Articles
TREE CROP BREEDING: MISSING THE ORCHARD FOR THE LEAVES?
Article number
1028_2
Pages
29 – 40
Language
English
Abstract
Tree crop breeding differs from agronomic and vegetable crop breeding owing to the large plant size and long seed-to-seed generation time, both of which constrain breeding progress.
Breeding success for all crops, however, requires the development of cultivars equal to the established commercial cultivars in all qualitative and quantitative aspects, including yield, while significantly improving specific commercially important traits.
Optimizing cultivar performance thus requires the optimization of all genetic, epigenetic, and genomic interactions contributing to final phenotype.
Because the agronomic and vegetable crops are primarily seed propagated, the inherent genomic and genetic changes during meiosis have limited breeding manipulations to the optimization of intra- and inter-allelic interactions through well-established qualitative (Mendelian) and quantitative methods.
Marker-assisted-selection (MAS) is particularly useful for manipulating such, primarily additive, genes.
Because most commercially important tree crops are vegetatively propagated, commercially proven, elite clones have been optimized through long-term, performance-based traditional selection methods for interactions not only at the genetic level but also at the epigenetic and genome levels.
Thus, while molecular-based MAS strategies developed primarily in the agronomic crops have effectively improved response to selection for many oligogenic traits, their value for improving complex quantitative traits such as yield remains largely unproven.
In addition, their inherently reductionist approach to cultivar improvement ignores the higher-order epigenetic and genome interactions and so inherently limits potential breeding gains.
While strategies for characterizing and perhaps optimizing such higher order interactions are becoming available, the inherent complexities and resultant low probability of optimizing the full range of all desired interactions may require improvements in our capacity to generate/evaluate very large breeding populations from parents carefully selected at the genetic, epigenetic and genome level.
Breeding success for all crops, however, requires the development of cultivars equal to the established commercial cultivars in all qualitative and quantitative aspects, including yield, while significantly improving specific commercially important traits.
Optimizing cultivar performance thus requires the optimization of all genetic, epigenetic, and genomic interactions contributing to final phenotype.
Because the agronomic and vegetable crops are primarily seed propagated, the inherent genomic and genetic changes during meiosis have limited breeding manipulations to the optimization of intra- and inter-allelic interactions through well-established qualitative (Mendelian) and quantitative methods.
Marker-assisted-selection (MAS) is particularly useful for manipulating such, primarily additive, genes.
Because most commercially important tree crops are vegetatively propagated, commercially proven, elite clones have been optimized through long-term, performance-based traditional selection methods for interactions not only at the genetic level but also at the epigenetic and genome levels.
Thus, while molecular-based MAS strategies developed primarily in the agronomic crops have effectively improved response to selection for many oligogenic traits, their value for improving complex quantitative traits such as yield remains largely unproven.
In addition, their inherently reductionist approach to cultivar improvement ignores the higher-order epigenetic and genome interactions and so inherently limits potential breeding gains.
While strategies for characterizing and perhaps optimizing such higher order interactions are becoming available, the inherent complexities and resultant low probability of optimizing the full range of all desired interactions may require improvements in our capacity to generate/evaluate very large breeding populations from parents carefully selected at the genetic, epigenetic and genome level.
Authors
T.M. Gradziel
Keywords
genome, epigenetic, MAS, clone, luxuriance, cultivar breeding
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