New QTLs involved in the control of stigma position in tomato

The tomato mating system was strongly affected by domestication events. Mutations disrupting self-incompatibility paralleled by changes retracting the stigma position (SP) within the staminal cone conferred strict autogamy and self-fertility to the cultivated forms. Although major genes affecting these changes have been identified, SP control in domesticated forms retaining a non-inserted or a heat-inducible SP needs elucidation. To widen the possibility of identifying SP genetic determinants, we analysed the trait in four populations (two germplasm collections, a multiparental recombinant inbred and a biparental progeny) under different environmental conditions (normal and heat stressed). Overall, 36 markers significantly associated with the trait were discovered. Several co-localizations were found, both among regions firstly reported in this work and among them and previously reported positions. This supported the reliability of the analysis. Three of such regions, in the long arms of chromosome 1, 8 and 11, were validated in an independent segregating population and candidate genes in confidence intervals were identified among transcription factors and hormone, stress and cell-wall-related genes. In conclusion, the work supported the hypothesis that the SP phenotype is controlled by different key-genes in tomato, paving the way to identifying novel players and novel mechanisms involved in the regulation of herkogamy.