Genetic diversity within Colletotrichum lupini and its virulence on white lupin (Lupinus albus)

Summary

White lupin (Lupinus albus) is a grain legume known for its high protein content and quality, efficient nutrient acquisition and health benefits (Lambers et al., 2013, Arnoldi et al., 2015). Its high yield potential could make it a sustainable alternative to soybean in cooler regions (Lucas et al., 2015). However, since the 1980s anthracnose disease, caused by the air- and seed-borne fungal disease Colletotrichum lupini, threatens lupin cultivations worldwide (Nirenberg et al., 2002, Damm et al., 2012, Talhinhas et al., 2016). Even low levels of seed infestation can lead up to total yield loss (Thomas 2004, Diggle 2002). To assist white lupin breeding programs, we analyzed the genetic diversity of globally collected lupin-infecting Colletotrichum isolates by multi-locus sequencing (Pecchia et al., 2019, Dubrulle et al., 2019). First analyses indicate that all isolates belong to the species C. lupini and that the genetic diversity of isolates collected from Europe and Australia is lower compared with isolates collected from South America, showing different genetic groups. Pathogenicity tests with isolates representing the different genetic groups were performed on two white lupin cultivars, the susceptible variety Feodora and the tolerant breeding line Blu-25 from Erik von Baer. Combining the outcome of the genetic diversity analysis with virulence and morphological data, at least five different strains could be distinguished. The most widespread strain is also the most aggressive and is the cause of the current anthracnose epidemic in (white) lupin cultivation.