**7. Why MAS in plant breeding**

Justifications for the application of MAS in plant breeding fall into four broad areas that are relevant to almost all target crops [53, 54, 55] (i) traits that are difficult to manage through conventional phenotypic selection because they are expensive or time-consuming to meas‐ ure, or have low penetrance or complex inheritance; (ii) traits whose selection depends on specific environments or developmental stages that influence the expression of the target phenotypes; (iii) maintenance of recessive alleles during backcrossing or for speeding up backcross breeding in general; and (iv) pyramiding multiple monogenic traits (such as pest and disease resistances or qualitative traits) or several QTL for a single target trait with com‐ plex inheritance (such as drought tolerance or other adaptive traits). Introgression and pyra‐ miding of multiple genes affecting the same trait is a great challenge to breeding programs. The target cropping environments of many breeding programs require a combination of di‐ verse biotic stress resistances, agronomic and quality trait profiles, plus abiotic stress toler‐ ances to improve performance, yield stability, and farmers' acceptance. The greatest impact from MAS will only be realized when breeding systems are adapted to make best use of large-scale genotyping for both multiple target traits and the genetic background. The great‐ est benefits from this type of integrated molecular breeding approach will be to achieve the same breeding progress in a much shorter time than through conventional breeding, and from pyramiding combinations of genes that could not be readily combined through other means.
