SATrends Issue 21                                                                                                  August 2002                       
NEWS FROM THE DRY TROPICS:

1. Breaking New Ground with Groundnuts

In India, groundnut is grown on an estimated area of 8.1 million ha with a production of 7.45 million tons of pods. Though average productivity is increasing, it is still considerably lower than the world average. One of the reasons for low yield in the semi-arid tropics is the damage caused by such abiotic stresses as drought and low soil fertility, as well as by a number of diseases caused by fungi, bacteria, and viruses. Peanut clump virus is a serious problem in India and several West African countries. Annual losses incurred through this disease globally are nearly US$ 40 million.

After long, hard work, ICRISAT's first genetically modified groundnuts have reached the field trial stage. These groundnuts are engineered with the genes for resistance to the Indian peanut clump virus (IPCV), which is widespread in India.

PCV is transmitted by Polymyxa gramminis, a soil-borne fungus. It is difficult to control both because it can survive dormant in soil for years, and because suitable biocides or resistant genotypes are unavailable. Despite screening of more than 10,000 groundnut lines, no traditional sources of resistance to PCV have yet been identified.

Trans groundnut copy.jpg (6903 bytes)A research team led by Dr Kiran Sharma at ICRISAT’s Headquarters in India, after developing the technology for genetically transforming groundnut, introduced resistant genes into the IPCV. The strategy included transferring the coat protein and the polymerase gene of IPCV through Agrobacterium tumefaciens-mediated genetic transformation. After extensive molecular characterization of the transgenics and preliminary studies in the glasshouse, permission to carry out a field trial under controlled conditions was obtained from the Department of Biotechnology, Government of India. (Left, W Dar, K Sharma, and F Waliyar proudly examine the new babies)

The work began with genes obtained from the Scottish Crops Research Institute (SCRI), Dundee, Scotland. The work of sequencing and cloning the genes was undertaken collaboratively by ICRISAT and SCRI. ICRISAT pathologist Dr Farid Waliyar is testing these miracle groundnuts in India, while virologist Dr Philippe Delfosse is exploring the possibilities of testing them in West Africa against the African isolate of PCV.

According to Director General Dr William Dar, this is ICRISAT’s first major step towards addressing specific needs of the resource-poor farmers of the SAT through the application of biotechnological interventions for crop improvement.

For more information contact k.sharma@cgiar.org

 

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  2.A Custard Apple a Day....

The custard apple, hitherto used mainly in ice cream and milkshakes, has found an important new role for itself – as an inexpensive, environment-friendly method to control crop pests.

custard apples.jpg (9879 bytes)Custard apples (right) grow abundantly in India and other parts of the world. The fruits are tasty, though a nuisance to eat. Almost 30% of the weight of the fruit consists of seeds. But these irksome seeds have proved a bonus because they contain chemicals known as acetogenins, which are toxic to insects. ICRISAT and the Indian Institute of Chemical Technology, Hyderabad, working together to isolate the biologically active ingredients from the seeds, have succeeded in formulating extracts that farmers can use to fight pests cheaply and effectively.

2 and 3.jpg (10507 bytes)The seed extracts are fractionated to yield potions that work against different insect species. For example, hexane-soluble components reduced leaf disc feeding and larval massing of the armyworm (Mythimna separata), in laboratory tests. In field tests, the extracts controlled both the armyworm and the stem borer (Chilo partellus). Alcohol extracts were found to be nearly as toxic as nicotine sulfate, a commonly used but expensive chemical. Another important finding: seed extracts showed synergistic activity in combination with neem seed extract – ie, the combination is far more effective than either one used alone. This combination works well on several pests, including Callosobruchus chinensis, Rhizopertha dominica and Musca domestica nebulo. (Left, compare the unaffected pests on top with the ones treated with seed extract below)

The secrets of custard apple have long been known to farmers in India and elsewhere. Farmers in Vietnam, for example, use the apple’s oil to control rice leaf hoppers and plant hoppers. The oil, especially when used in combination with neem oil, reduces survival of the leafhopper (Nephotettix virescens) in rice and also reduces the transmission of rice tungro virus. Surveys on indigenous biocontrol methods have documented the use of extracts from Annona reticulata and Annona squamosa – both of which contain acetogenins – to control a number of pests: the cabbage aphid (Brevicoryne brassicae), the pulse beetle (Bruchus chinensis), the green scale (Coccus viridis), the cotton stainer (Dysdercus keonigii), the hairy caterpillar (Euproctis fraternal), the brown plant hopper (Nilaparvata lugens), the sawtoothed grain beetle (Oryzeaphilus surinamensis), the diamond-back moth (Plutella xylostella), the white-backed plant hopper (Sogatella furcifera) and the tobacco caterpillar (Spodoptera litura).

