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University of Limpopo (2021)

Characterisation of mmupudu (mimusops zeyheri) leaf rust in Limpopo Province

Monyela, Shadrack

Titre : Characterisation of mmupudu (mimusops zeyheri) leaf rust in Limpopo Province

Auteur : Monyela, Shadrack

Université de soutenance : University of Limpopo

Grade : M. Sc. Agriculture (Plant Protection) 2021

Résumé partiel
Mimusops zeyheri tree groves made up of seventeen trees collected from communities in Southern Africa were used in this study. The trees had high morphological variations in terms of growth rate, fruit (size and taste) and leaf (shapes and sizes) and their identification was made by communal people from where the trees were collected using their morphological characteristics. Generally, this evergreen tree is drought‒tolerant, salt‒tolerant and highly resistant to root-knot (Meloidogyne spp.) nematodes, along with various other pests. This could probably be attributed to high concentration of latex in aboveground organs. Some typical fungal rust symptoms have been observed believed to be the cause of high leaf abscission in certain groves. Currently, there is no report of leaf rust disease on M. zeyheri plants and the mechanism of resistance to other pests is not documented. The objective of this study was to (i) identify the pathogen associated with M. zeyheri leaf rust symptoms using morphological technique and to (ii) determine levels and types of potential defence chemicals and endophytes in M. zeyheri. Samples of M. zeyheri leaves showing rust like symptoms were collected from University of Limpopo, South Africa (23°53”10’S, 29°44”15’E) during summer in September 2018. Light compound microscope and electron microscope were used in the identification of the leaf rust spores. The species identity of the seventeen M. zeyheri trees that form a grove collection at University of Limpopo was confirmed using internal transcribed spacer (ITS) of ribosomal nuclear DNA. DNA extraction and sequencing was done with the help of Inqaba Biotechnologies. Obtained DNA sequences were aligned using CLUSTALX (2.0), with the phylogenetic tree constructed through the neighbour-joining method (NJM) in MEGA v. 5.1 programme. Evolutionary distances were computed using the Juke– Cantor method. Phytochemicals in leaves were identified and quantified using Liquid chromatography–mass spectrometry (LC–MS) at ARC-VOP. The pustules on the collected leaves contained reddish brown spores. The uredospores were oval and ellipsoidal under a light microscope. The size of spores ranged between 35-37 × 24-26 µm. The cell walls showed bilaminate structures with the outer layer hyaline. The warts were rod shaped with one subequatorial germ pore.

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