Molecular characterization of the pathogenic plant fungus Rhizoctonia solani (Ceratobasidiaceae) isolated from Egypt based on protein and PCR-RAPD profiles.

Twenty-one isolates of Rhizoctonia solani were categorized into three anastomosis groups consisting of AG-4-HG-I (eight isolates), AG-2-2 (nine isolates) and AG-5 (four isolates). Their pathogenic capacities were tested on cotton cultivar Giza 86. Pre-emergence damping-off varied in response to the different isolates; however, the differences were not significant. Soluble proteins of the fungal isolates were electrophoresed using SDS-PAGE and gel electrophoreses. A dendrogram of the protein banding patterns by the UPGMA of arithmetic means placed the fungal isolates into distinct groups. There was no evidence of a relationship between protein dendrogram, anastomosis grouping or level of virulence or geographic origin. The dendrogram generated from these isolates based on PCR analysis with five RAPD-PCR primers showed high levels of genetic similarity among the isolates from the same geographical locations. There was partially relationship between the genetic similarity and AGs or level of virulence or geographic origin based on RAPD dendrogram. These results demonstrate that RAPD technique is a useful tool in determining the genetic characterization among isolates of R. solani.

Haemolytic activity of Aeromonas species isolated in Libya.

Twenty seven Aeromonas strains (5A. hydrophila, 8A. sobria and 14A. caviae) isolated from children with diarrhoea and 34 Aeromonas strains (9A. hydrophila, 7A. sobria an 18A. caviae) isolated from children without diarrhoea were tested from haemolysin production. The results obtained showed that haemolysin production using human, horse or sheep erythrocytes was significantly associated with A.hydrophila and A sobria but not with A.caviae, regardless of whether these strains were isolated from children with or without diarrhoea. Human or horse rather than sheep erythrocytes are recommended for use in the haemolysin assay.

Variation in Sensitivity Among Some Isolates of Macrophomina phaseolina Isolated from Cotton Roots to Flutolanil Fungicide.

Toxicity of the fungicide Flutolanil was in vitro tested against 20 isolates of Macrophomina phaseolina and cotton seedlings of ten commercial cotton cultivars. The isolates were recovered from roots of cotton plants obtained from different cotton-growing areas in Egypt. Most of the tested isolates were sensitive to Flutolanil; however, they varied in sensitivity. Twenty-five percent of the isolates were highly sensitive where IC50 ranged from < 1 to 5.1 µg/ml, 20% of the isolates were sensitive where IC50 ranged from 15 to 30 µg/ml, 45% of the isolates were moderately sensitive where IC50 ranged from 46 to 58.5 µg/ml, and 10% of the isolates were not much sensitive (tolerant) where IC50 was > 100 µg/ml. Flutolanil was very safe on both shoots and roots of the tested cultivars (IC50 > 100 µg/ml). Treating cotton seeds with Flutolanil resulted in highly significant (P < 0.01) reductions in pathogenicity of 18 isolates and a significant reduction (P < 0.05) in pathogenicity of isolate M29. M1 was the only isolate, which was insensitive to the application of Flutolanil. In vivo toxicity to Flutolanil was not correlated with its in vitro toxicity. However, a highly significant correlation (r = 0.60, P < 0.01) was observed between pathogenicity of isolates and the in vivo toxicity of the fungicide.