lysergic acid [C. purpurea (Lorenz et al. 2007)];
trichothecenes, fumonisins, and zearalenone [Fusarium
spp. (Osborne and Stein 2007)]; and ochratoxins and
aflatoxins [(Penicillium spp. and Aspergillus spp. (Berthiller
et al. 2013)]. These mycotoxigenic fungi are present all
around the world and cause great losses to the world’s
agriculture. The disease caused by these molds reduces
seed vigor, crop yield, and grain quality, making them poisonous to animals and humans. Mycotoxins are produced in
the cereals, fruits, as well as in vegetables, in the field, and
during transportation, storage, and processing. The problem
of mycotoxins fluctuates from year to year, due to changes in
the environmental conditions favorable for the production of
mycotoxins and the development of the producing fungi.
The Food and Agriculture Organization (FAO) of the United
Nations and the European Union have set limits for the most
important mycotoxins in different crops, to avoid the
adverse effects toward animals and humans.
Soil-borne fungi and oomycetes that infect the seed or
roots cause important diseases. Damping-off is generally
caused by oomycetes such as Aphanomyces cochlioides on
sugar beet and more particularly Pythium spp. on most crops,
but fungi such as Rhizoctonia solani can also cause damage
in vegetables or forest nurseries. Conversely, necroses and
root and crown rots are mainly due to fungi (Thielaviopsis
basicola, R. solani), although oomycetes such as A.
euteiches are a real obstacle to grow legumes in temperate
countries (Persson et al. 1999). White mold of many vegetable crops is caused by Sclerotinia sclerotiorium and leads to
general wilting symptoms associated with water-soaked
lesions on stems, while sclerotia are formed inside stems.
Other fungi such as Fusarium oxysporum and Verticillium
dahlia also cause partial or general wilting, but they are
tracheomycoses because the fungi are able to penetrate the
roots to rapidly reach and colonize the vascular tissues
(Olivain et al. 2006).
Many foliar bacteria are phytopathogenic, such as
Erwinia amylovora (fire blight pathogen of pear and
apple), Xanthomonas campestris (which causes stalk lesions
and necrosis), or Pseudomonas syringae (causing cankers in
many fruit trees or brown necrotic spots on the glumes of
wheat) (Agrios 1997). Part of P. syringae epiphytes produce
IceC membrane protein, which has an ice nucleation activity
and promotes frost damage on strawberry (Lindow and
Brandl 2003). Some are soil-borne phytopathogenic bacteria
and are responsible for vascular disease (Ralstonia
solanacearum), soft rot (Pectobacterium carotovorum), or
gall (Agrobacterium tumefaciens, Streptomyces scabies).
Certain Agrobacterium tumefaciens carry the Ti plasmid
that confers them the ability to transfer genes to the plant
(Krimi et al. 2002; Tzfira and Citovsky 2006).
Box 11.2: Impact of Parasitic Microorganisms on Crop
Plants
Christian Steinberg
Diseases caused by parasitic microorganisms on crops
can result in food shortages and famines, and historically some of them have had a major impact on human
populations (Rosenzweig et al. 2000). Late blight of
potato, caused by the oomycete Phytophthora
infestans, was a major factor in the great famine in
Ireland (more than one million deaths out of a population of eight million inhabitants) and Irish emigration
to the USA (two million emigrants) in the years
1845–1849. In more recent times (1943), the fungus
Helminthosporium oryzae (Deuteromycete) resulted in
the death of more than two million people in India and
Bangladesh due to malnutrition caused by the destruction of rice crops.
The importance of crop losses due to diseases varies
according to the type of pathogen, pathogen inoculum
size, the development stage, and the genotype of the
plant, as well as soil properties, climatic factors, and
agronomic conditions (Agrios 1997). For the present
time, the estimation of Oerke et al. (1995) based on
eight major crops is 42 % of the yield (before harvest)
is lost due to biotic factors across the globe (31 % for
North America). Plant-parasitic microorganisms are
responsible for a third of these losses, the rest being
caused by insects and weeds. Loss due to diseases
(continued)
Box 11.2 (continued)
ranges from 28 % (for corn, soybean, and tobacco)
to 40 % (potato) of all losses of biotic origin. Each
year, yield loss due to diseases (before harvest) exceeds
$15 billion for potato, $20 billion for wheat, and
$50 billion for rice for the whole world (2008 estimate).
Currently, the extent of these damages increases
mainly due to the development of trade in seeds and
agricultural products and changes in farming methods,
such as agriculture intensification and a switch from
crop rotation to crop monoculture (Rosenzweig et al.
2000). The ongoing climate change will likely have
major repercussions on crops and diseases affecting
them.
