Floral morphology, pollen quality, and self-(in) compatibility in three natural Prunus interspecific hybrids

The occurrence of inter-specific hybrids between two species in nature has the potential ability to develop new fruit trees with desirable traits. In this study, flower morphology, viability, and in vitro germination of pollen grains and self-(in) compatibility, using fruit set (%) and fluorescence microscopy methods were examined in three promising natural Prunus interspecific hybrids [P. armeniaca × P. salicina (Bavanat) and P. cerasifera × P. armeniaca (Shiraz and Shahriar)]. Bavanat and Shiraz had the highest flower diameter, while the highest number and length of stamens, as well as stamen number/pistil length ratio, belonged to Shahriar. The highest and lowest pollen viability and in vitro germination were observed in Shahriar and Bavanat, respectively. In general, sucrose concentrations of 150 to 250 g/l increased in vitro pollen germination rate, although concentrations of more than 150 g/l had a negative effect on Bavanat. The three-year average (2018-2020) of final fruit set by self-pollination ranged from 0% in Shiraz to 1.3% in Shahriar. A strong positive correlation was found between the occurrence of twin pistils and the mean temperature from July-August in the previous year. According to field self-pollination and fluorescent microscopy, all three genotypes were considered self-incompatible and needed pollinizer varieties.