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Flavescence dorée (FD) is a destructive phytoplasma disease of European grapevines. Spontaneous and cultivar-dependent recovery (REC) may occur in the field in FD-infected vines starting the year following the first symptoms. However, the biological underpinnings of this process are still largely unexplored. In this study, transcriptome sequencing (RNAseq), whole-genome bisulphite sequencing (WGBS) and metabolite analysis were combined to dissect molecular and metabolic changes associated to FD and REC in leaf veins collected in the field from healthy (H), FD and REC plants of the highly susceptible Vitis vinifera 'Barbera'. Genes involved in flavonoid biosynthesis, carbohydrate metabolism and stress responses were overexpressed in FD conditions, whereas transcripts linked to hormone and stilbene metabolisms were upregulated in REC vines. Accumulation patterns of abscisic acid and stilbenoid compounds analysed in the same samples confirmed the RNAseq data. In recovery conditions, we also observed the persistence of some FD-induced expression changes concerning inhibition of photosynthetic processes and stress responses. Several differentially expressed genes tied to those pathways also underwent post-transcriptional regulation by microRNAs, as outlined by merging our transcriptomic data set with a previously conducted smallRNAseq analysis. Investigations by WGBS analysis also revealed different DNA methylation marks between REC and H leaves, occurring within the promoters of genes tied to photosynthesis and secondary metabolism. The results allowed us to advance the existence of a "molecular memory" of FDp infection, involving alterations in the DNA methylation status of REC plants potentially related to transcriptional reprogramming events, in turn triggering changes in hormonal and secondary metabolite profiles.

The increasing demand for hazelnut kernels is favoring an upsurge in hazelnut cultivation worldwide, but ongoing climate change threatens this crop, affecting yield decreases and subject to uncontrolled pathogen and parasite attacks. Technical advances in precision agriculture are expected to support farmers to more efficiently control the physio-pathological status of crops. Here, we report a straightforward approach to monitoring hazelnut trees in an open field, using aerial multispectral pictures taken by drones. A dataset of 4112 images, each having 2Mpixel resolution per tree and covering RGB, Red Edge, and near-infrared frequencies, was obtained from 185 hazelnut trees located in two different orchards of the Piedmont region (northern Italy). To increase accuracy, and especially to reduce false negatives, the image of each tree was divided into nine quadrants. For each quadrant, nine different vegetation indices (VIs) were computed, and in parallel, each tree quadrant was tagged as "healthy/unhealthy" by visual inspection. Three supervised binary classification algorithms were used to build models capable of predicting the status of the tree quadrant, using the VIs as predictors. Out of the nine VIs considered, only five (GNDVI, GCI, NDREI, NRI, and GI) were good predictors, while NDVI SAVI, RECI, and TCARI were not. Using them, a model accuracy of about 65%, with 13% false negatives was reached in a way that was rather independent of the algorithms, demonstrating that some VIs allow inferring the physio-pathological condition of these trees. These achievements support the use of drone-captured images for performing a rapid, non-destructive physiological characterization of hazelnut trees. This approach offers a sustainable strategy for supporting farmers in their decision-making process during agricultural practices. [ABSTRACT FROM AUTHOR]

Physiological and molecular mechanisms underpinning plant water stress responses still need deeper investigation. Particularly, the analysis of rootstock‐mediated signals represents a complex research field, offering potential applicative perspectives for improving the adaptation of fruit crops to environmental stresses. Nonetheless, fundamental knowledge on this subject needs to be widened, especially in some woody species, including European hazelnut (Corylus avellana L). To fill these gaps, we inspected dynamic changes in gas exchanges and stem water potential of two hazelnut genotypes, the 'San Giovanni' cultivar (SG), the non‐suckering rootstock 'Dundee' (D), and their heterograft (SG/D), during a drought stress treatment followed by recovery. Biometric and anatomical traits were measured at the beginning and end of water stress imposition. Additionally, differences in abscisic acid and proline contents were analysed in leaves and roots taken from well‐irrigated, stressed and recovered plants, in combination with expression profiles of candidate genes. Grafting with 'Dundee' rootstock positively affected the ability of 'San Giovanni' plants to endure drought by increasing their intrinsic water use efficiency and facilitating post‐rehydration recovery. Although anatomical adjustments occurred, we showed that the improved stress adaptation of grafted plants rather depended on biochemical modifications, resulting in increased root proline concentrations and leaf ABA accumulation both during water stress and recovery. We also proved that those metabolic changes were controlled by a differential reprogramming of genes involved in hormone metabolism and stress defence. Grafting with non‐suckering rootstocks could therefore represent a promising and environmentally‐friendly strategy for improving the adaptability of hazelnut to water deficit. [ABSTRACT FROM AUTHOR]

