Michael Mazourek Cornell University

Plant Breeding General Schemes– Recurrent Selection

• Straightforward• Many alleles possible in population

– Pedigree –creates new combinations of traits• See all permutations• Few alleles

– Backcross – good for introgressing trait into elite plant

• Dominant source– Easy – phenotypic difference in progeny

• Recessive source– Laborious – no phenotypic difference

Population Breeding• Mass Selection – simple recurrent selection

– Works best when environmental influence is minimal

– Plant Intercrossed or random mated population– Select best 5-10% of plants– Allow to intercross– Repeat

– Slowly but surely

Mendel

• Alleles – different forms for a gene that control a trait

• Dominant allele – written in CAPITAL LETTERS• Recesive allele – written in smalls

• True Breeding = Homozygous

• Cross dominant plant x recessive plant – Heterozygous offspring–AA x aa => Aa F1

Breeding with HybridsDominant traits•only needs to be inherited from one parent to appear in progeny – see it in the F1•visible if presentRecessive traits •needs to be inherited from both parents to appear in progeny•plant can be an invisible carrier Hybrid with dominant trait•may or may not be true breeding•Common for disease resistanceHybrid with recessive trait •progeny will be true breeding•Common for domestication traits

Pedigree Breeding• Make crosses to produce F2 population

– Sow large F2 (50-5,000 individuals)– Select best individuals and self-pollinate

• Plant F3 families– Select best individuals and self-pollinate

• Plant F4 families– Select best individuals and self-pollinate

• Plant F5 families– Select best families– Increase for replicated trials

• Generations to replicated trials variable

‘Amber Delight’

‘Bugle’ (Rupp Seeds) ‘Honeynut’ (High Mowing Seeds)

‘Amber Delight’

X

‘Amber Delight’

‘Bugle’ (Rupp Seeds) ‘Honeynut’ (High Mowing Seeds)

‘Amber Delight’

HybridHeterozygote for:PMRSome other genesNot many others

‘Amber Delight’

‘Bugle’ (Rupp Seeds)

‘Amber Delight’

PVPRestricts:Saved seed for commercial useSale of seed of first gen hybrids

Further generations non-restricted

From ‘Amber Delight’ to ‘898’‘Bugle’ ‘Honeynut’

‘Amber Delight’

X

Select plants in field for Powdery mildew resistanceProductivity

Test harvested fruit forBrixColorDry matter

F2 150 plants

F5 10 plants x 3 repsF4 10 plants

F3 10 plants

898

How Many Seed Should I Plant?• Crosses between uniform hybrids or inbreds

– at least 3 plants, not more than 6-10 plants– More if low seed yield crop

• Self pollinations of uniform hybrids or F1’s– At least 3 plants, not more than 6-10 plants– More if low seed yield crop

• F2 plants from selfing F1– At least 16 plants– sweet spot between 75 and 150– Depends on complexity of cross (x 5 rule)

Heterozygotes and Selection• Anthocyanins in jalapeño• Dominant

• Issue: – Cross green with purple– Discard green– Select best purple plant– Plant progeny– Most segregate for green

A aA AA Aaa Aa aa

‘Habanada’

X

F1

F2

P1 P2

3/4 1/4

X‘Habanada’

F1

P1 P2

X P2

BC1F1 population

BC1F2

Goal: Develop a sweet, striped (variegated) snacking pepper

Developing a sweet, striped (variegated) snacking pepper

Starting Parents:

‘Fish’:spicy, variegated

‘Lipstick’ sweet, non-variegated

Variegated (recessive)

Non-variegated (dominant)

X

1/4 of F2 progeny will be variegated

F1

Pungent(dominant)

Non-pungent(recessive)

X

1/4 of F2 progeny will be non-pungent

F1

Variegated (recessive)Pungent (dominant)

X

1/16 of F2 progeny will be non-pungent and variegated

F1

Non-variegated (dominant)

Non-pungent (recessive)

1/1616 x 5 = 80

Backcross Method (Dominant) aa x AA

aa x Aa

1 aaaa x 1 Aa

F1

BC1F1

BC2F1

1 aa1 AaBC3F1

BC3F2 1AA:2Aa:1aa

•Relatively simple•Population size small

•(~10 plants)•Not much gained

50% P1

75% P1

87.5% P1

93.25% P1

93.25% P1, 96.875% homozygous,

1 aaaa x 1 Aa

93.25% P1, 98.4375% homozygous,1AABC3F3

Slow Backcross Method (Recessive) AA x aa

AaF1

“BC1F1”

F2

1AA2Aa

AA x 1aa

X

Aa

1AA2Aa

AA x 1aa

X

“BC2F1” Aa

“BC1F2”

PurposefulWorks great if you can stand the wait

Population Sizes for Single Genes• Important formula:

ln(1-Probability)/ln(1-frequency) = # plants

Ex how many plants do you need to be 99% sure to find aa in F2 of AAxaa?

ln (1-0.99)/ln (1-0.25) = 16

How sure are you that you will find 1% contamination if you check 100 samples?

ln(1-P)/ln(1-0.01) = 100P=63%

Warning: formula for # to phenotype, does not include germination losses, deer damage, etc

Early Red Bell Pepper Project• EFAO, KASSI, Bauta Family Initiative

on Canadian Seed Security and more• Goal of developing an early red bell

pepper that thrives on participating grower farms

Ace -very early but pointy

Aristotle -cubic, broadly adapted, many disease resistances but late

F1 – several pollinated due to variation from crossing two hybrids

F2 – seed from earliest plants shared

Early Red Bell Pepper Project

One Generation of Selection• Cornell

– planted progeny from individual plants separately. (F3 families)

– chose best plants from best families.– Pruned and dug up selections– Self-pollinating greenhouse

• Ontario– Planted mix of F3 seed at multiple farms– Selected best individuals– Saved open pollinated seed– Dug up selections for self-pollination– Will recombine seed between farms for

2017

Acknowledgements• ACORN ECOSGN

• Lauren Brzozowski & Rachel Hultengren

• New Ontario seed friends– KASSI, EFAO, Bauta Family Initiative

• Chris Hernandez, Bill Holdsworth, Brian Leckie, Kyle LaPlant, Rachel Hultengren, Lindsay Wyatt

• Maryann Fink, Paige Reeves, Emily Rodekohr, Sara Shapleigh

• NOVIC Team• ESO-Cuc Team

Northern Organic Vegetable Improvement CollaborativeUSDA-OREI 2009-51300-05585

2014-51300-22223

ESO-Cuc: Addressing Critical Pest Management Challenges in Organic Cucurbit Production

USDA-OREI 2012-51300-20006

Breeding, Research, And Education Needs Assessment For Organic Vegetable Growers In The Northeast

USDA-AFRI 2014-67013-22409

Toward Sustainability FoundationDavid Rockefeller Fund