Biopriming enhances acclimatization stress tolerance and antioxidant defenses in micropropagated black chokeberry

Plantlets produced through micropropagation commonly experience physiological stress when transferred from in vitro to ex vitro environments, resulting in reduced growth and survival. This study investigated the potential of plant growth-promoting rhizobacteria (PGPR), including Bacillus sp., Bacillus mycoides , Pseudomonas sp., and Pseudomonas chlororaphis to support the acclimatization of Aronia melanocarpa cv. Viking and Nero. Morphological traits and antioxidant and oxidative stress markers were evaluated during the acclimatization. PGPR treatments affected antioxidant enzyme activities and oxidative stress markers, with responses varying according to the measured trait, bacterial treatment, cultivar, and sampling time. Treatment responses varied among bacterial strains, with B. mycoides and P. chlororaphis showing favorable numerical responses for several measured parameters. For shoot length, significant main effects of sampling time and a significant cultivar x sampling time interaction were detected, whereas the main effects of cultivar and PGPR treatment and the cultivar x PGPR interaction were not significant. The overall model for leaf count was not significant; therefore, apparent cultivar or treatment related differences for this trait were interpreted descriptively. Cultivar-dependent responses were observed for selected biochemical and oxidative-stress parameters with significant cultivar-related interactions. Survival analysis further indicated differences among PGPR treatments in the long-term acclimatization performance of the two cultivars. Survival analysis indicated significant differences among PGPR treatments for Nero (p < 0.001) but not for Viking (p = 0.176). Overall, the results indicate that PGPR can influence physiological and antioxidant responses during the acclimatization of micropropagated aronia, although the magnitude and significance of these effects depend on the measured trait and bacterial treatment.