CYTOEMBRYOLOGICAL ASPECTS OF INCOMPATIBILITY AMONG <i> Cerasus</i> Mill. UNDER DISTANT HYBRIDIZATION DURING BREEDING FORMS RESISTANT TO <i>Blumeriella</i> LEAF SPOT
The harmful fungal disease caused by Blumeriella jaapii (Rehm) Arx (syn. Coccomyces hiemalis Higgins) results in an early exfoliation, an attenuation of trees, a reduction of productivity, an abatement of resistance to cold. The most virulent population of disease agent was revealed in Krasnodar region. In Northern Caucasian Zonal Scientific Research Institute of Orchard Culture and Viticulture the authors crossed a slightly infected varieties of cherries and crab cherries with immune samples of Eastern-Asiatic species — Cerasus lannesiana № 2, C. serrulata Hally Tolivetta, C. subhirtella Pendula. They carried out also a comparative cytoembryological analysis of different crossing combinations. The authors investigated the pollen fertility, the growth of pollen tubes in pistil tissues and embryogenesis. The most compatible combinations of crossing at the progamic stage of fertilization were Nord Star × C. subhirtella Pendula, Nord Star × 3-116 (seedling from free pollination C. serrulata Hally Tolivetta × Polyanka), Molodezhnaya × ( C. lannesiana № 2 × Frants Iosif). The abnormalities in development of hybrid embryos were appeared after 18-25 days from pollination on a stage of the heart. This period is recommended for isolation of embryos with subsequent growing in vitro in order to overcome the postgamic incompatibility.