Horticulturae

Tree fruit and nut crops are a critical component of the global economy, producing at least 400 million tonnes of produce in 2022 and nourishing a growing population of approximately 8 billion humans every year. Improved cultivars and growing practices depend upon an understanding of the molecular basis of tree traits and physiology. Over the past 20 years, the proliferation of reference genomes for tree fruit and nut crop species has transformed the study of genetics in these crops, providing a platform for resequencing analyses of large populations, enabling comparative genomic analyses between distant plant species, and allowing the development of molecular markers for use in breeding. However, reference bias and poor transferability of markers limit widespread applicability in many instances. As third-generation sequencing has become more accurate and accessible, a greater number of reference genomes have become available, enabling higher-quality assemblies and wider sampling of genomic diversity. To facilitate the effective use of multiple closely related genomes to create a reference and comparative genomics platform, tools have been developed for the creation of pangenome graphs, a data structure using nodes connected by edges to represent multiple genomes and their sequence variations. Pangenome graphs allow for singular representations of diversity within a species or even a wider genus. Pangenomic analyses at the genus-scale (e.g., Malus, Citrus) have been conducted for Malus and Citrus, and more tree fruit and nut species are likely to follow. As the number of genome sequences and pangenome resources increases, the importance of generating great quantities of transcriptomic and phenomic data will increase as well. This data is essential in the drive to connect genes to traits and overcome traditional breeding bottlenecks, which is needed to develop improved tree fruit and nut crops, which can satisfy global demand.

Zinc oxide nanoparticles (ZnO NPs) have garnered increasing attention in agriculture due to their potential to enhance plant growth and nutrient use. This research investigates the concentration-dependent effects of ZnO NPs on young crabapple (Malus robusta) plants, addressing gaps in understanding how different concentrations influence plant development. A hydroponic experiment was conducted, applying foliar treatments of 200 mg L⁻¹ ZnSO₄ (S200) and 200, 500, and 1000 mg L⁻¹ ZnO NPs (N200, N500, N100). The control group (CK) was treated with deionized water (dH₂O). Growth parameters, antioxidant enzyme activity, and nutrient contents were measured to evaluate the impact of ZnO NPs on plant development and nutrient uptake. The results showed that N200 enhanced growth, increasing plant height by 22.64%, total dry weight by 49.36%, and root length by 116.07%. In contrast, N500 and N1000 induced oxidative stress, elevating H₂O₂ and MDA by 32.02~54.43% and inhibiting growth. N200 also improved nutrient uptake, increasing K, Ca, Fe, and Zn uptake fluxes by 84.92%, 112.12%, 185.15%, and 149.92%, respectively, whereas N1000 suppressed overall nutrient uptake but increased root Ca accumulation by 64.59%. These findings suggest that ZnO NPs can enhance plant growth and nutrient utilization at low concentrations, with potential implications for agricultural practices involving nanoparticle (NP)-based fertilizers.

Canavalia ensiformis (L.) DC. (Fabaceae) is used in Cuba in soils dedicated to coffee cultivation, contributing to soil nutrition and crop productivity. However, no rhizobial isolates are currently available for inoculating this legume in Chromic Eutric Cambisol soils. The aim of this study was to select rhizobial strains that promote the growth of C. ensiformis in Chromic Eutric Cambisol soils. Nodules were collected from C. ensiformis plants, surface-sterilized, and macerated to isolate potential rhizobia. The isolates were characterized based on cultural, morphological, and biochemical traits, and their symbiotic effectiveness was evaluated through in vitro inoculation assays in Macroptilium atropurpureum (siratro) plants. Inoculation trials were conducted under semi-controlled conditions and in the field between coffee rows. The number and dry weight of effective nodules, number of trifoliate leaves, and shoot dry biomass were measured. Nine bacterial isolates were obtained, grouped into four morphotypes, and assigned as possible members of the families Phyllobacteriaceae, Methylobacteriaceae, or Nitrobacteraceae. Under semi-controlled conditions, inoculation with three isolates increased the number of nodules (by 56–80%), the number of trifoliate leaves (by 20–45%), and shoot biomass (by 10–40%) compared to the non-inoculated treatment. Additionally, one of the isolates increased nodule dry weight by 27%. In the field between coffee row, increases were also observed in the number of trifoliate leaves (by 18–26%) and shoot biomass (by 15–24%). This study supports the selection of efficient rhizobia adapted to the edaphoclimatic conditions of Cuban coffee agroecosystems.