Genetic mapping of fruit texture in American cranberry reveals multi-trait QTL and a complex genetic architecture

Fruit texture is a key quality trait in cranberry (Vaccinium macrocarpon Ait.), with a direct impact on processing efficiency and overall profitability for the industry. To elucidate the genetic basis of cranberry texture, we conducted the first QTL mapping study in this crop implementing a fruit compression method with 10 mechanical texture traits in two biparental populations, CNJ02 (n=168) and CNJ04 (n=67), over two years. These 10 traits, associated with flesh hardness/stiffness and elasticity, showed similar phenotypic patterns of transgressive segregation and generally strong positive correlations. However, traits accounting for fruit size and shape effects (stress/strain-related traits and maximum contact pressure), together with slope-related parameters, exhibited consistently high heritability across populations, supporting their potential utility for breeding and genetic analyses. Genetic mapping revealed multiple consistently detected multi-trait QTL distributed across chromosomes 1,2,3,4,5,8,9,10,11 and 12, suggesting a complex genetic architecture. These genomic regions explained, on average, 4.67-18.6% of the phenotypic variance in CNJ02 and 10.97-27.75% in CNJ04. Candidate genes identified within these regions point to cell wall dynamics, including pectin modification, cellulose biosynthesis, and hemicellulose metabolism, as potentially relevant processes underlying cranberry fruit texture. Our findings provide loci in association with texture traits in cranberry and insights for the genetic improvement of this essential trait, informing the design of genotyping platforms and the implementation of genomic-assisted breeding approaches. Furthermore, we anticipate that these results will guide future studies aimed at optimizing postharvest fruit handling and management practices.