Agriculture Reference
In-Depth Information
Chapter 6
Effect of pesticides on leguminous
plants: An overview
Harpreet Kaur, Renu Bhardwaj, Vinod Kumar, Anket Sharma, Ravinder Singh and Ashwani Kumar Thukral
Department of Botanical and Environmental Sciences, Guru Nanak Dev University, Amritsar, India
6.1 Introduction
form of nitrogen is used by the plant to form organic
compounds such as proteins, nucleic acids, etc. This
nitrogen fixation plays an important role in the growth
and development of leguminous plants. The application
of pesticides negatively influences the growth of the
bacteria, the interaction between the symbiotic bacteria
and the legumes, the number of nodules and the activity
of nitrogenase enzyme, thereby reducing the rate of
nitrogen fixation. This reduction in nitrogen fixation
reduces the growth and yield of leguminous plants
(Fox
et al.,
2007). However, pesticide-tolerant strains
of bacteria can enhance the growth of legumes under
pesticide stress.
In terms of their importance to humans, the legumes
are second only to the Gramineae. They include impor-
tant grain species like pigeon pea (
Cajanus cajan
), pea
(
Pisum sativum
), broad bean (
Vicia faba
), chick pea (
Cicer
arietinum
), cowpea (
Vigna unguiculata
) and soybean
(
Glycine max
); pasture species like alfalfa (
Medicago
sativa
), clovers (
Trifolium
spp.), sweet clovers (
Meliotus
spp.), trefoil (
Lotus corniculatus
) and vetches (
Vicia
spp.);
and agroforestry species like members of the genera
Dalbergia
,
Pterocarpus
,
Gliricidia
,
Anadenathera
,
Erythrina
,
Calliandra
,
Parkea
and
Samanea
(Graham & Vance,
2003). Legumes contribute about 33% of the dietary
protein nitrogen requirement of humans (Vance
et al.,
2000). The quality and yield of legumes are drastically
reduced by pest infestations. So, to combat pest infesta-
tions and to maintain the quantity and quality of
legumes, a broad spectrum of pesticides are applied
(DDT, chlordane, aldrin, chlorpyrifos, etc.). Some of
these pesticides (e.g. DDT) are highly persistent and
non-biodegradable. There are three phases of pesticide
metabolism in plants (Karthikeyan
et al.,
2003). In phase
I reactions, pesticides are transformed by addition of
functional groups. In phase II reactions, phase I products
undergo conjugation with sugars, glutathione, phosphate,
amino acids and sulphate. Phase III reactions include
the formation of bound residues by co-polymerization
with molecules such as lignins (Singh, 2012).
Leguminous plants form symbiotic associations with
Rhizobium
bacteria, which live inside root nodules of the
plant and reduce atmospheric nitrogen. This reduced
6.2 Uptake, metabolism and
persistence of pesticides
Legumes such as cowpea, chickpea, field pea, pigeon
pea, green gram, faba bean, black gram, beans, lentil
and grass pea are important food sources. These crops
are susceptible to attack by various types of insect pest,
such as
Maruca vitrata
(spotted pod borer),
Helicoverpa
armigera
(pod borer),
Melanagromyza obtusa
(pod fly),
Etiella zinckenella
(spiny pod borer),
Sitona
sp. (pea and
bean weevil),
Ophiomyia phaseoli
(stem fly),
Empoasca
spp. (leafhoppers),
Aphis falae
and
Aphis craccivora
(aphids),
Spodoptera exigua
,
Spodoptera litura
and
Amsacta
spp. (defoliators),
Bruchus pisorum
and
Callosobruchus chi-
nensis
(bruchids),
Caliothrips indicus
and
Megaleurothrips
dorsalis
(thrips) and
Mylabris
spp. (blister beetles)
(Sharma, 2005).
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