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

Tomato is one of the most important vegetable crops with different breeding\r\nobjectives depending on its final destination, whether for fresh\r\nconsumption or for processing. Breeders have to meet the demands of the\r\nmarket, consumers and farmers, as well as environmental constraints and\r\npest outbreaks due to climate change. This requires a wide range of genetic\r\nvariability to be used in breeding programmes and the availability of\r\nimproved breeding lines and molecular markers linked to agronomic traits\r\nfor marker-assisted breeding.\r\nNext generation multiparent populations represent one of the best\r\nopportunities to meet all of these necessities. Here we describe SABER (\r\nSolanum lycopersicum Allele Biodiversity Enriched Resource), a multiparent\r\nadvanced generation intercross population (MAGIC) developed by crossing 7\r\nS. lycopersicum lines and a S. cheesmaniae genotype (LA1407). The 8\r\nfounders were crossed to develop two-ways, four-ways and, finally, eight\r\nways-hybrids which were subsequently self-pollinated for several\r\ngenerations. SABER population is currently at G11 stage and it is composed\r\nof 445 sister-lines.\r\nA preliminary genetic characterization of SABER was performed on 350\r\nselected individuals at G9 by Single Primer Enrichment Technology (SPET).\r\nRaw reads were aligned on the reference genome, filtered for MAF <0.05,\r\nmissing data at both site (>0.5) and individual (>0.2) levels. After LD\r\npruning, a final dataset of 2634 SNPs was obtained. SNPs resulted well\r\ndistributed along the 12 tomato chromosomes with some density peaks on\r\nchromosomes 3 and 4, while some poorly saturated regions seemed to be\r\npresent on other chromosomes. A new deeper characterisation is planned on\r\nall the 445 at the G11.\r\nThe same individuals were evaluated for agronomic and qualitative traits\r\nsuch as flowering, fruit size, weight, firmness and colour and °Brix level.\r\nTraits relevant to mechanical harvesting and industrial processing such as\r\ngrowth habit, jointed/jointless and presence/absence of green shoulder were\r\nalso evaluated. Field characterisation revealed a wide range of\r\nvariability, probably due to recombination of the wild parent with the\r\nother 7 tomato lines. Many traits related to fruit size were\r\nautocorrelated, and interesting results were observed for °Brix level and\r\nflowering intensity, which were negatively correlated with fruit size. In\r\naddition, the sister-lines with determinate plant canopy were associated\r\nwith increased fruit firmness, a trait particularly important for\r\nmechanical harvesting. A second phenotypic evaluation is planned for next\r\nyear.\r\nThese preliminary results have demonstrated the potential of SABER to\r\ngenerate new genetic and phenotypic variability for use by breeders in the\r\nnear future. In addition, the availability of genetic information and\r\nphenotypes on such a diverse population will allow the dissection of the\r\ngenetic basis of agronomic traits and the development of molecular markers\r\nfor more advanced plant selection systems.