Helminthosporium Sacchari Research Articles

Helminthosporoside, a Host-specific Toxin from Helminthosporium sacchari

Abstract Helminthosporoside has been isolated from the sugar cane fungus pathogen Helminthosporium sacchari. This compound is the first host-specific plant toxin to have a structure proposed for it. The toxin produces symptoms only on those clones of sugar cane that are susceptible to the fungus. Based on its spectral and chemical properties, the proposed structure of helminthosporoside is 2-hydroxycyclopropyl-α-d-galactopyranoside. A biological assay for its quantification based on the degree of symptom expression on sugar cane leaves is described. Helminthosporoside-14C can be isolated from cultures of H. sacchari that have been incubated with galactose-1-14C.

Partial Characterization and Use of a Host-Specific Toxin from Helminthosporium sacchari on Sugarcane

Partial Characterization and Use of a Host-Specific Toxin from Helminthosporium sacchari on Sugarcane

SEEDLING BLIGHT OF SUGAR‐CANE‐A NEW DISEASE CAUSED BY HELMINTHOSPORIUM SACCHARI BUTLER

The fungus Helminthosporium sacchari Butler, known to be the cause of eye spot, a common air‐borne disease of sugar‐cane leaves, is now shown to be the cause of an undescribed seed‐borne disease of sugar‐cane seedlings. It is therefore suggested that the disease should be renamed eye spot and seedling blight of sugarcane.The symptoms of seedling blight are described, and the pathogenicity of the fungus to sugar‐cane seedlings is confirmed. Incidence of seedling blight is shown to be markedly affected by the growing conditions, and disease‐escape is common. The two most important factors predisposing seedlings to attack appear to be (i) the relative humidity of the atmosphere, and (ii) the occurrence of a check to the continuous growth of the seedlings.With the discovery of the existence of seedling blight, eye spot assumes a particular significance in plant‐breeding plots, because it may be responsible for the loss of sugar‐cane seedlings, any one of which is potentially a desirable new variety.

A comparative study of species and strains of Helminthosporium on certain indian cultivated crops

Summary 1. Seven species or strains of Helminthosporium occurring on various cultivated grasses and one on ginger have been studied. 2. The symptoms of disease as seen in nature together with the morphology of the various forms under natural conditions have been described. 3. The eight fungi used were studied under different conditions of growth in artificial culture. The following were the main results : (a) Rate of growth depends on a number of factors, such as type of medium, amount of medium, presence or absence of light. There are certain strains, e.g. that from ginger, which show a slow growth-rate under all conditions tested. (b) The effect of temperature on growth also depends somewhat on the nature of the medium. The eight fungi show a certain amount of differentiation as regards the position of the optimal and maximal temperatures for growth and as regards sensitiveness to heating. (c) The macroscopic features of growth were found to vary very considerably. Details of the effect of cultural conditions on amount of aerial mycelium formation, colour formation, zonation, etc., are given in the text. (d) Certain microscopic growth features show a greater degree of constancy. Though amount of sporulation and spore measurements vary a good deal, spore shape and colour are markedly constant and therefore are of value for specific delimitation. 4. An extensive series of inoculation experiments was carried out with the following results: (a) Each fungus freely parasitises the host plant from which it was isolated. (b) Under artificial conditions at least, most of them are able to infect a number of hosts other than their own. (c) With the exception of two strains, all are able to produce the root-rot and foot-rot phases of disease in wheat and barley. (d) The intensity of the foot-rot and root-rot disease produced is markedly influenced by soil temperature, being greatest when the latter is in the neighbourhood of 30°C. 5. Of the eight forms studied, two have been assigned to new species. These are named Helminthosporium bicolor and Helminthosporium frumentacei . A strain from wheat is considered to be a variety of Helminthosporium halodes Drechs. and the strain from ginger to be Helminthosporium Maydis Nisikado and Miyake or a variety of the latter. The other forms are assigned to species already described. In the particular case of Helminthosporium Sacchari an amended diagnosis is given, with special reference to the size of the spores.

THE EYE-SPOT DISEASE OF SUGAR CANE

1. The "eye spot" disease which is caused by Helminthosporium sacchari Butler is serious on certain varieties of sugar cane in Porto Rico. 2. It is most severe on F.C. 306 and D. 109 with H. 109 as a poor third. The Uba and P.O.J. canes are most resistant. 3. The susceptibility varies with leaf structure, the higher the fiber content the greater the resistance. However, there appears to be some slight correlation with sucrose content. 4. The young leaves are more susceptible than the old leaves; the bases and upper surfaces more susceptible than the tips and lower surfaces. 5. The spores and sporophores germinate readily in water and penetrate the leaf without regard to the stomata. The greatest mycelial growth is in the parenchyma tissues. The spores are borne more abundantly on the lower than on the upper surface of the leaf. 6. The disease is most severe during the cool, wet months of the year. Temperature appears to be the most important environmental factor. 7. The most satisfactory control for Porto Rico at his time consists in the use of resistant varieties.