Chapter 19: Technical, economic and policy considerations on marker-assisted selection in crops

Due to their usefulness in characterizingand manipulating genetic factors responsiblefor qualitative as well as quantitativetraits,molecularmarkersareconsideredtobe valuable tools for crop improvement.Theseusesofmolecularmarkershavebeeninvaluable in helping researchers understandcomplex traits, dissect them intosingleMendeliangeneticfactors,andestablishtheirchromosomallocationsviatheuseoflinkagemapsand/orcytogeneticstocks.Availability of well characterized geneticlinkage maps is a prerequisite for taggingimportant agronomic or other traits withmolecular markers, enabling their use inMAS related activities. To date, however,few practical applications have been publishedfrom these studies. ...
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Chapter 19: Technical, economic and policy considerations on marker-assisted selection in crops Chapter 19 technical, economic and policyconsiderations on marker-assisted selection in crops: lessons fromthe experience at an international agricultural research centre H. Manilal William, Michael Morris, Marilyn Warburton and David A. Hoisington382 Marker-assisted selection – Current status and future perspectives in crops, livestock, forestry and fish SummaryMolecular markers and related technologies have been used extensively in geneticcharacterization and identification of loci controlling traits of economic importance inmanycropspecies.However,theapplicationofsuchtoolsforcropimprovementhasnotbeenextensive,atleastinthepublicsector.Althoughthereareclearadvantagesinusingmolecularmarkersastoolsforindirectselectionoftraitsofimportance,availableexamplesindicate that their use is restricted to traits with monogenic inheritance or when theinheritanceisconditionedbyafewgeneswithlargeeffects.Anotherimportantlimitationoflarge-scalemarkerapplicationsisthecostinvolvedinmarkerassays,whichmaybebeyondthecapacitiesofmanypublicplantbreedingenterprises.Foraneffectivemarker-assistedselection(MAS)activitytofacilitateongoingcropimprovementprogrammes,especiallyinthecontextofthedevelopingcountries,laboratorieswithadequatecapacityandadequatelytrainedscientificpersonnelaswellasoperationalresourcesarerequired.Althoughrecenttechnological advances such as single nucleotide polymorphisms (SNPs) and associatedassayprotocolsarelikelytoreduceassaycostssignificantly,formanyoftheseoperations,assayplatformswithsignificantcapitalinvestmentsincludingcomputationalcapacityarerequired. Coupled with these limitations, private sector domination of biotechnologyresearch with proprietary rights to important products and processes with immediatebenefits to developing countries may further constrain the benefits these technologiesmay offer to resource-poor farmers. Policy-makers in different national programmesandinternationaldevelopmentandresearchagencieshavearesponsibilitytosustainandaugmentthecapacityofnationalpublicagriculturalresearchorganizationstoensurethatbiotechnologytoolsandprocessesareinfusedappropriatelyintonationalresearchefforts.Theymustalsoensurethatanybiotechnologyeffortsundertakenarewellintegratedwithnationalcropimprovementactivities.Chapter 19 – Technical, economic and policy considerations on marker-assisted selection in crops 383introduCtion anyMAS-relatedactivity.Thus,whileitisDue to their usefulness in characterizing possibletocarryoutMAStosomedegreeand manipulating genetic factors respon- incerealssuchasrice,maizeandwheat,andsible for qualitative as well as quantitative inlegumessuchassoybean,forspeciessuchtraits,molecularmarkersareconsideredto as cassava and sweet potato, the so-calledbe valuable tools for crop improvement. “orphancrops”,geneticimprovementwithTheseusesofmolecularmarkershavebeen MAS may not yet be feasible. These cropinvaluable in helping researchers under- species may benefit more readily fromstand complex traits, dissect them into genetic modification arising from directsingleMendeliangeneticfactors,andestab- introduction of genes isolated from otherlishtheirchromosomallocationsviatheuse speciesororganisms,whichisnotthefocusoflinkagemapsand/orcytogeneticstocks. ofthischapter.Availability of well characterized genetic Citing practical lessons learned atlinkage maps is a prerequisite for tagging the International Maize and Wheatimportant agronomic or other traits with ImprovementCenter(CIMMYT)aswellasmolecular markers, enabling their use in findingsofstudiesconductedelsewhere,thisMAS related activities. To date, however, chapterdescribessomeactualandpotentialfew practical applications have been pub- applications as well as the advantages andlished from these studies. This paucity of disadvantages of MAS, and outlines pos-published studies may indicate the long- sible applications of MAS in developingterm nature of this research, or it might countryplantbreedingprogrammes.simply reflect the fact that marker tech-nologyhasbeenappliedtoplantbreeding leSSonS learned from CropSeffortsmostlybyscientistsworkinginthe Numerous scientific reports describeprivatesector(Hoisin ...