Identification of Macadamia integrifolia Leaf Blight Disease Caused by Pestalotiopsis colombiensis in China.

Abstract

Macadamia integrifolia, a tropical and subtropical fruit tree with significant economic and nutritional value, faces serious fungal disease problems during cultivation that severely affect yield and quality. In November 2024, leaf blight symptoms of M. integrifolia were observed in Menglian, Pu'er, Yunnan, China, with a disease incidence of 23% in the field. Initial symptoms included small spots that enlarged into circular to irregular lesions with red-brown centers and brown to black margins. Finally, the leaves turned yellow and became scorched, eventually leading to massive leaf shedding. Infected leaf samples were collected, and fungal strains were isolated, purified, and inoculated via spore suspension, followed by re-isolation. The strains were conclusively identified as Pestalotiopsis colombiensis (SWFUCB2, SWFUCB1) through an integrated approach combining DNA extraction, polymerase chain reaction (PCR), sequencing, phylogenetic reconstruction, and morphological characterization. This is the first report of P. colombiensis causing M. integrifolia leaf blight disease in China, filling a gap in research on this disease. This study provided important information for epidemiological research on this disease and the development of comprehensive leaf blight disease control strategies.