Overcoming unilateral breeding barriers between Lycopersicon peruvianum and cultivated tomato,Lycopersicon esculentum

Summary Treatment of Lycopersicon peruvianum stigmas with an artificial medium analogous to stigmatic exudate allowed pollen germination and growth on immature pistils. Growth of Lycopersicon esculentum pollen tubes to L. peruvianum ovules, an otherwise incompatible cross, was achieved following such treated bud-pollinations. No plantlets were recovered, although a few embryos from this cross at the globularity heart stage of development were excised at 22 days after pollination, indicating the presence of crossing failures as severe as in the reciprocal cross. Hybrid plants were obtained from the reciprocal cross, using as pollen parent an L. peruvianum line selected for congruity with L. esculentum. Bud pollinations to L. peruvianum, using these interspecific F₁ hybrids as the pollen parent, allowed viable embryo development and plantlet recovery. Resulting backcross plants, which possess approximately 1/4 L. esculentum genome in a L. peruvianum cytoplasm, may facilitate further introgression of the L. esculentum nuclear genes into in foreign cytoplasm.     

Overcoming Self-Incompatibility of Brassica napus by Salt (NaC1) Spray

The results of studies from 1982 to 1989 confirm that self-incompatibility (SI) of B. napus can be effectively overcome by spraying solutions of 2 — 10 % table salt (NaCl) during the flowering period. The optimum salt concentration was found to be 5 %. Spraying onto both stigma and stamen is better than onto only one of them, in particular better than spraying only onto the stamen. When self-pollination occurred at intervals of 1 to 32 hours after spraying 5 % NaCl solution upon stigma and stamen, the compatibility indexes fall slightly; they decrease considerably after 72 and 120 hours, but still then they stay higher than without spraying. After spraying 5 % NaCl solution at intervals of 4, 5, 8 and 24 hours, respectively, the compatibility indexes after self-pollination are almost equal to that of bud-pollination; this treatment is effective even at intervals of 48 or 72 hours after selfing. In practice, spraying 5 % NaCl solution every 3 to 5 days during the flowering period is enough for satisfying seed set of SI lines under field conditions.