2º Congreso Argentino De Fitopatología Libro de Resúmenes

2 º Congreso Argentino de Fitopatología
important diseases of wheat and colza (canola). We found that the
severity of blackleg, caused by Leptosphaeria maculans would
increase substantially due to increased thermal time after infection
(Butterworth et al. 2010). This may also be exacerbated by dysfunction
of host resistance, conferred by some resistance genes at elevated
temperatures (Huang et al. 2006). We also found that earlier flowering
of winter wheat would mean that suitable sporulation and infection
conditions for Fusarium graminearum would increase slightly and
additionally, increased cultivation of grain maize would substantially
increase inoculum production, leading to greater disease incidence
(Madgwick et al. 2011).
The findings for these two disease systems were extrapolated to
interpret likely changes in other systems. We predict that rusts and
powdery mildews will become more severe after mild weather in winter
and early spring (assuming some dry days will allow dispersal) but
less severe after particularly hot, dry weather in summer. Epidemics
of these obligate pathogens will therefore depend on combinations of
favourable and unfavourable summer and winter weather over more
than one season so that epidemics of these diseases will become
more sporadic. In contrast, summer droughts may favour certain
pathogens that produce lesions and fruiting bodies on dead plant
tissue because reduced destruction of crop residues (by molluscs
and other invertebrates) will lead to increased inoculum production
in the autumn. Generally there is a knowledge gap for understanding
pathogen survival and the timing of spore release to infect subsequent
crops, as different responses to the climate by the pathogen and crop
could lead to more or less infection (less or more disease-escape).
Where crops remain in their original regions or particularly at the
southern parts of their distribution, generally warmer conditions will
increase severity of autumn and winter-infecting root and stem rots,
while spring-infecting root and stem rots will advance with earlier crop
growth and so not change in relative severity. However, yield losses
from these diseases will also increase due to greater and earlier
transpiration stress caused by heat or drought. Effects of increased
CO 2 concentrations on plant pathogens also requires further research
as effects on systems already studied vary greatly from one pathogen
to another. Increased CO 2 will lead to denser crop canopies, which
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