The effect of pH value on the toxicity of culture filtrates ofHelminthosporium Sativum and on its possible correlation to extracellular nitrogen accumulation
Helminthosporium sativum P.K. & B. was grown on modified Fries No. 3 medium buffered at pH 4.7, 5.5, 6.7, and 7.8. The nitrogen content of the culture filtrate, mycelial growth and the toxicity of the filtrate (as measured by its wilt inducing capacity to lupin seedlings) were traced over 24 days. The correlation between nitrogen accumulation and the toxicity of the filtrates was clear in case of media originally buffered at 4.7, 5.5 and 7.8. On the other hand, there was no correlation between growth of the mycelial mats and toxin production. The toxicity of the filtrate was attributed to two substances at least, one of unknown composition produced during the accelerated growth phase, while the other is nitrogenous and produced during the decline growth phase i.e. autolytic in nature. Acidity of the medium favoured toxin production during the first two weeks of incubation. The toxicity of the filtrate remained stable within a wide range of pH between pH 3–9.4.
The pathogenicity of six strains of Helminthosporium sativum to three cereals with special reference to barley
The pathogenicity of 6 strains ofHelminthosporium sativum P.K. & B. isolated from either oats, wheat or barley was studied. Oats was resistant to all strains followed by wheat while barley was susceptible. Barley variety Balder was the most resistant while Piroline was the most susceptible. Susceptibility of Piroline was manifested by higher percentage infection, bigger necrotic areas and wilting of the infected leaf. Toxic filtrates of the different strains could reproduce necrosis, wilting or chlorosis on cut leaves. Response of Balder and Piroline was similar in the filtrates of three strains, while in those of the other three Balder was more resistant. Formation of at least 2 toxic substances in the host tissues, one responsible for wilting and the other for necrosis, was suggested. No correlation was found between the dimensions of the spore or the number of its constituent cells and the virulence of the strain.
Influence of Diluted Spent Wash of Sugar Industries Application on Yield of and Nutrient Uptake by Sugarcane and Changes in Soil Properties
A pot experiment was conducted to study the effect of irrigation with tube well water (S0) as well as with spent wash diluted for 25 (S25), 50 (S5O) and 100 (S100) times on yield of and nutrient uptake by sugarcane grown on Typic Chromustert. The results revealed that application of spent wash diluted at any level increased the sugarcane yield and nutrient uptake significantly over S0. Less diluted spent wash gave higher yield of biomass than the concentrated one. Though, there was tendency for slight increase in the soil salinity due to use of spent wash, yet the nutrient availability of P, K and S increased considerably. Further, there was indication of betterment in some physical conditions of soil.