marker-assisted selection in wheat - ictsd

204Marker-assisted selection – Current status and future perspectives in crops, livestock, forestry and fishfirst returns are realized, t. R v is computed asfollows (Hill, 1971):Rvtrd- r= V(1 - rT + 1d2d)( T - t + 1) r-1-r{1}where r d = 1/(1+d). For example, with d =0.08, T = 20 years, and t = 5 years, R v =32.58V. That is, the cumulative returns areequal to nearly 33 times the nominal annualreturns. For an infinite profit horizon,Equation {1} reduces to:RVrtv= =2 2 t–2(1 – rd) d (1 + d)and R v = 124.04V.The value of nominal annual geneticgain will now be compared with the annualcosts of a breeding programme, assuming afixed nominal cost per year. Costs, unlikegenetic gain, only have an effect in the yearthey occur. Assuming that annual costs areequal during the length of the breedingprogramme, and that first costs occur in theyear after the base year, C T , the net presentvalue of the total costs of the breeding programmeis computed as follows:CTCcrd(1 − r=1−rdTd)where C c = annual costs of the breedingprogramme. Using the same values for Tand d, C T = 9.82C c . Thus, with a profithorizon of 20 years, cumulative profit ispositive if V > 0.31C c . For an infinite profithorizon, C T = 12.5C c , and profit will bepositive if V > 0.1C c .Therefore, a breeding programme can beprofitable even if the nominal annual costsare several times the value of the nominalannual genetic gain. For example, considerVdT + 1d{2}{3}the United States of America dairy cattlepopulation, which consists of about tenmillion cows. Annual genetic gain is about100 kg milk per year. The value of a 1 kggain in milk production has been estimatedat US$0.1 (Weller, 1994). Thus, the nominalannual value of a 10 percent increase in therate of genetic gain (10 kg per year) is:V = (10 kg per cow per year)(US$0.1 per kg)(10 000 000 cows) =US$10 000 000 per year{4}The cumulative value with a profithorizon of 20 years and an 8 percent discountrate would be US$326 million, andbreak-even annual costs for a technologythat increases annual genetic gain by 10 percentare US$32 million per year. Thus, itwould be profitable to spend quite a lot fora relatively small genetic gain.The value of genetic gain to a specificbreeding enterprise will generally be lessthan the gain to the general economy. Thisis because most of the gains obtained bybreeding will be passed on to the consumers.Brascamp, van Arendonk and Groen (1993)considered the economic value of MASbased on changes in returns from semensales for a breeding organization operatingin a competitive market. In this case,a breeding firm that adopts a MAS programmecan increase its returns either byincreasing its market share or increasing themean price of a semen dose. Although thevalue of genetic gain will be less, relativelysmall changes in genetic merit can result inlarge changes in market share.current status of marker mapsin cattleCattle have 29 pairs of autosomes and onepair of sex chromosomes. All the autosomesare acrocentric, and map units are