Breeding with Genetically Modified Plants
Plant breeding aims at the genetic improvement of cultivated plants. Depending on the reproduction system of a plant the breeding process can last up to 15 years for crops and much longer for tree species. The breeding method is determined by the reproduc
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Breeding with Genetically Modified Plants Christian Jung
6.1
Genetic Variation in Plant Breeding
Breeding with transgenic plants is only justified when genetic variation within the primary and secondary gene pools of a species is too small or gene transfer by conventional techniques is difficult and time-consuming. There are a number of different means for increasing or even creating new genetic variation, like species hybridization, mutation induction and protoplast fusion, which have been frequently used to breed new varieties (Fig. 6.1). It is worth mentioning that neither plant cultivation nor commercialization of commodities has any legal requirements and a public discussion about these plants is also lacking. Therefore a breeder must carefully assess the different constraints of transgenic breeding before starting a breeding program which are the legal aspects and acceptance by farmers, consumers and stakeholders.
6.2
Breeding Aims
Plant varieties must meet the requirements of plant production under special environmental and economical conditions. Moreover, the demands of food and feed industry as well as the consumers’ preferences must be regarded. The yield potential is often the most important aim. Today’s varieties are elites with high-yielding potential due to countless rounds of recombination and selection. Yield potential is a typical quantitative character controlled by many genes. Thus high yielding varieties differ substantially from their wild relatives, landrace and any other non-adapted material. Therefore, transgenic material with C. Jung Plant Breeding Institute, Christian Albrechts University of Kiel, Olshausenstrasse 40, 24098 Kiel, Germany e-mail: [email protected]
F. Kempken and C. Jung (eds.), Genetic Modification of Plants, Biotechnology in Agriculture and Forestry 64, DOI 10.1007/978-3-642-02391-0_6, # Springer-Verlag Berlin Heidelberg 2010
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C. Jung genetic variation
wide crosses cell fusion
crosses with landraces
mutation
Increasing genetic variation
Crossing and recombination
high
crosses with elite material
artificial
transformation
genetic variation
natural
primary gene pool secondary gene pool
Selection
gene transfer
Variety
low
tertiary gene pool
Fig. 6.1 Methods for increasing genetic variation in plant breeding
poor-yielding capacities must be backcrossed several times with elite lines (see Sect. 6.3). The yield potential itself is not accessible to transgenic modification due to its polygenic nature. Plants are attacked by numerous pathogens and pests and they suffer from different environmental constraints like drought, heat, frost, water, salt and low soil pH. Therefore resistances or tolerances to these stresses are needed. These measures increase the yield stability of a crop. They are often a prerequisite for crop cultivation mainly when technical measures like pesticides are unavailable. It happens quite often that modern high-yielding varieties lack resistance or tolerance genes. Transgenic technology has been tremendous
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