Identification of Lasiodiplodia pseudotheobromae Causing Leaf Blight Disease of Thaumatococcus daniellii (Benn.) Benth (Sweet Prayer Plant)

Abstract

This study is aimed at isolating and identifying the common fungal pathogens causing leaf blight disease of Thaumatococcus daniellii known as the sweet prayer plant, using the molecular technique. It is a highly nutritional plant, used as laxatives, venom antidote, sedative and in the treatment of diabetes mellitus. Despite its global popularity owing to the usefulness of the leaves in food wrapping and packaging, it has been observed that the plants suffer severe leaf blight disease caused by fungal pathogens. Samples of leaves showing disease symptoms were collected from the Umuakali community in Omuma Local Government Area of Rivers State between June 2021 and October 2022. Fungal isolates were collected from leaves and morphologically identified. The DNA of the most common fungal isolate, SPP-01, was molecularly characterized using Internal Transcribed Spacer 1 (ITS-1) molecular markers. Sequences obtained were subjected to BLAST search in the GenBank database. The morphological results indicated that the SPP- 01 isolate was a Lasiodiplodia species. The molecular weight of the DNA of the isolate was over 550 Base Pairs. Based on sequence similarity, the DNA sequence of the isolate was 99% identical to Lasiodiplodia pseudotheobromae. A pathogenicity test of the isolated pathogen was carried out. Therefore, these findings showed that L. pseudotheobromae is the causal fungal pathogen of leaf blight disease of the sweet prayer plant. It is expected that this finding will promote the acquaintance of the fungal species associated with the sweet prayer plant and provide information for developing an effective disease management strategy for mitigating the losses caused by L. pseudotheobromae and also provide the basis for further study of potential mycotoxin effect of consuming disease leaves. To the best of our knowledge, this is the first report of molecular characterization of L. pseudotheobromae infesting sweet prayer plant in Rivers State.