Research Article Genetic comparison of the aggressive weed mould strains of Trichoderma harzianum from mushroom compost in North America and the British IslesS. MUTHUMEENAKSHI a1 p1 , A. E. BROWN a1 a2 and P. R. MILLS a1 a2 c1 p1 a1 Department of Applied Plant Science, The Queen's University of Belfast a2 Applied Plant Science Division, Department of Agriculture for Northern Ireland, Newforge Lane, Belfast BT9 5PX, U.K. Abstract Genetic characterization of 15 aggressive weed mould strains that were identified morphologically as Trichoderma harzianum (sensu Rifai) from mushroom compost in commercial units in North America (designated T. harzianum group 4) was undertaken using various molecular techniques. RFLP analysis of rDNA revealed homogeneity among these strains; a low level of polymorphism was detected in mitochondrial DNA. RAPD analysis also indicated a very high degree of homogeneity among the T. harzianum group 4 strains. Nucleotide sequence determination of the rDNA internal transcribed spacer (ITS) 1 revealed five base pair differences between T. harzianum groups 4 and 2. Comparison of molecular data on T. harzianum group 4 with that of T. harzianum group 2, which caused green mould epidemics in the mushroom industries of the British Isles, indicated that T. harzianum group 4 is not the same as group 2. (Accepted April 28 1997)Correspondence: c1 Corresponding author. p1 Present address: Department of Plant Pathology and Microbiology, HRI, Wellesbourne, Warwick, CV35 9EF. |