Abstract
Wild potato species continue to be a rich source of genes for resistance to late blight in potato breeding. Whilst many dominant resistance genes from such sources have been characterised and used in breeding, quantitative resistance also offers potential for breeding when the loci underlying the resistance can be identified and tagged using molecular markers. In this study, F1 populations were created from crosses between blight susceptible parents and lines exhibiting strong partial resistance to late blight derived from the South American wild species Solanum microdontum and Solanum pampasense. Both populations exhibited continuous variation for resistance to late blight over multiple field-testing seasons. High density genetic maps were created using single nucleotide polymorphism (SNP) markers, enabling mapping of quantitative trait loci (QTLs) for late blight resistance that were consistently expressed over multiple years in both populations. In the population created with the S. microdontum source, QTLs for resistance consistently expressed over three years and explaining a large portion (21–47%) of the phenotypic variation were found on chromosomes 5 and 6, and a further resistance QTL on chromosome 10, apparently related to foliar development, was discovered in 2016 only. In the population created with the S. pampasense source, QTLs for resistance were found in over two years on chromosomes 11 and 12. For all loci detected consistently across years, the QTLs span known R gene clusters and so they likely represent novel late blight resistance genes. Simple genetic models following the effect of the presence or absence of SNPs associated with consistently effective loci in both populations demonstrated that marker assisted selection (MAS) strategies to introgress and pyramid these loci have potential in resistance breeding strategies.
Highlights
Late blight, caused by the oomycete pathogen Phytophthora infestans, continues to present a challenge for potato production in temperate regions worldwide, and breeding for resistance is to be an important breeding objective
During the course of a breeding initiative to introgress resistance from wild species sources into an elite cultivated potato background we observed that resistance sourced originally from specific accessions of the wild potato species Solanum microdontum and Solanum pampasense exhibit quantitative inheritance patterns
In this study we report the identification of quantitative trait loci (QTL) underlying resistance in these sources, and validation of the use of linked polymorphisms for marker assisted selection (MAS)-driven pyramiding approaches in breeding
Summary
Late blight, caused by the oomycete pathogen Phytophthora infestans, continues to present a challenge for potato production in temperate regions worldwide, and breeding for resistance is to be an important breeding objective. During the course of a breeding initiative to introgress resistance from wild species sources into an elite cultivated potato background we observed that resistance sourced originally from specific accessions of the wild potato species Solanum microdontum and Solanum pampasense exhibit quantitative inheritance patterns. Genes 2020, 11, 732 and pest resistance loci are useful tools in the development of varietal resistance, the availability of genetic markers to efficiently track their introgression and enable strategies such as pyramiding multiple partial resistances to achieve a more complete resistance phenotype. In this study we report the identification of quantitative trait loci (QTL) underlying resistance in these sources, and validation of the use of linked polymorphisms for marker assisted selection (MAS)-driven pyramiding approaches in breeding. Its potential for use as a source of late blight resistance in potato breeding programmes has been well documented [6,7,8,9]
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