Cryptic self-incompatibility in mango (Mangifera indica L.)

Floral incompatibility systems are a common phenomenon in several plant species resulting in the avoidance of self-fertilization or crossing with genetically close genotypes favouring genetic exchange. The possible existence of self-incompatibility in some mango cultivars was put forward in old literature, but so far there is no conclusive information on a possible incompatibility system in this species. In this work we evaluate self-incompatibility in mango combining molecular and microscopic techniques. Thus, microsatellite markers were used to assess the paternity of fruits harvested from 'Osteen' and 'Kent' trees, located in a mango cultivar collection field at the IHSM La Mayora. The results showed a high percentage of cross-fertilization in 'Osteen' fruits (94%) and a lower percentage (48%) in 'Kent'. Due to the high percentage of cross-fertilization observed in 'Osteen' and previous observations showing no production problems in orchards planted with only this cultivar, a second experiment was performed in a field with just two cultivars in different opposite plots: 'Osteen' and 'Keitt'. A paternity analysis was made from the fruits harvested from trees belonging to both cultivars located at different distances from the pollen donor. The results showed a high percentage of fruits produced by self-fertilization especially in the trees farther away from the pollen donor. The molecular studies were complemented with microscopic analysis. Hand pollinations in vivo were performed between the cvs. Osteen, Kent and Kensington. Pollen tube growth in self-and cross-pollinations was similar, with no apparent incompatibility symptoms at the style level. Therefore, the results suggest the presence of a cryptic self-incompatibility system in mango that would favor cross-fertilization but, in the absence of pollen from other genotypes, self-fertilization would be possible.