crop improvements Flashcards
what were the early crops?
potatoes
wheat
barley
silk
flax
wood
are single point mutations often silent?
yes
what can a Combination of two silent mutations
by sexual reproduction can lead to?
an expressed mutation
what are the different types of mutations?
Silent mutations
Loss of function mutations (recessive)
Gain of function mutations (dominant)
classic plant breeding
1) Selection from natural variation within a species
2) Creating hybrids between selected ecotypes of that species
3) Repeat 1)-2) until you have an interesting trait
4) At all these steps, one has to test if the trait is stable and can be passed on to the progeny
methods of accelerated seed mutagenetics
Artificial irradiation (gamma, alpha, beta radiation)
Treatment with mutagenic chemicals (i.e. EMS)
Heat shock
Combinations
selection of traits
Yield
Stress resistance
Abiotic: Cold, heat, salinity, drought
Biotic: Pathogens (fungi, bacteria, insects)
Fruit quality, appearance, taste….
Shelf-life, homogeneous appearance
Nutritional value
Time to flowering
why back-crossing with parent strain
Clearing out other mutations
Maintaining desired trait
Re-establish general properties
Features of classic plant breeding
Definitely involves mutagenesis (=genetic modifications)
Totally random, but accelerated by mutagenic conditions
Totally uncontrolled and unpredictable
Success determined by smart screening methods to find traits
Absolutely no understanding at the molecular level
Considered natural, but being far from natural
improvement was based on the constant expansion/modification of the gene pool through
natural processes that promote mutations.
These include natural radioactivity (from space, volcanoes, soil…), UV light from the sun, stress conditions such as high temperature, pathogens, mal-nutrition, and finally sexual reproduction which can lead to combination of mutations
Accelerated seed mutagenesis
purposefully done with artificial irradiation (,β,γ radiation), treatment with chemicals (EMS), heat shock and combinations of those.
desirable traits
Traits can be crop yield, fruit quality, appearance, taste, shape, colour, texture, nutritional value
The homogeneous appearance of a crop is considered an important agronomic trait
because it promotes consumer confidence, less refuse, higher percentage sold
Liebig’s minimum law
Liebig’s minimum law simply states that plant growth is limited by the rate-limiting mineral in the soil. Any excess of other minerals will not help and they will be wasted
why use high tech greenhouses?
This is a growing trend because field losses to pathogens, slugs, insects and uncontrolled weather conditions are so high that the additional energy costs for artificial lights and controlled hydroponics with on-line mineral and pH stabilisation of circulating nutrient solutions are worth the investment
Also the harvesting process is easier, for instance tomatoes are grown with hydroponics and rails between the rows can harbour a slow moving platform on which people stand to harvest tomatoes on the vine and immediately place them into suitable container
what is intercropping?
the cultivation of two or sometimes three crops adjacent to each other in the same field
what is relay intercropping?
something in between intercropping and sequential cropping. A main crop is planted and allowed to establish itself hallway through its growth cycle, and instead of spending time pulling out weeds in between, a second crop is planted that can grow in between the bigger main cro
