Increased Drought Tolerance in Lagenaria siceraria by Indigenous Bacterial Isolates from Coastal Environments in Chile: Searching for the Improvement of Rootstocks for Cucurbit Production
Drought is one of the most limiting abiotic stresses for agricultural production, especially in horticultural crops grown in arid and semi-arid areas. In the present study, we evaluated the potential of bacterial isolates obtained from coastal environments in Chile to improve drought tolerance in Lagenaria siceraria, a plant species increasingly used as a rootstock for cucurbit cropping. Rhizosphere bacteria were isolated from Sicyos baderoa, the only native cucurbit species of the Chilean coast, from which four isolates with plant growth-promoting traits, such as indole-3-acetic acid production, phosphorus solubilization, nitrogen fixation, and siderophore production, were selected. These isolates were inoculated on two L. siceraria genotypes, Illapel and Osorno, under both normal irrigation and water deficit conditions. The results showed that Peribacillus frigoritolerans showed a clearer positive effect on biomass and net photosynthesis under water deficit in the Illapel genotype, increasing shoot biomass by up to ~75% and restoring net photosynthetic rates by up to ~260% relative to non-inoculated drought-stressed plants. In contrast, responses associated with Staphylococcus succinus and those observed in the Osorno genotype were mainly expressed as trait- and tissue-specific adjustments, consistent with a more stabilizing response rather than broad growth stimulation. Additionally, malondialdehyde levels were reduced by up to ~25%, while free proline accumulation increased by more than 100% under water deficit. In contrast, total phenolic compounds showed more variable responses, indicating genotype- and strain-specific adjustment of antioxidant metabolism. Overall, the observed responses were heterogeneous and strongly dependent on the specific strain–genotype–trait combination and, therefore, should be interpreted as preliminary evidence supporting the potential value of native rhizobacteria for improving early drought-related traits in cucurbit rootstocks. Among the tested strains, Peribacillus frigoritolerans emerged as the most promising candidate for enhancing early drought tolerance in responsive genotypes such as Illapel, while highlighting the need for follow-up studies under replicated nursery and field conditions, including grafted plants, multiple drought intensities and combined inoculant strategies.
Microbial consortia and their metabolic modulations as mechanisms of water deficit tolerance in strawberry plants
Introduction: One effective and ecologically sustainable strategy that has emerged to enhance plant resilience to water deficits induced by drought stress is the application of plant growth-promoting microorganisms (PGPM). Despite this progress, there remains a lack of clarity in identifying the most effective microbial consortia and understanding the nutritional and metabolic processes that contribute to the drought resilience of strawberry crops.Methods: Two effective microbial consortia were selected based on previous data: CS1 (Claroideoglomus claroideum + Naganishia albida + Paraburkholderia caledonica) and CS2 (Funneliformis mosseae + Candida guillermondii + Bacillus tequilensis) used for drought stress mitigation in plants. These were tested under two irrigation scenarios–well-watered and water-limited conditions, corresponding to 85% and 30% of their water holding capacity (WHC), respectively.Results: The co-inoculation of the CS1 consortium increased SDW by 38.23% compared to the control and 52.94% compared to CS2. Likewise, this consortium increased the concentrations of N, P, and K by 24.3%, 6.4%, and 25.7%, respectively, compared to the WS control. Finally, CS1 mitigated phytotoxic effects by activating flavonoid-type, fatty acids, and phenolic acid metabolites, as well as growth-regulating hormones, compared to the CS2 consortium and control plants, whose changes in specialized metabolism did not allow them to tolerate stress.Discussion: This study elucidated the molecular mechanisms by which microbial biostimulants increase drought tolerance.
Copper resistance and genetic determinants in Chilean strains of Clavibacter michiganensis the causal agent of bacterial canker of tomato
Genetic differentiation of native South American walnuts: a multi-marker approach to guide conservation and breeding
South American walnuts, including Juglans australis and J. boliviana, are valuable yet understudied native genetic resources. This study aimed to characterize the genetic diversity and population structure of 98 Juglans accessions from Bolivia and Argentina using a multi-tiered marker approach that combined DNA barcoding (ITS and matK regions) with high-resolution melting (HRM) pre-screening and 17 polymorphic microsatellite markers. Microsatellite markers were highly informative (mean PIC = 0.70), revealing substantial genetic diversity, with an average of 10.94 alleles per locus and a mean expected heterozygosity (He ) of 0.74. HRM analysis enabled rapid selection of the most informative barcode regions, while sequencing confirmed the phylogenetic placement of accessions within section Rhysocaryon. Population structure analysis based on microsatellite data provided the highest resolution, identifying three distinct genetic clusters (K = 3): the northern J. boliviana lineage (Cluster A), the southern J. australis lineage (Cluster B), and an introduced lineage (Cluster C). These results provide the first robust molecular evidence for genetic differentiation between native J. australis and J. boliviana. They also reveal significant introgression of exotic germplasm, confirmed by a high private allelic richness (PAr = 1.88) in the hybrid group. Overall, this study highlights the Andean region as a significant reservoir of Juglans diversity and establishes a validated genetic framework for distinguishing native South American species. These findings are essential for designing conservation strategies, defining management units, and guiding breeding programs, particularly by identifying distinct genetic lineages with potential use for timber production or as rootstocks for J. regia, likely due to their adaptation to local and subtropical soil conditions.
Integration of lipidomics and transcriptomics provides new insights into lipid metabolism in response to water deficit in Prunus spp. rootstock leaves
Abstract The mechanisms underlying the role of lipids in the response to water deficit in Prunus species have not yet been elucidated. To investigate these, a drought-tolerant rootstock (R40) and a drought-sensitive rootstock (R20) were exposed to well-watered (WW) and water deficit (WD) conditions. We combined physiological, lipidomics, and transcriptomics analyses to elucidate lipid dynamics in rootstock leaves and roots when coping drought. Data […]