Inheritance of sexual incompatibility in apricot

The study was carried out with 3‐ to 6‐year‐old apricot progenies from the breeding programmes of ARS in Fresno, California, USA and of CEBAS in Murcia, Spain. Progenies from 19 different crosses were studied to determine the inheritance of the genetic incompatibility trait. The 19 crosses included those where both parents were self‐compatible or both self‐incompatible, and also those where a self‐compatible parent and another self‐incompatible were crossed. Segregating progenies were studied either by bagging a sufficiently high number of flowers in balloon stage and determining the percentage of fruit set several weeks later or by following pollen tube growth with fluorescence microscopy. Results indicated that a monofactorial system with a multiallelic series appears to control the trait. Alleles for self‐compatibility would allow the pollen tubes to grow in any style and reach the ovules. Alleles for self‐incompatibility would stop the pollen tube growth if the same allele is present in the pollen grain and in the pistil.