Exploring the diversity of Sicilian almond germplasm to identify potential sources of Xylella fastidiosa resistance

The almond tree exhibits extensive variability in Italy, where recent studies reveal a heritage of over 500 accessions. The self-incompatibility of most almond cultivars, together with the widespread use of seeds for propagation, has significantly contributed to the diversification and richness of this vast genetic pool. Certain specimens are often genetically distinct, serving as an unexplored repository of genes related to agronomic traits, including adaptation, stress tolerance, productivity, and quality. Sicily and Apulia are the main Italian regions in terms of production and cultivated areas of almond trees, showing very rich germplasm resources. In 1999, Sicily inaugurated the “Living Almond Museum” in the “Valley of the Temples Park” in Agrigento housing approximately 250 accessions from the most significant almond cultivation areas, commonly denoted by traditional names associated with the cultivation area. Understanding this genetic diversity is pivotal for crucial research on new plants resistant to abiotic and biotic stress. Recently, the Xylella fastidiosa bacterium, which has already inflicted significant losses on Apulian olive production, has also been detected in Italian, Spanish, and French almond orchards, causing concern. Presently, the Department SAAF is engaged in a national project, OMIBREED, to consolidate ongoing research on genetic resistance to different strains of X. fastidiosa in Mediterranean crops. In this work, the genetic screening of 40 accessions of Sicilian almond germplasm has been conducted using molecular SSR markers and some putative candidate genes involved in resistance traits to abiotic and biotic stress in almond, identified from available published RNA sequencing data. The most diverse accessions will be used for screening the real resistance against X. fastidiosa in Apulia, where they will be inoculated with the bacterium. The authors thank the “SiciliAn MicronanOTecH Research and Innovation CEnter SAMOTHRACE (MUR, PNRRM4C2, ECS_00000022), spoke 3–University of Palermo S2-COMMs- Micro and Nanotechnologies for Smart and Sustainable Communities”.