An investigation of the present known
phomopsis species on conifers has been undertaken.
Eight species are differentiated and their synonomy
is given; two species are described provisionally as
new, - Phomopsis L.ontanensis n. sp. and P. Boycei n. sp.
The cultural life-history of Diaporthe
conorum, (Desm.) Miessl (syn.:D. occulta, (Fuck.) Mke.,
D. pitya, Sacc.) ls given. Monoascospore cultures of
D. conorum produced both the perfect and the imperfect
stage, Phomopsis occulta, Trav.. Monopycnidiospores
obtained from a culture derived from a monoascospore
isolation, reproduced the ascomycetous stage, D. conorum.
Diaporthe conorum produced the perfect
stage as readily from monoascospore cultures, as from
cultures derived from monoascus isolations, or the
mixture of two monoascospore strains. The addition
of Taka-diastase to cultures of D. conorum did not
appreciably stimulate perithecial production.
Phomopsis conorum, (Sacc.) Died.is a
species distinct morphologically and physiologically
from Phomopsis occulta (D. conorum). The perfect
stage of P. conorum, which inhabits not only cones
but other plant parts as well, is not known.
Limited tests in which strains of Phomopsis
Pseudotsugae, Wilson from Great Britain and the continent,
were mixed in culture, gave negative results
so far as ascogenous stage formation was concerned.
The perfect stage of this fungus as yet has not been
Phomopsis species isolated from conifers
showed a general agreement amongst their forms with
regard to the constancy and persistency of the culture
growth characteristics. This uniformity applied
equally to forms collected from hosts widely separated both geographically and phylogenetically.
Spore shape proved to be a valuable morphological character for the differentiation of species.
The shape of culturally-produced spores both A and B
showed generally excellent agreement with that of spores
produced in nature.
Variation in spore size occurred both for the
ascospores of Diaporthe conorum and the pycnidiospores
of the various Phomopsis species investigated. This
variation took place within a given specific range
which appeared to be fairly constant. It was found
that the specific range of the fungus species could
be determined by a study of forms of the particular
organism throughout its host range.
Neither the shape nor the size of ascospores'
was influenced by artificial growth of D. conorum on
broad- leaved host substrata. The relationship between
this conifer Diaporthe,and forms on broad -
leaved hosts is indicated.
The conifer Phomopses showed both wide and
extremely limited host relationships. Certain of
the species are now known to be widely distributed geographically occurring on a comparatively large
number of hosts, e.g., P. occulta, occurred on 14
host genera and its habitat included both North
America and Europe. Species such as P. ahietina
appeared to be limited to a single host, and to the
smaller branches of that host. This fungus is known
only to occur on the continent in Germany and France.
In artificial inoculation experiments, negative results were obtained in attempting to infect
Abies pectinata with Phomopsis abietina, (Hart.)
Wilson et Hahn.
Negative results are also reported for
Phomopsis conorum upon Pseudotsuga Douglasii, and for
P. occulta from the same host.
A discussion upon the formation and germination
of the B or filamentous spore is given, together
with a brief consideration of sex in the genus
Diaporthe. There were evidences of sex isolation in
the group Diaporthe; for strains of this ascomycete
were fully capable of reproducing the perfect stage
from monoascospore isolation cultures. Strains
of Phomopsis occulta isolated from nature rarely produced
the perfect stage. Only two cases were ob-
served. Eighty-one forms of Phomopsis occulta continued
to reproduce the imperfect stage generation
after generation on both hard agars and natural media
In all 177 forms of conifer Phomopses (8 species) were
observed in culture and the perfect stage was found
only in two instances.