A. Chahal et al., A FERTILE REVERTANT FROM PETALOID CYTOPLASMIC MALE-STERILE CARROT HASA REARRANGED MITOCHONDRIAL GENOME, Theoretical and Applied Genetics, 97(3), 1998, pp. 450-455
A spontaneously derived fertile plant was recovered from a petaloid cy
toplasmic male-sterile (CMS) carrot inbred line. Genetic analysis indi
cated a single nuclear gene was responsible for the restoration to fer
tility. Within a family segregating for the nuclear restorer in combin
ation with the sterility-inducing cytoplasm, fertile plants were recov
ered that could not restore fertility when crossed to sterile genotype
s. Genetic analysis indicated cytoplasmic reversion for fertility, and
Southern analysis, comparing mtDNA organization of the fertile revert
ant and its CMS progenitor, identified mitochondrial genome rearrangem
ents. Hybridization of cosmids representing a 108-kb subgenomic circle
of the sterile line to DNA of a fertile maintainer and fertile revert
ant lines indicated a similar mtDNA organization for these genotypes t
hat was distinct from that of the sterile line. Six restriction fragme
nts totalling 43.2 kb were common to the fertile maintainer and revert
ant and absent in the sterile; other restriction fragments totalling 3
8.2 kb were present only for the sterile line. Unique fragments of low
stoichiometry, two for the fertile maintainer and three for the rever
tant, distinguished these lines. The reversion to fertility in the ste
rile line could have resulted from the amplification of a mitochondria
l submolar genome highly homologous to that found in the fertile maint
ainer line.