Author
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Blackmer, Jacquelyn |
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Submitted to: International Congress of Scientific Knowledge
Publication Type: Abstract Only Publication Acceptance Date: 10/5/2006 Publication Date: 2/10/2007 Citation: Blackmer, J.L. 2007. Host-plant Resistance to Insects: Historical and Current Perspectives. International Congress of Scientific Knowledge. The Second International Congress of Scientific Knowledge in Campos dos Goytacases, RJ, Brazil, October 5-8, 2006, Vol. 5 No.10, Page 95. Interpretive Summary: Technical Abstract: Numerous strategies have been employed in the control of insects, but since the 1950s there has been a heavy reliance on insecticides. These insecticides, while incredibly efficient, have given rise to numerous problems including insecticide resistance leading to pest resurgence, emergence of secondary pests, loss of natural enemies and environmental contamination. The idea of a multi-faceted tactic to control insects gave rise to the Integrated Pest Management (IPM) approach. IPM programs are designed to keep pest population levels below some predetermined economic threshold level using economical, ecologically sound, socially acceptable, and sustainable technologies. One of the principle elements of IPM includes the development of host plants that are resistance to insect pests. The earliest report of resistance to insects dates back to 1782, when Hessian-fly (Mayetiola destructor) resistant wheat was identified. However, breeding for resistance to insects did not begin in earnest until the 20th century when knowledge of genetics and breeding methods made it possible. It was not until the 1920s when Reginald Painter of Kansas State University developed a Hessian-fly resistant variety of wheat that host-plant resistance (HPR), as we know it today, was born. The advantage of HPR, however, was not fully appreciated until the mid-1960s when overdependence on insecticides like DDT led to crop failures and environmental catastrophes. Host-plant resistance, as defined by Reginald Painter is “the relative amount of heritable qualities possessed by the plant which influence the ultimate degree of damage done by the insect.” Today we recognize several types of resistance including antixenosis, antibiosis, tolerance, and ecological resistance. The first two types of resistance involve plant traits that influence either the insects’ host acceptance or the host-plants suitability, while tolerance relates to the plants ability to tolerate populations of insects without sustaining economic losses. Ecological resistance, on the other hand, occurs when there are shifts in environmental conditions or when pests or other environmental stressors cause damage to the plant. These factors lead to enhancement of the plants’ defense mechanisms, which can alter their nutritional value or suitability. To complicate matters, numerous biotic and abiotic factors can influence the expression and magnitude of resistance, and interactions between the plant and these factors must be considered in any breeding program. Regardless of how successful we are at selecting resistant varieties, insects are supremely designed and suited for detecting and selecting appropriate host plants. They receive and process a plethora of information via their visual, olfactory and gustatory receptors. Inappropriate host-plant decisions could result in a total loss or reduction in their reproductive output, so over time they have evolved efficient ways of processing the information they perceive. Due to the complexity of these interactions, successful HPR programs should include a plant breeder, an entomologist, a geneticist and a molecular biologist. A variety of techniques and bioassays are used in assessing the suitability of plant varieties, and consequently, there have been a number of successful programs involving varieties resistant to insects. More recently genetically-modified organisms (GMOs) have entered the picture, usually in the form of plants that express the Bt (Bacillus thuringiensis) toxin. HPR is an environmentally friendly tactic that provides protection against insect pests, and it is often compatible with other tactics. HPR technology often leads to a reductions in pesticide use and can slow down the rate of resistance to insecticides. The disadvantages include the time required for development of resistant varieties, these varieties so |
