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North-West University (2020)

Characterization of wheat nematodes from cultivars in South Africa

Lamula, Siphamandla Qhubekani Njabuliso

Titre : Characterization of wheat nematodes from cultivars in South Africa

Auteur : Lamula, Siphamandla Qhubekani Njabuliso

Université de soutenance : North-West University

Grade : Doctor of Philosophy in Environmental Sciences 2020

Résumé partiel
Plant-parasitic nematodes (PPNs) naturally live in soil and attack small roots, but some species inhabit and feed in bulbs, buds, stems, leaves, or flowers. This leads to plant weakness and they often appear to suffer from drought, excessive soil moisture, sunburn or frost, as well as mineral deficiency or imbalance. According to the South African Plant-Parasitic Nematode Survey (SPPNS) and National Collection Nematodes (NCN) databases, 453 plant-feeding nematodes have been recorded in South Africa and species identified from wheat have not been included on the database as a result of not being georeferenced and the need to update information on NCN database. The aim of the current study is to characterize and document wheat nematodes that occur in South African wheat producing areas with an emphasis on morphological and molecular identification. A total of 776 composite rhizosphere soil and root samples was collected from 56 localities over two seasons in 7 provinces ; the Free State (FS), KwaZulu-Natal (KZN), Northern Cape (NC), Mpumalanga (MP), Limpopo (L), North West (NW) and Western Cape (WC) provinces. The majority of samples collected were in WC (452), FS (120) and NC (160), as these are the major producers of wheat in South Africa. Nematodes were extracted from soil and root samples by modified decanting and sieving baermann-funnel technique, followed by the adapted sugar centrifugal-floatation. Nematodes were extracted from kernels by means of soaking the samples in tap water for 24 hours and decanting the extract through a 20 μm sieve. Nematode species were identified basis on morphological features, while prominence values (PV), frequency of occurrences and abundances were calculated for each genus. Individuals from the following genera were identified from the following provinces : Free State : Pratylenchus, Spiral (Rotylenchus, Scutellonema and Helicotylenchus), Criconema and Dolichodorus ; KwaZulu-Natal : Melodogyne, Pratylenchus, Criconema, Helycotylenchus (Spiral) and Longidorus ; Northern Cape : Pratylenchus, Criconema and Spiral ; Western Cape : Pratylenchus, Rotylenchus, Scutellonema, Helicotylenchus, Coslenchus, Tylenchus and Xiphinema.

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