Genetic mapping with Allele Dosage Information in TetraploidUrochloa decumbens(Stapf) R.D. Webster Reveals Insights into Spittlebug (Notozulia entrerianaBerg) Resistance

AbstractUrochloa decumbens(Stapf) R.D. Webster is one of the most important African forage grasses in Brazilian beef production. Currently available genetic-genomic resources for this species are restricted mainly due to polyploidy and apomixis. Therefore, crucial genomic-molecular studies such as the construction of genetic maps and the mapping of quantitative trait loci (QTLs) are very challenging and consequently affect the advancement of molecular breeding. The objectives of this work were to (i) construct an integratedU. decumbensgenetic map for a full-sibling progeny using GBS-based markers with allele dosage information, (ii) detect QTLs for spittlebug (Notozulia entreriana) resistance, and (iii) seek putative candidate genes involved in resistance/defense against pathogens. We used theSetaria viridisgenome as reference to align GBS reads and selected 4,240 high-quality SNPs markers with allele dosage information. Of these markers, 1,000 were distributed throughout nine homologous groups with a cumulative map length of 1,335.09 cM and an average marker density of 1.33 cM. We detected QTLs for resistance to spittlebug, an important pasture insect pest, that explained between 4.66% and 6.24% of the phenotypic variation. These QTLs are in regions containing putative candidate genes related to resistance/defense against pathogens. Because this is the first genetic map with SNP autotetraploid dosage data and QTL detection inU. decumbens, it will be useful for future evolutionary studies, genome assembly, and other QTL analyses inUrochloaspp. Moreover, the results might facilitate the isolation of spittlebug-related candidate genes and help clarify the mechanism of spittlebug resistance. These approaches will improve selection efficiency and accuracy inU. decumbensmolecular breeding and shorten the breeding cycle.