sacchariolens (Fox 1986). Matsumoto and Tajimi (1988, 1990) reported life-history
strategy determined by sclerotium production and continuous variation associated
with habitat differences within isolates of T. incarnata and T. ishikariensis. Naiki
and Ui (1977) studied the population of sclerotia of R. solani in soil, which causes
“crown rot” disease of sugar beet, and reported that most of the sclerotia distributed
in rhizosphere and surface soil, and the highest number of sclerotia per soil was
observed in the closest to the roots of infected plants. As mentioned above, survival
of sclerotia in soil has been mostly reported for plant pathogenic fungi to understand
the survival structure against various conditions in soil. Naiki and Ui (1969)
examined the life of sclerotia in soil using 2 types of isolates of R. solani. In terms
of the observations of the germinate ratio and inner cell structure, it was concluded
that sclerotia of R. solani could survive at least 1 year in soil. Experiment on the
changes in the number of the propagules of Macrophomina phaseoli (Maubl.) Ashby
by soil plate method demonstrated the half-life of the sclerotia in soil as
0.65–3.59 years, 1.88 years in average (Watanabe 1973). The decay of sclerotia of
Sclerotium cepivorum under field conditions in New Zealand soils was observed at a
significant proportion after just 2 months in soil, supposedly caused by adverse
environment conditions and subsequent attack by microbes, after which numbers
declined in soil slowly over a period of 2 years (Harper et al. 2002).
Sclerotia of Sclerotium rolfsii are known to have involuted structure such as rind,
cortex, medulla, and an intermediate layer (Chet et al. 1969). On the contrary, simple
sclerotia formed by Rhizoctonia solani have uniformed structure constructed with
almost ordinary cells of mycelium. Sclerotia are also known to contain “reserve
substances” for germination, such as lipids in Cenococcum geophilum (Massicotte
et al. 1992), Pisolithus tinctorius (Grenville et al. 1985a), Paxillus involutus
(Grenville et al. 1985b; Moore et al. 1991), protein in P. involutus (Grenville et al.
1985b; Moore et al. 1991), and carbohydrates in both P. tinctorius (Grenville et al.
1985a) and P. involutus (Grenville et al. 1985b; Fox 1986; Moore et al. 1991). Fox
(1986) studied the sclerotium-like bodies of Hebeloma sacchariolens and suggested
that they played a major role in short-term nutrient storage. Moore et al. (1991)
reported the chemical composition of reserve substance and cytoplasm of the cells of
P. involutus. Protein bodies (electron opaque granules) were characterized by phosphorus (P) and accompanying cations (Mg, S, Ca, Ni), and cytoplasm was characterized by lower levels of P, Ca, and Mg. The products of sclerotia of Paxillus
involutus was also analyzed in culture and the presence of phosphates associated
with protein, lipid, and glycogen granules was detected inside the sclerotia (Moore
et al. 1991).
Chet et al. (1967) examined the possible biochemical role of the components in
Sclerotium rolfsii Sacc. Fox (1986), Moore et al. (1991), and Massicotte et al. (1992)
studied the morphology and ultrastructure of sclerotia in a culture of ectomycorrhizal
fungi and some ectomycorrhizal fungi (e.g., Paxillus involutus, Cenococcum
geophilum) are known to form sclerotia (Trappe 1964, 1969; Grenville et al.
1985b; Fox 1986; Moore et al. 1991; Massicotte et al. 1992).
The development of sclerotia, which has been caught eyes of researchers since the
late 19c, was confirmed to have three main types, Loose type, Terminal Type, and
1 Introduction
3
strategy determined by sclerotium production and continuous variation associated
with habitat differences within isolates of T. incarnata and T. ishikariensis. Naiki
and Ui (1977) studied the population of sclerotia of R. solani in soil, which causes
“crown rot” disease of sugar beet, and reported that most of the sclerotia distributed
in rhizosphere and surface soil, and the highest number of sclerotia per soil was
observed in the closest to the roots of infected plants. As mentioned above, survival
of sclerotia in soil has been mostly reported for plant pathogenic fungi to understand
the survival structure against various conditions in soil. Naiki and Ui (1969)
examined the life of sclerotia in soil using 2 types of isolates of R. solani. In terms
of the observations of the germinate ratio and inner cell structure, it was concluded
that sclerotia of R. solani could survive at least 1 year in soil. Experiment on the
changes in the number of the propagules of Macrophomina phaseoli (Maubl.) Ashby
by soil plate method demonstrated the half-life of the sclerotia in soil as
0.65–3.59 years, 1.88 years in average (Watanabe 1973). The decay of sclerotia of
Sclerotium cepivorum under field conditions in New Zealand soils was observed at a
significant proportion after just 2 months in soil, supposedly caused by adverse
environment conditions and subsequent attack by microbes, after which numbers
declined in soil slowly over a period of 2 years (Harper et al. 2002).
Sclerotia of Sclerotium rolfsii are known to have involuted structure such as rind,
cortex, medulla, and an intermediate layer (Chet et al. 1969). On the contrary, simple
sclerotia formed by Rhizoctonia solani have uniformed structure constructed with
almost ordinary cells of mycelium. Sclerotia are also known to contain “reserve
substances” for germination, such as lipids in Cenococcum geophilum (Massicotte
et al. 1992), Pisolithus tinctorius (Grenville et al. 1985a), Paxillus involutus
(Grenville et al. 1985b; Moore et al. 1991), protein in P. involutus (Grenville et al.
1985b; Moore et al. 1991), and carbohydrates in both P. tinctorius (Grenville et al.
1985a) and P. involutus (Grenville et al. 1985b; Fox 1986; Moore et al. 1991). Fox
(1986) studied the sclerotium-like bodies of Hebeloma sacchariolens and suggested
that they played a major role in short-term nutrient storage. Moore et al. (1991)
reported the chemical composition of reserve substance and cytoplasm of the cells of
P. involutus. Protein bodies (electron opaque granules) were characterized by phosphorus (P) and accompanying cations (Mg, S, Ca, Ni), and cytoplasm was characterized by lower levels of P, Ca, and Mg. The products of sclerotia of Paxillus
involutus was also analyzed in culture and the presence of phosphates associated
with protein, lipid, and glycogen granules was detected inside the sclerotia (Moore
et al. 1991).
Chet et al. (1967) examined the possible biochemical role of the components in
Sclerotium rolfsii Sacc. Fox (1986), Moore et al. (1991), and Massicotte et al. (1992)
studied the morphology and ultrastructure of sclerotia in a culture of ectomycorrhizal
fungi and some ectomycorrhizal fungi (e.g., Paxillus involutus, Cenococcum
geophilum) are known to form sclerotia (Trappe 1964, 1969; Grenville et al.
1985b; Fox 1986; Moore et al. 1991; Massicotte et al. 1992).
The development of sclerotia, which has been caught eyes of researchers since the
late 19c, was confirmed to have three main types, Loose type, Terminal Type, and
1 Introduction
3