SATrends Issue 36                                                                                                                   November 2003

ICRISAT’s Transgenic Pigeonpea

1. ICRISAT’s Transgenic Pigeonpea
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ICRISAT has achieved another global first in agricultural research. Field trials have been launched for genetically modified pigeonpea resistant to a major insect pest, the legume pod borer (Helicoverpa armigera).

 Adult Helicoverpa trying their best to attack the pigeonpea.
How important is this pest? The pod borer was responsible for 50% of all pest-induced losses for all crops in India during the 1997/98 cropping season. Crop losses to pod borer cost the country $475 million, despite the use of insecticides worth $211 million. Researchers have recognized that host plant resistance is the most effective management option.

ICRISAT's Director General Dr William Dar says, 'This is an important step that addresses the specific needs of the resource-poor farmers of the semi-arid tropics through effective biotechnological intervention. Pigeonpea is an important crop that supports the livelihoods of the farm families living in these rainfed areas.'

ICRISAT scientists developed the technology for genetically transforming pigeonpea, and introduced the synthetic Bt Cry1Ab gene that offers resistance against lepidopteran insect pests like pod borer. The strategy included transferring the Cry1Ab gene and the soybean trypsin inhibitor through Agrobacterium tumefaciens-mediated genetic transformation. The Cry1Ab gene is extracted from the bacteria Bacillus thuringiensis.

After extensive molecular characterization of the transgenics and insect bioassays in the glasshouse, permission to conduct a field trial under controlled conditions was obtained from the India's Department of Biotechnology.

This work provides a significant breakthrough in the fight against Helicoverpa armigera. The control for the pest is currently based on heavy insecticide use. Helicoverpa populations, however, are adept at developing resistance to insecticides in several countries, rendering insecticide application ineffective. Intensification of agriculture has aggravated the pest problem, and farmers are resorting to frequent use of more toxic insecticides.

More than 14,000 pigeonpea accessions were screened for resistance to Helicoverpa armigera by the Institute and collaborating national agricultural research organizations. However, these genotypes have not been used widely. The level of tolerance provided in these genotypes is low, and some of the lines are susceptible to major fungal diseases.

After an initial contained field trial, the transgenic pigeonpea crop will go through a second season of contained trial at ICRISAT-Patancheru to generate more data on biosafety. Once successful, ICRISAT will collaborate with its national partners to implement open field trials.

For further information contact k.sharma@cgiar.org.

2. All Systems Go!
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Rather than focus on individual crops, ICRISAT looks at the complete farming system. Better soil fertility management, opportunities for cash cropping, ways to use available resources more effectively, ways to reduce risk in a highly variable environment... On-farm research by Team ICRISAT in Zimbabwe's Tsholotsho district combines these components into an integrated whole. The first step is to test the individual components on farm under typical smallholder conditions.

One set of field trials focuses on the use of farmyard manure. Inorganic fertilizer is expensive, but many households have access to cattle manure, and combining manure with small quantities of fertilizer can produce startling yield improvements. Other trials compared two different sources of phosphorus. Which one provides a bigger increase in legume yield? This is part of a broader effort to expand legume cultivation.

Smallholder farmers in Tsholotsho commonly grow three legumes - cowpea, bambara nut and groundnut - but only on small patches of land, and using unimproved landraces. The project aims to encourage farmers to grow legumes more widely, and more systematically - for example, in rotation or intercropped with cereals. More legumes means higher soil fertility, more protein in the diet, plus cash from the sale of surplus produce.

 Scientists help farmers to plan
and 'plot' the trials on their fields
.

The trials are conducted on farmers' fields. They are planned jointly by farmers, ICRISAT scientists and national research and extension staff. Importantly, they are implemented by the farmers themselves. At present, 30 farmers are involved, 15 for legumes trials, 15 for maize. A recent field day was organized to showcase the trials process and the results achieved. Several hundred people attended: farmers, headmen and other community leaders, and research and extension staff. The visitors examined six fields of maize, cowpea, groundnut and bambara nut. At each field the host farmer explained the technology being tested, and answered questions. ICRISAT staff provided additional technical information.

Legume benefits are not always obvious. At one groundnut field, for example, the visitors found no great differences between fertilized and non-fertilized plots, except that fertilized plants were a little greener. But when the farmer pulled out a few plants from each of the treatments the differences were clear. Differences were clearly visible in the number of pods per plant, depending on what fertility management method had been used. Plants in unfertilized plots had the fewest pods.

ICRISAT's farmer-participatory approach is working. People involved in the project (as well as their neighbors when they see the results) are changing their farming methods. Small changes, perhaps, but they add up. And for farmers who have always operated at barely subsistence levels, the new technologies have opened new doors to prosperity.

For more information contact s.twomlow@cgiar.org.

3. Debarring the Dreaded Downy Mildew
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It could look very pretty in a dry flower arrangement, but downy mildew, caused by the fungus Sclerospora graminicola, is a destructive disease with a taste for Indian pearl millet hybrids. The pearl millet-growing area in India today is 10 million ha, 60% of it grown with hybrids. Surveys in the 2003 rainy season in the Indian states of Gujarat, Rajasthan and Haryana revealed that 30 different hybrids were grown by farmers. Of these, 24 hybrids were from private seed companies.

