Host resistance, epidemiology and integrated management of faba bean, chickpea and lentil diseases

• University of Adelaide, Australia
• Department of Agriculture, Western Australia, Australia
• NSW Department of Primary Industries, Australia
• Agriculture Victoria, Australia

Improved management of faba bean, chickpea and lentil diseases is vital for yield improvement and sustainability in production systems in many developing as well as developed countries. These food legumes (pulses) are an integral and important component of cereal cropping systems, due to their capacity to incorporate atmospheric nitrogen into the soil - a process that benefits the legumes and subsequent crops. Rotation of cereals with legumes also provides a disease, insect and weed break for cereal crops, and reduces the use of pesticides and nitrogen fertiliser.

Over the last decade, new varieties of legume crops emanating from collaborative work between ICARDA and national agricultural research systems in South Asia, China and West Asia/North Africa (WANA) have opened up new cropping areas and increased production. Production has also increased in Australia. However, recent epidemics of certain fungal diseases affecting the leaves of these pulses have led to heavy crop losses. This project brought together experts from around the world to gain a better understanding of the most important fungal diseases of pulses and how to manage them.

The major objectives of the project were to study aspects of the epidemiology of major fungal diseases affecting cool-season food legumes in South Asia, China, WANA and Australia; also to study and characterise the variability of the pathogens causing these diseases and to evaluate legume germplasm and breeding materials with the aim of finding sources of resistance to the above-mentioned diseases. The final objective was to develop and refine integrated disease management technologies then promote their use with farmers.

The studies took place under laboratory, plastic house and field conditions to fill in missing critical information on factors affecting the distribution, development and spread of these diseases. Scientists determined variability in virulence of pathogen populations on a range of host varieties and evaluated germplasm, including breeding lines of faba bean, chickpea and lentil originating from the ICARDA/Australia project, for disease resistance and adaptation. They also initiated the development of computer-based simulation models of epidemics to improve disease forecasting and to use as decision-support tools for disease management (e.g. methods and timing of fungicide application).

The Ascochyta pathogen causing blight of chickpea and lentil was known prior to the project, but it was unclear how this pathogen was transferred. Epidemiological studies revealed that the pathogen is harboured on crop stubble left from the previous season, after exposure to cold, moist conditions. Winter chilling requirements for the fungi suggest that cool autumn conditions (below 10C) will begin this process.
Management control strategies have been developed, in part through computer simulations of different temperature and rainfall interactions. These strategies included spraying with agents to control the pathogen at an earlier time when autumn conditions are colder and suitably moist. Proper crop hygiene and rotation are also important, even when conditions do not favour the pathogen. An integrated disease management package developed for controlling chickpea Ascochyta blight was tested on farmers fields in Syria (through ICARDA), and early results indicate the package is effective.
Several national programs are promoting an Ascochyta management package, based on two strategically timed fungicide applications to chickpea varieties with improved resistance. In varietal tests the researchers were able to identify good resistance to most pulse diseases. They also identified lines of faba bean with combined resistance to Ascochyta blight, chocolate spot, Cercospora leaf spot and some viruses, and chickpeas with resistance to Ascochyta blight and vascular wilt. This should lead to the development of new disease-resistant pulse varieties within a decade.
New Kabuli chickpea lines with improved resistance and yield were scheduled for release in 2004 and 2005. Researchers also identified some resistance to Botrytis Grey Mould in lentil. Faba bean varieties with resistance to chocolate spot, Ascochyta blight, rust and root rot, and lentil lines with resistance to Ascochyta have also been identified in Australian trials. New lines of faba bean resistant to Ascochyta blight and chocolate spot have been released, and good levels of wilt resistance were identified in some commercial lines available in Australia. But more work is needed for chickpea.