Breeding Schemes - An Introduction to Plant Breeding - page 59

Which parent combination will provide the
most productive single cross hybrid and what
would the expected yield be? Which parent com-
bination will provide the most productive three-
way cross hybrid and what would the expected
yield be? Which parent combination will provide
the most productive double cross hybrid and what
would the expected yield be?
Explain why the most productive double cross
combination (from the prediction equation), may
not result in the most commercially suited hybrid
cultivar.
(7) In order to justify development of hybrid cultivars
it is necessary to have some method of produc-
ing inexpensive hybrid seed. Outline three systems
that have been used to produce hybrid seed and
indicate the advantages or disadvantages of each
system.
(8) 'Russet Burbank' has been the predominant
potato cultivar in the Pacific Northwest for many
years. You have been asked to design a breed-
ing programme that will produce cultivars that
can replace some of the Russet Burbank acreage.
Outline the breeding design you would use, indi-
cating: (a) five breeding objectives; the breeding
scheme (use diagrams if necessary), indicating
number of clones evaluated and selected at each
stage.
(9) In order to produce a hybrid cultivar using cyto-
plasmic male sterility you require three types of
genotypes. Describe the difference between the
three types required, and describe how commer-
cial production will be conducted.
(10) You are to embark on a backcrossing study
designed towards convergence breeding. You have
at your disposal two genotypes coded C and M.
Genotype C is a cytoplasmic male sterile line,
but one that does not have very good hybrid
combining ability; genotype M has great hybrid

combining ability and is male fertile (without
a male fertile restorer gene). Design a scheme
(listing each operation necessary) that will result
in a genotype which is 95% the genotype of the
M line but is cytoplasmically male sterile.
(11) Mass selection and recurrent phenotypic selection
are often used in developing out-pollinating cul-
tivars. Describe the main difference between the
selection methods and indicate any problems that
each selection method could have in a breeding
programme.
(12) You are walking along a deserted beach in
Southern California (are there any of these left?)
and you inadvertently kick a brass oil lamp. On
picking up the lamp you gently rub the side and -
poof! - a 20 foot tall genie appears! ' Oh master! '
says the genie,' I can grant you two wishes ' (well
times are hard and the old three wishes thing does
not apply any more). You think for a few min-
utes then say ' I would like you to conjure me up
the most wonderful plant that exists within the Uni-
verse, so that I can grow it on my farm in Idaho and
make millions of dollars in profits '. Poof! This plant
appears before you. A plant species that has never
appeared on earth before.
As a plant breeder, list five questions you would
ask the genie about the biology of this plant
that would help you design a cultivar develop-
ment programme to increase the value of it as
acrop.
Having sorted that out, you begin to think of
your other wish. ' I would like you to tell me the
formula for chemical apomicts ' (a chemical, when
applied to a crop will result in 100% apomictic
seed from the crop). ' Well ' says the genie. ' I can
do this, but, you must specify which crop species the
chemical will work on ' (it can only work on one
chosen species). What crop species would you
chose to have apomictic seeds, and why?