(Arachis hypogaea Linnaeus)
Groundnut, an important cash
crop, is an annual legume. Its seeds are a rich source of edible oil (43-55%) and protein
(25-28%). About two thirds of world production is crushed for oil and the remaining one
third is consumed as food. Its cake is used as feed or for making other food products and
haulms provide quality fodder.
Botanically cultivated groundnut can be classified into two
subspecies which mainly differ in their branching pattern: subspecies hypogaea with
alternate branching and subspecies fastigiata with sequential branching. Each subspecies
is again divided into two botanical varieties; subsp. hypogaea into var. hypogaea
(virginia) and var. hirsuta; and subsp. fastigiata into var. fastigiata
(valencia), var. vulgaris (spanish), var. peruviana, and var. aequatoriana.
In trade, the bold-seeded types are referred to as Virginia, the small seeded as Spanish,
and a third type Runner is also recognized. The flowers are born in the axils of the
leaves mostly near the base of plant and have generally yellow petals. It is a self
pollinated crop. After fertilization stalk of ovary elongates and forms peg which contains
fertilized ovules at the tip. The growth of peg is positively geotropic until it
penetrates soil to some depth (7 cm). The tip then becomes diageotropic and ovary starts
developing into a fruit called pod which contains seeds. Generally it takes about 60 days
from fertilization to full pod maturity.
Sufficient variability exists in groundnut for various
morphological and economic traits: seed size, (17-124 g 100-seeds-1), seed color (white,
light rose, rose, red, purple, white blotched with purple red), number of seeds pod-1
(1-5), and pod length (11-83 mm) and pod breadth (9-27 mm).
Groundnut originated in the southern Bolivia/north west Argentina
region in south America and is presently cultivated in 108 countries of the world. Asia
with 63.4% area produces 71.7% of world groundnut production followed by Africa with 31.3%
area and 18.6% production, and North-Central America with 3.7% area and 7.5% production.
Important groundnut producing countries are China, India, Indonesia, Myanmar, Thailand,
and Vietnam in Asia; Nigeria, Senegal, Sudan, Zaire, Chad, Uganda, Cote d'Ivory, Mali,
Burkina Faso, Guinea, Mozambique, and Cameroon in Africa; Argentina and Brazil in South
America and USA and Mexico in North America.
The ideal growing conditions for groundnut are well-drained, light
colored, loose friable, sandy loam soil, availability of optimum moisture in pod zone, and
an optimum mean daily temperature of about 30 0C. It can be grown either as a sole crop or
in combination with other crops in inter or mixed cropping. Early leaf spot, late leaf
spot, rust, and Sclerotium rolfsi among fungal diseases; bud necrosis virus, tomato
spotted wilt virus, peanut stripe virus, and rosette among virus diseases; and jassids,
thrips, termites, leaf miner, Spodoptera, and white grub among insect pests, and
aflatoxin contamination are important biotic factors. Among abiotic stresses drought, low
pH, and low temperatures are important. These occur in various combinations in Asia,
Africa, and Americas.
Development of high-yielding cultivars of desired duration having
resistance/tolerance to single or multiple stresses and developing stress management
strategies are the main objectives of groundnut improvement programs in the world
including the one at ICRISAT. At ICRISAT, these objectives have been adequately supported
by Genetic Resources Program which maintains 13, 460 groundnut accessions including 197 of
wild Arachis species from 89 countries. The wild Arachis species are reservoir of
genes for high levels of resistance to various stresses. Our efforts have yielded
management strategies including genetic resistance for rust, late and early leaf spots,
aflatoxin, rosette, and peanut bud necrosis virus. We have developed short- and
medium-duration and confectionery varieties with multiple tolerance/resistance. More than
50 germplasm/breeding lines which originated from ICRISAT have either been released as
cultivars or are in on-farm trials in 25 countries of Asia and Africa. Now these cultivars
are beginning to be used in the production systems, specially those characterized by low
inputs and resources poor farmers. Fifteen other improved germplasm are used in the
national breeding programs. These would result in capacity building of National programs
in developing technologies for sustainable groundnut production.
Novel techniques such as genetic transformation, molecular markers
added selection, and gene transfer from alien sources are yet to make an impact on