Multiple QTL for horticultural traits and quantitative resistance to Phytophthora infestans linked on Solanum habrochaites chromosome 11.
Bottom Line: Fine mapping of this resistance QTL using near-isogenic lines (NILs) revealed some co-located QTL with undesirable effects on plant size, canopy density, and fruit size traits.A total of 34 QTL were detected across all traits, with 14% exhibiting significant QTL × environment interactions (QTL × E).QTL for many traits were co-located, suggesting either pleiotropic effects or tight linkage among genes controlling these traits.
Affiliation: Plant Sciences Department, University of California-Davis, Davis, California 95616.Show MeSH
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Mentions: The linkage map for the chromosome 11 introgressed region from S. habrochaites was 9.4 cM and spanned markers TG194 to TG400 (Figure 1). The average marker spacing was 0.5 cM and the largest gaps were each 1.5 cM in length, with one between markers At2g22570 and At5g16710 and another between At1g44790 and cLEX4G10. Comparison of our genetic map with the SL2.5 S. lycopersicum tomato genome sequence build (http://solgenomics.net) allowed estimation of the physical extent of S. lycopersicum DNA displaced by the S. habrochaites introgression. The 9.4-cM region from TG194 to TG400 corresponded to a physical distance of approximately 48.6 Mbp in S. lycopersicum and spans the centromere (Figure 2). With a mean of 5.17 Mbp per cM, this is 6.9-times higher than the genome-wide average ratio of genetic distance to physical distance, 750 kb per cM (Tanksley et al. 1992). The most intense recombination suppression occurred in the pericentromeric region between TG147 and At2g14260, where 1 cM corresponded to approximately 31.3 Mbp. Conversely, other parts of the chromosome 11 introgressed region from S. habrochaites exhibited slightly increased recombination relative to the genome-wide average (Figure 2). According to the ITAG 2.4 annotation of tomato chromosome 11, the interval from TG194 to TG400 contains 1473 genes. However, because a S. habrochaites genome sequence is not publicly available, the physical size and gene space of the introgression cannot be determined currently.
Affiliation: Plant Sciences Department, University of California-Davis, Davis, California 95616.