Study of Early Selection in Tree Breeding 4. Efficiency of Marker-Aided Early Selection (MAES)

One of the main attractions of Marker-Aided Selection (MAS) in tree breeding is its potential for early selection through juvenile traits as Marker-Aided Early Selection (MAES). The theoretical advantages of incorporating molecular markers into early selection in tree breeding are examined. Equations were derived to answer the following questions: (1) how effective is the use of markers for early selection relative to conventional late (mature) selection? (2) what is the efficiency of using markers for early selection relative to early selection based on morphological traits? (3) how effective is incorporating markers into an early selection index relative to an early selection index based on morphological traits alone? (4) what are the efficiencies when MAS is used only for withinfamily selection in the combined family and within family selection approach, relative to selection using combined family and within family phenotypic information alone? and (5) how effective is selection when MAES is used for within-family selection only in the combined family and within family early selection approach, relative to early selection using combined family and within family phenotypic information alone? These equations could be used to compare relative efficiencies of MAES and QAES (QTL-Aided Early Selection) relative to traditional phenotypic selection in breeding programs. For Marker-Aided Early Selection or QTL-Aided Early Selection to be applicable in tree breeding populations, it may be necessary to demonstrate that efficiency from MAES or QAES is higher than efficiency of early selection using less expensive early phenotypic traits. Furthermore, the relative efficiency of MAES or QAES is higher when genetic correlation of early-mature trait and/or heritability of the early trait is lower and is less for full-sib family than for half-sib family selection.