Abstract:

Black rot is one of the main diseases of cauliflower（Brassica oleracea L. var. botrytis L.，
2n = 18，CC）. Somatic hybrids were obtained by asymmetric cell fusion between susceptible cauliflower
cultivar‘Korso’and resistance black mustard line‘G1/1’（B. nigra，2n = 16，BB）. Different advanced
generations were got after years of selfing and backcrossing. According to the characters of the plants such
as leaf morphology and flower curd，the somatic hybrids were classified into four types. Type M：having
characters between cultivated‘Korso’and wild species‘G1/1’. Type M-K：having traits between two
parents and bias to‘Korso’. Type -K：having most cauliflower-like phenotypes. Type K：exactly
cauliflower-like type. The results of resistance identification from year 2010 to 2014 showed that disease
index （DI）of‘Korso’were in 44–57，and DI of‘G1/1’were in 12–32 for the inoculated pathogenic
bacterium. The DI were gradually increased in hybrids from type M to type M-K，type -K and type K
displaying the high resistance，resistance to tolerance degree，respectively. The results of phenotype
evolution and resistance tracing showed that cauliflower-like morphology changes occurred in S1BC4，S5，
S1BC3 and BC3，and along with the morphology changes，DI of black rot increased sharply. Little DI
difference was detected among lines with the same or similar derivation. Further resistance identification
was carried out in 2015 in the selfed progeny lines. Overall，the DIs showed a downward trend in most of
the lines and only increased in a few lines. Plants from the same derivation showed the similar changing
trend indicating that the disease resistances in the progenies became stable after years’ selection. Up to
now，six promising lines displaying significant black rot resistance compared with the receptor parent
‘ Korso ’ were obtained ，which including PFCN13-15-4.1 ， PFCN13-15-5.1 ， PFCN13-29-1.1 ，
PFCN13-29-1.2，PFCN13-14-1.1 and PFCN13-14-1.2，respectively.

Key words: cauliflower, black mustard, somatic hybridization, black rot disease, resistance transfer
breeding