Abstract
BackgroundThe timing of grape ripening initiation, length of maturation period, berry size and seed content are target traits in viticulture. The availability of early and late ripening varieties is desirable for staggering harvest along growing season, expanding production towards periods when the fruit gets a higher value in the market and ensuring an optimal plant adaptation to climatic and geographic conditions. Berry size determines grape productivity; seedlessness is especially demanded in the table grape market and is negatively correlated to fruit size. These traits result from complex developmental processes modified by genetic, physiological and environmental factors. In order to elucidate their genetic determinism we carried out a quantitative analysis in a 163 individuals-F1 segregating progeny obtained by crossing two table grape cultivars.ResultsMolecular linkage maps covering most of the genome (2n = 38 for Vitis vinifera) were generated for each parent. Eighteen pairs of homologous groups were integrated into a consensus map spanning over 1426 cM with 341 markers (mainly microsatellite, AFLP and EST-derived markers) and an average map distance between loci of 4.2 cM. Segregating traits were evaluated in three growing seasons by recording flowering, veraison and ripening dates and by measuring berry size, seed number and weight. QTL (Quantitative Trait Loci) analysis was carried out based on single marker and interval mapping methods. QTLs were identified for all but one of the studied traits, a number of them steadily over more than one year. Clusters of QTLs for different characters were detected, suggesting linkage or pleiotropic effects of loci, as well as regions affecting specific traits. The most interesting QTLs were investigated at the gene level through a bioinformatic analysis of the underlying Pinot noir genomic sequence.ConclusionOur results revealed novel insights into the genetic control of relevant grapevine features. They provide a basis for performing marker-assisted selection and testing the role of specific genes in trait variation.
Highlights
The timing of grape ripening initiation, length of maturation period, berry size and seed content are target traits in viticulture
The genetic control of flowering has been extensively studied in the model plant Arabidopsis thaliana [3,4]
The 20 MseI/EcoRI combinations provided a total number of 1380 AFLP markers
Summary
The timing of grape ripening initiation, length of maturation period, berry size and seed content are target traits in viticulture. Berry size determines grape productivity; seedlessness is especially demanded in the table grape market and is negatively correlated to fruit size. These traits result from complex developmental processes modified by genetic, physiological and environmental factors. Phenology is the most important attribute involved in the adaptation of grapevine, as other crops, to its growing environment and to climatic changes [1,2]. It is a complex trait, which results from the interaction of various developmental quantitative characters such as flowering, veraison and fruit ripening. In the last years the grapevine orthologs of some Arabidopsis flowering genes have been cloned and characterized: VvMADS1, an AGAMOUS/SHATTERPROOF homologue [6]; VvMADS2 and VvMADS4, related to the SEPELLATA genes, VvMADS3, homologous to AGAMOUS-LIKE6 and 13, and VvMADS5, homologous to AGAMOUS-LIKE11 [7,8]; VFL, the homologue of LEAFY [8,9]; VAP1 and VFUL-L, respectively homologous to APETALA1 and FRUITFULL-like [8,10]; VvTFL1, the homologue of TERMINAL FLOWER1 [8,11,12]; VvFT and VvMADS8, respectively homologous to FLOWERING TIME and SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1
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