Florida Department of Citrus

Strawberry flavor is a key factor in consumer acceptance and is highly influenced by volatile aroma compounds. Multiple consumer and trained panel sensory studies indicate that γ-lactones are among the most important aroma compounds in strawberry, imparting sweet, fruity aromas. We quantified γ-lactones in Fragaria × ananassa and Fragaria vesca to explore the genetic basis for lactone production in the two species using genome wide association study (GWAS). We developed a haplotype-phased genome assembly for a high lactone cultivar to explore previously published expression quantitative trait locusand fruit ripening RNA sequencing data to identify candidate genes in Fragaria × ananassa. We leveraged knowledge from Fragaria × ananassa to identify candidate genes in F. vesca and validated one gene from each strawberry species using fruit transient gene expression assays. We found that a novel Enoyl CoA hydratase/isomerase gene in Fragaria × ananassa, FaECH, increases concentration of γ-lactones while a similar but nonhomologous gene, FvECH-like, increases γ-lactones in F. vesca. Additionally, the major gene shown to control γ-decalactone production in Fragaria × ananassa, FaFAD1, has a homolog in F. vesca, FvFAD1, that underlies a strong GWAS. These results validate key γ-lactone biosynthesis steps in both strawberry species and provide tools to breed more flavorful strawberries.

The pepper Bs2 resistance gene confers resistance to susceptible Solanaceae plants against pathogenic strains of Xanthomonas campestris pv. vesicatoria carrying the avrBs2 avirulence gene. Previously, we generated Bs2-transgenic Citrus sinensis plants that exhibited enhanced resistance to citrus canker caused by Xanthomonas citri subsp. citri (Xcc), although the underlying mechanisms remained unknown. To elucidate the molecular basis of the early defense response, we performed a comparative transcriptomic analysis of Bs2-expressing and non-transgenic plants 48 h after Xcc inoculation. A total of 2022 differentially expressed genes (DEGs) were identified, including 1356 up-regulated and 666 down-regulated genes. In Bs2-plants, 36.8% of the up-regulated DEGs were associated with defense responses and biotic stress. Functional annotation revealed major changes in genes encoding receptor-like kinases, transcription factors, hormone biosynthesis enzymes, pathogenesis-related proteins, secondary metabolism, and cell wall modification. Among hormone-related pathways, genes linked to ethylene biosynthesis and signaling were the most strongly regulated. Consistently, endogenous ethylene levels increased in Bs2-plants following Xcc infection, and treatment with an ethylene-releasing compound enhanced resistance in non-transgenic plants. Overall, our results indicate the Bs2 expression activates a complex defense network in citrus and may represent a valuable strategy for controlling canker and other Xanthomonas-induced diseases.

ABSTRACTEndophytic fungi are known to improve plant resistance to stress and enhance plant performance. A comprehensive understanding of the mechanisms underlying endophytic fungi‐mediated systemic resistance is crucial for the widespread adoption of these fungi as beneficial biological control agents. To unravel the complex interactions between tomato and endophytic fungi, we compared the transcriptomic responses of tomato plants induced with Trichoderma harzianum, T. afroharzianum, T. atroviride and Pochonia chlamydosporia. RNA‐seq datasets were used to assess the common expression patterns in defence‐related pathways. Our analysis revealed that a group of common key genes were significantly induced in all investigations examined. Additionally, we observed that 20 transcripts related to anion transport, which is crucial for early plant immune responses, were consistently enriched in all the studies. These findings highlight the conserved and specific nature of plant–endophyte interactions and their potential for enhancing plant resistance through targeted genetic manipulation and breeding for long‐lasting resistance.

