Maculans

Maculans is a Latin species epithet meaning spotted and is used in the scientific names of several organisms. The most widely known example is Leptosphaeria maculans, a filamentous ascomycete fungus that causes blackleg disease in Brassica crops, especially oilseed rape and canola. The species was historically described in its asexual form as Phoma maculans. Leptosphaeria maculans is a globally distributed pathogen of temperate regions and is a major constraint on Brassica production due to stem cankers, yield losses, and potential plant death.

Lifecycle and disease symptoms: L. maculans survives on crop residues as pseudothecia and releases ascospores that infect young plants under favorable moisture conditions. Infected tissues show leaf lesions and necrotic symptoms before the fungus colonizes the stem base, leading to blackened cankers and, in severe cases, lodging or plant death. The pathogen can persist in the field for multiple years, making residue management important for disease control.

Taxonomy and nomenclature: The binomial Leptosphaeria maculans reflects the sexual stage of the fungus, while the asexual stage has been referred to as Phoma maculans in older literature. The species is studied within the Pleosporales, with resequencing efforts revealing insights into host interaction and evolution.

Management and research: Integrated disease management includes crop rotation, removal of infected residues, deployment of resistant Brassica cultivars carrying specific R genes, and targeted fungicide applications where appropriate. Genomic research has identified effector genes (AvrLm) that interact with plant resistance traits, informing breeding and surveillance efforts. Maculans as a term also appears in other, less prominent species names, but its prominence in plant pathology is tied to Leptosphaeria maculans and its impact on Brassica crops.