Biology Reference
In-Depth Information
improve the economic well-being of women
(Kaaya and Christie 2007).
Significance of Peanut
Peanut (groundnut) ranks second to soybean in
the world market trade of legume oilseeds both
in area grown and tonnage produced. Peanut is
grown in more than 100 countries (Nwokolo
1996), with a total production of 37.7 million
tons from 24.1 million hectares in 2010 (FAO
2012), with a mean productivity of 1.56 t/ha.
The five largest producers in the world in 2010,
based on pod tonnage, were China, India, Nige-
ria, the United States, and Senegal. Crop yield
per hectare varies from region to region with
the United States having the highest (3.7 t ha 1 )
among major producers, followed by China (3.4
tha 1 ), Brazil and Argentina with values of 2.7
tons per hectare, and Senegal, Nigeria, and India
with yields of 1.0 to 1.1 tons per hectare (FAO
2012). The crop is a rich source of oil (36-54%),
proteins (16-36%), and carbohydrates (10-20%)
(Knauft and Ozias-Akins 1995). Peanut is used
for its seed, which supplies essential minerals
such as zinc, iron, phosphorus, and calcium and
vitamins such as riboflavin, thiamine, niacin, and
vitamin E; peanut is also a major source of oil
with benefits for human health (The Peanut Insti-
tute 2004). In some countries, the haulm is used
as a source of fodder. Peanut, as a member of
the Fabaceae (Leguminosae), is capable of con-
verting atmospheric nitrogen into ammonia by
symbiotic nitrogen fixation. Thus, in addition to
being a food crop, peanut is capable of increas-
ing the fertility of the soil (Pimratch et al. 2004)
as a rotation crop. Peanut is important indus-
trially; the famous scientist George Washington
Carver identified more than 300 uses for peanut
and peanut products over a century ago.
Peanut is well suited to contribute signifi-
cantly to poverty reduction in the developing
world, with a potential to accelerate the achieve-
ment of the United Nation's Millennium Devel-
opment Goal of halving world poverty by 2015,
because more than 90% of world production is
realized in developing countries (FAO 2012). In
Africa, women typically have the responsibility
for post-harvest processing and sale of peanut,
and thus improvement in yields is expected to
Genetic Structure of Peanut
(Groundnut)
Origin of the Genus Arachisand
Sections within the Genus
In 1753, Linnaeus described the domesticated
peanut as Arachis hypogaea , depicting peanut
as a weed with underground fruits, unlike most
angiosperms. The Arachis genus was placed
within the Leguminosae (Fabaceae) family.
Within this family, the major grain legumes are in
the Papillionoideae, which is further subdivided
into several clades, among them are the Phase-
oloids (milletoids or warm season legumes)
that include the genera Glycine , Phaseolus , and
Vigna , Galegoids (cool season legumes) includ-
ing Pisum , Medicago , Lens , and Vicia , and the
Genistoids, which include Lupinus (Doyle and
Luckow 2003; Lewis et al. 2005). Arachis is dis-
tinct from these, belonging to the Dalbergoids,
which includes peanut and Stylosanthes .
According to Gregory and Gregory (1979)
and Krapovickas and Gregory (1994), the genus
developed in the southwestern part of Mato
Grosso do Sul, Brazil or northeast Paraguay,
because what appeared to be the morphologically
most ancient species of the genus, A. guaranit-
ica Chodat. and Hassl. and A. tuberosa Bong. ex
Benth., are still growing in that area. This would
be consistent with Stylosanthes being the pro-
genitor genus, in agreement with molecular phy-
logenetic work (Lavin et al. 2001). Wild species
of Arachis have been collected in Brazil, Bolivia,
Paraguay, Argentina, and Uruguay (Krapovickas
and Gregory 1994; Singh and Simpson 1994;
Jarvis et al. 2003).
Based on morphological and cross-
compatibility data and geographic distribution,
it has been proposed that the genus has evolved
into species that fit into nine taxonomic sections
(Krapovickas and Gregory 1994), which include
the morphologically most ancient section
Trierectoides with its two species with three
Search WWH ::




Custom Search