Food legumes provide high quality protein at low cost. During growth these crops fix nitrogen and reduce inoculum build-up of cereal diseases. Chickpeas, faba beans and lentils are important in West Central, South and East Asia and North Africa. Diseases, however, are a major constraint to productivity and despite recent improvements further yield increases and greater sustainability of production are possible. Diseases, biology and host resistance will be examined through germplasm screenings to help identify new sources of disease resistance. This will also inform the development of disease management packages to be evaluated in farming systems. Benefits from better disease resistance and disease management technologies for lentil, chickpea and fababean will flow into the ACIAR mandate region in two main ways. ICARDA has many networks and collaborative projects for improvement of these crops in Asia and distributes better technologies and the products of its breeding programs to Afghanistan, Bangladesh, Bhutan, China, India, Korea DPR, Korea Rep, Nepal, Sri Lanka, Thailand, Vietnam. Benefits will also flow to Asia from a range of ACIAR projects which involve pulse improvement in Nepal, China, Bangladesh, India, Afghanistan and Iraq.
Several new resistant sources to major diseases affecting pulse crops were identified at ICARDA and will be shared with the Australian and other national breeding programs.
Australian pulse varieties and advanced breeding lines have been exposed to potential pathogen diversity. This permitted a pre-emptive screening of Australian lines for diseases not yet encountered in Australia such as chickpea and lentil Fusarium wilts. Efforts have been deployed by Australian breeding programs to improve the levels of resistance to major diseases prevailing in Australia.
A glasshouse screening method has been developed (University of Adelaide and SARDI) for an emerging faba bean leaf disease in southern Australia, Cercospora leaf spot. The method has enabled the identification of resistant breeding lines.
Different isolates of the main pathogens affecting chickpea and faba bean were tested for their pathogenicity. No isolates were able to overcome the resistance that existed in the respective hosts of the test isolates. However, results did show that there were significant differences in isolate aggressiveness found amongst isolates of A. fabae and B. fabae of faba bean.
Different factors influencing disease development (host plant resistance, fungicides spray (including new ones), sowing date(s) and timing of foliar application) of chickpea Ascochyta blight were studied, both at CLIMA Australia and in Syria, to refine the integrated disease management package identified earlier. This is to ensure cost effective production of chickpea and that the most appropriate chemicals are used only when necessary to avoid their adverse effect on the environment. Foliar sprays at 4 and 7 weeks after emergence were found essential to protect chickpea Kabuli (Flip 503 CLIMA, Flip 530 CLIMA and Flip97-537D CLIMA) and desi tolerant lines (FLIP 97-504 C) from chickpea Ascochyta blight. Two timely foliar sprays with Chlorothalonil were found more effective than 3 Mancozeb foliar sprays. Similar results were obtained at Tel Hadya, Syria, One single spray with chlorothalonil and or Ortiva, 6 weeks after emergence, was sufficient to contol the disease on the tolerant cultivars (Ghab 3 and Ghab 4). However, the susceptible cultivars (ILC 263 and Ghab 1) required 3 foliar sprays to control the disease.
To achieve the cheapest fungicide management program, chickpea growers must also observe other aspects of the crop establishment package. That is, selecting a paddock that is remote from where chickpeas were grown in the previous year (both on their own and their neighbours' properties) and which has not grown chickpeas for at least 3 years, then sowing during the recommended time determined by yield and disease risk considerations.
Environmental conditions and proximity to faba bean stubbles were found to be linked with the amount of A. fabae isolated from lesions on trap plants. Results showed a strong correlation between cumulative spore release and cumulative rainfall.
A very strong correlation was evident between foliar infection in faba bean and seed discoloration scores due to Ascochyta blight. Of particular interest is the proportion of lines with very low scores for both foliar and seed infection.
Experiments showed that the critical period for chocolate spot infection in faba bean occurred 6 to 9 weeks after sowing and that disease expression from these infections may not occur until after flowering. This finding is very important for timing the protective sprays against this disease.
Results related to the timing of ascospore release for chickpea Ascochyta blight will be used to further refine and validate the "Chickpea Blight Appraisal" model. The concept of this model is to provide growers with a prediction of when ascospores showers are likely to occur, so that time of sowing and fungicide spray applications can be optimized to reduce the risk of yield limiting levels of chickpea Ascochyta blight.
Seed testing for infection and discoloration by Ascochyta lentis has identified lentil breeding lines with resistance to pod and seed infection equal to or better than 'Northfield" (ILL5588). These include the lines 98-014L*00H050, CIPAL412, 97-004L*00H021, 97-021L*00H007 and 94-009L*99H158. This is very encouraging for the development of lentil cultivars with "dual resistance" to both Ascochyta lentis and Botrytis spp, thus requiring little need for protection by foliar fungicides.