412
Y. Moe ¨nne-Loccoz et al.
trichothecenes, fumonisins, and zearalenone [Fusarium
spp. (Osborne and Stein 2007)]; and ochratoxins and
aflatoxins [(Penicillium spp. and Aspergillus spp. (Berthiller
et al. 2013)]. These mycotoxigenic fungi are present all
around the world and cause great losses to the world’s
agriculture. The disease caused by these molds reduces
seed vigor, crop yield, and grain quality, making them poisonous to animals and humans. Mycotoxins are produced in
the cereals, fruits, as well as in vegetables, in the field, and
during transportation, storage, and processing. The problem
of mycotoxins fluctuates from year to year, due to changes in
the environmental conditions favorable for the production of
mycotoxins and the development of the producing fungi.
The Food and Agriculture Organization (FAO) of the United
Nations and the European Union have set limits for the most
important mycotoxins in different crops, to avoid the
adverse effects toward animals and humans.
Soil-borne fungi and oomycetes that infect the seed or
roots cause important diseases. Damping-off is generally
caused by oomycetes such as Aphanomyces cochlioides on
sugar beet and more particularly Pythium spp. on most crops,
but fungi such as Rhizoctonia solani can also cause damage
in vegetables or forest nurseries. Conversely, necroses and
root and crown rots are mainly due to fungi (Thielaviopsis
basicola, R. solani), although oomycetes such as A.
euteiches are a real obstacle to grow legumes in temperate
countries (Persson et al. 1999). White mold of many vegetable crops is caused by Sclerotinia sclerotiorium and leads to
general wilting symptoms associated with water-soaked
lesions on stems, while sclerotia are formed inside stems.
Other fungi such as Fusarium oxysporum and Verticillium
dahlia also cause partial or general wilting, but they are
tracheomycoses because the fungi are able to penetrate the
roots to rapidly reach and colonize the vascular tissues
(Olivain et al. 2006).
Many foliar bacteria are phytopathogenic, such as
Erwinia amylovora (fire blight pathogen of pear and
apple), Xanthomonas campestris (which causes stalk lesions
and necrosis), or Pseudomonas syringae (causing cankers in
many fruit trees or brown necrotic spots on the glumes of
wheat) (Agrios 1997). Part of P. syringae epiphytes produce
IceC membrane protein, which has an ice nucleation activity
and promotes frost damage on strawberry (Lindow and
Brandl 2003). Some are soil-borne phytopathogenic bacteria
and are responsible for vascular disease (Ralstonia
solanacearum), soft rot (Pectobacterium carotovorum), or
gall (Agrobacterium tumefaciens, Streptomyces scabies).
Certain Agrobacterium tumefaciens carry the Ti plasmid
that confers them the ability to transfer genes to the plant
(Krimi et al. 2002; Tzfira and Citovsky 2006).
Box 11.2: Impact of Parasitic Microorganisms on Crop
Plants
Christian Steinberg
Diseases caused by parasitic microorganisms on crops
can result in food shortages and famines, and historically some of them have had a major impact on human
populations (Rosenzweig et al. 2000). Late blight of
potato, caused by the oomycete Phytophthora
infestans, was a major factor in the great famine in
Ireland (more than one million deaths out of a population of eight million inhabitants) and Irish emigration
to the USA (two million emigrants) in the years
1845–1849. In more recent times (1943), the fungus
Helminthosporium oryzae (Deuteromycete) resulted in
the death of more than two million people in India and
Bangladesh due to malnutrition caused by the destruction of rice crops.
The importance of crop losses due to diseases varies
according to the type of pathogen, pathogen inoculum
size, the development stage, and the genotype of the
plant, as well as soil properties, climatic factors, and
agronomic conditions (Agrios 1997). For the present
time, the estimation of Oerke et al. (1995) based on
eight major crops is 42 % of the yield (before harvest)
is lost due to biotic factors across the globe (31 % for
North America). Plant-parasitic microorganisms are
responsible for a third of these losses, the rest being
caused by insects and weeds. Loss due to diseases
(continued)
Box 11.2 (continued)
ranges from 28 % (for corn, soybean, and tobacco)
to 40 % (potato) of all losses of biotic origin. Each
year, yield loss due to diseases (before harvest) exceeds
$15 billion for potato, $20 billion for wheat, and
$50 billion for rice for the whole world (2008 estimate).
Currently, the extent of these damages increases
mainly due to the development of trade in seeds and
agricultural products and changes in farming methods,
such as agriculture intensification and a switch from
crop rotation to crop monoculture (Rosenzweig et al.
2000). The ongoing climate change will likely have
major repercussions on crops and diseases affecting
them.
412
Y. Moe ¨nne-Loccoz et al.