Identification, Distribution, and Pathogenicity of Lasiodiplodia Species Causing Avocado Stem-End Rot in Peru

Avocado (Persea americana Mill.) production in Peru is economically impacted by stem-end rot (SER) and branch canker (BC). Although Lasiodiplodia species are recognized pathogens of BC, the etiology of SER remains understudied. From 2018 to 2022, healthy-looking fruits and symptomatic branches were collected from twelve 'Hass' groves across seven Peruvian regions. Lasiodiplodia spp. were frequently isolated, detected in 86.4% of SER samples and 95.4% of BC samples. Morphological and multilocus phylogenetic analyses identified L. theobromae (n = 374), L. pseudotheobromae (n = 113), L. laeliocattleyae (n = 42), L. brasiliensis (n = 4), Lasiodiplodia sp. (n = 1), and L. euphorbiaceicola (n = 1). Koch's postulates were fulfilled for all six species on inoculated Hass fruits using isolates obtained from SER and BC samples, with controls remaining symptomless. Pathogenicity was also confirmed for five species recovered from BC samples on stems of 1-year-old trees. Aggressiveness varied significantly among isolates, suggesting isolate-specific virulence. This study represents the first report of L. theobromae, L. pseudotheobromae, L. laeliocattleyae, L. brasiliensis, and L. euphorbiaceicola as causal agents of SER, and of L. brasiliensis and Lasiodiplodia sp. associated with BC of avocado in Peru. These findings provide novel insights into the diversity and pathogenicity of Lasiodiplodia species affecting avocado and highlight the importance of species-level identification to guide disease management.