Pulse crops (food legumes) are the second most planted crops in Bangladesh after rice, reflecting the importance of pulses as a source of protein in Bangladeshi diets. The dominant pulse crops are lathyrus, lentil, chickpea, black gram and mungbean, and the Gangetic Plain in the country's west is the main area of pulse cropping. But cereals yield better, and pulse crops grown in similar conditions do not reach their potential.
Chickpea in particular is important, providing a high-level source of protein (21.7%) along with complex carbohydrates, dietary fibre, unsaturated fats and essential vitamins and minerals. Yet chickpea yields have fallen below expectation while demand remains at a constant high. Much excess demand is met from imports rather than domestic growth-between 1995 and 1999 FAO reported imports of chickpea rose by more than 50,000 tonnes.
The decline in chickpea production is due largely to a single factor - the foliar disease Botrytis Grey Mould (BGM). Epidemics of BGM have reduced yields, leading to shortfalls in seed supplies. The lack of control against BGM has eroded farmers' confidence in planting chickpea. In Australia similar outbreaks of BGM have the potential to become epidemics. Known treatments - seed dressings and multiple fungicide applications - can control BGM but are too expensive for Bangladeshi farmers and unsustainable in Australia. Another form of control is needed, and an integrated disease management (IDM) approach offers the best strategy for both countries.
The project aimed to better manage outbreaks of BGM and thus increase yield of chickpea and stability of yield over seasons, by optimising its cultivation in traditional chickpea-growing areas of Bangladesh and focusing both in Bangladesh and Australia on the implementation of integrated disease management (IDM) strategies.
The project team assembled and screened a wide range of chickpea germplasm against BGM under field conditions at sites in Bangladesh and Nepal where there is reliable disease pressure. The scientists collected Botrytis cinerea isolates for glasshouse screening and molecular studies, and sought to confirm that resistance is transferable by screening promising lines under Australian conditions. They also compared suitability of lab and field screening techniques for use in genetic enhancement.
Tasks included establishing seed-testing protocol for BGM infection and bulking up of seed for the High Barind Tract of Bangladesh, also producing and distributing to farmers in Bangladesh the seed of chickpea germplasm with less BGM susceptibility. The scientists worked to establish village-level seed production in BGM-prone areas of Bangladesh, and undertook operational-scale comparisons of ICM treatment including BGM management implemented within traditional farming practices.
The project team sought to fine-tune and demonstrate (on-farm) integrated disease management packages in Bangladesh and Australia, and to train Bangladeshi scientists in recently evolved on-farm research and development techniques, foliar disease resistance screening and breeding.
Field screening to identify chickpea lines with resistance to BGM took place in Bangladesh over four seasons. Nearly 500 genotypes were screened in 2002-03, 208 in 2003-04, 200 in 2004-05 and 281 in 2005-06. From the second season onwards, entries comprised promising selections from the previous season and some new entries. Field screening was also carried out at the BGM-endemic site of Tarahara, Nepal, in 2002-03, but further screening was discontinued due to the security situation there.
There were clear differences in reaction to BGM, as measured on a 1 to 9 rating scale at each location in all seasons. Apart from the first season, there was a reasonable correlation (negative) between disease score and seed yield. Some lines with moderate levels of resistance were identified, with a consistent reaction across sites and seasons.
Screening for BGM resistance under controlled environment conditions proceeded from 2003-04. At ICRISAT in India, one-quarter of those screened were rated 'moderately resistant' but none as 'resistant'. The same set of entries was also screened for Ascochyta blight resistance and 51 were rated as 'resistant'. There was no clear correlation between BGM resistance and Ascochyta blight resistance, but nine lines were identified as relatively resistant to both diseases in both seasons.
In 2003-04 138 genotypes were screened for BGM resistance in a glasshouse at Horsham in Victoria, under a similar protocol to ICRISAT. Resistance ratings at Horsham were not consistent with assessment elsewhere, in field screening in Bangladesh or in the growth room at ICRISAT. Nevertheless, it was possible to identify eight lines with relatively greater resistance in both growth room and field.
Isolates of Botrytis cinerea were collected in Bangladesh, India, Nepal and Australia and subjected to PCR-based microsatellite DNA analysis. For the Bangladesh isolates, there was a high degree of variation within subpopulations and the total population, indicating a high adaptive potential of the fungus to chickpea. This suggests that multiple resistance genes and mechanisms will be required if durable resistance is to be achieved. Environmental conditions restricted sampling in Australia, thus the extent of genetic variability of the fungus in Australia, and the degree of similarity between Australian and Bangladesh populations, is not yet established.
A seed infection and germination test for assessing chickpea seed for infection with Ascochyta rabiei in Australia was also found suitable for Botrytis cinerea. This protocol was demonstrated to Bangladeshi scientists visiting Australia in 2005; it was later evaluated by staff at one of the BARI On-Farm Research Division offices prior to the 2005-06 growing season.
A series of on-farm trials was conducted in Bangladesh in order to evaluate various components of disease and crop management under farmers' conditions and merge them with the evolving integrated crop management (ICM) package for chickpea. On-farm variety evaluations were conducted to determine farmers' preferences for varietal characteristics, as a guide in developing future BGM-resistant varieties.
From the 2002-03 season ICM packages incorporating best-bet technologies for BGM management along with other optimum agronomic packages, were assembled and tested in farmer-managed operational scale plots (666 m2) and compared with adjacent plots where prevailing farmers' practice was followed. Yield increases in five districts due to ICM were around 20-50%. The same degree of response to ICM was found from evaluations in 2003-04. In three additional districts the yield response was 30-60% increase. Follow-up demonstrations during 2004-05 resulted in district mean yields that exceeded 1 tonne per ha, making chickpea very competitive with other cropping options for the Rabi (winter) season.
Links:
[1] http://www.aciar.gov.au/country/Bangladesh
[2] http://www.aciar.gov.au/programarea/Crop Improvement and Management