Single berry development - a new phenotyping and transcriptomics paradigm

Most present knowledge on berry development has been obtained from a random sampling of hundreds of berries to average their diversity of the experimental plot. According to recent studies, such heterogeneous samples formed from non-synchronized berries of mixed developmental stages are unsuitable for detecting fast physiological and molecular changes. Thus, it is necessary to revisit the physiological and transcriptional bases of berry ripening. Here we report the in-depth study of the late-ripening program in three genotypes. Berry expansion during the second growth phase was characterized on-vine through image analysis. Hundreds of sampled berries were individually analyzed for primary metabolites to calculate their respective accumulation rates with high precision. These primary individual fluxes and the growth kinetics allowed us to distinguish targeted developmental stages further investigated through RNA profiling. Single berry monitoring evidenced sharp developmental phases during which specific genes or pathways are quickly switched ON or OFF. The comparison between Syrah and the two microvines showed phenotypic differences in late-ripening stag-es in vines grown in the field (Syrah) and microvines (MV032 and MV102) grown in the greenhouse. This study shows that new high-throughput single berry phenotyping methods are required to compare unambiguous developmental stages in physiological or genetic studies.