Contents - Faperta

84 Biotechnological Approaches for Pest Management and Ecological Sustainability
pests through conventional breeding, wide hybridization, marker-assisted selection, and
genetic transformation will signifi cantly contribute to sustainable crop protection and environmental
conservation. Varieties with adequate levels of resistance to insect pests will
encourage farmers to reduce insecticide application, and thus minimize the environmental
hazards. Such varieties will provide safer farm environments and produce with lower
insecticide residues. Development of crop cultivars with resistance to insects would provide
an effective complementary approach in integrated pest management (IPM). Resistant
or less susceptible cultivars would also provide an equitable, environmentally sound, and
sustainable pest management tool. Therefore, we need to make a concerted effort to transfer
insect resistance genes into genotypes with desirable agronomic characteristics, and with
adaptation to different agroecosystems.
In spite of the importance of HPR as a component of IPM, breeding for resistance to
insects has not been as successful as breeding for disease resistance (Sharma, 2002). This is
largely because of the relative ease with which insect control is achieved through insecticide
use, and the slow progress in developing insect-resistant cultivars as a result of the
diffi culties involved in ensuring adequate insect infestation for resistance screening. To
breed for resistance to insect pests, it is important to have optimum levels of natural infestation
or ability to rear the insects on artifi cial diets in the laboratory. Insect-rearing programs
are expensive and, in some cases, it may not produce the behavioral or metabolic
equivalent of an insect population in nature. However, with the development of insect
resistance to insecticides, adverse effects of insecticides on natural enemies, and public
awareness of environmental conservation, there has been a renewed interest in the development
of crop cultivars with resistance to insect pests in the national programs. The
establishment of International Agricultural Research Centers (IARCs), and the collection
and evaluation of germplasm for insect resistance in several crops has given a renewed
impetus to the identifi cation and use of HPR in pest management.
With the domestication of plants, farmers harvested the seeds from the plants that were
able to withstand adverse environmental factors, including insect pests and diseases. The
plants that were resistant to insect pests survived until crop harvest where the herbivore
pressure resulted in plant mortality, or their proportion decreased over time where the
herbivore pressure did not result in plant mortality. This process led to natural selection of
plants with resistance to biotic and abiotic stresses prevalent in an ecosystem. Because of
this unintentional but continuous selection of plants with resistance to insect pests, several
varieties with resistance to insects were selected by the farmers (Sharma, 2002). The best
examples of this process are shoot fl y-resistant sorghum landraces cultivated during the
post-rainy season in India, and head bug resistance in guineense sorghums in West Africa
(Sharma, 1993, 1996; Sharma et al., 1997, 2003b). Resistance of plants to insects enables a
plant to avoid or inhibit host selection, oviposition, and feeding, reduce insect survival,
retard development, and tolerate or recover from injury from insect populations that
would otherwise cause greater damage to other genotypes of the same species under similar
environmental conditions (Smith, 1989). Resistance of plants to insects is the consequence
of heritable plant characteristics that result in a plant being relatively less damaged
than the plant without these characters. The ability of plants to resist insect damage is
based on morphological and biochemical characteristics of the plants, which affect the
behavior and biology of insects, and thus infl uence the extent of damage caused by the
insect pests. Resistance traits are preadaptive and genetically inherited characters of the
plant that increase their chances of survival and reproduction. Plant resistance to insects
is relative, and the level of resistance is expressed in relation to resistant and susceptible
genotypes of the same species under similar environmental conditions. Conventional host