Trends in host plant resistance for the control of insect crop pests

VICKI TOLMAY, ARC-Small Grain Institute

During April this year, the International Plant Resistance to In sects Workshop, also known as IPRI, was held in Marrakech, Morocco.

It was the 21st biennial workshop, which is a specialised forum for agricultural researchers who use host plant resistance for the control of insect pests. The 2014 meeting was organised by the Institut National de la Recherche Agronomique (INRA), the Association Marocaine de la Protection des Plantes (AMPP), the International Plant Resistance to Insects Working Group (IPRI) and the International Centre for Agricultural Research in the Dry Areas (ICARDA). This workshop is seen as the most important forum for the exchange of information on host plant resistance to insects in the world.

Approximately 100 participants from 36 countries (from the continents of Asia, Africa, Europe, America and Australia) attended the three day long workshop. A special emphasis was placed on host plant resistance to hessian fly, with several awards being given to researchers working on the control of this pest. Hessian fly is a very severe pest of wheat, which occurs in many wheat producing regions of the world, but is luckily not found in South Africa.

Russian wheat aphid was also one of the prominent pests that were discussed. This aphid occurs in all wheat producing regions of the world, except Australasia. In South Africa, new biotypes of Russian wheat aphid have overcome all but three of the commercial cultivars, and breeders are now making use of novel and effective resistance genes found within collections of bread wheat lines kept in special germplasm banks throughout the world.

Seven presentations were made on Russian wheat aphid research conducted in South Africa. Five studies were conducted by students and staff at Stellenbosch University while the other two presentations highlighted research from the ARC-Small Grain Institute and Rhodes University.

The use of natural resistance from the host plant species to control insect pests is a safe and very environmentally responsible method of pest control. The most obvious benefit is that producers save millions because they do not need to use pesticides to protect their crops. Additionally, in regions where cropping is influenced by climate change and shrinking profit margins, these resistant crops are very valuable.

Crops relating to food security, like wheat, maize, rice and grain legumes featured prominently in the discussions. No less than four major pests of wheat are currently controlled using host plant resistance, namely Russian wheat aphid, hessian fly, greenbug and sunn pest.

Information was however not limited to these crops, with presentations being made on insect resistance in vegetable crops such as tomato, paprika and cabbage, fruit crops such as citrus and even thrips resistance in chrysanthemum flowers.

Most research currently being done can be categorised into the following four research areas:

Biotechnology: Molecular markers

A lot of research funding is currently being directed towards the use of biotechnology and particularly the use of molecular markers to follow resistance whilst speeding up the breeding process.

Biotechnology: Metabolomics

Many efforts are being focused on understanding the exact processes within the plant that cause it to be resistant. The chemical processes involving metabolites within the plant cells are studied using advanced technologies in order to understand which genes are being activated to protect the plant from insect attacks.

Biotechnology: Biotype characterisation

Modern DNA-technology is being utilised to tell the difference between biotypes of the same species of pest insect. A biotype is a strain of the original species that differs in its ability to injure resistant plants. The formation of resistance breaking biotypes is the biggest challenge facing the use of host plant resistance for pest control.

Focused exploitation of germplasm collections

Germplasm collections around the world contain thousands of wild relatives of crop species and it can be quite problematic for researchers to identify the lines that have natural resistance to the pests, in among all the others. The latest way of overcoming this problem is to focus attention on only the lines that come from regions where the pest insect endemically occurs, as lines from these areas have the highest chance of being resistant.

The next IPRI Workshop will be held in 2016 in Cape Town.