Rhizina Undulata Research Articles

Observations of Damage of a Secondary Nature Following a Wild Fire at the Otterford State Forest

SYNOPSIS An inspection of stands damaged in the wild fire that occurred during October 1984 revealed that trees seriously damaged and still growing under severe stress are exposed to attack of a secondary nature in the form of the fungus Rhizina undulata, the bark beetle Ips erosus and Cerambycid beetles.

Asci of the Pezizales. VI. The apical apparatus of Morchella esculenta, Helvella crispa, and Rhizina undulata. General discussion

Morphological, developmental, and cytochemical examinations were made with light and electron microscopy on the apical apparatuses of Morchella esculenta, Helvella crispa, and Rhizina undulata, all species with large, stipitate apothecia. Ascus tips in R. undulata were markedly thinner walled than the rest of the ascus, while those in M. esculenta and H. crispa were slightly thinner than the rest of the ascus wall. Lipid bodies were detected in developing asci of H. crispa and M. esculenta. Their unique occurrence in asci of members of the Morchellaceae and Helvellaceae may have taxonomic significance. With the electron microscope, opercula were distinguished cytochemically in all three species. In H. crispa and M. esculenta dehiscent zones were found to be restricted in the inner layer of the ascal wall. Characters of the apical apparatuses of H. crispa and M. esculenta suggest greater taxonomic relatedness between these species than with any other operculate group. The apical apparatus of R. undulata differed notably from the other species.The present series of studies has demonstrated distinct variability of the operculate ascus and its apical apparatus in morphology, cytochemistry, and development. Several major forms of the apical structures were observed. These examinations support the chemotaxonomic and cytological investigations on representatives of the Pezizales made previously by Arpin and Berthet. Outside of the Thelebolaceae, members of the Pezizales are chiefly characterized by the operculate dehiscence of their asci. Members of the Thelebolaceae eject their spores through a variety of dehiscent mechanisms. Present examinations of those representatives of the Thelebolaceae with functionally operculate apparatuses, i.e., Lasiobolus and Coprotus, support their transferrance to the Pyronemaceae. Taxa which form nonoperative opercula, i.e.,Ascozonus and Trichobolus, also show closer affinities with the Pyronemaceae than with the nonoperculate representatives of the Thelebolaceae. The nonoperculate members of the Thelebolaceae apparently do not belong in the operculate Discomycetes. The operculate ascus wall is structurally compared with the pored and bitunicate ascus walls. The terms 'bitunicate' and 'unitunicate' are redefined.

The Influence of Harvesting on Silviculture

SYNOPSIS Refers to the present harvesting systems practised by the Usutu Pulp Company Ltd. The practical influence of these systems on the silviculture of exotic conifers grown under a 15-year pulpwood regime are discussed. The effects of mechanical and draught animal skidding on the site and subsequent stocking and survival are described. The adverse effects of slash disposal by burning e.g. soil erosion; occurrence of Rhizina undulata (Root Rot Fungus), are also discussed and related to the 1972 abolition of burning as a method of slash disposal. The problems of site preparation and establishment presented by the different patterns of residual slash created by the present harvesting systems are described together with current practices to minimise these problems. Investigations into the mechanical break-up of slash and improved site preparation are reviewed. The influence of the road requirements for the present harvesting systems is briefly summarised. The improved utilization of the raw material off the site via mobile or roadside chipping and its effect on subsequent silviculture practices is discussed. Possible future trends in harvesting practices at Usutu and their influence on silviculture are then presented.

Rhizina undulata on Picea abies transplants

At least three quarters of the sites of brash fires in a mainly coniferous area on peat in Co Tyrone, Northern Ireland were clonised by Rhizina undulata. On each of these sites an average of eight newly planted Picea abies died within five years. No more deaths were recorded during a further three years. Deaths of Picea abies seldom occurred where there had been no fire or on fire sites on hardwood stumps in the same area.

Rhizina undulata. A review of research in the Netherlands1

AbstractResearch on killing of coniferous trees caused by the fungus Rhizina undulata Fr. ex Fr. in the Netherlands is reviewed. Aspects of the fungus’ pathogenicity, its biology and pyrophilous nature, and means to restrict or avoid damage in young plantations and older stands are discussed.

Studies on Rhizina undulata: II. Observations and experiments in east anglian plantations

Typical attacks by Rhizina undulata Fr. on young conifers are described. Root systems of freshly cut conifer stumps usually provide the food bases required by R. undulata for colonization of bonfire sites, but under certain conditions these may be provided by standing conifers. Evidence is given for the existence of a narrow zone beneath fires and at their margins where heating is sufficient to stimulate germination of R. undulata ascospores. The presence of ascospores alone is sufficient for the colonization of suitable fire sites. Experiments demonstrating the pathogenicity of R. undulata are described.

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.

Damage by Rhizina Undulata in Coniferous Plantations

Damage by Rhizina Undulata in Coniferous Plantations

Sexuality in Rhizina Undulata Fries

1. The sexual process has not heretofore been studied in any member of the Rhizinaceae. The examination of Rhizina undulata Fries is therefore of considerable interest. 2. Material for study was collected at Ithaca, New York, and a paper describing the origin of the apothecium in this species has already been published (27). 3. The vegetative mycelium is parasitic on the roots of trees, and develops profusely in the soil. On the surface of the ground or on parasitized roots minute primordia of fruit-bodies are developed. These are composed of undifferentiated hyphae which form at the periphery a somewhat indefinite palisade layer. 4. After the ascocarp primordium has attained a diameter of approximately 1 mm., certain hyphae near its center are transformed into archicarps. As many as 8 archicarps may be developed in a single ascocarp. 5. The individual archicarp develops by the rapid growth and transformation of an ordinary multicellular hypha. Its cells are multinucleate from the first. The nuclei increase greatly in number by repeated division and the archicarp soon takes on a dense Opaque appearance. 6. An antheridium is absent. 7. The archicarp develops in some cases as a loose coil, and in others winds irregularly among the other hyphae, but tight coils have not been found. The number of cells in a single archicarp has been found to vary from 10 to 19 or more. 8. The terminal cell of the archicarp is small and attenuated, and at maturity shows disorganized protoplasmic contents. It has been here from analogy termed the trichogyne, but it certainly does not function. 9. As the archicarp approaches maturity a single, very prominent, deeply staining, hemispherical or convex pad appears on each side of the transverse septa. These pairs of deeply staining pads apparently represent a swelling of the wall due to gelatinization at that point. They later fuse and finally disappear, leaving a large pore in the septum. 10. Approximately one-half of the cells of the archicarp lying at the center of the coil now put out ascogenous hyphae. The remaining basal and apical cells fail to bud, and their nuclei and cytoplasm flow through the pores in the transverse septa into the ascogonial cells, and thence into the ascogenous hyphae. II. With the outward flow of nuclei and cytoplasm into the ascogenous hyphae, the cytoplasm in the ascogonial cells of the archicarp becomes pronouncedly vacuolated. The nuclei are then seen to lie in pairs. In preceding stages the dense nature of the protoplasm and the crowding of the nuclei render the demonstration of a paired condition extremely difficult. Pairs of nuclei in the archicarp have been seen only in cells giving rise to ascogenous hyphae. 12. Careful search has failed to demonstrate stages of nuclear fusion in the ascogonial cells or in the ascogenous hyphae. 13. Paired nuclei are also present in the ascogenous hyphae. Neither conjugate nor simple divisions have been demonstrated. 14. Crozier formation takes place, but elaborate systems of hooks at the ends of the ascogenous hyphae have not been found. Nuclear fusion occurs in the young ascus.