Table grapes are highly susceptible to Botrytis cinerea infections during the bloom period. After reaching the flower development stage, B. cinerea remains quiescent until berry ripening or gives rise to blossom blight under specific climate conditions. A research study was conducted on the Chilean Central Valley during the 2018–2019 growing season. Flowers of Vitis vinifera cv. Thompson Seedless were collected and B. cinerea was isolated together to a second and morphologically different species, characterized by white mycelium and low to no sporulation (11.4% of total isolates). Three randomly selected isolates within this population were genetically examined and identified as Botrytis prunorum based on a phylogenetic multilocus approach using partial regions of genes RPB2, HSP60, and G3PDH or NEP1 and NEP2. Pathogenicity tests showed that B. prunorum infects and causes wilting in healthy table grape flowers. B. prunorum isolates were able to infect Thompson Seedless berries, inducing lesions between 13.11 and 41.53% with respect to the lesion diameter generated by B. cinerea B05.10. The fungicide sensitivity was evaluated. The three genetically characterized isolates were sensitive to boscalid and to cyprodinil/fludioxonil mixture with a mean EC₅₀ value of 5.5 µg/ml and 0.065 µg/ml, respectively. However, loss of sensitivity to fenhexamid was determined, with a mean EC₅₀ value of 5.13 µg/ml. Our understanding about blossom blight in V. vinifera has been limited to B. cinerea. Here we associated B. prunorum as a second causal agent of this disease in Chile. This data represents a first approach to the epidemiological characteristics of B. prunorum associated with blossom blight in table grapes.

Pseudomonas syringae pv. syringae is the main causal agent of bacterial canker in sweet cherry in Chile, causing significant economic losses. Cultivars exhibit diverse susceptibility in the field and the molecular mechanisms underlying the differential responses remain unclear. RNA-seq analysis was performed to characterize the transcriptomic response in cultivars Santina and Bing (less and more susceptible to P. syringae pv. syringae, respectively) after 1 and 7 days post-inoculation (dpi) with the bacterium. Symptoms of bacterial canker became evident from the fifth day. At 1 dpi, cultivar Santina showed a faster response to infection and a larger number of differentially expressed genes (DEGs) than cultivar Bing. At 7 dpi, cultivar Bing almost doubled its DEGs, while cultivar Santina tended to the normal DEG levels. P. syringae pv. syringae infection downregulated the expressions of key genes of the photosynthesis process at 1 dpi in the less susceptible cultivar. The results suggest that the difference in susceptibility to P. syringae pv. syringae is linked to the timeliness of pathogen recognition, limiting the bacteria’s dispersion through modeling its cell wall, and regulation of genes encoding photosynthesis pathway. Through this study, it has been possible to progress the knowledge of relevant factors related to the susceptibility of the two studied cherry cultivars to P. syringae pv. syringae.

Bacterial canker caused by Pseudomonas syringae pv. syringae (Pss) is responsible for substantial loss to the production of sweet cherry in Chile. To date, the molecular mechanisms of the Pss–sweet cherry interaction and the disease-related genes in the plant are poorly understood. In order to gain insight into these aspects, a transcriptomic analysis of the sweet cherry cultivar ‘Lapins’ for differentially expressed genes (DEGs) in response to Pss inoculation was conducted. Three Pss strains, A1M3, A1M197, and 11116_b1, were inoculated in young twigs, and RNA was extracted from tissue samples at the inoculation site and distal sections. RNA sequencing and transcriptomic expression analysis revealed that the three strains induced different patterns of responses in local and distal tissues. In the local tissues, A1M3 triggered a much more extensive response than the other two strains, enriching DEGs especially involved in photosynthesis. In the distal tissues, the three strains triggered a comparable extent of responses, among which 11116_b1 induced a group of DEGs involved in defense responses. Furthermore, tissues from various inoculations exhibited an enrichment of DEGs related to carbohydrate metabolism, terpene metabolism, and cell wall biogenesis. This study opened doors to future research on the Pss–sweet cherry interaction, immunity responses, and disease control.

