Abstract

Media summary

Key words

Chickpea, Botrytis grey mould, screening, breeding, integrated crop management, international collaboration

Introduction

Botrytis grey mould (BGM), caused by Botrytis cinerea, is an intermittent and damaging disease of chickpea (Cicer arietinum L.) in Australia, but is a major impediment to sustained production of chickpea in Bangladesh (Bakr et al 2002). In recent years the area under chickpea production in Bangladesh has declined from about 100,000 ha to 16,000 ha. The future of chickpea production in Bangladesh hinges on the development of an integrated crop management system and BGM resistant cultivars that will allow reliable production in the presence of BGM and insect pests. In Australia, BGM has receded as an economic problem following the emergence of ascochyta blight in the late 1990s as fungicides used to manage ascochyta blight have also controlled BGM. The imminent release of ascochyta blight resistant varieties, coupled with a reduced reliance on fungicides, will again make the provision of an integrated management system for BGM, including BGM resistant cultivars, a high priority.

Crop management practices that can reduce the severity of BGM in chickpea have been demonstrated in small plot trials in Bangladesh, Nepal and north-eastern India (Pande et al 2002). These practices include delayed sowing, wide row spacing, use of erect plant types and mixed cropping. However, there have been limited attempts to develop integrated BGM management packages by combining these various practices on an operational scale in the fields of resource-poor farmers of Bangladesh.

A collaborative project has been established between researchers in Australia, Bangladesh and India with the aim of increasing chickpea production in both Australia and Bangladesh through improved control of BGM. Two major objectives of this project are to search for improved host resistance amongst disparate germplasm sources (including annual Cicer species); and to implement integrated disease management strategies.

This paper discusses progress on two specific components of this international project; the screening of a wide range of chickpea germplasm against BGM; demonstration of integrated disease management packages in Bangladesh through on-farm demonstrations.

Methods

Screening for Botrytis Grey Mould resistance.

Four hundred and seventy six genotypes, including 369 breeding lines and cultivars from Australian breeding programs, were screened in BGM field nurseries at Jessore (23° 03’ N, 89° 10’ W) and Ishurdi (24° 00’ N, 89° 00’ W) in Bangladesh in 2002-03. A sub-set of 60 entries, was also screened in a BGM field nursery at Tarahara (26° 40’ N, 87° 17’ W) in Nepal.

The BGM disease nursery at Ishurdi relied on natural infection of BGM but disease development was accelerated by increasing the humidity through the use of a misting system. Mist was applied for 30 minutes five times per day in February and March. The BGM nurseries at both Jessore and Tarahara were exposed to natural disease development, receiving neither Botrytis cinerea inoculum nor irrigation to elevate humidity. All three BGM screening nurseries were unreplicated due to limited quantities of seed, but the susceptible variety Nabin was repeated after every four test entries to observe disease uniformity across each experiment. Plots were 2 m long and separated from their neighbours by 35 cm, each plot was sown with 25 seeds. All plots in each nursery were scored for BGM on three occasions, the first at the start of flowering, the second and third scores were taken 10 and 20 days later respectively. Plots were scored on a 1 to 9 scale where 1 = no lesions and 9 = lesions common on all plants, more than 75% of canopy dead. Only the final disease score is presented in this paper as it gave the best differentiation between genotypes.

On-farm evaluation of Integrated Crop Management practices.

There were 100 comparisons of “improved practice” (ICM package) compared to “local practice” in selected sub-districts of five districts in Bangaldesh (Jessore, Faridpur, Jhenidah, Magura, Rajbari). At each sub-district paired comparisons were established in side-by-side field scale plots of about 0.06 ha laid out in clusters of five around a village to give dispersed replication. In both improved and farmer practices, seed and fertilizer were hand broadcast (seed rate 50 kg/ha) on undisturbed soil, usually after harvest of transplanted aman (rainy season) rice, mostly between 21 November to 15 December. Seed and fertilizer were incorporated immediately by cross-wise ploughing, usually by bullock or power tiller, and laddering (leveling). For other management practices a set strategy was used for the improved practice treatment and farmers selected the local practise (Table 1).

Table 1. Management details of on-farm evaluations of ICM package.

Results

Screening for Botrytis Grey Mould resistance

Disease development was severe at Tarahara and Ishurdi and no seed was harvested at either site. Moderate disease developed at Jessore. Genotypic variation in disease reaction was shown in all three screening nurseries; however, the very severe disease experienced at Ishurdi meant that few entries fell outside the highly susceptible class (Table 2). Comparison of the 60 genotypes which were tested at all 3 nurseries shows that some genotypes had consistently high scores, while others had generally variable scores that included relatively low ratings at one or more sites compared to the mean of all genotypes (Figure 1). No genotypes had a relatively low score at all sites.

