Fungi Causing Anthracnose and Foliar Blight in Plumeria spp. in Mexico

Frangipani (Plumeria spp.: Apocynaceae) is a small ornamental tree native to Mexico, susceptible to significant diseases such as anthracnose and foliar blight in hot, dry environments. Understanding the diversity of pathogens responsible for these diseases is crucial for developing effective disease management strategies. This study aimed to identify the pathogens responsible for these diseases. In February 2020 and 2021, symptoms of anthracnose and foliar blight were observed on frangipani plants in recreational areas of Morelos and Sinaloa, Mexico. Isolations from diseased leaf tissue resulted in the recovery of 12 Colletotrichum isolates from P. rubra and 18 Alternaria isolates from P. obtusa. After morphotype grouping, a representative isolate from each group was identified by morphology and phylogenetic reconstruction (ITS, act, gapdh, rpb2 and tef1) as Colletotrichum karstii, Colletotrichum siamense, Alternaria destruens and Alternaria burnsii. For pathogenicity testing, a conidial suspension was sprayed onto the leaves of 90-day-old plants, while control plants were sprayed with sterile distilled water. All inoculated fungi were pathogenic, reproducing the characteristic symptoms of the disease, while control plants remained symptomless. The fungi recovered from symptomatic plants were morphologically identical to the inoculated fungi, fulfilling Koch's postulates. This is the first report of A. burnsii and A. destruens causing foliar blight in P. obtusa, and C. siamense and C. karstii causing anthracnose in P. rubra. These findings contribute valuable insights for developing effective disease management strategies.