Rb gene introgression from Brassica carinata to Brassica oleracea
Black rot caused by bacterium Xanthomonas campestris pv. campestris (Pammel) Dowson (Xcc) is one of the most devastating diseases of Brassica crops. Breeding and use of resistant cultivars is considered to be one efficient way to control black rot. However, there is no available white cabbage (Brassica oleracea var. capitata) cultivar resistant to three and more races of Xcc on Russian seed market until now. The aim of this study is to transfer race specific black rot resistance from Ethiopian mustard PI199947 to white cabbage by interspecific hybridization. Ethiopian mustard (B. carinata) line PI199947 ‒ donor of a single dominant black rot resistance gene (Rb, resistance to 1, 3, 4 and 5 races) ‒ was crossed to susceptible tetraploid (4n=36) white cabbage (B. oleracea) line Bu1. Ovules/embryo culture were used to rescue embryos and to develop two reciprocal interspecific hybrids B. oleracea-carinata (OC) and B. carinata-oleracea (CO). Both OC and CO were resistant to Xcc races 1, 3 and 4 (race 5 was not used for inoculation) and it was confirmed a dominant mode of Rb-gene inheritance and the absence of cytoplasmic effects on black rot resistance. OC and CO had 3n=4x=35 chromosomes, they were partially fertile. OC and CO were reciprocally backcrossed by di- and tetraploid white cabbage lines. A BC1 progeny chromosome numbers varied from 18 to 29 and from 34 to 36 when crossed to di- and tetraploid B. oleracea lines, respectively. Resistance/susceptibility segregation to a particular Xcc races was observed. Out of 92 total number of BC1 plants, 19 were resistant to all three Xcc races, 3 of them had 18 chromosomes and white cabbage phenotype.
Zubko, O., Monakhos, S. and Monakhos, G. (2018). Rb gene introgression from Brassica carinata to Brassica oleracea. Acta Hortic. 1202, 107-112
black rot, white cabbage, resistance, B. oleracea, B. carinata, Xanthomonas campestris, race, interspecific hybridization