The current investigation highlighted the dual role of Azospirillum lipoferum AL-3 as an antagonist of the early blight pathogen that also induced resistance. Incorporation of this microbe in conventional agricultural systems could reduce management costs and environmental pollution.