Agriculture Reference
In-Depth Information
Fig. 5.17.
Results from a device for the rapid detection and immunoquantification
of airborne pathogen spores. The relationship between colour intensity as measured
by light absorbance at 450 nm in microtitre wells of a spore-trapping device and
the number of conidia of
Botrytis cinerea
trapped in the wells. The colour was
developed using an enzyme-linked immunosorbent assay (ELISA) created using
Botrytis
-specific monoclonal antibodies (from Kennedy
et al
., 2000. Courtesy of
Applied and Environmental Microbiology
).
There are several important soil-borne fungal diseases of allium crops that
invade roots or stem bases. As with other types of pathogen, there is a range
from those specific to allium
s
to those that attack many crop species. Entwistle
(1990) has written a review and bibliography on these diseases, and they are
described and illustrated in Schwartz and Mohan (2008). The diseases and
their causal pathogens are listed in Table 5.6.
The root diseases of alliums all have a number of features in common. All
these organisms can infect roots and most can penetrate below-ground shoot
tissue and infect the stem base. Pink root is exceptional in that it is confined to roots
and the dry outer sheaths of the shoot base. The symptoms of disease, as might be
expected from the destruction of roots, are those associated with water or nutrient
stress. Leaves lose turgor, wilt, become yellow and ultimately die, and plants
become stunted and may collapse. The symptoms are aggravated by drought.
Early attack can result in the failure of emergence or the collapse of seedlings.
The diseases tend to group very roughly into those of cool temperate
climates and those of warmer regions, depending on their temperature
requirements (see Table 5.6). However, in mid-latitude Mediterranean
