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Genetic Improvement

Constraints to Rapid Improvement. Long juvenile periodLarge tree sizeSelf-incompatibilityCannot backcross to same cultivar. Commercial Apple Cultivars. Most apple cultivars arose from chance seedlings, but recently from breeding programsChance seedlings: ?Delicious', Golden Delicious', ?Granny S

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Genetic Improvement

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    1. Genetic Improvement

    2. Constraints to Rapid Improvement Long juvenile period Large tree size Self-incompatibility Cannot backcross to same cultivar

    3. Commercial Apple Cultivars Most apple cultivars arose from chance seedlings, but recently from breeding programs Chance seedlings: ‘Delicious’, Golden Delicious’, ‘Granny Smith’, ‘Ginger Gold’, ‘Cameo’ Breeding programs: ‘Fuji’, ‘Gala’, ‘Braeburn’ ‘Jonagold’, ‘Honeycrisp’, ‘Pink Lady’, ‘Pacific Rose’

    4. Commercial Cherry Cultivars Chance seedlings: ‘Bing’, ‘Lambert’, ‘Napoleon’ (‘Royal Ann’) Breeding programs: ‘Van’, ‘Lapins’, ‘Sweetheart’ (British Columbia) ‘Rainier’, ‘Chelan, Tieton, ‘Glacier’, ‘Index’, Olympus’ (WSU-Prosser)

    5. Traditional Breeding Techniques Collect & store pollen from pollen donor Emasculate flowers (remove stamens) of maternal parent Apply pollen to stigma of maternal parent when receptive Isolate flowers to prevent insect pollination Collect seeds; stratify & scarify if necessary Grow seedlings Evaluate fruit

    6. Seedling Crosses

    7. Genetic Variation

    8. Apple Breeding Programs United States Minnesota – ‘Honeycrisp’ New York (Cornell Univ.) since 1895 ‘Cortland’, ‘Empire’, ‘Jonagold’ Arkansas, Ohio, Illinois, New Jersey, Washington (1994) Private – Zaiger Genetics, CA Canada British Columbia, Quebec, Nova Scotia, Manitoba

    9. Australia – ‘Pink Lady’ England – ‘Fiesta’ Japan Aomori – ‘Mutsu’, ‘Tsugaru’ Morioka – ‘Fuji’, ‘Akane’, ‘Sansa’ Netherlands – ‘Elstar’ New Zealand ‘Gala’, ‘Braeburn’, ‘Splendour’, ‘Pacific Rose’, ‘Jazz’ Swizterland – ‘Arlet’

    10. Other Belarus, Belgium, Brazil, China, Czech Republic, Finland, France, Germany, Greece, Hungary, India, Italy, South Korea, Latvia, Lithuania, Mexico, Norway, Poland, Romania, Russia, South Africa, Spain, Sweden, Yugoslavia

    11. Apple Breeding Goals Disease & insect resistance Apple scab Powdery mildew Fire blight Fruit quality Flavor & texture Nutrition (? vitamin C) Reduced flesh browning (? polyphenol oxidase) Allergenicity (? Mal d1 allergen ? stress & pathogen induced)

    12. Apple Scab

    13. Apple Scab 6 genes for resistance Breeders primarily concentrated Vf gene Discovery of race 6 in 1993 Induced scab on nearly all Vf selections Other sources of resistance: Vm from M. micromalus & M. astrosanguinea 804 susceptible to race 5 Vr & Vx from Russian seedling R12740-7A’ showed differential resistance Recent discovery of race 7: New dominant resistant gene Vfh discovered

    14. Polygenic resistance exists in some cultivars ‘Antonovka’, ‘Discovery’, ‘James Grieve’, ‘Dulmener Rosenapfel’ & 2 old Italian cultivars Durable Apple Resistance in Europe Detect & characterize durable sources of resistance to scab & powdery mildew in local European cultivars Market study & consumer preference for new resistant cultivars “Reducing chemical input in apple production in response to consumer and grower's environmental concerns by increasing the durability of natural disease resistance” http://www.inra.fr/Angers/DARE/

    15. Powdery Mildew

    16. Powdery Mildew Many commercial cultivars used in breeding are highly susceptible Examples: ‘Ginger Gold’ & ‘Honeycrisp’ Difficulties in breeding for resistance: Poor understanding of races & their geographical locations Poor correlation of reaction to pathogen between seedling & mature trees Resistant genes: Pl1 from Malus x robusta & Pl2 from M. x zumi Proposed Pl-m gene from highly resistant open pollinated seedling of ‘Starking Delicious’ & Malus species

    17. Cherry Breeding Goals Smaller tree size Increased precocity Heavy, consistent yields Reduced susceptibility to cracking Self-compatibility Good fruit quality (size, color & flavor) Resistance to diseases Extended harvest season Improved adaptation to climatic extremes

    18. Cherry Cracking

    19. Bacterial Canker

    20. Biotechnology Molecular markers & mapping Early identification of resistance genes Genetic transformation First reported in apple in 1989; now most major cultivars have been transformed Expression of endochitinase enzyme from Trichoderma increased scab resistance & reduced tree vigor Rol genes from Agrobacterium rhizogenes reduced shoot growth & increased root growth Bacterial lyses genes from silk moth increased fire blight resistance

    21. Mutations During rapid cell division at shoot apex: Some cells may be fragment or not divide equally ? daughter cells are genetically different Usually unnoticed, unless occurring in apical cells of bud ? different shoots and/or fruits (called “bud sport”) Chimera When mutations occur in only some part of the plant organ

    22. Chimeras

    23. Sectorial chimera (mutation)

    24. Types of Chimeras

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