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

Avocado (<i>Persea americana</i> Mill.) production in Peru is economically impacted by stem-end rot (SER) and branch canker (BC). While <i>Lasiodiplodia</i> 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. <i>Lasiodiplodia</i> spp. were frequently isolated, detected in 86.4% of SER samples and 95.4% of BC samples. Morphological and multilocus phylogenetic analyses identified <i>L. theobromae</i> (<i>n</i> = 374), <i>L. pseudotheobromae</i> (<i>n</i> = 113), <i>L. laeliocattleyae</i> (<i>n</i> = 42), <i>L. brasiliensis</i> (<i>n</i> = 4), <i>Lasiodiplodia</i> sp. (<i>n</i> = 1) and <i>L. euphorbiaceicola</i> (<i>n</i> = 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 one-year-old trees. Aggressiveness varied significantly among isolates, suggesting isolate-specific virulence. This study represents the first report of <i>L. theobromae</i>, <i>L. pseudotheobromae</i>, <i>L. laeliocattleyae</i>, <i>L. brasiliensis</i>, and <i>L. euphorbiaceicola</i> as causal agents of SER, and of <i>L. brasiliensis</i> and <i>Lasiodiplodia</i> sp. associated with BC of avocado in Peru. These findings provide novel insights into the diversity and pathogenicity of <i>Lasiodiplodia</i> species affecting avocado and highlight the importance of species-level identification to guide disease management.