EGT and Mass Selection. PLS 664 April 10, 2007. Early Generation Testing. Objective: identify those populations that are likely to contain superior lines Strategy: eliminate those populations of low potential from the inbreeding process
April 10, 2007
Recall that there is all of the additive variance
among F2:3 lines and one-half of the additive
variance within F2:3 lines
In later generations of F2 derived lines, there is
still all of the additive variance among lines,
and considerable variance within lines, as
Method #1 = Selection of individuals within a heterogeneous
population. Choosing favorable/desirable plants and harvesting
Method #2 = Sampling seed from selected individuals to plant
the next generation.
1958: Plant out heterogeneous
population of F3oat seed. Using
a lawn clipper, cut oat plants to
uniform height (determined by check cultivar).
Harvest only top 10 cm in order to select against
Collected seed will be composed
of complete panicles, partial
panicles, or no panicle.
Evaluated 75 plants from the unselected group of each generation,
75 plants from the selected group of each generation, and 75 plants
of a pure line check.
Significant reduction plant height = 0.47” generation-1
Associated shift towards earliness = 0.23 days cycle-1
Shift towards higher yields = 0.41 grams plot-1. Non-significant
h2D = heritability of directly selected trait
h2I = heritability of indirectly selected trait
rg DI = genetic correlation between D&I traits
Linear change in seed size
Progress for high protein- low oil was best in large seed/high specific
Progress for high oil - low protein was best in small seed/low specific
** This is an example of selections and sampling being performed
simultaneously on the harvested seed.
Selection can be applied to 1) individual plants, 2) seeds.
Selection involved is 1) artificial selection, 2) naturalselection,
Selection for 1) one trait, 2) multiple traits
Sampling methods :
1) random sample of selected seeds bulked
2) equal quantities of seeds harvested & bulked from selected
3) selection performed on seeds which are used to plant out the
next generation. (Selection & sampling done simultaneously).