273A plant breeding program is a cyclical process aimed at the development of new
cultivars, whereby each cycle consists of three major phases (Fig. 1 ; Gepts 2002 ;
Ceccarelli 2009 ): (i) generating genetic variability: this includes making crosses,
inducing mutation, introducing exotic germplasm, and using genetic engineering
techniques; (ii) selection and testing to identify superior recombinants: in self-
pollinated, cross-pollinated, and vegetatively propagated crops, which is done with
different methods such as marker-assisted selection, introgression of quantitative
trait loci (QTL), or use of high-throughput phenotyping platforms, and which termi-
nates with the identification of potential cultivars; (iii) release, distribution, and
adoption of new cultivars: the yield testing in MET is either the last step of the
second phase or the first step of the third. Two additional steps are often included as
essential components of a breeding program, namely, setting the objectives and
evaluating the program in terms of reaching those objectives. These two steps come
before and after, respectively, the three phases mentioned earlier (Ceccarelli 2015 ).
8.1 Germplasm Development
Crop genetic diversity, created through natural and human selection over millennia
and complemented by the diversity present in wild relatives of crop plants, provides
the raw material that can be employed by scientists to improve crop productivity
Fig. 1 Comparison of various plant breeding methods
Breeding and Genetic Enhancement of Dryland Crops