INTRODUCTION TO PLANT BREEDING

AGRONOMY 815 / COURSE NOTES

P. STEPHEN BAENZIGER, 338 Keim Hall, 472-1538

DEPARTMENT OF AGRONOMY / UNIVERSITY OF NEBRASKA

BULK POPULATION METHOD


Briggs and Knowles, Chapt. 12
Fehr, Chapt. 22
Developed by Nilsson-Ehle (1908) - winterhardy wheat.


Method:


    P1  x  P2             etc.

x x x x x x x x
x x x x x x x x            F1         50 - 100 plants. Can vary considerably.
x x x x x x x x

o o o o o o o o o o 
o o o o o o o o o o        F2         Plants (approx. 5000, but can 
o o o o o o o o o o                   vary) are grown and seed harvested
o o o o o o o o o o                   and bulked from all plants.
o o o o o o o o o o

o o o o o o o o o o        F3         1/50 - 1/100 ha. plots are grown
                                      (about 5000 plants) from bulked
o o o o o o o o o o        F4         seed of all plants in the previous
                                      generation.  Can do some artificial
                                      selection (ex., rope wicking for
                                      height).
o o o o o o o o o o        F5

x x x x x x x x x x
x x x x x x x x x x                   Space plant 5000 to 10000 seed.
x x x x x x x x x x        F6         Select 250 - 1000 plants or family
x x x x x x x x x x                   rows.
x x x x x x x x x x

x  x  x  x  x  x  x
x  x  x  x  x  x  x                   Selected progeny rows are grown
x  x  x  x  x  x  x        F7         and superior 20 -100 rows are
x  x  x  x  x  x  x                   harvested.



                    Preliminary yield trials.
         F8         Further selections made based
                    on line performance.
 



    F9  -  F11                        Further yield trials.

ADVANTAGES:

Bulk method is simple, convenient and inexpensive. 'Natural' selection can be enhanced by growing bulks under stress conditions, e.g., disease, insect, drought. Can use mass selection to modify the bulk. Can replicate bulks and determine performance or test in multiple environments. Can drop bulks at any time.

DISADVANTAGES:

Lines selected from the bulk that appear to be segregating may need to be reselected to obtain uniformity. There is a risk that desirable genotypes may be lost from the population; e.g., short plants may be at a disadvantage in competition with tall plants. COMPETITION IS NOT THE SAME AS NATURAL SELECTION. Will know little about the genetic structure of the population. Natural selection is not always beneficial.

Bulk method is particularly suited to small grains where space plantings are an abnormal condition.

In contrast to the pedigree method little information is obtained from early generations.