Rubro: Frutales

Fecha inicio: 01/05/2022

Fecha termino: 31/03/2026

Participación INIA: Ejecutor principal

Descripción: Bunch compactness (BC) has enormous economic and management implications for the wine and table grape industry. BC has rachis or cluster architecture (CA) as one of its main determinants, being considered as synonyms by most authors, and abbreviated as CA/BC. There is a high relationship between the susceibility to fungal diseases and BC, derived from both the reduced ventilation and the difficulty for pesticides to properly cover berries in tighter bunches. Also, friction between berries is a source of epidermis disruion, and as such, a port of entry for pathogens. Bunches shape also determines the cost of labor, which is heavily demanded in many varieties to obtain the oimal arms number and position, and rachis length as well. Hence, among the traits evaluated during the development of new varieties, CA/BC is one of the most relevant ones to be considered. In this context, understanding the genetics of this trait would become key for table grape breeding. In recent years, a series of QTLs, SNPs and candidate genes associated with this trait have been reported. For instance, one of the first papers dealing with the identification of QTLs and genomic regions, including candidate genes associated to CA and various sub-traits, came from our group at La Platina (Correa et al., 20), based on a biparental population (Ruby x Sultanina). In that case, rachis length, lateral shoulder length and node number along the central axis were the most relevant sub-traits identified, with heritabilities averaging 70% which predict their selection response and efficiency in plant breeding, and implying the existence of major genes that are possible targets for marker assisted selection. Other groups (mainly those from the Instituto de Ciencias de la Vid y el Vino, ICVV, from Logroño, Spain; and the Federal Institute for Grapevine Genetics, from Geilweilerhof, in Pfalz, Germany) have also provided important contributions to the understanding of these traits. They arrived to similar conclusions, adding the total number and weight of berries per bunch as a critical factor for the overall bunch compactness (BC). The Spanish team have identified a discrete number of genes associated with BC, using a set of ca. 100 grapevine varieties, through the sequencing and SNPs detection on 183 candidate genes. Using this approach, a small set of SNP markers have been associated to the three most relevant sub-traits defining BC. Among these genes, VviUCC1, an uclacyanin-type gene, codes for a plant-specific cell-wall protein involved in fibers formation and lignification processes ((Tello et al., 2020). Our own studies related to post-harvest berry drop highlighted the protagonic role of genes linked to lignin-formation in the performance of the pedicel, the last segment of the rachis where berries are attached (García-Rojas et al., 2018; Meneses et al., 2020). By their side, the German team has arrived to similar results, identifying another set of genes, including a growth regulator factor named VvGRF4 (Rossmann et al., 2020). However, even when this data set is very promising, the complexity of the trait and the genetic background used to obtain this information does not necessarily fit the requirements of table grape breeding. Moreover, there is no information regarding the role of each gene or gene set in the determination of each CA/BC sub-trait, nor on the existence of some type of gene expression coordination among them, with the participation of regulatory factors. Considering these antecedents, this project proposes to expand the search of the genetic determinants of cluster architecture and bunch compactness using a diverse panel of varieties (including table grape as well as wine cepages) and breeding lines, aiming to target genes that could be closely associated to this trait. From a general perspective, the main aims of this project will be i) to identify the genes which explains the most of the phenotypical variance for the CA/BC phenotype, ii) to evaluate the whole and individual gene expression levels of contrasting varieties for CA/BC, iii) to determine and confirm the existence of polymorphisms present in those genes; and based on this information, iv) to establish the start point in order to develop selection markers for this complex trait, that could be later on evaluated and validated on table grape populations available from the INIA's or a third party breeding program.