marker-assisted selection in wheat - ictsd

Chapter 8 – Marker-assisted selection in maize 137the success of MAS depends on access tohigh-quality phenotypic data, means willhave to be found to decrease the cost ofphenotypic information while maintainingor increasing its quality. Alternatively,a greater proportion of budgets needsto be devoted to collecting phenotypicinformation.Achievements of maize breedingprogrammes with MASIn some important ways, maize breeding hasgradually changed since the mid 1990s withthe advent of genomics. Genetic principleswere always an important component ofmodern maize breeding and now geneticinformation of various types is seeping intobreeding schemes. MAS is the connectionbetween the growing pool of geneticinformation and actual plant breeding.Establishing and enhancing this connectionhave been important achievements.For the simplest breeding scenario,programmes in the private sector havedemonstrated that MABC is an effective androutine method to backcross one or moretransgenes into established elite inbred lines,the direct parents of commercial hybrids.Hybrids with effective combinationsof transgenes have been very successfulin the market. Consequently, MAS hasaccelerated the delivery of some productsto the market; an important achievement incompetitive economies.Programmes in the private sector have alsodemonstrated a sufficient degree of efficacyof MAS methods to secure protection ofintellectual property in patents. Methods,ideas and linkage relationships have beenincluded in claims of patents or patentapplications related to MAS (e.g. US5 492547 1996; US6 455 758B1 2002; US2005/0144664A1 2005; WO2005/000006A22005; WO2005/014858A2 2005), or theestablishment of marker-trait associations(e.g. US5 746 023P 1998; US6 368 806B12002; US6 399 855B1 2002). Given themagnitude of the investments made in maizebreeding by the private sector, receivingsuch a legal position may be a valuableachievement for the owner of the patent.The efficacy of MAS for forwardbreeding of complex traits has yet to befirmly established. Positive results fromcalibration studies have been reported,but although accounts of MAS-derivedcommercial varieties have been made(Eathington, 2005), the impact on actualbreeding and the development of newcommercial hybrids has not been disclosedto a significant extent (Johnson, 2004;Niebur et al., 2004; Crosbie et al., 2006). Atthis point in time, it is therefore too early tomake a definitive and databased assessmentof this aspect of MAS.The history and cost of the geneticgain achieved through MAS will certainlyvary among target environments. In someregions of the world, such as the centralUnited States, maize breeding achievedsteady genetic gains in grain yield forseveral consecutive decades prior tothe advent of MAS (Duvick, Smith andCooper, 2004). Nevertheless, the cost perunit gain has increased as more resourcesare needed for phenotypic evaluation inmore environments (Smith et al., 1999).However, the advent of applied genomicsand the discovery of many genes and genefunctions, coupled with MAS, could reducethe dependence on costly phenotypicinformation for breeding. In regions wherebiotic and abiotic stress factors are moreimportant than in the central Unites States,MAS may be very effective. Ultimately, thevalue and achievements of MAS will dependon the ecological and socio-economiccontext of the target environment.