Like they say, a custard apple a day keeps the plant doctor away!

For more information contact h.sharma@cgiar.org

 

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3.Gerrymandering the Gene Pool

Part 4: Marker-Assisted Breeding

Continuing from Part 3 of the subject (Molecular Mapping) published in last month’s SATrends, we now bring you the concluding part of the series.

The main goal of plant breeding is to genetically improve the economic value of crop production either through increased production and reliability of production, or through increased product quality.

One way to influence the production of a crop is by improving the distribution of assimilates in the crop by translocating more sugars in to the grains and less to the vegetative plant parts. Another way is by rendering the crop more resistant to pests or diseases, or more tolerant of environmental stress.

Reduced plant height is determined by a single gene. Because plants with this gene are dwarfed, more assimilates can be directed to the grains instead of the leaf and stem. Similarly, resistance to plant diseases is largely controlled by a small number of genes.

Before the use of molecular markers was refined, breeding for traits determined by a single gene was a tedious process. One major disadvantage was that tests on disease or pest resistance are often limited to a certain stage in the development of the plant. Often, only one generation could be screened per year.Mapping and MAS figures.jpg (14592 bytes)

The application of molecular markers and genetic maps can greatly improves the efficiency of the breeding process is considered. First, molecular markers are environmentally neutral – a DNA fragment from the seedling stage of sorghum ICSV 745 accession in India amplified by a polymerase chain reaction, is identical to the fragment amplified from a fully-grown ICSV 745 accession plant in Mali. Second, the positions of the markers on the genetic linkage map indicate that the gene for an associated trait is to be found nearby – they are linked.

Thus, molecular markers have enormous potential for positive impact on plant breeding. They can significantly increase the speed of the selection process and enable geneticists to clone a chosen gene. Once cloned, the selected gene can be used to enrich genotypes lacking that particular trait.

 

To make this application of molecular markers successful, plant breeders, physiologists, pathologists, statisticians and molecular biologists need to work hand-in-hand. The inputs of all five disciplines are of equal importance when working towards a second green revolution.

For more information contact c.t.hash@cgiar.org or r.folkertsma@cgiar.org

 

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4. Mineral and Manure: A Winning Combination

Poor soil fertility is, after drought, the single most important constraint to smallholder farmers in Africa. Some scientists would even reverse this order, assigning more importance to the latter constraint. Through untold generations of cereal cropping, soil nutrients have been drastically depleted. How to replenish these lost nutrients? Manure supplies are limited because livestock herds are small, and few smallholders can afford expensive chemical fertilizer.

ICRISAT scientists therefore tried something new – they focused on improving the efficiency with which farmers use mineral fertilizer. For example, banded application, or concentrating fertilizer application in the area close to plant roots, will provide almost the same benefit as broadcasting of fertilizer, at a fraction of the cost.

The FAO Projet Intrants, hosted by the Ministere Nigerian du Developpement Agricole, in partnership with various NGOs, recently conducted an experiment in southwestern Niger comparing three alternative fertilizer-efficient methods – DAP (di-ammonium phosphate), DAP+urea and NPK to a crop of pearl millet. They also examined how to maximize yields (and profits) by combining chemical fertilizer with manure. Two types of manure were compared, each combined with the different types of fertilizer – manure transported from the field, and high-quality manure from the family kraal, where livestock are corralled at night.

giant millet copy.jpg (9737 bytes) The results of the two-year study (2000-01) showed clearly that even small quantities of fertilizer can make a big difference (left). For example, a combination of DAP and kraal manure gave yields as high as 613 kg ha-1 – more than four times the yield from non-manured, unfertilized fields.

Method of application is crucial: use the right method, and small amounts of fertilizer can work wonders. The method used in this experiment was hill placement. A small quantity of fertilizer (often carefully hand-measured) was placed immediately around the seed at the time of sowing.

