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<p>Walnut (<i>Juglans</i> spp.) is one of the most economically important temperate nut tree species, valued worldwide for its highly nutritious kernels rich in unsaturated fatty acids, antioxidants and health-promoting phytochemicals. Owing to its wide natural distribution and high genetic diversity, walnut represents a key species for genetic conservation and modern breeding programs. However, conventional walnut improvement has been slow due to its long juvenile period, strong heterozygosity and the limited precision of phenotype-based selection. The advent of molecular technologies has revolutionized walnut research by enabling accurate germplasm characterization, hybrid verification, genetic diversity analysis and marker-assisted breeding. This review summarizes the progression of molecular tools applied in walnut research, from early isozyme analyses to polymerase chain reaction (PCR)-based markers such as restriction fragment length polymorphisms (RFLPs), random amplified polymorphic DNA (RAPDs), amplified fragment length polymorphisms (AFLPs) and inter-simple sequence repeats (ISSRs), which significantly contributed to genetic mapping and diversity studies. The subsequent adoption of highly polymorphic and reliable markers, including simple sequence repeats (SSRs) and single nucleotide polymorphisms (SNPs), further strengthened genetic analysis and breeding efficiency. With recent advances in next-generation sequencing (NGS), genome-wide association studies (GWAS), genomic selection and clustered regularly interspaced short palindromic repeats (CRISPR)-based genome editing, walnut genomics has entered a phase of unprecedented resolution and precision. Furthermore, integrative omics approaches such as transcriptomics, proteomics and metabolomics are providing deeper insights into gene function and regulatory networks. Overall, this review highlights the historical and current molecular advances in walnut research and emphasizes how emerging genomic technologies can accelerate breeding progress and help overcome long-standing reproductive and genetic constraints in walnut improvement.</p>

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Molecular Breeding and Omics-Driven Improvement of Walnut (Juglans regia L.): From Classical Markers to Genome Editing

  • 期刊论文

  • 发表日期：

    2026年3月26日

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  • E. Manikandan,
  • Deepika,
  • Shagun Sharma,
  • Pankaj Kumar,
  • Pramod Verma,
  • Kourosh Vahdati

摘要

Walnut (Juglans spp.) is one of the most economically important temperate nut tree species, valued worldwide for its highly nutritious kernels rich in unsaturated fatty acids, antioxidants and health-promoting phytochemicals. Owing to its wide natural distribution and high genetic diversity, walnut represents a key species for genetic conservation and modern breeding programs. However, conventional walnut improvement has been slow due to its long juvenile period, strong heterozygosity and the limited precision of phenotype-based selection. The advent of molecular technologies has revolutionized walnut research by enabling accurate germplasm characterization, hybrid verification, genetic diversity analysis and marker-assisted breeding. This review summarizes the progression of molecular tools applied in walnut research, from early isozyme analyses to polymerase chain reaction (PCR)-based markers such as restriction fragment length polymorphisms (RFLPs), random amplified polymorphic DNA (RAPDs), amplified fragment length polymorphisms (AFLPs) and inter-simple sequence repeats (ISSRs), which significantly contributed to genetic mapping and diversity studies. The subsequent adoption of highly polymorphic and reliable markers, including simple sequence repeats (SSRs) and single nucleotide polymorphisms (SNPs), further strengthened genetic analysis and breeding efficiency. With recent advances in next-generation sequencing (NGS), genome-wide association studies (GWAS), genomic selection and clustered regularly interspaced short palindromic repeats (CRISPR)-based genome editing, walnut genomics has entered a phase of unprecedented resolution and precision. Furthermore, integrative omics approaches such as transcriptomics, proteomics and metabolomics are providing deeper insights into gene function and regulatory networks. Overall, this review highlights the historical and current molecular advances in walnut research and emphasizes how emerging genomic technologies can accelerate breeding progress and help overcome long-standing reproductive and genetic constraints in walnut improvement.