Downy mildew infected panicle of
pearl millet in a farmer's field.

Despite favorable weather for both the crop and the disease, several hybrids were disease free. Others, however, recorded incidence as high as 80%. Public sector hybrids BK 560, Pusa 23, GHB 316 and GHB 558 recorded low disease incidence, while ICMH 451, which is already notified for withdrawal, recorded up to 90% incidence in some fields. HHB 67, the most popular and earliest maturing (within 70 days) hybrid from CCS Haryana Agricultural University, after almost 10 years of large-scale cultivation, recorded up to 30% disease. Among the private sector hybrids, JKBH 125, JKBH 126, MLBH 308, MRB 2210, Nandi 3 and Pioneer 7688 were resistant, while some others, such as Ankur, Deepak 18, Khamadhenu 51, and NK 1602 recorded more than 50% disease incidence in certain fields (Table 1).

Table: Performance of some popular pearl millet hybrids to downy
mildew disease in farmers' fields during the 2003 rainy season.

Hybrid

Source

Downy mildew incidence (%)

GHB 316

Public sector

  0

GHB 558

Public Sector

  0

BK 560

Public Sector

  7  (4-10)

Pusa 23

Public Sector

12  (0-40)

HHB 67

Public Sector

  9  (0-30)

ICMH 451

Public Sector

49  (10-90)

 

 

 

JKBH 125

Private Sector

  0

JKBH 26

Private Sector

  0

MRB 2210

Private Sector

  0

Nandi 3

Private Sector

  0

Pioneer 7688

Private Sector

  0

MLBH 308

Private Sector

  5 (2-10)

Deepak 18

Private Sector

85 (78-90)

Khamadhenu 51

Private Sector

64 (58-70)

NK 1608

Private Sector

39 (18-80)

Values in parenthesis are range of downy mildew incidence across fields

Downy mildew control involves both host plant resistance and chemical seed treatment. ICRISAT's assistance in managing the disease is significant. This assistance is threefold.

  • Providing downy mildew-resistant parental lines to both public and private sector oganizations.
  • Monitoring the performance of these hybrids through disease surveys in farmers' fields in collaboration with the All India Coordinated Pearl Millet Improvement Project, thus fine tuning cultivar replacement strategy
  • Providing a downy mildew screening service to limited materials to facilitate a resistance breeding program.

ICRISAT developed a new version of HHB 67 through resistance gene transfer in parental lines using marker-assisted backcrossing. This new version, which is as good as the original hybrid for its agronomic performance, is likely to be commercialized in Haryana and parts of Rajasthan.

Greater hybrid diversity, use of resistant parental lines in hybrid breeding, and timely information about performance in farmers' fields have helped avoid epidemics. This year's pearl millet production has been highly beneficial to farmers and seed industries.

For more information contact r.thakur@cgiar.org

4. Seed from Schools
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Smallholder farmers in Africa often report that they would gladly adopt new varieties of sorghum and millet if only they could get seed. This is a serious, long-standing problem in many countries, and for most crops. ICRISAT and its partners have proposed several innovative solutions. One is to use primary schools as seed production and distribution centers.

The program is now in its third season and the report card says, 'Excellent, can do even better!'

Several partners are involved – the schools and the surrounding communities, ICRISAT, the Christian Council of Tanzania, the Diocese of Central Tanganyika, the district administration, as well as the Ministries of Agriculture and Education. The schools are located at most 25 km apart, so that every community can get seed easily, within cycling distance. ICRISAT provided each school with foundation seed; agriculture teachers from every school (farming is part of the curriculum) were given training courses on seed production; the government seed agency sent staff to provide advice on seed quality and certification standards.

The program kicked off in Dodoma, the capital of Tanzania, which lies in the drought-prone central region and has always been a traditional sorghum/millet area. Three varieties adapted to the dry, variable conditions were chosen:

  • Sorghum variety Pato: early-maturing, high-yielding, white-grained
  • Pearl millet varieties Okoa and Shibe: early-maturing, high-yielding, resistant to downy mildew.

All three were developed by ICRISAT with NARS partners in southern Africa.

Tanzanian school children
proudly show off their sorghum field
.

Some schools lost their entire seed crop due to excessive rainfall (a welcome change from drought!), pests and birds (huge flocks of Quelea weavers). Even so, the 50-odd schools in Dodoma last season produced 38 tons of sorghum seed and 6 tons of pearl millet – enough to plant over 6000 hectares.

The program is expanding rapidly. This season, 150 schools in four districts are involved. Pigeonpea has been added to the crop mix, and will be intercropped with sorghum and millet. This dovetails with another ICRISAT initiative in the same region – a new, highly efficient sorghum/pigeonpea intercropping system. Specific varieties and management practices have been developed and tested for the new system. Adoption is growing, and will grow even faster once the schools program begins pumping seed into the system.

For more information contact e.monyo@cgiar.org.