ISHS Acta Horticulturae 695: I International Symposium on Tomato Diseases
MINING TOMATO GENOME SEQUENCE DATABASES FOR MOLECULAR MARKERS: APPLICATION TO BACTERIAL RESISTANCE AND MARKER ASSISTED SELECTION |
| Authors: | W. Yang, S.A. Miller, J.W. Scott, J.B. Jones, D.M. Francis |
| Keywords: | Xanthomonas euvesicatoria, Xanthomonas vesicatoria, Xanthomonas perforans, Xanthomonas gardneri, single nucleotide polymorphisms (SNP), genetic mapping, Lycopersicon esculentum, plant breeding |
| Abstract:
Bacterial spot is an economically important disease of tomato (Lycopersicon esculentum Mill.) grown for processing and fresh-market. The disease is caused by as many as four species of Xanthomonas. The development of varieties with resistance has been difficult due to the emergence of new species and races, the lack of a correlation between a hypersensitive response and resistance in the field, and the quantitative inheritance of resistance. In addition, the best-characterized sources of resistance to bacterial spot have been L. esculentum breeding lines or plant introductions, and the use of molecular marker assisted breeding has been limited due to the low levels of genetic polymorphisms. To discover genetic differences appropriate for the characterization of bacterial spot resistance we have developed a set of single nucleotide polymorphisms (SNPs) through a pipeline that involves data mining, estimation of intron position, de novo sequencing, and experimental verification. The frequency of SNPs in introns is 5.3 fold higher than SNPs in coding regions. We have used molecular markers to characterize an Inbred Backcross population derived from PI 114490 conferring resistance to multiple races of bacterial spot. A putative QTL on chromosome 11 explained 14.6% of the variation for T2 resistance, 63.8% of the variation for T3 resistance, and 44.3% of the variation for T4 resistance. Minor QTLs conferring resistance to either T2 or T4 were found on different chromosomes. We have further used SNP markers to select for recombinants that bring resistance to bacterial speck and race T1 of bacterial spot into coupling phase. | |
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