A roadmap of tissue culture and biotechnology in European hazelnut (Corylus avellana L.).

The increasing interest in European hazelnut (Corylus avellana L.) cultivation registered in the last years has led to a significant increase in worldwide hazelnut growing areas, also involving regions characterized by a marginal presence of hazelnut orchards. Despite this increasement, world production still relies on the cultivation of few varieties, most of which are particularly suitable to the environment where they have been selected. Therefore, it is necessary to develop new cultivars with high environmental plasticity capable of providing constant and high-quality productions in the new environments and under the climatic change conditions of traditional growing areas. Over the years, many molecular markers for genetic breeding programs have been developed and omics sciences also provided further information about the genetics of this species. These data could be of support to the application of new plant breeding techniques (NPBTs), which would allow the development of cultivars with the desired characteristics in a shorter time than traditional techniques. However, the application of these methodologies is subordinated to the development of effective regeneration protocols which, to date, have been set up exclusively for seed-derived explants. A further aspect to be exploited is represented by the possibility of cultivating hazelnut cells and tissues in vitro to produce secondary metabolites of therapeutic interest. This review aims to consolidate the state of the art on biotechnologies and in vitro culture techniques applied on this species, also describing the various studies that over time allowed the identification of genomic regions that control traits of interest.

Chromosome-level genome assembly of Japanese chestnut (Castanea crenata Sieb. et Zucc.) reveals conserved chromosomal segments in woody rosids.

Japanese chestnut (Castanea crenata Sieb. et Zucc.), unlike other Castanea species, is resistant to most diseases and wasps. However, genomic data of Japanese chestnut that could be used to determine its biotic stress resistance mechanisms have not been reported to date. In this study, we employed long-read sequencing and genetic mapping to generate genome sequences of Japanese chestnut at the chromosome level. Long reads (47.7 Gb; 71.6× genome coverage) were assembled into 781 contigs, with a total length of 721.2 Mb and a contig N50 length of 1.6 Mb. Genome sequences were anchored to the chestnut genetic map, comprising 14,973 single nucleotide polymorphisms (SNPs) and covering 1,807.8 cM map distance, to establish a chromosome-level genome assembly (683.8 Mb), with 69,980 potential protein-encoding genes and 425.5 Mb repetitive sequences. Furthermore, comparative genome structure analysis revealed that Japanese chestnut shares conserved chromosomal segments with woody plants, but not with herbaceous plants, of rosids. Overall, the genome sequence data of Japanese chestnut generated in this study is expected to enhance not only its genetics and genomics but also the evolutionary genomics of woody rosids.

Is It Possible to Produce Certified Hazelnut Plant Material in Sicily? Identification and Recovery of Nebrodi Genetic Resources, in vitro Establishment, and Innovative Sanitation Technique From Apple Mosaic Virus.

Eight Sicilian cultivars of hazelnut (Corylus avellana L.), namely-Curcia, Nociara Collica, Panottara Collica, Panottara Galati Grande, Parrinara, Panottara Baratta Piccola, Enzo, and Rossa Galvagno, registered into the Italian Cultivar Register of fruit tree species in 2017 were selected from Nebrodi area and established in vitro. The aim of the work was to carry out the sanitation of the cultivars and get virus-free plants from the most important viral pathogen threat, the apple mosaic virus. Virus-free plant material is essential for the production of certified plants from Sicilian hazelnut cultivars, complying the CE (cat. CAC) quality and the technical standards established in 2017 for voluntary certification by the Italian Ministry of Agricultural, Food and Forestry Policies (MIPAAF). In this study, we investigated the possibility of establishing in vitro true-to-type and virus-free hazelnut plantlets via the encapsulation technology of apexes. The in vitro shoot proliferation rates were assessed for the different cultivars, sampling periods, temperature treatments, and type of explant used for culture initiation. Viability, regrowth, and conversion rates of both conventional meristem tip culture (MTC) and not conventional (MTC combined with the encapsulation technology) sanitation techniques were evaluated.

Early embryo achievement through isolated microspore culture in Citrus clementina Hort. ex Tan., cvs. 'Monreal Rosso' and 'Nules'.

Microspore embryogenesis is a method of achieving complete homozygosity from plants. It is particularly useful for woody species, like Citrus, characterized by long juvenility, a high degree of heterozygosity and often self-incompatibility. Anther culture is currently the method of choice for microspore embryogenesis in many crops. However, isolated microspore culture is a better way to investigate the processes at the cellular, physiological, biochemical, and molecular levels as it avoids the influence of somatic anther tissue. To exploit the potential of this technique, it is important to separate the key factors affecting the process and, among them, culture medium composition and particularly the plant growth regulators and their concentration, as they can greatly enhance regeneration efficiency. To our knowledge, the ability of meta-Topolin, a naturally occurring aromatic cytokinin, to induce gametic embryogenesis in isolated microspores of Citrus has never been investigated. In this study, the effect of two concentrations of meta-Topolin instead of benzyladenine or zeatin in the culture medium was investigated in isolated microspore culture of two genotypes of Citrus. After 11 months of isolated microspore culture, for both genotypes and for all the four tested media, the microspore reprogramming and their sporophytic development was observed by the presence of multinucleated calli and microspore-derived embryos at different stages. Microsatellite analysis of parental and embryo samples was performed to determine the embryo alleles constitution of early embryos produced in all tested media, confirming their origin from microspores. To our knowledge, this is the first successful report of Citrus microspore embryogenesis with isolated microspore culture in Citrus, and in particular in Citrus clementina Hort. ex Tan, cvs. 'Monreal Rosso' and 'Nules.'