Genomic Investigation of Traits Associated with Nut and Kernel in a Full-Sib Population of European Hazelnut

This study investigates the genetic basis of fruit traits in European hazelnut ( Corylus avellana L.), with a focus on identifying the genetic determinants that influence nut and kernel traits as well as the genes associated with flowering time. The research aims to shorten hazelnut breeding cycles and understand the genetic interplay affecting these traits. Using a mapping population from 'Tonda Gentile delle Langhe' (TGdL) and 'Merveille de Bollwiller' (MB) cultivars (175 F1 progeny), extensive phenotyping and genotypic analysis were conducted. Quantitative trait loci (QTL) analysis identified 131 QTLs (52 major) associated with 12 nut and kernel traits were identified across the 11 LGs with 68 on the TGdL map and 63 on the MB map. Among them stable QTLs over the three years were detected on TGdL map (nine QTLs on five LGs) and MB map (13 QTLs on four LGs). The most interesting were on MB_04 and MB_05 LGs for fruit size traits, on TGdL_04 and TGdL_11 for fruit shape traits and on MB_02 for cluster traits. Through exploration of candidate genes within these regions a linkage between nut and kernel traits and flowering time were identified, along with candidate genes involved in key developmental processes such as cell proliferation and circadian clock regulation. Notably, genes affecting flowering time were also linked to fruit development traits, suggesting a genetic connection. Our findings highlight a significant genetic overlap between nut and kernel traits and flowering time, providing valuable genetic markers for use in hazelnut breeding programs. This research underlines the potential for using molecular breeding techniques to enhance trait selection efficiency, thereby supporting the development of new hazelnut varieties with improved quality and adaptability to changing environmental conditions. These insights are crucial for advancing sustainable agricultural practices and meeting the increasing global demand for hazelnuts.