Several additional new sources of resistance to major diseases affecting pulse crops were identified at ICARDA and will be shared with the Australian and other national breeding programs.
Additional Australian pulse varieties and advanced breeding lines have been exposed to exotic pathogens and diverse pathogen populations. This permitted pre-emptive screening for diseases not yet encountered in Australia such as chickpea and lentil Fusarium wilts.
Efforts were made by Australian breeding programs to improve the levels and deployment of resistance to major diseases prevailing in Australia.
At ICARDA, over 200 isolates of A. fabae were collected in Syria, single-spored, characterized morphologically, and are currently being analyzed using molecular markers
A refined methodology for efficient screening of chickpea for resistance to Ascochyta blight was developed at ICARDA, using alternative sources of inoculum and different inoculation timings
Three emerging new diseases (Stemphylium blight in lentil, Cercospora leaf spot and Tomato wilt spotted virus in faba bean) are under investigation in Australia. Chickpea Fusarium wilt and cyst nematode are gaining importance in Syria
The work at the University of Adelaide and SARDI explored options for the management of the new emerging disease on faba bean, Cercospora leaf spot, including the identification of resistant breeding lines.
The work at CLIMA continues to improve the IDM package for the control of chickpea Ascochyta blight
Screening of lentil and chickpea germplasm for resistance to Botrytis grey mould at DPI-Horsham in 2005 revealed a wide range of reactions to Botrytis grey mould. Results were encouraging with the breeding of Botrytis grey mould resistant lines expected in the near future. Lines having the Canadian cultivar "Indianhead" as a parent appeared to be most resistant to infection by Botrytis spp
Evaluation of diverse germplasm and breeding materials at ICARDA led to the identification of new sources of resistance to major diseases affecting chickpea, faba bean and lentil. These new sources of resistance will help diversify the existing pool of resistant germplasm and will be shared with Australian and other national breeding programs.
Australian pulse varieties and breeding lines continued to be exposed to exotic pathogens and diverse pathogen populations at ICARDA. This permitted pre-emptive screening for diseases not yet encountered in Australia such as a new A. rabiei pathotype variant (to which all Western Australian lines tested were susceptible), and chickpea and lentil Fusarium wilts. Comparative analysis of pulse pathogen populations in Australia and Syria is warranted to ensure that future pre-emptive screening targets the diversity of pathogen populations (races, pathotypes, etc) that are exotic to Australia.
At ICARDA, pathotype and molecular analyses of Syrian A. fabae populations revealed high pathotype diversity, the presence of complementary mating types (MAT1-1 and MAT1-2) in most fields (and on single infected leaves), and high genotypic diversity of the pathogen. This contrasted sharply with the low level of Ascochyta blight resistance in Syrian faba bean landraces. AFLP markers were identified that are useful for population level analysis of A. fabae.
Australian breeding programs continued to improve the levels and deployment of resistance to major diseases prevailing in Australia (e.g. chickpea and faba bean Ascochyta), including multiple disease resistance, as is the case with combined resistance to faba bean chocolate spot and Ascochyta blight diseases.
Studies were initiated at ICARDA towards the development of an integrated package for the management of faba bean Ascochyta blight under Syrian conditions. The package combines host resistance (new disease-resistant multi-lines), sowing date and limited fungicide application.
A new damaging disease of chickpea (Verticillium wilt) is currently being investigated at ICARDA. Chickpea Fusarium wilt and cyst nematode continue to gain importance in Syria
The University of Adelaide and SARDI screened the faba bean germplasm obtained from the Vavilov collection for sources of resistance to Ascochyta blight. Considerable variation was observed in the response of accessions to the disease, ranging from moderately resistant or resistant through to very susceptible.
The work at CLIMA involved evaluation and development of a robust, but economic, disease management package for improved varieties, including epidemiology research to validate the "Chickpea Blight Appraisal" model, which will provide growers with a prediction of when ascospore showers are likely to occur.
The 2006 season was the driest on record for most of Australia's agricultural regions and followed a summer that was also very dry. Consequently experimental and commercial fields suffered and relatively little disease was observed.
Screening of lentil and chickpea germplasm at DPI-Horsham in 2006 for resistance to Botrytis grey mould (BGM) was successful and lines were identified with a wide range of reactions to BGM. Results were encouraging with the selection of advanced breeding lines within CIPAL (Coordinated Improvement Program for Australian Lentils) germplasm, which showed improved resistance to both Ascochyta and Botrytis infection.
Links:
[1] http://www.aciar.gov.au/country/Bangladesh
[2] http://www.aciar.gov.au/iarc/International Centre for Agricultural Research in the Dry Areas
[3] http://www.aciar.gov.au/programarea/Crop Improvement and Management