| Popis: |
Muscadine grapes (Vitis rotundifoliaMichx.) are a specialty crop cultivated in the southern United States. Muscadines (2n=40) belong to theMuscadiniasubgenus ofVitis,while all other cultivated grape species belong to the subgenusEuvitis(2n=38). The berry color locus in muscadines has been mapped to a 0.8 Mbp region syntenic with chromosome 4 ofV. vinifera. In this study, we identified glutathione S-transferase4 (GST4) as a likely candidate gene for anthocyanin transport within the berry color locus. PCR and KASP genotyping identified a single intragenic SNP (C/T) marker corresponding to a proline to leucine mutation within the muscadineGST4(VrGST4) that differentiated black (CC and CT) from bronze (TT) muscadines in 65 breeding selections, 14 cultivars, and 320 progeny from two mapping populations. Anthocyanin profiling on a subset of the progeny indicated a dominantVrGST4action, with no allele dosage effect on total anthocyanin content or composition of individual anthocyanins. Proanthocyanidin content was similar in the seeds of both black and bronze genotypes, and seeds had much higherVrGST3expression and lowerVrGST4expression than skins.VrGST4expression was higher in post-veraison berries of black muscadines compared to pre-veraison berries, but no changes in gene expression in pre- and post-veraison berries were observed in the bronze muscadine cultivar.VrMybA1expression was higher in post-veraison berries of both black and bronze muscadines. These results suggest that berry pigmentation in muscadines is regulated by a mechanism distinct from theMybAgene cluster that is responsible for berry color variation inV. vinifera. |