The study was able to evaluate the performance (both yield and profitability) of hill-placed application of different formulations of mineral fertilizer. At the same time, it estimated yield response under different biophysical and management conditions.

In addition, the study is helping monitor the adoption of hill-placed fertilizer application. Data from these and similar experiments being conducted elsewhere in West Africa are helping to develop practical recommendations for soil fertility management. These studies provide hard numbers that can be used to compare yields and returns from alternative investment options, and suggest how best farmers can maximize returns from their small investments.

These results are applicable not only to West Africa, but across the semi-arid tropics of the world.

For more information contact b.gerard@cgiar.org

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Highlights of Previous Issues:

July 2002: Gerrymandering the Gene Pool• Peanut Paternity Suit?• The Winds of Change in West Africa• Insect Problems? Try a Little Wax and Hair

June 2002: Gerrymandering the Gene Pool• Tribal Treasure Troves• The Return of the Native• Poverty and the Perch

May 2002: Gerrymandering the Gene Pool• Snap, Crackle, and Pop• Checking Africa's Pulse• High Tech for an Old Problem

April 2002: Disaster Relief with a Difference• From Crop to Tabletop• Golden Millet, Naturally!• The "Green" to "Blue" Water Continuum

March 2002: On the Wild Side• A Handful of Seed• Here's to Fungus - hic!

February 2002: 36 Percent -- and Rising• Of Stalk and Livestock• Stalking the Enemy• Sorghum Scoop from Mali

January 2002: Back to the Drawing Board• Weed Better, Weed Faster• With Minds of their Own!• Closing Ranks against the Pod Borer

December 2001: It's a bird! It's a plane! No, it's a Super scientist! •   Viva Sorgo! • Small is Big! • Abortion Leads to Rebirth

November 2001: Sorghum Products: Poised to Take Off • Cash from Cattle Food • Empowerment Through Technology • Outwitting an Unfair Bug

October 2001: Backing a Winner • More than a Thousand Words • Sowing a New Future for Eritrea • A Casting Coup: Farmers' Day 2001

September 2001: Don’t Get Left on the Shelf • Nigeria Targets ‘Groundnut Leprosy’ • Two Heads Are Better than One • Desperately Seeking Seeds

August 2001: Finding Chinks in the Armour •   Brazilian Farmers get a Boost from the Sahel • Sahelian Partners Smash the Ivory Tower • What You See is What You Get - Simulation Modeling for Successful Farming

July 2001: Balaji Makes IT Waves • A Hot Date in the Sahel • It All Adds Up • More from Less • That's the Way the Cookie Crumbles

June 2001: Space-Age Partnership in West Africa • Bad Taste is Good • Out of Africa • Seed Priming: Rhapsody in Simplicity

May 2001: Dodging Drought in Kenya • Vietnam and ICRISAT Save Watersheds • Farmers Enrich Malawi's Soils • Groundnut Mystery Disease Identified

April 2001:Women Farmers Guide Scientists in Namibia •   Ashta Puts it Faith in IPM • Sahelian Farmers Place Their Bets • China and Pigeonpea: Love at Second Sight

March 2001: Agriculture: an Ally Against Global Warming? • Breaking the Spell of Witchweed • Groundnut Taking Root in Central Asia and the Caucasus • Zimbabwean Smallholders Drive the Research Agenda

February 2001: Somalia: Seeds Deliver Hope Amidst Chaos • The CGIAR Fights Desertification in Africa • Creating the World's First Molecular Marker Map of Chickpea • Aflatoxin and Cancer: Cracking a Hard Nut in Developing Countries

January 2001: Things Grow Better with CokeŽ: Micro-fertilizer System Sparks 50-100 Percent Millet Yield Increases in the Sahel • Groundnut (Peanut) Production Accelerates in Vietnam •   Pigeonpea Broadens Farmer's Options in Sudan •   Private Sector Invests in Public Plant Breeding Research at ICRISAT.

December 2000: International Symposium on SAT Futures • Centers Team Up to Help East Timor • Spatial Variability in Watersheds • World's First Cytoplasmic Male-Sterile Hybrid Pigeonpea • Groundnut (Peanut) Variety Boosts Malawian Agriculture • National Researchers Persevere in El Salvador • ICRISAT Celebrates India-ICRISAT Day • ICRISAT and World Vision International Work Together in Southern Africa.