Genetic Basis and Molecular Breeding Strategies for Processing Quality in Chestnut (Castanea spp.)

Processing quality in chestnut (Castanea spp.) is a complex trait jointly determined by fruit development, postharvest metabolic changes, and responses to processing. However, its genetic basis and regulatory networks remain poorly understood. This review provides an integrated framework linking product-specific processing requirements with their biochemical basis, candidate genes, and molecular breeding strategies. Starch composition and fine structure primarily determine cooked texture, storage hardening, and digestibility; starch degradation and sugar metabolism affect sweetness and thermally induced flavor formation; and phenolic substrates, together with oxidative enzymes, determine browning potential and color stability. We review the biochemical basis underlying these traits and summarize candidate genes and regulatory pathways involved in starch synthesis and structural modification, starch-to-sugar conversion, enzymatic browning, flavor formation, and the accumulation of nutritional and bioactive compounds. Nevertheless, stable quantitative trait loci, favorable haplotypes, and causal genes associated with chestnut processing quality remain insufficiently validated. Future research should develop product-oriented, standardized phenotyping systems and integrate multi-environment genetic analyses, multi-omics network dissection, marker-assisted selection, genomic selection, and gene editing to elucidate the genetic mechanisms underlying chestnut processing quality and enable the precision breeding of processing-specific cultivars.