Hybrid Breeding I

Question 1

Explain the difference between gametophytic and saprophytic self-
incompatibility.

Answer 1

A. Gametophytic self-compatibility occurs if the pollen genotype is the same as the female genotype. Therefore, gametophytic self-combability is determined by the genotype of haploid pollen. The haploid genotypes shouldn’t be the same.
B. Saprophytic self-incompatibility is determined by the diploid genotype of the sporophyte gene controlled by SI locus

Question 2

Name the requirements for the utilization of CMS in hybrid seed production
and the difficulties occurring with the attempts to meet these

Answer 2

 Maximum expression of male sterility (100 %)
 No or only minor negative side effects of CMS on other traits (vigor, yield,
disease resistance)
 Environmentally stable expression of maintainer genotypes in CMS-inducing
cytoplasm
 Maximum restoration of hybrids (close to 100 %) independent of seed parent
and environment
 Simple inheritance of maintainer / restorer characters
Note: If product needs not to be seed-fertile (e.g., beet, onion), pollinator line need
not carry restorer gene(s), otherwise it must.
Problems:
 Efficient sterility and restoration are rare and can be very laborious to
construct.
 Cytoplasm often has deleterious effects on vigor, yield, and disease resistance
 Reduced selection efficiency in early backcrossing generations

Question 3

Discuss the utilization of CMS with respect to the role of environment in the
expression of this system.

Answer 3

System needs to be environmentally stable. At least in the environments I am
breeding for.

Question 4

In which case would you prefer a mechanical emasculation in HYB over any
of the hybrid mechanisms described previously? OR When can hand emasculation be preferred over CMS in Hybrid seed production?

Answer 4

-
In maize: easy to emasculate per hand, because the male inflorescence is on
top of the plant, and so a self-fertilization can be prevented by cutting of the
male bloom
-
In tomato: Hermaphroditic flower  more time and cost intensive then in
maize, but each single pollinated flower produces one fruit with more than 100
seeds  the effort is worth it

Question 5

c. When can hand emasculation be preferred over CMS in Hybrid seed production?

Question 6

How would you design a hybrid breeding program if you knew all the genes
involved in fertilization?

Answer 6

First, decide if a sterility, or self-incompatibility system applies to my crop.
Second, establish the necessary lines for the parental line’s development (A lines, maintainer and restorer lines).
Third, develop the parents and test the crosses.