Discovery of plastid gene mutations causing albinism in chimeric Cornus cultivars (Cornaceae)

Chimera plants are becoming popular due to their ornamental and aesthetic appeal. Here, we examined the complete plastid genomes (plastomes) and 45S nuclear ribosomal DNAs (nrDNAs) from green and albino leaf tissues (GLT and ALT) of five Cornus cultivars ( Cornus florida Cherokee Daybreak and four Cornus kousa cultivars). We identified deleterious plastome mutations unique to the ALT of three cultivars: a missense mutation (Y29D) in matK (Cherokee Daybreak) impairing transcript splicing, a 1-bp deletion in rpoB (Melanie), and a 7-bp tandem repeat insertion in ycf3 (Doudou). The latter two induced frameshifts and premature stop codons. Rutban and Tom Wood exhibited identical GLT and ALT plastome sequences, and no 45S nrDNA variations were detected across any cultivars. Furthermore, phylogenetic analyses clustered these cultivars within big-bracted dogwoods and resolved the maternal lineage of the hybrid Rutban as C. florida , correcting prior ambiguities. We also developed five specific molecular markers (two intergenic high-resolution melting and three gene-specific) that successfully discriminated these morphologically similar cultivars. These findings elucidate the diverse genetic causes of albinism and highlight plastid super-barcoding for precision breeding.