Agriculture Reference
In-Depth Information
Climate change is likely to alter the distribution and severity of soil
borne diseases affecting both intensive and low-input agricultural produc-
tion systems. Naturally occur ring disease suppressive soils have been
documented in a variety of cropping systems, and in many instances, the
biological attributes contributing to suppressiveness have been identi-
fied. While these studies have often yielded an understanding of opera-
tive mechanisms leading to the suppressive state, significant difficulty
has been realized in the transfer of this knowledge into the development
of effective field-level disease control practices. Early efforts focused on
the inundative application of individual or mixtures of microbial strains
recovered from these systems, and known to function in specific soil sup-
pressiveness. However, the introduction of biological agents into nonna-
tive soil ecosystems typically fails to yield commercially viable or consis-
tent levels of disease control. Of late, greater emphasis has been placed on
manipulation of the cropping system to manage resident beneficial rhizo-
sphere microorganisms as a means to suppress soil borne plant pathogens.
One such strategy is the cropping of specific plant species or genotypes, or
the application of soil amendments with the goal of selectively enhancing
disease suppressive microbial communities.
Three essential components are required simultaneously for a disease
to occur: a virulent pathogen, a susceptible host and a favorable environ-
ment for multiplication often referred to as the 'disease triangle.' Cli-
mate change, as well as sometimes fulfilling the last link of that triangle,
can also drive evolutionary change in pathogen populations by forcing
changes in reproductive behavior (Gregory et al., 2009). One of the most
challenging aspects of adapting crops to climate change will be to main-
tain their genetic resistance to pests and diseases, including herbivorous
insects, arthropods, nematodes, fungi, bacteria and viruses. Breeding for
host resistance will continue to have a pivotal role in offsetting the adverse
impact of climate. Rising temperatures and variations in humidity affect
the diversity and responsiveness of agricultural pests and diseases and are
likely to lead to new and perhaps unpredictable epidemiologies (Gregory
et al., 2009). Factors driving new outbreaks include extraordinary climat-
ic events and trends in temperature selecting pathogens and their natural
enemies towards new critical thresholds for inoculums survival. Disease
cycle components such as survival, infection, colonization processes and
latency period, in addition to production and dispersal of inoculum, are all
affected.
