Most flowering species including Brassica genera have genetically controlled ability to out-crossing (gametophytic or sporophytic self-incompatibility – SI). In Brassica, self-incompatibility is sporophytically controlled by a single multiallelic locus, termed the S locus, with more than 100 haplotypes identified so far. From the breeding practice point of view, outcrossing is desired for obtaining acceptable yield level. So, the aim of the present study was to estimate the self-incompatibility and crossability in interspecific hybridization of five chosen Brassica species. The crossed species were: B. napus var. oleifera cv. Californium, B. carinata, B. fruticulosa, B. rapa ssp. pekinensis as well as two varieties of B. oleracea (var. alboglabra and var. gongyloides). The mode of pollination consist of diallel cross-pollination. The pollination was done in the glasshouse of Genetic and Plant Breeding Department of the Poznan University of Life Sciences. The crossability was evaluated on the base of the pollen germination index (PGI) and seed set in all tested cross combinations. The observations of pollen grains germination and pollen tubes penetration were made in pistils of female component of interspecific crosses. They showed unilateral incompatibility in the crosses between B. rapa ssp. pekinensis and B. napus var. oleifera cv. Californium (used as paternal form) as well as bilateral incompatibility in crosses between B. napus and B. oleracea var. alboglabra. Generally, better pollen germination and penetration of pollen tubes were observed in a cross combination where B. napus was used as a maternal parent. Both pre-zygotic and post-zygotic incompatibility barriers were found between analyzed species.

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