6. Transforming plants as a means of crop protection against insects.
Outlook on Agriculture, 19, 3, 1990, pp. 170-183
In this paper the progress is discussed which is being made towards producing plants by introducing insect control genes into crops by plant genetic engineering.
Some 13% of the world's crops are lost directly to insect predations, with further losses attributable to plant diseases for which insects act as the transmission vectors.
It is estimated that in 1988 nearly 4 billion US dollars were spent on applying chemical insecticides to protect just three crops - cotton, maize and rice - from their insect pests. These crops account for approximately half the total worldwide insecticide usage.
More than 99.9% of the chemical applied, enters the environment in ways which have a number of undesirable consequences, such as the destruction of beneficial insects, promotion of secondary pests and contamination of food chains. No-one alive today is free from detectable levels of organochlorides derived from insecticides.
The use of crop varieties which are inherently resistant to, or at least tolerant of, insect pests would provide a solution to this problem. Such varieties have the advantages that protection is provided when and where required for maximal control of insect pests, and is confined within the plant, thereby restricting its effect to crop-eating insects. The production of such resistant lines has been a goal of many conventional plant breeding programs. Unfortunately there is often no source of inherent resistance in the germplasm which is available for breeding purposes in a particular crop, even using modern wide-crossing and embryo rescue techniques.
Plant genetic enginering could help to overcome this problem since, once a system for the stable transformation of a particular crop has been developed, genes may be introduced into the breeding lines from any source. Such sources can include unrelated plants, animals, microbes or even wholly synthetic genes. This opens up a virtually unlimited source of germplasm variability from which useful traits may be selected.
Transformation systems have now been developed for most of the major crop species and for many other, locally important ones.
With the transformation system available, the key question becomes that of where to obtain useful genes for transfer. Two logical sources of insect control genes have been exploited so far: insect pathogenic microorganisms and plants themselves.
These sources are discussed in this paper.
The authors conclude that every encouragement should be given to careful attempts to investigate the claims that the approach of transforming plants to insect pest control is:
- user-friendly - there are no application costs or sophisticated technology involved in the use of such material on the farm; genetically engineered seed would be handled in exactly the same way as unmodified seed;
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Latin America, Brazil, field trial, VA-mycorrhiza, integrated plant protection, rubber trees
FELDMANN, F. et al.
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