Ascospore Germination Research Articles

Germination of ascospores of Hypoxylon mammatum in living aspen

Ascospores of Hypoxylon mammatum germinated in the sapwood of naturally occurring trembling aspen. Observed germination never exceeded 7%. There appeared to be no clear relationships between percentage germination and the age of the wound, location in the sapwood, age of the tree, or weather conditions during the incubation period.

Growth of Wallrothiella arceuthobii on artificial media

Ascospore germination and growth of Wallrothiella arceuthobii (Peck) Sacc. on artificial media is reported. Germination was enhanced by yeast extract or by increasing the agar content of media. Yeast extract was required to sustain growth.

Phenethyl alcohol induced germination of ascospores of Neurospora.

Phenethyl alcohol (PEA) can activate dormant ascospores of Neurospora. Between 4 to 8×10-8 M PEA solutions induce germination of ascospores of N. crassa and N. tetrasperma equal to or higher than that of those activated by heat. This PEA effect is significantly greater than that of related chemicals and of other compounds known to induce fermentative metabolism.

A New Species of Neurospora from Soil of West Pakistan

SUMMARY A new homothallic species of Neurospora, N. lineolata is described. The fungus was isolated from soil collected in the vicinity of Lahore, West Pakistan. Of the three other homothallic species with bipolar ascospores, N. lineolata most closely resembles N. africana; it differs, however, from this species by having narrower ascospores with numerous indistinct ribs and intercostal veins, and larger, beaked perithecia. Ascospore germination in N. lineolata is uni- and bipolar. The bipolar pattern appears to predominate. N. lineolata represents the twelfth species now placed in the genus Neurospora. A key to all species in the genus is provided. During the present decade new species of Neurospora have been reported with surprising frequency. Prior to 1960 only 7 species were included in the genus. With the publication of this communication the total number now recognized rises to 12. Five new species have been discovered within a span of less than 7 years. All of the new species are homothallic and have been isolated from soil. This development, however, has not been entirely unsuspected, for when Nelson et al. (5) described the second new species of this decade, Neurospora dodgei Nelson & Novak, they suggested that Neurosporas were probably much more common members of the soil mycoflora than heretofore believed. They speculated that the discovery of additional species from soil should be facilitated by the application of a selective isolation technique developed by Novak and Backus (6). It did not take long for these speculations to be substantiated. Mahoney, Huang and Backus (3) report in a current communication the discovery of two new species, N. galapagosensis Mahoney & Backus and N. africana Huang & Backus, from tropical soil. They employed the selective isolation technique of Novak and Backus (6) in their

MUTANTS OF NEUROSPORA CRASSA PERMEABLE TO HISTIDINOL

IN Neurospora, L-histidinol is the immediate precursor of L-histidine, as shown by the isolation of L-histidinol dehydrogenase and the study of its catalytic functions (AMES 1957; CREASER, BENNETT and DRYSDALE 1965). The failure of histidine mutants, with the histidinol dehydrogenase function intact, to grow on histidinol, suggests that histidinol cannot enter the cell. However, CATCHESIDE ( 1960) and WEBBER, CASE and GILES (quoted in WEBBER 1960) have independently obtained variants of histidine mutants that can grow on histidinol. CATCHESIDE (1960) suggested that the mutation might involve a change in the system (permease) by which histidine is transported. The transport of histidine is connected with that of several amino acids. Growth of histidine mutants is inhibited by combinations of a neutral (especially aromatic) amino acid with arginine or lysine (HAAS, MITCHELL, AMES and MITCHELL 1952) and this was shown by MATHIESON and CATCHESIDE (1955) to be due to the prevention of histidine uptake. The present work sought to determine which genes were able to mutate to allow entry to histidinol and, by comparative physiological experiments, to discover the functions of the normal alleles of these genes. Such work should contribute to an understanding of these mutations and the mechanism of inhibition of uptake of histidine. MATERIALS AND METHODS The strains used were the wild type Emerson a and the mutants 30300 (arg-3) argininerequiring; K4-58 (his-3) histidine-requiring; AB9 (lys-4) lysine-requiring; 65001 (nt) nicotinictryptophan-requiring and E151 72 (sfo) sulfonamide-requiring. Strains permeable to histidinol will be described later. The minimal media of VOGEL (1964) and WESTERGAARD and MrrcHmL (1947), with appropriate supplements, were used for vegetative growth and crosses, respectively. VOGEL’S medium plus 0.5% L-sorbose and 0.1% sucrose (SS) with suitable supplements was used for scoring progeny. VOGFL’S medium plus 0.5% L-sorbose, 0.0125% D-glucose and 0.025% D-fructose (SGF) with suitable supplements was used for the isolation of mutants and germination of ascospores. The quantities of supplements (mg per 100 ml medium) used routinely for crosses, maintenance and scoring of cultures were as follows: 20 L-arginine HCI, L-citrulline, L-histidine HCl.H,O, L-lysine HCl; 60, L-histidinol2HCl; 1, nicotinamide. Cultures were tested for ability to grow on histidinol by inoculating conidia on solid VOGEL’S medium supplemented with histidinol; scoring was usually possible after 3 days of incubation at 25°C. It may be noted that K458 (his-3) also grows very poorly on solid medium containing histidinol but much less as compared to strains permeable to histidinol. Tests for sjo and nt were also done on solid VOGEL’S medium, sjo being scored after 1-2 days of incubation at 34°C.

