marker-assisted selection in wheat - ictsd

Chapter 8 – Marker-assisted selection in maize 141for such high precision phenotyping ascan be seen from their active recruiting oftrait-specific phenotyping scientists oftenlocated in targeted areas where the trait ofinterest can be more easily measured (e.g.positions dedicated to drought toleranceand located in arid regions of the world).In order to further the implementationof MAS in breeding, increased numbersof marker data points will be required.Private corporations have established orare developing the capacity to producehundreds of millions of data points peryear in service laboratories, distinct fromresearch units. Besides, smaller “biotech”companies are developing technologies thatcould reduce the cost of each marker datapoint to a mere few United States cents.Moving to marker systems that are notbased on gels is permitting the automation ofmost laboratory steps. Data points are beingproduced around the clock with laboratorytechnicians working in shifts. Here again,private companies are actively recruitinghighly qualified technology specialists aswell as laboratory managers whose role ismore to optimize the running of productionplants than dwell on the science. Beyondlaboratories, plant handling is becoming abottleneck to high-throughput protocols.High-throughput facilities have to beestablished and equipped at continuousnursery sites potentially to handle millionsof plants per year.There is little doubt that the largestprivate maize breeding programmes areinvesting very heavily in the implementationof MAS. Unless regulatory issues changedramatically, MABC will remain thepreferred means of delivering transgenesto the market. Faster MABC protocols willalways represent a potential commercialadvantage in an area where competition isfierce and a one-year advantage may meanmuch on the market. Most recent investmentshave been directed at implementing MARSin breeding. The size of the investmentin this approach seems to suggest thatprivate corporations have more insight intoits benefits compared with conventionalbreeding than has been reported publicly.Genotype-driven breeding should alsoallow faster development of specializedvarieties as the maize market becomes moreand more fragmented based on end-use ofthe harvest: animal feed (silage or grain),ethanol, dry or wet milling. Favourablealleles for traits of interest are likely tobe spread across more than two linestherefore requiring the assembly of allelesfrom many different sources in a singleinbred line. Proposals have been made toachieve such goals (Peleman and van derVoort 2003), although software tools todetermine the optimal breeding schemesare not yet available to generate these“ideal” genotypes.Maize breeding is likely to changemore in the coming 10 or 20 years thanit has over the past 50. Developing newhybrids efficiently now requires integratingdata from many sources, sometimesbeyond maize, generating high-qualitygenotypic and phenotypic data neededfor the construction of “ideal” genotypes,and finally selecting phenotypically thebest individuals from populations ofmarker-assisted-derived materials. Manystakeholders beyond maize breeders nowtake an active part in the development ofnew varieties and therefore breeding willincreasingly become the responsibility ofgroups of individuals with complementaryskills than stand-alone breeders. Trainingof all to understand and challenge thecontribution of others will be critical tooperating multidisciplinary breeding teamsefficiently.