marker-assisted selection in wheat

394Marker-assisted selection – Current status and future perspectives in crops, livestock, forestry and fish500 000Figure 2Stylized economic model of a plant breeding programmeVarietal adoption stage400 000Net annual benefits (US$)300 000200 000100 000ResearchinvestmentstageVarietalreleasestage0-100 0001 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20Time (years)by developing a simple model of a plantbreeding programme and using it to comparethe returns with alternative inbredline conversion schemes based on conventionalselection and MAS. Two measures ofproject worth were used: the net presentvalue (NPV) of the discounted streams ofcosts and benefits, and the internal rate ofreturn (IRR) to the investment.Figure 2 depicts the stylized “variety lifecycle” assumed by the model. The stream ofcosts and benefits associated with the development,release and adoption by farmers ofan improved variety can be divided intothree stages: a research stage during whichthe variety is developed; a release stageduring which the variety is evaluated andregistered for release, and commercial seedis produced; and an adoption stage duringwhich the variety is taken up and grownby farmers. During the first two stages,net benefits are negative, because costsare incurred without any benefits beingrealized. During the third stage, net benefitsturn positive as the variety is takenup and grown by farmers; they continueto increase until the peak adoption level isachieved and then decline when the varietyis replaced by newer varieties.The model was used to estimate theNPV and IRR of conventional and markerassistedinbred line conversion schemes.Research cost data were taken from theCIMMYT case study. Plausible values wereused for key parameters relating to the varietalrelease and adoption stages (for details,see Morris et al., 2003). Figure 3 shows thestreams of annual net benefits generated byeach of the two breeding schemes. Annualnet benefits are calculated as follows:NB t = (GB t - VR t - RC t )where:NB = net benefitsGB = gross benefits (calculated as areaplanted to the variety x incrementalbenefits associated with adoption)