275et al. 2014 , 2015 ). A list of crop varieties released by Dryland Agricultural Research
Institute, Iran for adaptation to drylands is given in Table 2.
Abiotic stresses aggravated by climate change pose a serious threat to the sus-
tainability of crop yields and account for substantial yield losses. Scientific knowl-
edge of the processes of abiotic stress tolerance in crops continues to develop and
guides conventional breeding and genetic engineering of new crop cultivars. The
modern tools of cell and molecular biology have shed light on control mechanisms
for abiotic stress tolerance, and for engineering stress-tolerant crops based on the
expression of specific stress-related genes (Pande et al. 2015 ).
Allard and Bradshaw ( 1964 ) inditaed that variety types where the genetic struc-
ture implies high levels of heterozigosity and/or heterogeneity are less sensitive to
environmental variation and are, therefore, more stable-yielding. Such types may
sometimes offer fewer opportunities for maximizing the yield potential. Within a
given variety type, breeding successfully for this trait relies on the adoption of a
heritable or repeatable stability measure as a selection criterion. Given the high
sampling error, the assessment of yield stability requires numerous test environ-
ments (at least eight) to guarantee reliability (Kang 1998 ). Therefore, direct selection
for yield stability may be limited by high costs and can be recommended, even
when it has high priority, only for elite material in the final testing stages. The
choice of parental germplasm with recognized yield stability and of, if possible, a
convenient variety type, can play a major role in breeding for more stable crop
yields. In addition, indirect selection for higher yield stability may be attempted by
selecting for agro-physiological traits that have proved to be strictly associated with
stability (Annicchiarico et al. 2005 ).
8.3 Participatory Varietal Selection
The centralized plant breeding techniques of the green revolution have yielded good
results in more favorable agricultural environments. However, most low-resource
farmers in marginal areas have not benefited from these varieties. As an alternative
to centralized breeding, farmer participatory approaches using participatory varietal
selection (PVS) and participatory plant breeding (PPB) can be used. PPB is an
extension of PVS. In PPB, farmers are actively involved in the breeding process,
from setting goals to selecting variable, early generation material. In PVS, farmers
are given a wide range of new cultivars to test for themselves in their own fields. In
PPB programs, the results of PVS were exploited by using identified cultivars as
parents of crosses. Participatory research, which allows farmers, research scientists
and extension agents to conduct research together, is essential particularly for iden-
tifying the traits preferred by farmers. Farmers’ fields provide a multitude of diverse
environments which allow exploiting GE interaction effect between the farmers’
fields and research stations given that in most cases, and particularly under semi-
arid conditions, they are different (Ceccarelli and Grando 2007 ). In addition, farm-
ers may use different selection criteria from those used by the breeders. Conventional
Breeding and Genetic Enhancement of Dryland Crops