Studies of the Periodicity of Spore Discharge and Germination in Lichens

Studies of the Periodicity of Spore Discharge and Germination in Lichens

Ultrastructural changes during germination of ascospores of Neurospora tetrasperma.

SUMMARY: A technique is described for fixing and embedding dormant ascospores of Neurospora tetrasperma, whose impermeability has made them difficult subjects for electron microscopy. The ultrastructure of dormant and germinating spores has been compared. Endoplasmic reticulum occurs relatively infrequently in dormant ascospores whereas germinating ones have large amounts. An unusual structure, consisting of concentric membranes of varying degrees of complexity, appears after activation and disappears after extension of the germ tube. This membrane complex is continuous with the endoplasmic reticulum and may be its origin during germination. Mitochondria in dormant ascospores are larger and less numerous than in germinating ones. Two new elements of the ascospore wall are described, one of which may contribute to the relative impermeability of these forms. Nuclei increase in number during germination, but the exact number of divisions is not known.

Acetate-onutilizing mutants of Neurospora crassa. I. Mutant isolation, complementation studies, and linkage relationships.

Sixty mutants of Neurospora crassa unable to grow on acetate as sole source of carbon, but able to utilize sucrose, were isolated. On the basis of complementation tests, they were divided into seven groups, each group representing a different gene. Six of the genes have been mapped; no two are closely linked. These loci have been designated acu-1 to acu-7. Mutations at four of these loci result in poor germination of ascospores.

Studies on Rhizina undulata: I. Mycelial growth and ascospore germination

Growth rates of Rhizina undulata Fr. on malt agar and in tubes of soil are given. Ascospore germination is stimulated by heating, especially over the range 35–45 ° C, for certain periods. There is some evidence that exudates from heated pine roots also stimulate germination. A small proportion of ascospores survive for two years on glass slides buried in soil. In jars of soil incubated at 22 ° mycelial development of R. undulata from ascospores occurs only if the soil is acidic and fresh conifer roots are present; these conditions are also required for colonization of bonfire sites in East Anglia.

FACTORS AFFECTING THE GERMINATION OF SPORES OF HYPOXYLON PRUINATUM

The optimum temperature for germination of ascospores of Hypoxylon pruinatum was 32 °C. and for conidia was 25 °C. Ascospores germinated best at pH 6.1. Both conidia and ascospore germination was inhibited on both unwounded and freshly wounded aspen bark. Inhibition was greatest on freshly wounded bark. Ascospore germination was 1.9% after 96 h on 2% malt agar containing 660 p.p.m. pyrocatechol, while complete inhibition occurred at 330 p.p.m. of the chemical in distilled water. Experiments suggest that the 48-h delay in spore germination was not due to the direct action of contaminating microorganisms.

A PHYSIOLOGICAL STUDY IN THE GENUS TYMPANIS

Three species of Tympanis (Helotiales) were studied in culture. The common carbohydrates were well utilized with the exception of sucrose. Approximately equal growth was made on organic and inorganic nitrogen. Only one species was totally deficient for thiamin and biotin. All species had an optimum growth temperature of 25 °C and a broad pH optimum of pH 3–5. Temperature variations produced marked cultural changes in two species. A preliminary study of the chemical properties of two pigments, and observations on fruiting habits, ascospore discharge, and ascospore germination of one species are reported.

