RA 00110.pdf - OAR@ICRISAT

making it possible to grow a number of generations
per year. Pearl millet plants can grow to maturity in
a 5-cm pot and produce 100 or more seeds. In the
opinion of the author, these and other characteristics
make pearl millet the "Drosophila" of the plant
kingdom.
Pearl millet is an important food grain in Africa
and India. It is a high quality forage in the United
States, Australia, and South America. However,
there is new interest in growing pearl millet for grain
in the USA because it is drought tolerant and produces
high quality grain. Pearl millet tolerates low
fertility and low soil pH, but responds positively to
more favorable soil and water conditions.
Evolutionary History and
Domestication of Pearl Millet
Based on evidence of genetic diversity within the
genus in Africa, it is generally accepted that pearl
millet originated there. More specifically, the Sahelian
Zone from western Sudan to Senegal appears to
be the center of origin (Harlan 1975). Various
reports indicate pearl millet has been grown for
thousands of years (Brunken 1977, Burton and
Powell 1968, Rachie and Majmudar 1980). In the
last 200-300 years, pearl millet has been given a
number of genera and species names such as P.
glaucum L. and P. typhoides (Burm.) Stapf and
Hubb. In 1976 it was renamed P. americanum (L.)
Leeke (see Terrell 1976). Those interested in more
detailed discussions on the taxonomy, origin, domestication,
and evolutionary history of pearl millet
should consult Brunken (1977), Jauhar (1981), Rachie
and Majmudar (1980), and Stapf and Hubbard
(1934).
Gene Pools
Pennisetum is a genus with over 140 species (Brunken
1977) divided into five sections: Gymnothrix, Eu-
Pennisetum, Penicillaria, Heterostachya, and BrevivaJvuia
(Stapf and Hubbard 1934). Pearl millet
belongs to the Pcnicillaria section. The literature
and observations by the author at the Royal Botanic
Gardens, Kew, U K , indicate that most of the wild
Pennisetum species are found in Africa. However,
there are a number of reports of Pennisetum species
being collected in other countries. There are specimens
of Pennisetum species on record at Kew from
Israel, Japan, India, Australia, New Zealand, Polynesia,
Mexico, Central and South America, and
other countries, including many in Africa.
The Pennisetum genus has species with chromosome
numbers in multiples of x = 5, 7, 8, and 9 (see
Table 1, Hanna and Dujardin In press, and Jauhar
1981). In the x = 5 group is P. ramosum (2n = 10). The
x = 7 group includes pearl millet and its wild weedy
subspecies (2n = 14), P. purpureum (2n = 28), and P.
schweinfurthiii (2n = 14). Pennisetum massaicum
(2n = 16 and 32) is the only known species in the x - 8
group. The remainder of the species where chromosome
numbers have been established belong to the x
= 9 group. Ploidies reported range from diploid to
octoploid (Jauhar 1981). Both sexual and apomictic
species as well as annual and perennial species are
included in the genus.
The diverse germplasm in Pennisetum, both within
and between species, offers possibilities for use in
improving pearl millet and to produce interspecific
hybrids with forage potential. The ease with which
the wild germplasm can be manipulated and used
will vary both within and between species. One way
of classifying the wild or exotic germplasm is by the
ease with which it can be introgressed into the cultivated
species. A system of primary, secondary, and
tertiary gene pools has been suggested for dividing
the wild germplasm (Harlan and de Wet 1971).
In Pennisetum, the primary gene pool includes the
wild, grassy, and weedy P. americanum subspecies
(2n = 14), monodii and stenostachyum that readily
cross with pearl millet and produce fertile hybrids
(Table 1). Monodii is the true weedy subspecies
found mainly in the Sahelian Zone of Africa in an
east-west line from Senegal to Ethiopia. It is found
"as a natural colonizer on sandy soils in disturbed
habitats such as seasonal stream beds and roadsides
as well as a weed near human habitations'* (Brunken
1977). Inflorescences are 2-20 cm long with loosely
arranged involucres that readily shatter (Brunken
1977). Inflorescence length in about 100 accessions
that the author observed ranged from 2-12 cm.
Involucral bristles are densely plumose. Stems are
thinner and leaves are narrower than those of most
pearl millet accessions. Most flower in response to
short day length.
Monodiiis a rich source of germplasm that can be
used to improve pearl millet. Data indicate that it is
an excellent source of genetic diversity for new cytoplasms,
stable cytoplasmic sterility, pest resistance
(disease and insect), fertility restoration, hybrid
vigor, etc. Based on intuition and five years of
research with monodii, the author believes that this
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