Mapping of the Cladosporium fulvum resistance gene Cf-16, a major gene involved in leaf mold disease in tomato

Tomato (Solanum Lycopersicum) is widely cultivated and consumed in the world. Tomato leaf mold, caused by Cladosporium fulvum (C. fulvum), is one of the most devastating diseases in tomato production. To date, some tomato leaf mold resistance (Cf series) genes used in production gradually lose resistances, with the continuous and violent differentiation of C. fulvum physiological races. The Cf-16 gene derived from the cultivated variety Ontario7816 has shown good resistance in field trials for many years, but several studies have reported the mapping of the Cf-16 gene, it has not been cloned, limiting the utilization in tomato breeding. Here, we mapped Cf-16 for the first time using a comprehensive strategy including bulk segregation analysis , genome resequencing and SSR molecular markers. Genetic analysis revealed that Cf-16 resistance in Ontario7816 is controlled by one major dominant locus. The Cf-16 gene was mapped in a region of 2.6 cM at chromosome 6 between two markers, namely, TGS447 and TES312, by using an F2 population from a cross between the resistant cultivar Ontario7816 and susceptible line Moneymaker. Two NBS-LRR (nucleotide-binding-site-leucine-rich repeat) resistance genes, namely, XM_004240667.3 and XM_010323727.1 were identified in this interval. They are strong candidates for the Cf-16 gene. The mapping of Cf-16 may speed up its utilization for breeding resistant tomato varieties and represents an important step forward in our understanding of the mechanism underlying the resistance to tomato leaf mold.