Transfer of Powdery Mildew Resistance from Brassica carinata to B. oleracea

Abstract

Powdery mildew is a fungal disease of crucifers, caused by Erysiphe polygoni D.C. and it can be problematic during seed increase in green-houses. Crosses were made between Brassica carinata (Ethiopian mustard) accession (PI 360883) and B. oleracea cultivars `Titleist' and `Cecile' to transfer resistance to powdery mildew to B. oleracea germplasm. It was not possible to obtain interspecific hybrids between Ethiopian mustard and B. oleracea through natural seed set. However, interspecific hybrids and backcross one (BC1) progenies were produced via embryo rescue following sexual crosses. Four interspecific hybrid plants were produced with the aid of embryo rescue from cultured pistils with B. carinata as the maternal parent, and their interspecific origin was confirmed through plant morphology and analysis of RAPD polymorphisms. No interspecific hybrids were obtained when `Titleist' was used as a maternal parent. Interspecific hybrid plants were male sterile and they were used as maternal parents to produce BC1 plants. Twenty one BC1 plants were obtained through natural seed set and embryo rescue, although embryo rescue was not necessary to produce first backcross generation plants. When tested in greenhouse with powdery mildew, all interspecific hybrids and eight of the BC1 plants were resistant to the disease. Crosses are being made to produce BC2 plants with 2n = 18 chromosomes for introgression of the resistance in B. oleracea.