Agriculture Reference
In-Depth Information
identity in the fi nal bred variety via seed propagation. Likewise, allog-
amous species with a long juvenile phase (such as many fruit and nut
trees) or diffi cult seed production (e.g., banana, sugarcane, garlic) are con-
ventionally crossed to produce a segregating generation, and selection is
carried out already in the F
1
generation, while the genetic identity of the
(hybrid) cultivar is guaranteed thereafter via clonal (vegetative) propaga-
tion. In contrast, for annual allogamous crops, production in a low-input
system must rely on the performance of the whole population instead of
focusing on yields of single individuals, since the key for performance
maintenance over generations depends on a diversifi ed genetic pool within
the population. Selection under low input in allogamous species will thus
increase the frequency of alleles in the population that are responsible for
acceptable yields at marginal conditions, rather than producing single,
genetically homogenous hybrid lines that may lack adaptive alleles due
to selection at high-input conditions. This strategy has been successfully
demonstrated for maize [153]. Evidence of feasibility of breeding for low
input systems by using landraces as starting material has been recently
shown for barley [154]. Outperformance of selection under low-input over
high-input systems has been demonstrated by Ceccarelli et al. [155], in
which barley cultivars selected under low-input yielded up to 54% more
under stress conditions than the cultivars selected under high-input, in the
same conditions.
Low heritability of agronomic traits (thus, little potential for crop im-
provement) in local populations has been reported for oat [156] and faba
bean [157]. In these cases, the genetic basis of the population under study
might be too narrow and alleles of interest may have been lost or not lo-
cally introduced. These cases are more common in regions far from the
centers of speciation or distribution of the crop and it can often be resolved
with introduction of new germplasm in the population. This underscores
how important breeding techniques developed over the last century should
be applied to advance local breeding initiatives, in order to create pro-
grams to attend the specifi c demands and needs of farmers in a bottom-up
approach, but without forfeiting the scientifi c approach. Diverse breed-
ing techniques have been developed to take advantage of natural genetic
variation available and to actively involve the participation of farmers in
the process.
