Phytophthora capsici is one of the top ten oomycete plant pathogens infecting a wide range of economically important crops. P. capsici was first reported to infect chile pepper (Capsicum annuum L.) in New Mexico Agricultural Research Station in Las Cruces, NM, and is currently a major threat on chile pepper production worldwide. The pathogen affects multiple plant parts at all stages of growth leading to death and significant economic losses. The diseases caused by P. capsici are difficult to eliminate which can be attributed to its broad host range, complexity of the inheritance of disease resistance, its global distribution, and diversity of the pathogen population. This study aims to analyse global distribution and diversity of P. capsici isolates infecting different hosts including Cucumis sativus, Cucurbita pepo, Capsicum annuum, Cucurbita maxima, Piper nigrum, Solanum lycopersicum, and Theobroma cacao by examining mitochondrial genes (secY, cox2, nad9, rps10) using Clustal Omega. Phylogenetic analyses based on different mitochondrial genes revealed diversity of P. capsici isolates. Based on secY, cox2, and nad9 genes, clustering patterns are found based on both the host from which they were isolated from and their geographical origin, while for rps10 gene, most of the isolates are found in one cluster. Notably, a separate analysis focusing on P. capsici isolates collected from C. annuum showed five isolates from South Korea (P15103, P1514, P15157, P15160, and P15161) clustered together, as did three isolates from New Mexico (P10199, P1091, and P3605). Similarly, isolates P10736 and P3941 from China, along with P15155 and P6741 from South Korea, consistently clustered together across all four genes analyzed. Future genetic diversity studies will include analysing the pangenome of P. capsici isolates from Texas, Florida, Arizona, Illinois, New Jersey, and New Mexico, USA; and screening of C. annuum recombinant inbred lines using different isolates with varying levels of virulence. Understanding genetic makeup of isolates may provide insights of their pathogenicity. Meanwhile, the results of screening of C. annuum recombinant inbred lines will aid in understanding the inheritance of disease resistance. Altogether, these approaches can contribute to the development of more effective and sustainable disease management strategies against P. capsici.
