Descending death in soursop ( Annona muricata L.) caused by Lasiodiplodia theobromae in Nayarit, Mexico

The study consisted of identifying the causal agent of branch dieback in soursop in the municipalities of Compostela and San Blas, Nayarit, Mexico. Lasiodiplodia is a poorly studied pathogen regarding its pathogenicity and hosts in Mexico, reaffirming the need for studies involving morphological and genetic characteristics of Lasiodiplodia, especially due to the association with a complex of cryptic species. From the tissues of soursop showing apparent symptoms of dieback, 9 isolates were obtained with morphological macro and microscopic characteristics typical of Lasiodiplodia . Universal primers ITS4 and ITS5 allowed the molecular identification of Lasiodiplodia species, including L. theobromae (6 isolates), L. pseudotheobromae (1 isolate), L. venezuelensis (1 isolate), and L. iranensis (1 isolate). The pathogenicity of the L. theobromae isolate (4To2) was confirmed, marking the first report in Mexico for soursop cultivation, confirmed through molecular techniques. Its identity was corroborated by sequencing TEF1a using primers EF -728F and EF -986R. The isolated strain induced leaf wilting, branch death, and necrotic lesions in vegetative apices.