Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Abstract

Pathogenic variability in Mycosphaerella fijiensis Morelet, cause of black Sigatoka in banana and plantain.

Abstract

M. fijiensis strains (63) obtained from various Musa hosts in a range of different countries and localities were inoculated to juvenile plants of a standard set of Musa genotypes. Individual strains had consistent but different patterns of pathogenicity on the host set. Some genotypes (SF215, II-249 ('Saimea'), Grande Naine) were susceptible to practically all isolates. Others, e.g., T8 and Calcutta, were resistant to some isolates but susceptible to others. Strains from Papua New Guinea and the Pacific Islands exhibited a wide range of pathogenic diversity. Some strains from those regions were pathogenic on juvenile plants of genotypes commonly used as sources of resistance in breeding programmes (Calcutta, Paka and Pisang Lilin). It is suggested that these strains may threaten resistant progeny derived from those genotypes. Analysis of pathogenicity of strains collected over 4 years in Rarotonga, Cook Islands, confirmed field observations that Paka resistance is no longer effective on that Island. Paka virulence was found to be widespread in strains from the Pacific Islands and Papua New Guinea. Juvenile plants of Yangambi (AAA), generally considered to be resistant to M. fijiensis, were susceptible to strains which were virulent on Paka. It is concluded that the availability of pure cultures of strains with differential virulence on specific Musa genotypes will facilitate the analysis of the inheritance of resistance to M. fijiensis.