Grape texture characteristics are linked to one major qtl

Abstract

AIM: Berry texture and berry skin mechanical properties have high agronomic importance, related to quality and marketing requirements of wine, table and raisin grapes. Despite the efforts already made to detect molecular markers and candidate genes associated with berry texture, different QTLs were proposed until now, showing low contribution rates to the trait, likely due to difficulty in phenotyping. Searching for QTLs linked to berry texture, an F1 population of 154 individuals and their parents (‘Raboso Veronese’ and ‘Sultanina’) were used in this study.

METHODS: Density sorting by flotation was applied to reduce sample variability. One density class was selected achieving berries with a similar ripening stage. Mechanical properties were measured and normalized on berry diameter, surface, and volume. Hundred and ninety SSR molecular markers were used to produce a genetic map using JoinMap. MapQTL was applied searching for QTLs associated with berry texture traits. VviAGL11 expression profiling and co-expression analysis during grape ripening was evaluated using available transcriptomic datasets.

RESULTS: A major QTL was found on LG 18, with high LOD scores (from 25.07 to 31.92) and high phenotypic variance explained (from 53.2 to 63.5%) for all measured texture traits. Surprisingly, this major QTL showed association with SSR markers linked to VviAGL11, the main gene leading to stenospermocarpy. Data available on VviAGL11 expression and co-expression profiling during grape ripening strongly suggested that this gene may act on the traits of a ripe berry through the activation of some target genes involved in lipid and hormone metabolism, transport and in gene expression regulation.

CONCLUSIONS

Previous studies showed how difficult is determining the genetic control of berry texture. Our results clearly underline the major role played by a QTL located on LG18 and characterized by the presence of the well-known MADS-box gene VviAGL11.