Phenotypic, Hormonal, and Genomic Variation Among Vitis vinifera Clones With Different Cluster Compactness and Reproductive Performance

Abstract

Previous studies showed that the number of berries is a major component of the compactness level of the grapevine clusters. Variation in number of fruits is regulated by events occurring in the fruitset, but also before during the flower formation and pollination, through factors like the initial number of flowers or the gametic viability. Therefore, the identification of the genetic bases of this variation would provide an invaluable knowledge of the grapevine reproductive development and useful tools for managing yield and cluster compactness. We performed the phenotyping of four clones (two compact and two loose clones) of the Tempranillo cultivar with reproducible different levels of cluster compactness over seasons. Measures of reproductive performance included flower number per inflorescence, berry number per cluster, fruitset, coulure, and millerandage indices. Besides, their levels of several hormones during the inflorescence and flower development were determined, and their transcriptomes were evaluated at critical time points (just before the start and at the end of flowering). For some key reproductive traits, like number of berries per cluster and number of seeds per berry, clones bearing loose clusters showed differences with the compact clones and also differed from each other, indicating that each one follows different paths to produce loose clusters. Variation between clones was observed for abscisic acid and gibberellins levels at particular development stages, and differences in GAs could be related to phenotypic differences. Likewise, various changes between clones were found at the transcriptomic level, mostly just before the start of flowering. Several of the differentially expressed genes between one of the loose clones and the compact clones are known to be over-expressed in pollen, and many of them were related to cell wall modification processes or to the phenylpropanoids metabolism. We also found polymorphisms between clones in candidate genes that could be directly involved in the variation of the compactness level.

The dynamic mosaic phenotypes of flowering plants

“…Moreover, Grimplet et al . () found among‐genet variation in hormone concentrations and that phenotypic variation of mosaic traits paralleled gibberellin variation. Using SNP‐based estimates of relatedness coupled with parameters‐as‐data characterisation of within‐individual variation (see the ‘Measurement and analysis’ subsection), Kulbaba et al .…”

“…If temporal and spatial within‐individual variation arise from control of gene expression, does this control vary genetically among individuals, as is required for variation patterns to respond to natural selection? Studies comparing clonal replicates in different environments detected significant among‐genet variation for within‐individual variation in inflorescence characteristics, including architectural effects (Diggle, ; Grimplet et al ., ). Moreover, Grimplet et al .…”

Mechanisms and Candidate Genes for Seed and Fruit Set in Grapevine

“…First, seedlessness might contribute to lower cluster density. A loose cluster is a desired trait in grapevine breeding, as demonstrated by the extensive studying of bunch compactness [7,8]. This architecture leads to a considerably enhanced resilience to infections that decrease yield and compromise chemical and sensory properties of grapes and derived products [9,10].…”

VviUCC1 Nucleotide Diversity, Linkage Disequilibrium and Association with Rachis Architecture Traits in Grapevine

“…Aiming to identify additional candidate genes underpinning grapevine cluster compactness and rachis architecture, a series of comparative transcriptome analyses between Garnacha Tinta and Tempranillo Tinto clones differing in cluster compactness have been performed [ 30 , 31 ]. Among other genes, these analyses revealed a significant differential expression in an Uclacyanin I -like gene ( VviUCC1 ) between clones with compact and loose clusters [ 30 ].…”