Leaf blight in maize has complex causes
but can be combated

Prof Olubukola Oluranti Babalola

Leaf blight in maize poses a threat to food security but, although it has complex causes, it can be effectively managed. This is one of the findings of a group of NWU researchers who have been investigating this plant disease at the university's Molelwane farm in Mahikeng.

Their research shows that the disease defies many control measures because it is caused by multiple organisms, which in most cases interact to cause the leaf blight disease. That said, certain methods, specifically the use of bismuth sulphide nanoparticles, appear to be more effective in managing the disease.

The research team comprises principal investigator Prof Olubukola Oluranti Babalola, Dr Akinlolu Akanmu, a postdoctoral scientist, and Masego Seleke, an honours-degree student from the Laboratory of the Microbial Biotechnology Group in the Faculty of Natural and Agricultural Sciences.

Commenting on their finding on the effectiveness of bismuth sulphide nanoparticles in managing the disease, Prof Babalola says field trials are ongoing. If successful, the study could be recommended for broad-spectrum control of leaf blight diseases in maize.

Maize, a cereal crop, has an important dietary value in South Africa, she says.

"Despite the management practices to ensure adequate cultivation, some diseases, such as corn leaf blight, persist in the maize-growing area, causing a significant reduction in yield quality and quantity. The occurrence of this disease in maize plantations at the university farm, Molelwane, awakened the interest of researchers to investigate the disease."

The researchers' quest is to understand the reason for the persistence of these devastating diseases despite the management programme in place. Their investigations include examining the variations in the microbial diversities between diseased and healthy maize plants, focusing on the corn leaf blight disease on maize.

Upon investigation, using both morphological and molecular protocols, the disease was discovered to be caused by different fungal genera, ranging from different species of Diothidiomycetes, Epicoccum, Fusarium, Tiasrosporella, Eutiasporella, Bipolaris, Alternaria, Nigrospora and Phoma. "This confirms that multiple organisms cause the disease," Prof Babalola says.

The most harmful of these organisms are Bipolaris zeicola, Phoma herbarum, Epicoccun nigrum, Alternaria alternata and Fusarium brachygibbosum. They were subjected to in vitro control using nanoparticles of bismuth sulphide and graphitic carbon nitrides, synthesised by Timothy O Ajiboye, a postgraduate student from the NWU's subject group Chemistry.

A nanoparticle is a small particle ranging in size from 1 to 100 nanometres. It is specially prepared from the active ingredient of the source materials used to enhance its efficiency. The use of nanoparticles was considered essential since the disease has persisted across various management practices, from cultural to chemical control.