Occurrence, Sporulation and Pathogenicity Studies with Glomerella Cingulata Associated with Crown Rot of Boxed Bananas

SUMMARYPerithecia and acervuli of Glomerella cingulata occur on all above-ground parts of the banana plant in Honduras but are more abundant on the persistent bracts. Perithecia and acervuli were most abundant in the wet season; few were found during the hot, dry period. Ascospore discharge required moisture or long exposure to 100% relative humidity. Perithecia discharged viable ascospores in diminishing quantities during 6 weeks of periodic wetting and drying. Maximum germination of ascospores occurred in 6 hr at 100% relative humidity at which time 80% of the ascospores had formed appressoria. Mature perithecia were formed on bract tissue 6 days after inoculation, but failed to form at temperatures of 30 C or above although conidia form abundantly at 30 and 32 C. Mycelial growth was retarded at 35 C. The isolates varied in cultural characteristics and pathogenicity to banana crown tissue.

Root infection by ascospores of Ophiobolus graminis as a factor in epidemiology of the take-all disease

No infection of wheal seedling toots by ascospores of Ophiobolus graminis (Sacc.) Sacc. could be obtained when the roots were growing through unsterilized soil or sand, though infection of roots in completely sterilized soil or sand was readily obtained, thus confirming an earlier report by Garrett (1939) . But ascospores were regularly able to infect the exposed proximal pari of the seminal roots of wheat seedlings sown on the surface of natural, unsterilized soil. Further experiments have led to the conclusion that the normal soil microflora exerts a virtually complete biological control of ascospore infection of roots growing within the soil, usually by inhibiting ascospore germination. The occurrence of ascospore infection, in the manner described above, is thought to explain the origin of past outbreaks of take-all in wheat crops grown on the newly drained polders of the former Zuider Zee in the Netherlands.

SOME CULTURAL AND GENETIC ASPECTS OF A NEW HETEROTHALLIC SORDARIA

Fields, William G., and James Maniotis. (Wayne State U., Detroit, Mich.) Some cultural and genetic aspects of a new heterothallic Sordaria. Amer. Jour. Bot. 50(1): 80–85. lllus. 1963.— Sordaria heterothallis sp. nov., isolated from rabbit dung collected in Austin, Texas, is characterized as a spermatium‐prcducing, hcterothallic Sordaria with carbonous stromatic walls. Spermatia may germinate, but their low frequency of germination suggests their role in asexual reproduction is minor. The fungus was determined to be biotin‐ and thiamine‐deficient. A single pair of factors about 1.9 units from the centromere governs compatibility. Ordered tetrad analyses indicates regular segregation of factors for ascospore germination, the production of aerial mycelium and pigmentation. Intra‐ and intergeneric reactions stimulating protoperithecial production occurs between Sordaria heterothallis and the related species Sordaria brevicollis and Gelasinospora atilosleira.

Effect of Environment on Germination of Ascospores of Urnula craterium

SUMMARYAscospores of Urnula craterium were subjected to various environments to determine their effect on germination. Percentage germination and length of germ tube were used to determine the response. Ascospores germinated over a wide temperature range, including 5° and 35° C. The optimum, based on germ tube elongation and percentage germination 16 hours after expulsion from the apothecium, was 20–30° C. Germination of some spores occurred at 35°, but the protoplasm was extruded from both germ tubes and ungerminated spores. There was no subsequent growth. Added nutrients increased germination, but 85% of the ascospores germinated without them. There was no subsequent growth, however. Growth from germinated ascospores was excellent on malt extract agar and Barnett's agar; the optimum for continued growth was 24–27°. C. Ascospores germinated over a range of pH from 2.5 to 9.5; the optimum was 5.3 for germination and germ tube elongation. Light had no effect on germination, but it affected longevity. Germination of ascospores stored 383 days at 20–25° C was 10% for storage in light and 40% for storage in dark. The ascospores germinate in less than 2 hours and germ tube elongation is rapid at optimum temperatures.

Effect of Environment on Germination of Ascospores of Urnula Craterium

Urnula craterium (Schw.) Fr. is believed to be the perfect stage of Conoplea globosa (Schw.) Hughes (6), (Strumella coryneoidea Sacc. & Wint.), which causes an important canker disease of oak and several other hardwoods (5). Germination of ascospores of U. craterium has not been studied critically, although Davidson (5) observed that 90 to 100% of the ascospores shot from an apothecium germinated within 3 to 4 hours on cornmeal agar. Ascocarps from felled bur oak, Quercus macrocarpa Michx., in the spring of 1959 provided fresh material for investigation of ascospore germination. The possible importance of ascospores in long distance spread of the canker disease fungus stimulated this study.