Table 2. Number of entries in five disease reaction classes in BGM nurseries at Tarahara (Nepal), Ishurdi and Jessore (Bangladesh).

Figure 1. Disease reaction (BGM score) for the eight entries having the highest and eight entries having the lowest mean BGM score amongst the common set tested at Ishurdi, Jessore (Bangladesh) and Tarahara (Nepal).

On-farm evaluation of Integrated Crop Management system.

Widespread and severe infestations of BGM resulted from unusually frequent and heavy rain during March and early April. For example, at Ishurdi 99 mm of rain was recorded on 13 days between 11 March and 5 April and at Jessore 153 mm fell on 12 days in the same period. Three of the five replicate village level comparisons are not presented as three or more replicates were abandoned. In all except one of the five replicate village level comparisons, the improved practice plots gave a higher yield (18-194% more) than the local practice (Table 3).

In 11 of the 17 on-farm comparisons where yields from all plots were available, the average yield of both production practices was less than 500 kg/ha. In some comparisons, farmers thinned particularly dense stands in an attempt to slow disease development, however this appeared to have little effect in improving yields due to the continuing wet weather and prolific vegetative growth.

Conclusion

Preliminary screening in disease nurseries in Bangladesh and Nepal has demonstrated genotypic variation in their reaction to BGM. However, variability in the response of genotypes across sites indicates that pathogen variability exits, additionally, the measurement of resistance was difficult with large spatial variability within sites on a scale that could not be adequately corrected by reference to checks. As no genotypes had a relatively low score at all sites a greater diversity of germplasm needs to be evaluated. This data indicates the potential for raising the level of host resistance within otherwise adapted genotypes by pyramiding different genes for resistance. It is clear that under moderate to high disease pressure even the most resistant genotypes likely to be developed in the near future will need a production package incorporating agronomic and chemical options to minimize the disease impact.

Grain yields were invariably higher with the ICM than with the farmers’ local practice, although yields were low overall. It is not clear whether increased yields were due to the effect of the fungicidal spray or greater ability of Barichola 5 (or ICCL 87322), compared with ‘local’ varieties, to form pods under conditions of severe BGM infestation. Where yields of more than 1 t/ha were obtained, in some plots at Bagherpara, Monirampur, Kaliganj and Madhukhali sub-districts, farmers used more than two fungicide and insecticide sprays. Low yields (generally <1 t/ha) with ICM may have been due in part to inadequate training of farmers and project staff which resulted in ill-timed interventions to control both BGM and pod borer. This indicates that there is considerable scope for ICM procedures to achieve higher and more stable yields of chickpea in Bangladesh provided farmers and extension staff receive adequate training in the effective and timely implementation of these procedures. Further screening of the germplasm and demonstrations of improved ICM packages are required and are currently being undertaken. The social and economic impact of improved chickpea ICM packages will be undertaken in the third year of the collaborative project.

Table 3. Mean grain yields (kg/ha) for villages (usually 5 replicated comparisons) of on-farm comparisons of ‘improved’ practice (ICM) with ‘local’ practice in sub-districts within five districts of Bangladesh, 2002-03 season.

Probability of significant treatment difference according to a two-tailed "t" test.

ICCL 87322 instead of Barichola 5 was used in the ICM treatment.

Acknowledgements

We acknowledge the financial support from the Australian Centre for International Agricultural Research (ACIAR). We also acknowledge the Australian Coordinated Chickpea Improvement Program (ACCIP), Bangladesh Agricultural Research Institute (BARI), Centre for Legumes in Mediterranean Agriculture (CLIMA), ICRISAT (India) and the Department of Agriculture Western Australia for their collaboration.

References

Bakr, M.A., Hussain S.A., Afzal M.A. and Rahman M.A. 2002 Chickpea status and production constraints in Bangladesh. In: Bakr, M.A., Siddique, K.H.M., Johansen, C. (Eds.). Integrated management of botrytis grey mould of chickpea in Bangladesh and Australia. Summary Proceedings of a Project Inception Workshop, Bangladesh Agricultural Research Institute, Joydebpur, Gazipur, Bangladesh, June 2002, pp19-32

Pande S., Singh G., Rao J.N., Bakr M,A,,Chaurasia P.C.P., Joshi S., Johansen C., Singh S.D., Kumar J., Rahman M.M. and Gowda C.L.L. 2002. Integrated management of botrytis grey mould of chickpea. Information Bulletin No. 61, International Crops Research Institute for the Semi-Arid Tropics, Patancheru 502 324, Andhra Pradesh, India.