Yerko Lovera

Chile is a global leader in the fruit industry; however, the sector faces significant yield losses due to phytopathogens and an urgent need to reduce reliance on chemical fungicides. Induction of plant defenses and priming offer sustainable alternatives by activating the plant’s innate immune system. This study aimed to evaluate the ability of native Pseudomonas protegens strains and their formulations to trigger plant defense responses in five agronomically important fruit crops: kiwifruit (Actinidia chinensis var. deliciosa), walnut (Juglans regia), cherry (Prunus avium), blueberry (Vaccinium corymbosum), and grapevine (Vitis vinifera). Under controlled conditions, a randomized block design was implemented with four treatments, including P. protegens strains and their formulations, as well as a chemical elicitor (acibenzolar-S-methyl) as a positive control. Foliar treatments were applied, and leaf tissues were sampled at 1 day, 7 days, and 14 days post-inoculation. Transcriptional responses were quantified via qPCR using the ΔΔC_t method, targeting key defense-related genes, including pathogenesis-related proteins (pr1, pr2, pr3, pr5, pr10) and enzymes of the phenylpropanoid and signaling pathways (pal, chs, ppo, lox9, glc). This study provides a molecular framework for understanding how biological inducers modulate defense-related gene expression in perennial crops. The results highlight the potential of native bacteria to be integrated into sustainable integrated pest management programs, offering an alternative strategy to trigger defense-related transcriptional activation in fruit perennial crops.

Chile is a global leader in the fruit industry; however, the sector faces significant yield losses due to phytopathogens and an urgent need to reduce reliance on chemical fungicides. Induction of plant defenses and priming offer sustainable alternatives by activating the plant’s innate immune system. This study aimed to evaluate the ability of native Pseudomonas protegens strains and their formulations to trigger plant defenses responses in five agronomically important fruit crops: kiwifruit (Actinidia chinensis var. deliciosa), walnut (Juglans regia), cherry (Prunus avium), blueberry (Vaccinium corymbosum), and grapevine (Vitis vinifera). Under controlled conditions, a randomized block design was implemented with four treatments, including P. protegens strains and their formulations, as well as a chemical elicitor (acibenzolar-S-methyl) as a positive control. Foliar treatments were applied, and leaf tissues were sampled at 1 day, 7 days, and 14 days post-inoculation. Transcriptional responses were quantified via qPCR using the ΔΔC_t method, targeting key defense-related genes, including pathogenesis-related proteins (pr1, pr2, pr3, pr4, pr5, pr10), and enzymes of the phenylpropanoid and signaling pathways (pal, chs, ppo, lox9, glc). This study provides a molecular framework for understanding how biological inducers modulate stress memory in perennial crops. The results obtained highlight the potential of native bacteria to be integrated into sustainable integrated pest management programs, offering an alternative strategy to enhance fruit crop resilience through the activation of natural plant defense responses.

Grapevine (Vitis vinifera L.) is an economically important fruit crop cultivated worldwide. However, its production and fruit quality are severely constrained by powdery mildew (Erysiphe necator) and Botrytis bunch rot (Botrytis cinerea) diseases. Increasing concerns regarding chemical fungicide resistance and environmental sustainability highlight the urgent need to develop alternative and more sustainable disease management strategies. This study assessed the field efficacy of Pseudomonas protegens-based formulations (TANIRI^® WP at 1 g·L⁻¹ and MaxGrowth at 1 mL·L⁻¹) within an integrated disease management program in cv. Chardonnay. Defense-related gene expression analysis revealed that biological treatments predominantly up-regulated pr1, pr2, and pr10 in both leaves and berries. In contrast, the chemical inducer acibenzolar-S-methyl (ASM) triggered earlier but less consistent induction of pr1 and pr2, alongside transient activation of pal and lox9. Repeated field applications of P. protegens formulations moderately reduced the severity of Botrytis bunch rot (20.89%) and powdery mildew (6.14%), though control levels remained below conventional sulfur/Bacillus subtilis-based treatments (30.04% and 13.56%, respectively). Overall, these findings suggest that biological inducers could complement conventional management practices for grapevine health. In particular, P. protegens may act mainly by systemically inducing host defense responses and partially suppressing pathogen development under field conditions.