Occurrence of Brown Rot of American Plum Caused by Monilinia fructicola in Missouri

Abstract

Prunus americana (wild plum) is commonly found in Missouri and many other U.S. states from Texas to Massachusetts. In May 2022, P. americana fruits exhibiting brown rot symptoms were observed in Cole County, Missouri. The symptoms include brown rot and mummified fruits. Advanced symptoms include fruits covered with fungal growth. A single-spore isolate (PAM-1) was recovered from fruits showing brow rot symptoms. The PAM-1 isolate cultured on potato dextrose agar (PDA) grew a 100 mm diameter Petri dish in seven days. The colony was off-white to light brown in color, circular, and showed concentric rings. The colony had entire margins and produced abundant conidia on PDA. The conidia ( n = 50) were 12.07 µm long and 7.64 µm wide. The conidia are oblong to lemon-shaped and hyaline. The polymerase chain reaction with ITS1 and ITS4 primers generated 508 bp DNA sequence which showed 100% identity to Monilinia fructicola (GenBank accession nos. FJ515894.1 and EF207419.1). Pathogenicity tests on both wounded and unwounded fruits exhibited similar symptoms. Control fruits did not show any symptoms. Based on the disease symptoms, pathogen morphology, molecular characterization, and pathogenicity test the pathogen was identified as M. fructicola. To our knowledge, this is the first scientific report showing M. fructicola as a causal organism of brown rot of wild plum in Missouri.