GENETIC ENGINEERING OF TRAITS AFFECTING QUALITY
Gene technology already has a strong impact on plant breeding by
providing cultivars that are tolerant to herbicides, resistant to fungi, pests
and viruses, or that have been rendered male sterile: Are there also im-
plications for quality characters in crops, fruit and vegetable? From 1987
to 1997, 4,279 field trials (U.S.: 3,315 and EU: 964) at over 15,000 field
sites were approved or acknowledged by the authorities. Since January
1994, 86% of all field releases in the U.S. have been approved as noti-
fications under the simplified regulation, which has been effective since
- Derivatives of approximately 50 different plant species have been
field-tested to date. The most frequent crops that have been subject to
genetic engineering in the U.S. and Europe are summarized in Figure
2.1. Corn is the major crop being field-tested, followed by potato, tomato,
soybean, rapeseed, cotton and sugarbeet. Of the field releases in EU and
the U.S., 26% correspond to fruit and vegetable crops, with potato (444)
and tomato (428) leading the field far ahead of melon and squash (132)
and radicchio (35). Infrequent crops with five or less issued field test-
ings include barley, broccoli, cabbage, calendula, carrot, cauliflower,
cranberry, eggplant, grapevine, onion, orange, papaya, pea, pepper, plum,
raspberry, strawberry, sugarcane, sweet potato, walnut, watermelon and
zucchini.
These transgenic plants have been released with a wide variety of
modifications. Among the field testings in the U.S., herbicide tolerance
is ranked first followed by insect resistance and product quality (Fig.
2.2). Product quality comprises one fifth of the field releases and may
thus be considered as a significant objective of genetic engineering. Of
the commercialized transgenic crops, which amounted to 12.8 million
ha (31.5 million acres) worldwide in 1997, however, quality traits have
a portion of less than 1% while herbicide tolerance, insect resistance and
virus resistance are the dominant traits with a portion of 54, 31, and
14%, respectively (James, 1997).
Among the fruit and vegetable crops, tomato has become the para-
digm of “high-tech” plant breeding, mainly because of its relative small
and simple genome, which favors gene mapping and isolation, its good
in vitromanipulation and transformation properties, its autogamous re-
productive system allowing for easy inbreeding and production of ho-
mozygous genotypes, its refractory nature with respect to crossability
with wild Lycopersiconspecies, which urges the breeder to think of non-
Genetic Engineering of Traits Affecting Quality 25