Establishment of an in vitro regeneration system and genetic transformation of the Tunisian 'Maltese half-blood' (Citrus sinensis): an agro-economically important variety

The Role of Italy in the Use of Advanced Plant Genomic Techniques on Fruit Trees: State of the Art and Future Perspectives

Climate change is deeply impacting the food chain production, lowering quality and yield. In this context, the international scientific community has dedicated many efforts to enhancing resilience and sustainability in agriculture. Italy is among the main European producers of several fruit trees; therefore, national research centers and universities undertook several initiatives to maintain the specificity of the 'Made in Italy' label. Despite their importance, fruit crops are suffering from difficulties associated with the conventional breeding approaches, especially in terms of financial commitment, land resources availability, and long generation times. The 'new genomic techniques' (NGTs), renamed in Italy as 'technologies for assisted evolution' (TEAs), reduce the time required to obtain genetically improved cultivars while precisely targeting specific DNA sequences. This review aims to illustrate the role of the Italian scientific community in the use of NGTs, with a specific focus on Citrus, grapevine, apple, pear, chestnut, strawberry, peach, and kiwifruit. For each crop, the key genes and traits on which the scientific community is working, as well as the technological improvements and advancements on the regeneration of local varieties, are presented. Lastly, a focus is placed on the legal aspects in the European and in Italian contexts.

A dual sgRNA-directed CRISPR/Cas9 construct for editing the fruit-specific β-cyclase 2 gene in pigmented citrus fruits

CRISPR/Cas9 genome editing is a modern biotechnological approach used to improve plant varieties, modifying only one or a few traits of a specific variety. However, this technology cannot be easily used to improve fruit quality traits in citrus, due to the lack of knowledge of key genes, long juvenile stage, and the difficulty regenerating whole plants of specific varieties. Here, we introduce a genome editing approach with the aim of producing citrus plantlets whose fruits contain both lycopene and anthocyanins. Our method employs a dual single guide RNA (sgRNA)-directed genome editing approach to knockout the fruit-specific β-cyclase 2 gene, responsible for the conversion of lycopene to beta-carotene. The gene is targeted by two sgRNAs simultaneously to create a large deletion, as well as to induce point mutations in both sgRNA targets. The EHA105 strain of Agrobacterium tumefaciens was used to transform five different anthocyanin-pigmented sweet oranges, belonging to the Tarocco and Sanguigno varietal groups, and 'Carrizo' citrange, a citrus rootstock as a model for citrus transformation. Among 58 plantlets sequenced in the target region, 86% of them were successfully edited. The most frequent mutations were deletions (from -1 to -74 nucleotides) and insertions (+1 nucleotide). Moreover, a novel event was identified in six plantlets, consisting of the inversion of the region between the two sgRNAs. For 20 plantlets in which a single mutation occurred, we excluded chimeric events. Plantlets did not show an altered phenotype in vegetative tissues. To the best of our knowledge, this work represents the first example of the use of a genome editing approach to potentially improve qualitative traits of citrus fruit.

Micropropagación in vitro de naranja agria (Citrus aurantium L.) a partir de segmentos nodales

La naranja agria (Citrus aurantium L.) presenta un alto valor nutricional y gastronómico en el distrito de Huacho, Lima, Perú, pero en la actualidad se considera una especie en peligro de desaparecer del distrito y alrededores por problemas fitosanitarios. Para la recuperación y repoblación de esta especie se planteó emplear técnicas biotecnológicas para la obtención de plantas libres de patógenos. Por lo tanto, el objetivo de la presente investigación fue micropropagar in vitro naranja agria a partir de segmentos nodales. Los segmentos nodales de naranja agria fueron desinfectados en diferentes concentraciones de NaClO, luego se introdijeron en medio de cultivo MS (Murashige y Skoog) adicionado con BAP, KIN y AG3 para la fase de multiplicación, posteriormente se transfirieron a medios MS adicionado con IBA y ANA para la fase de enraizamiento. La evaluación del porcentaje de contaminación se realizó a los diez días, la evaluación de formación de brotes en fase de multiplicación se realizó a los 30 días y la evaluación de enraizamiento a los 30 días. En la fase de desinfección y establecimiento in vitro se logró obtener 0% de contaminación y 0% de oxidación de los explantes. En la fase de multiplicación in vitro los mejores resultados se obtuvieron en el medio de cultivo M8 generando 4,7 brotes por explante. Y finalmente en la fase de enraizamiento el medio E4 permitió obtener 94,7% de explantes enraizados, 23,4 mm de longitud de raíz y 2,2 raíces por explante.