The editorial discusses the use of biostimulants and green biotechnological strategies to enhance sustainable crop production in challenging climates due to climate change and limited resources. While these approaches have shown promise in controlled experiments, their effectiveness in field applications remains inconsistent. Various studies presented in the editorial highlight the impact of environmental factors on the performance of biostimulants, with better results observed in tropical and subtropical climates compared to temperate regions. Additionally, the importance of genotypic differences, interactions with native soil-microbial communities, and methodological challenges in testing these strategies are emphasized as key areas for future research. [Extracted from the article]

SUMMARY: The main bottleneck in the application of biotechnological breeding methods to woody species is due to the in vitro regeneration recalcitrance shown by several genotypes. On the other side, woody species, especially grapevine (Vitis vinifera L.), use most of the pesticides and other expensive inputs in agriculture, making the development of efficient approaches of genetic improvement absolutely urgent. Genome editing is an extremely promising technique particularly for wine grape genotypes, as it allows to modify the desired gene in a single step, preserving all the quality traits selected and appreciated in elite varieties. A genome editing and regeneration protocol for the production of transgene‐free grapevine plants, exploiting the lipofectamine‐mediated direct delivery of CRISPR–Cas9 ribonucleoproteins (RNPs) to target the phytoene desaturase gene, is reported. We focused on Nebbiolo (V. vinifera), an extremely in vitro recalcitrant wine genotype used to produce outstanding wines, such as Barolo and Barbaresco. The use of the PEG‐mediated editing method available in literature and employed for highly embryogenic grapevine genotypes did not allow the proper embryo development in the recalcitrant Nebbiolo. Lipofectamines, on the contrary, did not have a negative impact on protoplast viability and plant regeneration, leading to the obtainment of fully developed edited plants after about 5 months from the transfection. Our work represents one of the first examples of lipofectamine use for delivering editing reagents in plant protoplasts. The important result achieved for the wine grape genotype breeding could be extended to other important wine grape varieties and recalcitrant woody species. [ABSTRACT FROM AUTHOR]

The first serious outbreak of Flavescence dorée (FD) in Piedmont (North-West Italy) dates back to 1998 in the Tortona area (Alessandria province). FD is a serious quarantine-worthy disease transmitted by the leafhopper Scaphoideus titanus Ball. Different Vitis vinifera L. biotypes react differently to the phytoplasma, in particular as to the accumulation of polyphenols in leaves. In this experimentation, we observed and described concentration and accumulation of the main classes of polyphenols in entire leaves and in leaf blades and veins of two varieties, Nebbiolo and Barbera, displaying different levels of susceptibility to FD. Their well-known different reactions could be related, at least partially, to leaf polyphenols, both as to concentrations and profiles. Nebbiolo displayed some specific traits: i) the higher percentage of incidence over totals of individual molecules known to be powerful antioxidants (caftaric acid over coutaric acid; quercetin glycosides over other flavonols); ii) the higher concentration of flavanols in veins with respect to Barbera and their wider profile (astilbin and a taxifolin-glycoside, this last accumulating exclusively in Nebbiolo).

Along with the ongoing climate change, drought events are predicted to become more severe. In this context, the spray‐induced gene silencing (SIGS) technique could represent a useful strategy to improve crop stress resilience. A previous study demonstrated that the Arabidopsis mutants for a glutathione S‐transferase (GST) gene had increased abscisic acid (ABA) levels and a more activated antioxidant system, both features that improved drought resilience. Here, we used SIGS to target a putative grape GST gene (VvGST40). Then, ecophysiological, biochemical and molecular responses of 'Chardonnay' cuttings were analysed during a drought and recovery time‐course. Gas exchange, ABA and t‐resveratrol concentration as well as expression of stress‐related genes were monitored in not treated controls, dsRNA‐VvGST40‐ and dsRNA‐GFP‐ (negative control of the technique) treated plants, either submitted or not to drought. VvGST40‐treated plants revealed increased resilience to severe drought as attested by the ecophysiological data. Analysis of target metabolites and antioxidant‐ and ABA‐related transcripts confirmed that VvGST40‐treated plants were in a priming status compared with controls. SIGS targeting an endogenous gene was successfully applied in grapevine, confirming the ability of this technique to be exploited not only for plant protection issues but also for functional genomic studies. Summary Statement: Here, we used the innovative SIGS technique to functionally characterize a glutathione‐S‐transferase (VvGST40) gene in grapevine which indeed showed an improved resilience when submitted to severe water stress treatment. [ABSTRACT FROM AUTHOR]