Abstract
Lupin cultivation worldwide is threatened by anthracnose, a destructive disease caused by the seed- and air-borne fungal pathogen Colletotrichum lupini. In this study we explored the intraspecific diversity of 39 C. lupini isolates collected from different lupin cultivating regions around the world, and representative isolates were screened for their pathogenicity and virulence on white and Andean lupin. Multi-locus phylogeny and morphological characterizations showed intraspecific diversity to be greater than previously shown, distinguishing a total of six genetic groups and ten distinct morphotypes. Highest diversity was found across South America, indicating it as the center of origin of C. lupini. The isolates that correspond to the current pandemic belong to a genetic and morphological uniform group, were globally widespread, and showed high virulence on tested white and Andean lupin accessions. Isolates belonging to the other five genetic groups were mostly found locally and showed distinct virulence patterns. Two highly virulent strains were shown to overcome resistance of advanced white lupin breeding material. This stresses the need to be careful with international seed transports in order to prevent spread of currently confined but potentially highly virulent strains. This study improves our understanding of the diversity, phylogeography and pathogenicity of a member of one of the world’s top 10 plant pathogen genera, providing valuable information for breeding programs and future disease management.
Highlights
Lupin cultivation worldwide is threatened by anthracnose, a destructive disease caused by the seed- and air-borne fungal pathogen Colletotrichum lupini
Lupin anthracnose caused by C. lupini is the most important disease in lupin cultivation worldwide, affecting all economically important lupin species such as blue (Lupinus angustifolius L.), white (L. albus L.), Andean (L. mutabilis Sweet.), yellow (L. luteus L.) and ornamental lupin (L. polyphyllus Lindl.)[20]
Two genetic groups (I and II) are distinguished within C. lupini based on vegetative compatibility groups (VCG)[38], the internal transcribed spacer (ITS) r egion[37] and multilocus phylogeny of the ITS, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), CHS-1, HIS3, ACT, TUB2 (β-tubulin 2), HMG (HMG box region) and APN/MAT1 (Apn2-Mat[1,2-1] intergenic) loci[39]
Summary
Lupin cultivation worldwide is threatened by anthracnose, a destructive disease caused by the seed- and air-borne fungal pathogen Colletotrichum lupini. Only two groups within C. lupini have been distinguished, with most of the reported strains belonging to group II39, intraspecific diversity is thought to be greater as a high diversity was found in a Chilean C. lupini collection using random amplified polymorphic DNA (RAPD) markers[40] and a distinct lupin infecting C. acutatum group was identified in Ecuador based on the ITS r egion[41] This suggests that highest intraspecific diversity is found in South America, which is believed to be the center of origin of members belonging to clade 1 of the C. acutatum species complex[10,15]
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