axenic culture with Scots pine (Pinus sylvestrisL.)
seedlings (Berch and Castellano 1986 ).
Four genera are currently known:Endo-
gone,Peridiospora,Sclerogone, andYoungio-
myces(Gerdemann and Trappe 1974 ; Wu and
Lin 1997 ; Yao et al. 1996 ). Species ofEndogone,
Sclerogone, andYoungiomyceswere described
and illustrated by Yao et al. ( 1996 ).
A fifth genus, Densospora P.A. McGee
(McGee 1996 ), with Glomus-like spores, is
included in Endogonales because it produces
ectomycorrhizae.Densospora, however, does
not produce zygospores or arbuscules and can-
not be comfortably included in either Endogo-
nales or Glomeromycota.
Dibartono et al. ( 2011 ) presented evidence
that fungi similar toEndogonemay have been
mycorrhizal associates of early land plants. Sev-
eral extant species ofEndogoneare mycorrhizal
with the earliest branch of the liverworts. These
mycorrhizal species ofEndogoneresemble the
fungi found in the Rhynie Chert fossil plant
Nothia aphyllaLyon ex El-Saadawy & Lacy
(Krings et al. 2007 ). Members of Glomeromy-
cota (Schu ̈ssler et al. 2001 ) were the endomy-
corrhizal associates of the land plants that
evolved later, including the thalloid liverworts.
Members of Glomeromycota are present in the
roots of plants in early Devonian Rhynie Chert
(Krings et al. 2007 ; Taylor et al. 2003 , 2014 )
[cf. zygomyceteous fossils reviewed by Krings
et al. ( 2013 )].
b) Mucorales
The members of Mucorales [Fig.8.4(30–41)] are
saprobes or facultative (nonhaustorial) para-
sites in nature that can usually be grown axeni-
cally in the laboratory. The thallus generally
consists of coenocytic hyphae, and spores are
formed in sporangia [Fig.8.4(30, 31, 33, 34, 41)],
sporangiola [Fig.8.4(32, 37)], or merosporangia
[Fig.8.4(40)]. The typical zygospore (O’Donnell
1979 ) has a rough, carbonaceous zygosporan-
gium and differentiated, nonappendaged,
opposed suspensors [Fig.8.4(35)]. The sexual
spore contains a single endospore with a hya-
line wall and an eccentric globule [Fig.8.4(36)].
Appendaged suspensors are produced by some
taxa (Absidia, Phycomyces, Radiomyces).
Pilaira,Pilobolus,Blakeslea,Choanephora, and
Poitrasiaproduce zygospores with apposed sus-
pensors. Phycomyces has large rough-walled
zygospores with tongslike appendaged suspen-
sors (O’Donnell et al. 1978 ). The members of
Mucorales can form chlamydospores but rarely
produce yeast cells [Fig.8.4(38, 39)].
Thirteen Mucorales families have been
recognized (Benny et al. 2001 ) based on mor-
phological characters (Alexopoulos et al. 1995 ;
Hawksworth et al. 1995 ). The phylogenetic
analysis of O’Donnell et al. ( 2001 ) and Voigt
and Wo ̈stemeyer ( 2001 ), however, demon-
strated that most of the morphologically based
Mucorales families that contain two or more
genera are not concordant with clades based
on molecular data. A critical examination of
the morphological characters did reveal which
were phylogenetically informative (O’Donnell
et al. 2001 ), such as trophocyst formation by
Pilobolus andUtharomyces(Kirk and Benny
1980 ; Page 1962 ).
Fourteen families currently are recognized
(Voigt 2012 ) in Mucorales based on the results
of a sequence-based data set; they are discussed
by Voigt ( 2012 ) and Hoffmann et al. ( 2013 ). The
new families and subfamilies (Table8.1) men-
tioned by Voigt ( 2012 ) have been validated
(Kirk 2012 ; Kirk and Voigt 2012 ).
Important new taxa, all supported by phylo-
genetic analyses, include the revisedAbsidias.l.
(Absidias.s.,Lentamyces,Lichtheimia,Siepman-
nia), new species inApophysomycesandSakse-
naea, and some mesophilic species of
Rhizomucor that have been transferred to
Mucor; species in the latter three genera can
cause mucormycosis (Alvarez et al.2010a,b,
2011 ;Hoffmann 2010 ;Liu 2011 ;Luetal. 2013 ).
AnewMucor-like genus,Isomucor,hasbeen
described, andCalcarisporiella, formerly an ana-
morphic ascomycete, is now recognized as a
member of Mucoromycotina, possibly Mucor-
ales (Hirose et al. 2012 ; de Souza et al. 2012 ).
Cunninghamella, Pilaira, and Rhizopus
were monographed or revised (Zheng and
Chen 2001 ; Zheng and Liu 2009 ; Zheng et al.
2007 ). These classifications are supported by
phylogenetic studies (Liu et al. 2001 , 2007 ,
2012 ).
The genera Dicranophora,Spinellus, and
Syzygites(Mucorales) are found in nature only234 G.L. Benny et al.