BackgroundDiaprepes abbreviatus is a major pest causing severe root damage and yield loss in over 150 species, with a complex life cycle that hinders effective control. Limited genomic and transcriptomic resources have restricted molecular insights into its biology. De novo transcriptome assembly provides a practical approach for reconstructing the full set of transcripts in organisms without a reference genome, enabling the identification of novel genes and isoforms as well as the study of gene expression patterns.ResultsWe performed RNA-seq across seven developmental stages of D. abbreviatus, generating a high-quality de novo transcriptome assembly comprising 991,860 unique transcripts and 505,007 unigenes with 99.2% completeness based on BUSCO analysis. Gene structure annotation predicted 75,895 coding sequences with an average length of 1,079 bp. Comparative transcriptomic analysis of adult males and females identified 16,082 significantly differentially expressed transcripts, emphasizing distinct sex-biased gene expression patterns. Functional classification revealed major enrichment in metabolism, signal transduction, transport, and developmental processes. Additionally, genes related to mitochondrial function, muscle structure, and detoxification pathways exhibited clear sex-specific expression. Gene Ontology (GO) and KEGG pathway analyses further emphasized enrichment in detoxification, xenobiotic metabolism, and hormonal regulation pathways. We further validated this differential expression data by RT-qPCR analysis.ConclusionsWe present a high-quality de novo transcriptome assembly of D. abbreviatus with detailed, stage-specific transcript coverage. The identification of key developmentally regulated genes offers valuable insights into the molecular mechanisms underlying their biology. This resource lays the groundwork for future functional studies and the development of targeted pest management strategies, contributing to sustainable control of this economically important pest.Supplementaryy InformationThe online version contains supplementary material available at 10.1186/s12864-025-11880-8.

Citrus production has declined globally due to the devastating impacts of citrus greening or huanglongbing (HLB). Citrus trees impacted by HLB lose root mass up to 80%, have limited canopy and declining fruit yields due to limited water and nutrient uptake capacity. Thus, managing soil fertility is essential in sustaining citrus production by ensuring optimal plant nutrition and productivity. This study evaluated fertilizer products to enhance the performance of HLB-affected citrus trees. The 6 treatments included a basal conventional fertilizer blend, 2 soil- and 3 foliar-applied fertilizers replicated 6 times in a randomized complete block design in Lake Alfred, FL. Data collected included soil and leaf nutrient concentrations, soil pH, canopy size, fruit yield and juice quality and digital images of roots. Soil pH showed a significant positive correlation with Ca, Mg, Zn, and B while exhibiting a significant negative correlation with S, P, and Fe. The soil-applied fertilizers provided more plant-available nutrients overall. Nova Hi Peak foliar treatment showed more soil nutrient concentration across all treatments. There were no significant differences in canopy volume and yield between treatments across the years. There was a significant difference between Titratable acidity and total soluble solids ratio in 2023 and 2024. Nova Hi Peak and Polysulphate resulted in higher root traits. Foliar fertilization with Nova HiPeak improved citrus canopy size, root morphology, and fruit yield. Combining foliar applications like Nova HiPeak and granular fertilizers such as Polysulphate improved the nutrient availability in the soil and juice quality.

Abstract Sieve Element Occlusion (SEO) proteins are subunits that form P-protein filaments in phloem. These filaments play a structural role and contribute to plant defense by reversible sieve plate (SP) blockage. This mechanism is particularly important in Citrus trees affected by Huanglongbing (HLB), as SEO genes are highly induced in susceptible species Citrus sinensis upon Candidatus Liberibacter asiaticus (CLas) colonization. Given the limited information on this gene family in Citrus, we analyzed 27 SEO genes within the Rutaceae family, with a focus on genera closely related to Citrus, to better understand their potential roles in HLB tolerance. Genomic sequences revealed conserved exon-intron structures similar to Arabidopsis, while promoter regions contained a higher number of light-responsive Cis-elements, along with elements associated with growth, development, stress responses, and phloem-specific gene expression. Subcellular localization identified the cytoplasm as the primary site, with additional predictions for the plasma membrane and mitochondria. Phylogenetic analysis categorized SEO proteins into five subgroups, refining their classification in Citrus. Lately, protein interaction networks indicated strong connections with proteins involved in coordinated immune responses. These findings improve the understanding of SEO protein dynamics and evolutionary conservation, highlighting their role in phloem biology. Further investigation of these SEO genes and their promoters in the plant response to HLB could help identify specific targets for developing disease-tolerant citrus varieties through genetic engineering.