SATrends Issue 64 March 2006
  • Sorghum with muscle!
  • If in trouble, go wild!
  • Redheads beware
  • A home where the buffalo roam?

  • 1. Sorghum with muscle!
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    Micronutrient malnutrition is not a glaring health hazard such as HIV/AIDS or tuberculosis, but it exists all the same, and causes blindness, anaemia, (and sometimes even death) especially among women and pre-school children, in the semi-arid tropics (SAT), which is home to more than half of the world’s population.

    Micronutrient malnutrition is primarily the result of diets poor in bio-available vitamins and minerals [mostly iron (Fe) and zinc (Zn)]. Sorghum is a staple food and daily diet for millions of people in the SAT, making it an excellent medium through which increased iron, zinc and pro-vitamin A could reach the consumer. Crop varieties selected and/or bred for this purpose through a plant breeding approach will complement existing approaches (such as other fortified foods and medical pills), and at a fraction of the cost of existing approaches.

    ICRISAT is carrying out pre-breeding research for bio-fortified sorghum as part of a HarvestPlus project to assess the potential of plant breeding technology to combat micronutrient deficiency. The initial results indicated significant genetic variability for Fe, Zn and phytates (which reduce bio-availability of Fe and Zn) and limited variability for β-carotene content. The significant genetic variability coupled with high broad-sense heritability and absence of genotype × environment (managed soil fertility level) interaction for Fe, Zn and phytates offers good prospects.


    PVK 801, a mold resistant variety.

    Several varieties with high Fe and Zn, and low phytate content, compared to trial mean (45.4 ppm Fe, 21.8 ppm Zn and 6.1 mg g-1 phytates), have been identified. Notable are: Hybrid seed parents with high Fe content (46.0 – 48.7 ppm) ICSB 561, ICSB 675, ICSB 52, and ICSB 484; high Zn content (25.7 – 26.5 ppm) ICSB 418 and ICSB 484; and low phytate content (4.3 – 6.4 mg g-1) ICSB 675, ICSB 74, ICSB 38 and ICSB 39. Restorer parents/varieties with high Fe content (48.7 – 55.3 ppm) ICSR 40, IRAT 204, PVK 801 and ICSV 93046; high Zn content (23.1 – 30.3 ppm) IRAT 204, ICSV 93046, ICSR 90017 and ICSR 40; and low phytate content (2.6 – 4.7 mg g-1) ICSR 165, Lade Samrudhi, IRAT 204 and ICSV 21005.

    Assuming 5% Fe and 25% Zn bio-availability, ICRISAT envisages improving sorghum with grain micronutrient density [base level (mean Fe and Zn contents of popular varieties) + 30 ppm Fe and 12 ppm Zn contents] through conventional plant breeding to meet the daily requirements.

    For more information contact s.ramesh@cgiar.org or b.reddy@cgiar.org

    2. If in trouble, go wild!
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    Do you realize that every plant under cultivation in the present day was once wild? Plant evolution under domestication has led to the evolution of modern day crops, but the same process has narrowed the genetic base of the crops. The challenge today is to produce crops with high yield, disease and pest resistance, drought and salinity tolerance, in an environment friendly manner.

    In times of major epidemic or to broaden the genetic base, crop improvement scientists return to the wild relatives of crop plants, as these offer a variation that was lost in the long process of evolution and domestication. The process to tap wild relatives of crop plants is not a straightforward process, but advances in scientific research combined with enthusiasm and commitment, has resulted in many success stories. Here are excellent examples where wild relatives have improved the crop plants:

    Wheat: The history of wheat goes hand-in-hand with human civilization! Wheat breeders discovered close to 30 independent disease resistance genes in wild introgressions, which has increased wheat varieties. The sources of resistances came from rye, Agropyron and wild emmer wheat.

    Rice: Traits for resistance to bacterial blight, brown planthopper, white-backed planthopper, grassy stunt, and other traits such as hull color, pigmented pericarp, were introgressed from wild species from different gene pools. Derivatives from many of these sources are in commercial cultivation.

    Tomato: Commercially available hybrids of tomato have disease resistance genes and quality characters introgressed from many wild sources. An important gene was introduced from Lycopersicon pennellii, which increased the level of provitamin A (β-carotene) in the fruit more than 15-fold.


    (L to R) Wild species of Arachis, Cajanus and Cicer.

    ICRISAT mandate legumes

    Pigeonpea: wild relatives of pigeonpea have been sources of genes/traits for CMS, high protein lines, dwarfing genes. phytophthora blight and salinity tolerance . Apart from this, there is a major emphasis at ICRISAT to transfer resistance of the plant to the Helicoverpa pod borer.

    Groundnut: Wild Arachis are sources of resistance to important fungal diseases, insect pests, nematodes, and drought. Scientists have succeeded in accessing these important traits for the improvement of the crop.

