SABER: A MULTIPARELTAL POPULATION TO INCREASE VARIABILITY FOR TOMORROW’S TOMATO BREEDING

Tomato is one of the most important vegetable crops with different breeding objectives depending on its final destination, whether for fresh consumption or for processing. Breeders have to meet the demands of the market, consumers and farmers, as well as environmental constraints and pest outbreaks due to climate change. This requires a wide range of genetic variability to be used in breeding programmes and the availability of improved breeding lines and molecular markers linked to agronomic traits for marker-assisted breeding. Next generation multiparent populations represent one of the best opportunities to meet all of these necessities. Here we describe SABER ( Solanum lycopersicum Allele Biodiversity Enriched Resource), a multiparent advanced generation intercross population (MAGIC) developed by crossing 7 S. lycopersicum lines and a S. cheesmaniae genotype (LA1407). The 8 founders were crossed to develop two-ways, four-ways and, finally, eight ways-hybrids which were subsequently self-pollinated for several generations. SABER population is currently at G11 stage and it is composed of 445 sister-lines. A preliminary genetic characterization of SABER was performed on 350 selected individuals at G9 by Single Primer Enrichment Technology (SPET). Raw reads were aligned on the reference genome, filtered for MAF <0.05, missing data at both site (>0.5) and individual (>0.2) levels. After LD pruning, a final dataset of 2634 SNPs was obtained. SNPs resulted well distributed along the 12 tomato chromosomes with some density peaks on chromosomes 3 and 4, while some poorly saturated regions seemed to be present on other chromosomes. A new deeper characterisation is planned on all the 445 at the G11. The same individuals were evaluated for agronomic and qualitative traits such as flowering, fruit size, weight, firmness and colour and °Brix level. Traits relevant to mechanical harvesting and industrial processing such as growth habit, jointed/jointless and presence/absence of green shoulder were also evaluated. Field characterisation revealed a wide range of variability, probably due to recombination of the wild parent with the other 7 tomato lines. Many traits related to fruit size were autocorrelated, and interesting results were observed for °Brix level and flowering intensity, which were negatively correlated with fruit size. In addition, the sister-lines with determinate plant canopy were associated with increased fruit firmness, a trait particularly important for mechanical harvesting. A second phenotypic evaluation is planned for next year. These preliminary results have demonstrated the potential of SABER to generate new genetic and phenotypic variability for use by breeders in the near future. In addition, the availability of genetic information and phenotypes on such a diverse population will allow the dissection of the genetic basis of agronomic traits and the development of molecular markers for more advanced plant selection systems.