This document discusses potato breeding. It covers vegetative propagation which allows any genotype to be propagated but risks disease transmission, and autotetraploidy which results in complex inheritance patterns. Potatoes originated in South America and were domesticated by indigenous peoples before being brought to Europe. The document outlines flower and seed characteristics, methods for flower induction, endosperm balance number requirements for successful crosses, and genetics considerations like heterozygosity. It also discusses using diploids for introduction of new genes and more efficient selection, repolyploidization techniques, breeding goals like disease resistance and quality traits, and issues with true potato seed cultivation.

1. Breeding Potato
Chapter 21

2. Vegetatively propagated
• Advantages
– any genotype can be propagated, no need for
inbreeding etc.
• Disadvantages
– disease transmission: Vira, bacteria
– tubers heavy to transport (lots of water)
– storage problems (diseases, sprouting)

3. Autotetraploidy
• Complex tetrasomic inheritance
– complicated segregation pattern
– increased dominance effects
• Tolerance to interspecific crossing
– Solanum tuberosum can be crossed with many
other Solanum species to widen gene pool
– interploidy crosses

4. Origin of Potato
• South America
– Andean, Peruvian (Mexican) area
– domesticated by south american indians
• Came to Europe with the Spanish
– further breeding in Europe

5. Flower and seed characters
Simple emasculation
Many seeds per fruit

6. Flower induction
• Long day (above 12 hours)
• Remove tubers
• Girdling or stem restriction
• Grafting onto tomato etc.
• Often incompatibility or sterility

7. Endosperm Balance Number
(EBN)
Succesful crosses have
2:1 female:male EBN
Female give two
gametes
to endosperm
Triploid block
(4x) x (2x)
EBN of new clones
to be determined
from crossings

8. Genetics of potato
• Heterozygosity
– a1a1a1a1(monoallelic)
– a1 a1a1 a2 (un balanced diallelic)
– a1 a1 a2a2 (balanced diallelic)
– a1 a1 a2 a3 (triallelic locus)
– a1 a2 a3 a4 (tetraallelic locus)
• Tetraallelic loci the most heterozygous
• They also form most epistatic interactions

9. Diploids and selection
• Diploids from wild species or from S.
Phureja crosses
• Diploid potatoes bring in new genes
(resistance, quality etc)
• Diploids more efficiently selected then
tetraploids

10. Repolyploidisation
• Protoplast fusion
– (2x) x (2x) gives (4x)
• (4x) x (2x)[unreduced gamete] gives (4x)
• (2x) x (2x)[both unreduced gametes] = (4x)
• Unreduced gametes from first or second
meiotic division gives heterozygous diploid
gametes to have more alleles in each locus
• Why not chromosome double????

11. Include resistance from wild
diploid
• Cross wild 2x with adapted 2x
• select for resistance
• backcross to another adapted 2x
• select for resistance
• repolyploidize (4x) x (2x) or (2x) x (2x)
• Select seed plants (disease resistance)
• Select cloned rows (tuber appearence)
• Select cloned plots (Yield, quality etc)

12. Breeding goals
• Earliness
– early potatoes, late types, industry types
• Heat, frost and drought tolerance
• Disease resistance
– late blight (Phytophthora infestans), horizontal
or broad resistance
– Vira: X, A, Y, leaf roll, S, spindle tuber
– Bacteria: Ring spot

13. Breeding goals
• Consumed
– Form, size, colour, taste, cooking quality
• Processed
– Chips, french fries (reducing sugars = brown rings)
– Starch: Size, extractability, starch quality

14. True potato seed (TPS)
• Cultivars propagated by seed
– should be diploid if reasonable uniform
– may eliminate virus and bacteria problems
– easy to transport disease free seed material
– no storage problems (in warm countries)
• TPS not generally succesful
– small seed plants starts slowly
– uniform seed production is problematic
(inbreeding depression)