A study of two sub-tropical microcyclic rusts

57 Pages·2.877 MB·English

by  Shuttleworth, Floyd S

A STOUT CP TWO SUB-TROPICAL MICROCYCLIC HJSTS
By
Floyd S* Shuttleworth
Submitted to the Faculty of the
Graduate School in partial fulfillm ent of
the requirements for the degree
Doctor of Philosophy
in the
Department of Botany
Indiana University
1950
ProQuest Number: 10296454
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TABLE OF CONTENTS
INTRODUCTION....................................... l
DEFINITION OF TERMS........................... 2
PREVIOUS INVESTIGATIONS. . . . . 4
MATERIALS AND METHODS...................... 7
RESULTS AMD DISCUSSION.................. 10
Bros podium trgjasf ormans • • 10
Nuclear behavior . . . 14
Cellular inclusions. • ZZ
Inoculation Experiments 27
Puocinia emeliae. • « « • . 28
Nuclear behavior . . . 29
Inoculation experiments 32
CONCLUSIONS .......................... 32
SUMMARY . . . ................................... 33
ACKNOWLEDGMENTS. • • ...................... 36
LITERATURE CITED . . . . . . . . 37
ILLUSTRATIONS • • • • • • • • •
A STUDY OF TWO SUB-TROPICAL MICROCYCLIC RUSTS
INTRODUCTION
Although the TJredinales have been studied cytolc^jically
since the publication of Schmitz's (70) paper describing the
binucleate condition found in the mycelium and urediospores
of Coleosporium oampanulae (Fers.) Lev., there is much yet to
be learned concerning the morphology and nuclear behavior in
this important group of obligate parasites. Especially have
the tropical and sub-tropical species been neglected. In
the opinion of Jackson (41) and most other modern students
of the Uredinales (85), the short-cycle forms are considered
to be the most recently derived species and thus are the
expression of the present day evolutionary trend. Accordingly,
there is greater variation among the microcyclic species than
among the macrocyclic species.
In order to determine whether the sub-tropical short-
cycle forms exhibit the same degree of variation as do the
temperate forms which have been investigated, a study was
begun concerning two sub-tropical microcyclic species,
Pros podium transf ormans (E.& E.) Cumm., a parasite of Tecama
stans (L.) H.B.K., and Puccinia emeliae P. Eernw, a parasite
of Emelia sonchifolia (L.) DC., both of which occur in South
Florida and throughout the West Indies.
It was not the original purpose of this investigation to
study the cytochemistry of either the fungi or the hosts, or
to inquire into the larger field of the nature of host-parasite
relations, but eellular inclusions in the infected leaves of
Tacoma stans were so prominent in a ll microscopic preparations
that certain cytochemical tests were made in an attempt to
determine the nature of these inclusions*
DEFINITION CF TERMS
Many of the terms used in discussions of rust behavior
have had various connotations as used by different writers*
Therefore, it seems advisable to define the most controversial
ones in the sense in which the terms are used in this paper*
The terms wbasidiumn and Mbasidiosporen w ill be used
instead of the older but s till widely used terms ”pr ©mycelium”
and ”sporidium”. The older terms are most appropriate if the
rusts and smuts are plaoed in a separate class, as suggested
by Bessey (10). The term wbasidiumM should, in the strict
sense, include the teliospore, which is supposedly homologous
with the hypobasidium of the Auriculariales. However, this
paper shall follow the usual practice of restricting the term
to inolude only the germ tube and the cells cut off from it.
The term ”basidial stalk—cell” w ill designate only the basal
cell of the germ tube in those cases in which the basal cell
-3
does not produce spares*
The term "alternation of generations" w ill be avoided
inasmuch as the uninucleate and the binucleate phases in the
rusts do not always aot either as gametophyte or sporophyte*
It is possible that these non-conforming actions may be
considered as exceptions in the same sense as apospoxy and
apogaxoy are considered as exceptions in the higher plants*
and thus the term "alternation of generations" be s till
applicable to the higher fungi* However* as it is a controver­
sial term* it w ill not be employed in this report*
"Diploidisation" is another tern which has been interpreted
in a number of different ways* Many would object to the use
of this term as applied to the origin of the binucleate
condition in the fungi* If the diploid condition must be
restricted to the presence of the double number of chromosomes
in the same nucleus* then the term would not generally apply*
as the latter condition in most species of rust is limited to
a single cell* However* in the binucleate* or n / n condition,
the double number of chromosomes* derived from both sexes* is
present in the same cell* and the double complement of genes
exerts its influence as effectively as it would if the genes
were in the same nucleus* (See Buller (13)* for a fuller
discussion of this phenomenon). Such a binucleate condition
produces a very extensive mycelium in most rusts* Before
*•4—
meiosis, the conjugate nuclei fuse, except in a few species
(41,42), and crossing-over occurs with, probably as much,
