@incollection{icrisat4328,
       booktitle = {Sorghum improvement in the new millennium},
           title = {Alternative cytoplasmic male sterility systems in sorghum and their utilization},
       publisher = {International Crops Research Institute for the Semi-Arid Tropics, Patancheru 502 324, Andhra Pradesh, India},
         address = {Patancheru, Andhra Pradesh, India},
          author = {B V S Reddy and A Ashok Kumar and S L Kaul},
           pages = {132--144},
            year = {2008},
         journal = {Sorghum improvement in the new millennium},
             url = {http://oar.icrisat.org/4328/},
        abstract = {In sorghum, Stephen and Holland (1954) discovered cytoplasmic male sterility
(CMS) designated as milo cytoplasm in the progenies of a cross between two
cultivars, milo and combine kafi r, with milo as the female and kafi r as the male.
Male-sterile plants to the extent of 25\% were observed in the F2 generation of the
above cross when milo was used as female and not as male. The male-sterile
segregants from this cross produced male-sterile hybrids when crossed with the
kafi r parent and fully fertile hybrids when crossed with the milo parent. Thus, it was
recognized that kafi r could be used as a maintainer of this source of CMS. Since
the progeny received the cytoplasm from the female, it was hypothesized that the
milo parent had a male sterility-inducing cytoplasm and dominant genes for pollen
fertility, whereas the combine kafi r parent contained a normal (fertile) cytoplasm
but the recessive male-sterile genes. All progenies of the milo{$\times$}combine kafi r cross
contained milo (sterility-inducing) cytoplasm, but those that also inherited the
homozygous recessive genes from the kafi r parent were male-sterile. The malesterile
plants in the milo{$\times$}combine kafi r cross were used as females in repeated
backcrossing with kafi r as the male parent. At the end of seven backcrosses, the
entire genome of kafi r was transferred into the milo cytoplasm. This resulted in
two morphologically similar versions of the combine kafi r (CK 60) parent: a malesterile
combine kafi r (CK 60A) and a male-fertile combine kafi r (CK 60B). The
male-sterile lines are designated as A-lines and their maintainer lines as B-lines.
Subsequently, several sources of CMS systems (A1, A2, A3, A4, A5 and A6) (Table
13) were discovered.}
}