AGSC 231 Principles of Agronomy Plant Breeding Relationship
AGSC 231 Principles of Agronomy - Plant Breeding Relationship By S. K. Yau, revised May 2010
Content l What is plant breeding? l Why needs plant breeding? l Genotype by environment interaction l General methods of plant breeding
What is Plant Breeding? § “Plant breeding is the genetic adjustment of plants to the service of man” Frankel § Plant breeding is the art and science of changing and improving the heredity of plants § “Breeding. . is evolution directed by the will of man” Vavilov § Simply, development of new plant varieties
Is this plant breeding ? Was the farmer doing plant breeding? If not, who was the breeder?
Brief introduction Plant breeding is not a new process Ø Early men learned how to select seed from wild plants for growing Ø Only in last century, knowledge of genetics changed plant breeding into a science.
Brief introduction (cont. ) Striking benefits, especially since 1940 s. E. g, benefits from hybrid corn and sorghum probably exceed the cost of all agricultural research in USA Crop Average gain per year Maize 92 kg / ha Soybean 18. 8 kg / ha Sorghum 1 -2 % Wheat 0. 7 %
Why do we need plant breeding? l to improve production and quality l increase crop area / intensity l increase input e. g. fertilizers, irrigation increase yield per unit area improved cultivar* without increasing input
What is cultivar? Ø cultivated variety, abbreviated as cv, synonymous with variety Ø What is variety? Ø In agriculture, a variety is a breed of plants having distinctive morphological and/or genetical and/or performance from other varieties within the same species.
What advantages does plant breeding have over cultural practices? v Save repeated input: v Can improve quality: cultural practices to improve yield - fertilization, irrigation, application of chemicals for pest control - must be repeated for each season. Hereditary improvement is more or less permanent. in most cases, cultural practices cannot improve quality significantly. v Environmental friendly: Chemicals not environmental friendly.
Clarification * This does not mean that we can ignore cultural practices. In most cases, both are needed to have maximum effects.
Genotype by environment (g x e) interaction
What is g x e interaction? Inconsistent performance of genotypes in different environments, or Differential response of varieties to different environmental conditions
Graphical illustration of genotype-by -environment interaction new cv yield old cv input e. g. N fertilizer, irrigation
Yield (t/ha) N fertilizer (kg/ha)
Bonus question: does the following table show G x E interaction? Seed yield of 2 chickpea varieties sown in winter and spring in Syria Spring sowing Winter sowing Syrian Local 865 kg / ha 824 kg / ha ILC 482 708 kg / ha 1839 kg / ha Varieties
General methods of crop improvement v Introduction from another place v Selection within local landraces v Hybridization and subsequent selection (not exclusive of each other)
What is a landrace? H H H usually a population with large variability known to be grown by farmers in an area for a long time origin usually not known
A typical plant-breeding field
When to use these methods? Depends on circumstances: è Introduction definitely is used when a new crop is needed è When there are local landraces and they have not been fully exploited, selection within local landraces should be the first step of a breeding program è When there is no locally adapted landrace, or when it has been fully exploited, one has to start hybridization
Common misconception With the development of molecular genetic techniques, it has been grossly over-claimed that conventional plant breeding can be replaced! Molecular techniques can complement, but so far has not replaced conventional plant breeding!
l Any questions? Comments?
Summary ü Plant breeding is genetic improvement of our crops ü Advantages over cultural practices: quality improvement, environment friendly, & semi-permanent. ü Plenty examples of accomplishment ü G X E interaction refers to the different performance of varieties over dissimilar sites ü General methods of plant breeding: introduction, selection with landraces, and hybridization followed by selection
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