POSSIBILITIES FOR THE USE OF REMOTE HYBRIDIZATION IN THE GENUS CUCUMIS FOR THE DEVELOPMENT OF GENETIC DIVERSITY

The genetical diversity of cucumber (Cucumis sativus L.) does not give a possibility to solve the problem on resistance to powdery mildew (Sphaerotheca fuliginea Poll) downy mildew (Pseudoperonospora cubensis Berkand Curt/Rost). Genes for resistance to these pathogens has been found only in wild species of Cucumis, derived from Africa (Cucumis ficifolius A. Rich, C. anguria L. and C. metuliferus Naud). These species were widely used in our breeding programme aiming to transfer the genes for resistance in Cucumis sativus. One of the main obstacles of this research was the non-crossability due to genetic remoteness, between C. sativus (2n=14) and the above mentioned species (2n=24). Irrespectively of the application of different pollination techniques valuable genes had not been transferred in the genome of C. sativus. Our attempts to use bridge hybrid Cucumis melo var. agrestis x Cucumis melo var. flexiosus to obtain resistant lines with C. sativus were also not successful. Remote hybrids have been obtained only in crosses of species and accessions with identical genome. The two populations of C. sativus ssp. rigidus var. Sikimensis, C 80351 and C 78383 (2n = 14), proved to be very vital and less susceptible to powdery and downy mildew. Phenological and morphological studies were carried out and the reaction to Sph. fuliginea and Ps. cubensis in segregating progenies (F2 and F3) and backrosses (F1P1, F2P1, F2P1P1), was also investigated. As a result we selected four gynoecious lines and seven monoecious lines possessing valuable characters, such as tolerance to one or two of the pathogens, female type plants and good fruit quality.