Different Capability of Native and Non-native Plant Growth-Promoting Bacteria to Improve Snap Bean Tolerance to Ozone

Kittipornkul, Piyatida; Thiravetyan, Paitip; De Carlo, Anna; Burkey, Kent; Paoletti, Elena

Different Capability of Native and Non-native Plant Growth-Promoting Bacteria to Improve Snap Bean Tolerance to Ozone

2021

Kittipornkul, Piyatida | Thiravetyan, Paitip | De Carlo, Anna | Burkey, Kent | Paoletti, Elena

The air pollutant ozone (O₃) is a phytotoxic oxidative stressor, leading to visible foliar injury and plant growth decline. Plant growth-promoting bacteria (PGPB) are emerging as an eco-friendly tool for improving plant growth under stress. In order to test PGPB as a tool for alleviating O₃ stress in plants, an O₃ sensitive genotype (Phaseolus vulgaris L. cv S156) was inoculated with native (rhizobacterial; B1 and B2) and non-native PGPB (Bacillus megaterium and B. amylolequefaciens) and exposed to realistic O₃ exposure (ambient, AA with AOT40 = 0.53 ppm per hour, and twice ambient ozone concentration, 2XAA, AOT40 = 1.84 ppm per hour). The promoting effect was assessed by quantifying visible foliar O₃ injury (PII), chlorophyll a fluorescence (Fv/Fm), contents of hydrogen peroxide (H₂O₂), malondialdehyde (MDA) and nitric oxide (NO), ethylene emission, 1-aminocyclo-propane-1-carboxylate (ACC) deaminase enzyme activity, above- and below-ground biomass. BM, BA and B1 showed higher ACC deaminase enzyme activity and Fv/Fm, while ethylene emission, PII, H₂O₂, MDA and NO contents were lower in the BM, BA and B1 plants than in the B2 and non-inoculated plants under 2XAA. Only BA increased above- and below-ground biomass under AA and 2XAA. We conclude that PGPB are able to ameliorate O₃ stress through induction of systemic resistance; the level of bacterial ACC deaminase is one of the good markers for identifying effective strains and may be tested as an agricultural practice for improving crop yield under O₃ pollution.

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