Strategies for Major Genes One gene at a time Gene rotation Gene ...

Strategies for Major GenesOne gene at a timeGene rotationGene “pyramids”MixturesRegional deploymentWorking With Minor Genes

Minor Gene Resistance• Often multiple gene inheritance• Often recessive• Usually gives incompleteresistance• Can be more complicated towork with• Not highly specific• Tends to be stable over time

Minor Gene Resistance• Often more available thanwe think• Simply purging the mostsusceptible materialcan be very useful• Inheritance is much lesscomplex than once thought

Estimating Number ofGenes and Hertitability• Statistical, quantitativegenetic approaches• QTL approaches• Both give same answer

Minor Gene ResistanceCommonly only 2-4 genes identifiedOften 1 or 2 that contributemajority of effectHeritability usually moderate tohigh

Estimating Number ofGenes and Hertitability• Statistical, quantitativegenetic approaches• QTL approaches• Both underestimate genenumber• Both depend on populationsize

Barley Stripe RustPop. Size Number of QTL50 3100 4150 5200 5.5300 6409 8

Barley Stripe Rust• Number of QTL increasedwith population size• ID QTL with biggest effectwith small population size• ID additional QTL withsmaller effects with largerpopulation size

Components of ResistanceLength of latent periodInfection efficiencyLesion sizeSporulation rateLength of infectious period

etween the Republic of Ghana and the China Development BankCorporation moved today.(Moved by the Hon. Vice Chairman of the Finance Committee, Mr.Alfred W. G. Abayateye and seconded by the Hon. Chairman of theFinance Committee, Mr. James Klutse Avedzi)11. MOTIONQuestion put and agreed toThat this Honourable House adopts the Report of the Joint Committeeon Finance and Mines & Energy on the Five Party Agreement amongthe Government of the Republic of Ghana, the Bank of Ghana, theGhana National Petroleum Corporation, UNIPEC Asia CompanyLimited and the China Development Bank Corporation under theMaster Facility Agreement between the Republic of Ghana and theChina Development Bank Corporation.(Moved by the Hon. Vice Chairman of the Finance Committee, Mr.Alfred W. G. Abayateye and seconded by the Hon. Member forSekondi, Papa Owusu-Ankomah)Question proposed: Debate arisingQuestion put and motion agreed to12. The House accordingly resolved as follows:WHEREAS1. By the provisions of Article 181(5) of the Constitution the termsand conditions of any international business or economictransaction to which the Government of Ghana is a party shallnot come into operation unless the said terms and conditionshave been laid before Parliament and approved by Parliamentby a Resolution supported by the votes of a majority of allMembers of Parliament;[10]

Can be relatively easy tomaintain minor generesistance once youhave it

Stripe RustPuccinia striiformisVIDAL L., INRA

Use of Top Crosses toMaintain Minor Genesfor Stripe RustResistance WhileImproving Other Traits

Stuff HappensXXXX

Effects of InterplotInterference (uredia/tiller)Isolated Adjacent tCultivar3x4 m 2x2 m 1/4x1 mL98 1000 500 2300Sultan 750 250 1700Volla 110 40 700Julia 17 12 450Vada 1 15 130Range 1000X 42X 18X

Test with Single Race orMultiple Races?No. races No. ofto which lesionsCultivar resistant per cm 2Zenith 64 2Kataktara 55 14Kano 51 40 39Lacrosse 19 66KTH 4 94

Vertifolia Effect

Percent of Willamette Valley WinterWheat Acreage Planted to ‘Foote’Year Percent2001 222002 502003 502004 512005 322006 4

Lessons:The Vertifolia Effect can bereal“Perfect Storms” do happen

QTL Analysis and MAS

Source: CAST

QTL Analysis and MAS

Molecular Breeding• Biology and engineering are verydifferent• High-quality phenotyping is stillthe most important ingredient of aresistance breeding program, andthis likely will always be so

Strategies for Major GenesOne gene at a timeGene rotationGene “pyramids”MixturesRegional deploymentWorking With Minor Genes

Single Gene at a Time“Use It Till You Lose it”• May be needed as a stopgapmeasure• In general, don’t go there- Puts growers at risk- Disruptive to breedingprograms

Pyramids or Combinationsof Major Genes• Useful in increasing durabilityof major genes• More complex than usingsingle genes• Takes time to determinewhich combinations workbest

Mixtures or Blends ofMajor Genes• Can be highly effective• Should be considered moreoften• Results variable, empiricaltesting critical

Regional Deployment• Likely very useful if done• Is it feasible?

Minor Gene Resistance• It’s hard to go wrong withthis approach• May take a bit more effortup front• Likely to eliminate a lot ofheadaches in the longerterm

Tolerance

Don’t Forget About IPMPotato late blight severity:Susceptible, no fungicide = 100%Weekly fungicide = 56%Minor gene resistance = 46%Resistance + fungicide = 9%

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