K. Oroji Salmasi - Department of Horticulture, Karaj Branch, Islamic Azad University, Karaj, Iran.
R. Gharesheikhbayat - Temperate Fruits Research Center, Horticultural Science Research Institute, Agricultural Research, Education and Extension Organization, Karaj, Iran.
S. M. Miri - Department of Horticulture, Karaj Branch, Islamic Azad University, Karaj, Iran.
M. Pirkhezri - Temperate Fruits Research Center, Horticultural Science Research Institute, Agricultural Research, Education and Extension Organization, Karaj, Iran.
D. Davoodi - Department of Nanotechnology, Agricultural Biotechnology Research Institute of Iran, Karaj, Iran.

Self-incompatibility and late spring frosts are the most important limiting factors in Asian apricot (Prunus armeniaca L.) production. Therefore, it is important to develop late-blooming and self-compatible genotypes in apricot breeding programs in order to increase yield, and in some cases to eliminate the need for pollinizers. This study was carried-out to evaluate the phenology and self-(in)compatibility in cv. Shahroudi and twenty-five apricot promising genotypes under Karaj environmental conditions during ۲۰۱۹-۲۰۲۰ growing seasons. Apricot genotypes flowered from early to late March (۳rd to ۲۶th March), and fruits harvested from early to late June. Genotype ۴۹۹ was identified as a late blooming genotype. In vitro pollen germination varied from ۰.۰ to ۷۴.۰%, and showed no correlation with fruit set. Fruit set studies showed ۱۷ genotypes were self-compatible (fruit set of ۵.۲ to ۴۴.۲%). The fluorescent microscopic examinations of the pollen tube growth in the style confirmed ۱۱ genotypes as self-compatible, with at least one pollen tube reaching the ovary. Combining the results of the three primers designed from the first and second Prunus S-RNase introns, ۱۱ S-alleles were identified, among which S۶, Sc and S۲ were the most frequent. Two late-bloom and self-compatible genotypes ۴۴۷ and ۵۳۴ were selected, and several late-bloom or self-compatible genotypes were identified which can be used in future apricot breeding programs.

Apricot, fluorescence microscopy, fruit set, Pollen germination, S-allele