Genetics of Sordaria Fimicola. III. Cross-Compatibility Among Self-Fertile and Self-Sterile Cultures

Carr, A. J. H. (Univ. Coll. Wales, Aberystwyth), and Lindsay S. Olive. Genetics of Sordaria fimicola. III. Cross compatibility among self-fertile and self-sterile cultures. Amer. Jour. Bot. 46(2) : 81-91. Illis. 1959.—Cross-compatibility in Sordaria fimicola is shown to be dependent upon a number of factors controlling the sexual process, from hyphal anastomosis and nuclear migration on through to perithecial formation and nuclear compatibility. Fertile cultures which were incompatible through inability to anastomose were induced to cross by the use of a third culture which would anastomose with both. Certain spontaneous or irradiation-produced sterility mutants were found to be compatible if the sterility genes were at different loci, through complementation by the wild-type alleles. In some pairings, cross-karyogamy was preferential, and in one case, only hybrid perithecia were produced. Fully fertile recombinants segregated from these crosses in frequencies which indicated that the sterility loci were unlinked. Certain sterility genes were found to influence hyphal anastomosis, nuclear migration, and the development of fertile sector heterokaryons from the zone of anastomosis. Mutant factors at two loci in a U.V. mutant causing self-sterility were found also to be responsible for lethality in ascospore germination. Factors in one sterility mutant controlled the production of a sterility-inducing substance which diffused into the medium. In some crosses, complementation of two sterile cultures towards fertility is shown to require a balanced nuclear ratio. Factors are described which increase the inhibitory effect of one sterility gene, while another factor was found to suppress its effect and thereby make the culture self-fertile. It is concluded that, since there is recombination between the sterility loci, these results do not represent the derivation of balanced heterothallism from a normally homothallic system, although it may lead by evolutionary progression to such a life cycle. The possible physiologic action of the sterility genes is discussed.

GENETICS OF SORDARIA FIMICOLA. III. CROSS‐COMPATIBILITY AMONG SELF‐FERTILE AND SELF‐STERILE CULTURES

Carr, A. J. H. (Univ. Coll. Wales, Aberystwyth), and Lindsay S. Olive. Genetics of Sordaria fimicola. III. Cross compatibility among self‐fertile and self‐sterile cultures. Amer. Jour. Bot. 46(2) : 81‐91. Illis. 1959.—Cross‐compatibility in Sordaria fimicola is shown to be dependent upon a number of factors controlling the sexual process, from hyphal anastomosis and nuclear migration on through to perithecial formation and nuclear compatibility. Fertile cultures which were incompatible through inability to anastomose were induced to cross by the use of a third culture which would anastomose with both. Certain spontaneous or irradiation‐produced sterility mutants were found to be compatible if the sterility genes were at different loci, through complementation by the wild‐type alleles. In some pairings, cross‐karyogamy was preferential, and in one case, only hybrid perithecia were produced. Fully fertile recombinants segregated from these crosses in frequencies which indicated that the sterility loci were unlinked. Certain sterility genes were found to influence hyphal anastomosis, nuclear migration, and the development of fertile sector heterokaryons from the zone of anastomosis. Mutant factors at two loci in a U.V. mutant causing self‐sterility were found also to be responsible for lethality in ascospore germination. Factors in one sterility mutant controlled the production of a sterility‐inducing substance which diffused into the medium. In some crosses, complementation of two sterile cultures towards fertility is shown to require a balanced nuclear ratio. Factors are described which increase the inhibitory effect of one sterility gene, while another factor was found to suppress its effect and thereby make the culture self‐fertile. It is concluded that, since there is recombination between the sterility loci, these results do not represent the derivation of balanced heterothallism from a normally homothallic system, although it may lead by evolutionary progression to such a life cycle. The possible physiologic action of the sterility genes is discussed.

Physiology of the cell surface of Neurospora ascospores; entrance of anions and non-polar compounds

Acids like hydrogen fluoride, hydrazoic and fluoroacetic have been shown to prevent the germination of ascospores of N. tetrasperma when dormant spores are treated. On the other hand, propionate, cysteine and others are ineffective when used in this way. When activated ascospores were treated, much lower concentrations of the acids were sufficient to poison the spores. As in other systems, these substances are most effective at a pH below their pKa.

Physiology of the Cell Surface of Neurospora Ascospores. III. Distinction Between the Adsorptive and Entrance Phases of Cation Uptake

The germination of ascospores of Neurospora tetrasperma has been shown to be inhibited by continual incubation in very small amounts of metal cations. Of these, Ag+, and p-chloromercuribenzoic acid...