Wide hybridization in Brassica: cross barriers and studies on the F₁ hybrid and synthetic antidiploid of B. fruticulosa × B. campestris

Abstract

Crosses were made to obtain interspecific hybrids between B. fruticulosa (wild species ♀, 2n=16) × B. campestris (cultivar ♂, 2n=20). Although many pollen grains germinated and their tubes entered the style, only about 30% of the ovules received pollen tubes. Fertilized ovules aborted at various stages of development. A few hybrid seeds resulted from hand pollinations in the field, and they showed poor germination and seedling establishment. The in vitro culture of ovaries, ovules, and seeds increased the frequency of obtaining hybrid seeds and plants: the most effective method was ovary culture followed by ovule culture. The hybrid nature of the plants was confirmed through morphological, cytological, and electrophoretic studies. A meiotic analysis of F1 hybrids (2n=18) showed that they had 0-5 bivalents and were completely pollen sterile. Electrophoretic analysis of leaf esterases and acid phosphatases of F₁ hybrids revealed bands derived from each parent. Induced amphidiploids of F₁ hybrids contained mostly bivalents, and had about 50% fertile pollen.