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resistance and the enhanced rate of biodegradation in soil. Fungicide resistance is a
genetic adjustment by a microorganism that reduces the sensitivity to a fungicide. It
has become more apparent with the introduction of systemic and more selective
fungicides such as benomyl (Eckert 1988 ).
Biodegradation of fungicides and pesticides in soil is considered a driving factor
in the failure of many of these chemicals to control pests and diseases. It is charac-
terized by the utilization of these chemicals as the sole or supplemental source of
carbon, nitrogen, and other nutrients, or by the creation of specific environments
conducive to chemical degradation by soil microflora (Kaufman and Edwards
1983 ). Biodegradation has also been demonstrated for some pesticides including
chlorpropham, dalapon, endothall, metalaxyl and phenoxyalkanoates (Kaufman
and Edwards 1983 ; Al-Sa’di et al. 2008a).
6 Conclusion and Future Research
Crops in dry areas of the world face several biotic and abiotic challenges. Apart
from water scarcity and warmer climatic conditions, fungal diseases represent a
major threat to several crops (Pilet et al. 2005 ; de Miranda et al. 2010 ; Al-Sadi et al.
2011b, Al-Mawali et al. 2013 ; Al-Sadi et al. 2015a). The challenges faced by crops
are not only restricted to current diseases as many fungal pathogens have the poten-
tial to evolve and produce races or isolates with higher levels of aggressiveness or
tolerance to extreme environmental conditions (Chen et al. 2009 ; Al-Sadi et al.
2012 ; Al-Sadi 2013 ; Al-Sadi et al. 2013 , 2015b). This can result in the breakdown
of cultivar resistance, the development of fungicide resistance in new fungal genera-
tions, or the appearance of new host species for fungal pathogens. Ultimately, the
management of plant diseases becomes more challenging. Avoiding monoculture,
developing new cultivars with multigene resistance to major plant diseases, and
developing integrated disease management strategies are important for reducing the
potential for severe disease epidemics (Gilardi et al. 2013 ; Guo et al. 2015 ; Neher
et al. 2015 ; Zhu et al. 2015 ; Ahmad et al. 2016 ; Kazeeroni and Al-Sadi 2016 ).
Future research on plant diseases under dry environmental conditions should be
directed towards characterizing new disease epidemics and their population dynam-
ics, understanding the interactions between hosts, pathogens and environment, and
developing durable management strategies for the major diseases.
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