Maize Lethal Necrosis Disease
Maize is the most important crop in sub-Saharan Africa and South. Maize Lethal Necrosis Disease (MLND) is a disease that has caused crop losses of up to 90%-100% in African countries such as Kenya and Tanzania and also various areas in the US. MLND is formed by a double infection of Maize Chlorotic Mottle Virus (MCMoV) and any poty virus from the Potyviridae group. The disease is spread by vectors such as thrips from one plant to another. Besides crop loss, symptoms associated with MLND include dying leaves which leads to premature plant death, failure to tassel and sterility in male plants, and cobs which are malformed or rotting.
Currently, MLND does not occur in South Africa, however various poty viruses and vectors that has been associated with the virus does occur in SA. To ensure the necessary precautions can be taken to prevent this disease of causing a severe food security risk in South Africa, SANSOR is currently funding research together with the Maize Trust to evaluate the risk of MLND entering and spreading in South Africa.
Two surveys are being conducted to evaluate the current risk: Prof Johnnie van den Berg at the University of North West is the study leader conducting a vector survey on all major transport routes in South Africa, while Prof Gerhard Pietersen from the University of Stellenbosch together with Patho Solutions are doing a poty virus survey on the same route. Establishing the different vectors and viruses that is present in South Africa will enable us to establish the correct precautionary measure to ensure food security.
Brassica Stunting Disorder
With an annual global production of 71 million tons, brassica crops are of major importance in the agricultural industry (Faostat, 2016). An estimated total of 149 628 tons of cabbage and other brassicas are produced every year by both commercial and small-scale farmers in South Africa (SA) (Faostat, 2016). Over the last six years, Brassica stunting disorder has emerged as economically relevant disease that represent a permanent constraint to the production of brassica crops in South Africa.
A study of the South African Brassica stunting disease pathosystem
Taking into consideration the severe impact that BSD has had on brassica production since 2012, it was critically important to identify the disease causal agent(s) and its mode of transmission. To this end, a research project was launched in 2014 at the University of Johannesburg to investigate the BSD-pathosystem, with the aim to provide industry with information to develop knowledge-based control strategies.
Symptoms associated with the brassica stunting disease. (A) Severe stunting (circled), (B) flattening of the leaves, (C) purpling of the leaves, (D) poor root development, (E) blackening of the vascular tissue (phloem) and (F) reduced head size and or no head formation depending on time of infection.
The three morphological developmental stages of M. persicae, (A) nymphs and the wingless apterae and (B) the winged alate adult (Coleman, 2013).
The project has been partly or wholly funded by various companies within the South African agricultural Industry, which includes Sakata, Starke Ayres, SGASA, Syngenta, Bayer, McCain and SANSOR.
The key aim of the Brassica Stunting Disease (BSD) research project has been to contribute to a better understanding of the BSD-pathosystem that are affecting brassica crop production in South Africa. The information generated by the project are made available directly to the agricultural industry partners, to enable the development of more effective and integrated control strategies, to mitigate the economic effects of this plant disease and its insect vector.
The way forward
For the past two years (2018-2019) SANSOR have been funding this research project done by Dr Lindy Esterhuizen at the University of Johannesburg. In 2019, the aim of the BSD project will be to investigate the BSD pathosystem further, in order to clarify the exact nature of the causative agents of this disease.
Lepidoptera Insect Rearing Facility
SANSOR recently signed a MOU with the University of Pretoria to establish an insect rearing facility at the Forestry and Agricultural Biotechnology Institute at the University of Pretoria. The MOU’s were signed by Prof Stephanie Burton, DVC Research at UP and Dr Lukeshni Chetty General Manager at SANSOR.
The African stem borer, B. fusca, is the most important insect pest of maize in South Africa and is the target of several plant incorporated protectants (PIPs). In order to understand the potential distribution and spread of resistance in B. fusca to PIPs, an understanding of the extent, structure and spread of the genetic diversity is essential.
Importance to the Agricultural Industry
Understanding such population genetics, diversity and its distribution and spread – between populations on different hosts and different regions – is critical for resistance management and would also be important to understand the relevance of populations used in rearing for resistance screening. In addition, powerful new techniques make it possible to not only understand neutral genetic diversity at a more detailed level, but could aim to explore functionally relevant diversity, such as resistance mechanisms.
Such information would have relevance to deployment of other management options too, including pheromone use, biological control and potential future gene editing of pest populations.