New research shows significant differences in the genomes of American and Chinese chestnut trees, particularly in the nucleolus organizing region (NOR).

The Chinese chestnut has a larger and more condensed NOR with inactive DNA, while the American chestnut has a smaller, transcriptionally active NOR.

These genetic differences have implications for hybridization efforts to impart blight resistance to American chestnuts by crossing them with Chinese chestnuts.

The researchers used fluorescent in situ hybridization (FISH) to analyze the DNA arrangement and plan to further investigate using oligonucleotide FISH with specific DNA probes.

The aim is to produce American chestnut hybrids with both height and blight resistance, however, current hybrids do not yet have sufficient resistance for restoration.