regularity as it does in the Embry ophyta# In the hamothallic
species, the binucleate oondition m y arise by the failure of
a septum to form between daughter nuclei (12), and thus the
nuclei may not be of opposite sexes, Subse<juent behavior,
such as conjugate division, fusion, and reduction division,
would appear to indicate physiological differences between
these nuclei* Therefore, for the reasons given above, the
term ttdiploidisationw w ill be used in this paper to indicate
the initiation of the binucleate condition, without regard
to whether the two nuclei are of homothallic or of heterothallic
origin*
ERETCOtJS INSTIGATIONS
Detailed reviews concerning the cytology of rusts and
related fungi have been presented by Guilliermond (33),
Arthur et al* (6), Jachson (41), Lamb (45), Rioe (66, 67),
Buller (13), Gaumanu (20), and others* Therefore it seems
unnecessary at this time to review in detail the literature
covered by these authors* There have been reported certain
cycles of development which apply to many of the long-cycle
forms and to a number of short-cycle forms* These cycles
of development have come to be regarded as typical for the
Uredinales, <*nd a ll other nuclear behavior as variations
from these patterns# To refer to any behavior pattern as
typical is merely to imply that it has been found to occur
in the majority of species studied and to presume that it is
characteristic of the majority of species yet unstudied.
Such typical life-cycles are given herewith for a long-cycle
form as well as for a short-cycle form*
In most species of rusts studied, there is a definite
alternation of a uninucleate phase with a binucleate phase.
The first cell of the uninucleate phase is the cell of the
mature basidium with the uninucleate basidi os pores which it
produces subsequently* The basidiospore infects the host
and forms a more or less extensive uninucleate mycelium
between the host cells* This mycelium eventually produces
pycnia and aecial primordia* If the rust species is
haterothallic and the infection is of a single basidiospore
origin, the life-cycle ends at this point unless diploidisa-
tion by another infection occurs* If the mycelium of another
infection, supposedly of the opposite sex, should be in the same
host tissue and should come in contact with the mycelium, of
the first infection, fusion of cells w ill occur and tl®
binucleate condition w ill arise. Diploidisation may also
came about by the fusion of a pycniospore of the opposite
sex with the receptive hyphae of the first infection. In
■6*
hamofchallic species, the fusion cells and the resultant
diploidisation may be formed without the intervention of
another infection*
After diploidisation, the aeeium continues to develop
and produces binucleate aeciospores which can infect the
gpjpft host, if it is autoecious, or an alternate host, if
the species is heteroecious* This infection results in an
extensive development of a binucleate mycelium throughout
the tissues of the host. The binucleate xsycelium produces
binucleate urediospores, formed in a uredium and these
spores can reinfect the host* On the same nycelium, and
often within the samesorus, telia and teliospores are
eventually formed* The young teliospores are binucleate
but the conjugate raielei fuse as the spore natures* The
teliospore cannot cause infection directly* It germinates,
ordinarily after a rest period, into a germ tube, at the end
of which is out off a 4-spcred basidium. The fusion nucleus
has meanwhile undergone tiro mBiotic divisions, and the result­
ing nucleus of each of the four cells of the basidium is
haploid* Basidiospores are borne on short sterigmata through
whieh the nuclei of the basidial cells migrate into the
basidiospores*
Variations in the life-cycle in maorocyclio forms have
been reported by a number of investigators. (9,83)* Most
of the maorocyclic species which do vary are species which
are unstable in their life-eycles and contain physiologic
races in which one or more of the spore stages are lost.
In the microcyclic species, the aecial ana uredial, and
ofteh the pycrdal, stages are omitted. Also variations
in the nuclear cycle are common. It is difficult to refer
to any nuclear pattern as typical, but a pattern similar
to that described for the macrocyclic species, with the
omission of the aecial and uredial stages, has generally
been considered to be the most common. Diploidisation
occurs in the te lia l primordium or earlier in the life
cycle, and fusion of nuclei occurs in the mature teliospore.
However, uninucleate and entirely binucleate races are
also known* These and other differences w ill be discussed
later in this paper*
MATERIALS AND METHODS
Material of Tacoma stans, infected with Hrospodium
transfer mans, was collected at Coral Gables, Florida, aid
Nassau, Haw Providence, Bahamas. Collect ions were made
in Florida throughout the year and in the Bahamas during
July and December* leaf, stem, and Jfruit specimens were
obtained. Tacoma stans is a Bignoni&ceous tree commonly
planted as an ornamental in tropical aid sub-tropical
America. leaves of the Carduaceous weed, Emelia sonchi-
folia infected with Puocinia emeliae, were collected at