Disease severity and drought due to climate change present significant challenges to orchard productivity. This study examines the effects of spring inoculation with Pseudomonas syringae pv. syringae (Pss) on sweet cherry plants, cvs. Bing and Santina with varying defense responses, assessing plant growth, physiological variables (water potential, gas exchange, and plant hydraulic conductance), and the levels of abscisic acid (ABA) and salicylic acid (SA) under two summer irrigation levels. Pss inoculation elicited a more pronounced response in ‘Santina’ compared to ‘Bing’ at 14 days post-inoculation (dpi), and those plants inoculated with Pss exhibited a slower leaf growth and reduced transpiration compared to control plants during 60 dpi. During differential irrigations, leaf area was reduced 14% and 44% in Pss inoculated plants of ‘Bing’ and ‘Santina’ respectively, under well-watered (WW) conditions, without changes in plant water status or gas exchange. Conversely, water-deficit (WD) conditions led to gas exchange limitations and a 43% decrease in plant biomass compared to that under WW conditions, with no differences between inoculation treatments. ABA levels were lower under WW than under WD at 90 dpi, while SA levels were significantly higher in Pss-inoculated plants under WW conditions. These findings underscore the influence on plant growth during summer in sweet cherry cultivars that showed a differential response to Pss inoculations and how the relationship between ABA and SA changes in plant drought level responses.

One of the causal agents of bacterial canker is Pseudomonas amygdali pv. morsprunorum—Pam (formerly Pseudomonas syringae pv. morsprunorum). Recently detected in Chile, Pam is known to cause lesions in the aerial parts of the plant, followed by more severe symptoms such as cankers and gummosis in the later stages of the disease. This study presents the design of PCR and LAMP detection methods for the specific and sensitive identification of Pseudomonas amygdali pv. morsprunorum (Pam) from cherry trees. Twelve Pseudomonas isolates were collected, sequenced, and later characterized by Multi-locus Sequence Analysis (MLSA) and Average Nucleotide Identity by blast (ANIb). Three of them (11116B2, S1 Pam, and S2 Pam) were identified as Pseudomonas amygdali pv. morsprunorum and were used to find specific genes through RAST server, by comparing their genome with that of other Pseudomonas, including isolates from other Pam strains. The effector gene HopAU1 was selected for the design of primers to be used for both techniques, evaluating sensitivity and specificity, and the ability to detect Pam directly from plant tissues. While the PCR detection limit was 100 pg of purified bacterial DNA per reaction, the LAMP assays were able to detect up to 1 fg of purified DNA per reaction. Similar results were observed using plant tissues, LAMP being more sensitive than PCR, including when using DNA extracted from infected plant tissues. Both detection methods were tested in the presence of 30 other bacterial genera, with LAMP being more sensitive than PCR.

Climate change is intensifying the simultaneous occurrence of biotic and abiotic stresses in fruit crops, but yet the molecular mechanisms underlying plant responses remain poorly understood. The physiological and transcriptomic responses of two sweet cherry (Prunus avium L.) cultivars, Santina and Bing, grafted onto Gisela 12, were investigated under single and combined stresses imposed by Pseudomonas syringae pv. syringae and water deficit. Although biomass, gas exchange, and hormone accumulation showed only minor changes, combined stress triggered distinct cultivar-dependent transcriptional reprogramming. The cultivar Bing exhibited a pronounced response with 4261 differentially expressed genes (DEGs), characterized by strong repression of photosynthetic processes and activation of defense- and hormone-related pathways. In contrast, the cultivar Santina showed a moderate response with 674 DEGs, primarily reinforcing structural and secondary metabolism. Cultivar-specific modulation of abscisic acid sensitivity was associated with the contrasting regulation of WRKY40 and Sin3-like repressors, despite comparable ABA levels. Strikingly, both cultivars upregulated the GIGANTEA gene, underscoring its role as a central regulatory hub linking circadian rhythm, stomatal function, and hormonal crosstalk under dual stress. Collectively, these results reveal non-additive, genotype-specific transcriptional strategies in sweet cherry trees, providing insights into stress integration in fruit trees and identifying regulatory genes that may inform breeding and management strategies for resilience under climate change.