    Chickpea: Wild Cicer have high levels of resistances to Helicoverpa, botrytis grey mold, ascochyta blight, cyst nematode and some rare characters such as induction of androgenesis or apomixes.

    For more information contact n.mallikarjuna@cgiar.org

    3. Redheads beware
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    The red hairy caterpillar (RHC), Amsacta albistriga, is a pest of several rainy season crops in Asia. The RHC infestation is sporadic, but the devastation is widespread. Due to the prolonged diapause, larval migratory behavior and irregular adult emergence, chemical protection alone is not sufficient.


    The red hairy caterpillar.

    Farmers manage the pest by manually collecting and destroying the larvae. However, investment and timely availability of labor in large areas make this method impractical. ICRISAT’s research resulted in utilization of the Nuclear Polyhedrosis Virus (NPV) to kill the RHC. Further studies to find effective virus production strategies led to the utilization of field-collected larvae for NPV production.

    The RHC larval populations were collected from three hotspots in Andhra Pradesh (Nalgonda, Ananthapur and ICRISAT sites) during August 2004–05. Studies revealed a second generation of the pest, which, together with the prolonged emergence of moths, confirmed the widespread occurrence of RHC.

    RHNPV was isolated and multiplied at ICRISAT laboratories. The mass production technique involved putting up an aluminum or polythene grid/enclosure (10 cm height) to confine the larvae inside the shaded enclosure. RHC larvae (3–5 instars) were released into the enclosure, and fed with plants already inoculated with the virus. The infected larvae showed the mortality symptoms from the 5th day after inoculation.


    Aluminum grid to confine larvae.

    Eco-friendly options for larvae collection

    • Apply NPV 15–20 days after crop sowing and repeat the spray at 10-day interval with RHNPV @ 5 ml in 1.5 x 1012 POBs per ha.
    • Fix polythene sheet (12” wide strip) along the border of the crop too provide a barrier and to divert the migrating larvae into a trap.
    • Use sunflower (10–12 plants/sq m) as a trap crop and two rows of cowpea or field bean as border crop along the main fields.
    • Dust the inside of a trench (12" deep and 12" wide) around the field with chemical, either with malathion or carbaryl or quinolphos.
    • Place Jatropa or Ipomoea or Calotropis twigs on the field bunds to attract larvae.

    The field technique for rearing larvae is advantageous, particularly in avoiding the handling of huge larval populations, rearing and inoculation. This would also facilitate farm level production and access to the biopesticide at the village level. The technique can serve as an option in the armory of the plant protectionist and would be an asset in managing the RHC pest.

    For more information contact g.rangarao@cgiar.org

    4. A home where the buffalo roam?
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    A survey of crop-livestock systems in Zimbabwe’s drought-prone Tsholotsho district has confirmed earlier known facts and raised some interesting new questions. The survey compared two areas: one close to Tsholotsho business center (high population density, high levels of degradation), and the other remote and thinly populated.

    Crops and livestock form an integrated system: crops provide food and fodder, while livestock provide draft power, cash, milk and manure. But as human populations grow, rangeland is giving way to crop fields, and grazing areas are shrinking, besides being over-used. Frequent droughts and institutional weaknesses (credit, extension, veterinary services) are contributing to a decline in animal health and per capita holdings. Twenty years ago the average household had nearly 100 cattle. Today, farmers with 50 cattle are considered wealthy; and the number of households with no cattle has increased substantially.

    Distance from a business centers and markets was an important factor. The further away from a population center, the better the herd size and grazing areas.


    Scientific Officer interviewing a Tsholotsho farmer.

    Farmers report that soil fertility and crop yields have declined over the years, as a result of nutrient mining and greater rainfall variability. Weed control is harder, for two reasons – labor shortages (in turn due to HIV/AIDS and out-migration) and the inexorable spread of couch grass (partly spread through livestock dung).

    Interestingly, fallow areas have expanded – although this is not necessarily a good thing. The expansion seems to have occurred in three ‘waves’. First, soon after independence, farmers moved from clay soils to sandy areas that were easier to cultivate. The 1990s saw an exodus to urban areas, in search of employment. And in recent years, an increasing number of played-out fields (low in nutrients and/or infested with couch grass) are being abandoned.

    This information tells us what is happening and why; enables us to understand local needs and priorities, and design practical, low-cost interventions to improve livelihoods. For example, farmers were keen to rebuild their herds, but were limited by fodder shortages during the dry season. ICRISAT is keen to work with farmer groups, NGOs and the national research and extension system to promote cultivation of bana grass, forage sorghum, forage legumes, and other alternatives. We are also looking at ways to link small-scale farmers to livestock markets, so that farmers have solid financial incentives to invest in managing livestock and feed/fodder resources.

    For more information contact a.vanrooyen@cgiar.org