Agriculture Reference
In-Depth Information
Chapter 6
Diseases Which Challenge Global Wheat
Production—Root, Crown, and Culm Rots
Richard W. Smiley, David Backhouse, Philippe Lucas,
and Timothy C. Paulitz
SUMMARY
date, using a seed drill that causes intense
soil disturbance in the seed row, and
protecting seedlings by applying a fungicide
to the seed. Only eyespot can be controlled
by applying fungicide to the foliage. Crop
management systems to control take-all and
eyespot are optimized using models.
(1) With few exceptions, root, crown, and
culm rots are especially prevalent in crop-
ping systems characterized by high residue
retention, reduced tillage, or high fre-
quency of host crops. Most of these dis-
eases are not yet effectively managed by
genetic resistance, fungicides, or biological
agents. Optimal disease management gen-
erally requires changing the soil environ-
ment to reduce survival of the pathogens
between susceptible host crops, or the vir-
ulence of pathogens during the infective
stage.
(2) Rotation to nonhosts is an effective man-
agement strategy for common root rot,
take-all, Cephalosporium stripe, and
eyespot but not crown rot, Pythium root
rot, or Rhizoctonia root rot.
(3) Other management practices that reduce
damage caused by several of these diseases
include preventing growth of volunteer
cereals and weed hosts during the interval
between crops, banding a portion of the fer-
tilizer below the seed, adjusting the planting
(4)
Severity of take-all and Rhizoctonia root
rot may increase at the beginning of a
wheat monoculture and then begin to
decline in severity. These disease-decline
phenomena are mediated through infl u-
ences of the soil microbiota.
(5)
Wheat cultivars with useful levels of resis-
tance are available to suppress damage by
common root rot, crown rot, Cephalospo-
rium stripe, and eyespot. Molecular
markers are used to detect resistance genes
in seedlings, and DNA-based real-time
polymerase chain reaction (PCR) assays
are available to identify and quantify these
pathogens in soil or plants. These assays
plus data interpretation based on disease
epidemiology have been used commer-
cially to predict potential grain yield loss
from several of these diseases.
INTRODUCTION
not yet effectively managed by genetic resistance
or by application of a fungicide or biological
control agent. The best management strategy for
many of these diseases continues to depend upon
Most wheat (
Triticum
spp.) diseases caused by
root-, crown- and lower culm-infecting fungi are
