The Russian wheat aphid, Diuraphis noxia (Mordvilko), is a serious worldwide pest of wheat and barley. Russian wheat aphid populations from Hungary, Russia, and Syria have previously been identified as virulent to D. noxia (Dn) 4, the gene in all Russian wheat aphid-resistant cultivars produced in Colorado. However, the virulence of Russian wheat aphid populations from central Europe, North Africa, and South America to existing Dn genes has not been assessed. Experiments with plants containing several different Dn genes demonstrated that populations from Chile, the Czech Republic, and Ethiopia are also virulent to Dn4. The Czech population was also virulent to plants containing the Dnx gene in wheat plant introduction PI220127. The Ethiopian population was also virulent to plants containing the Dny gene in the Russian wheat aphid-resistant 'Stanton' produced in Kansas. The Chilean and Ethiopian populations were unaffected by the antibiosis resistance in Dn4 plants. There were significantly more nymphs of the Chilean population on plants of Dn4 than on Dn6 plants at both 18 and 23 d postinfestation, and the Ethiopian population attained a significantly greater weight on Dn4 plants than on plants containing Dn5 or Dn6. These newly characterized virulent Russian wheat aphid populations pose a distinct threat to existing or proposed wheat cultivars possessing Dn4.

En Afrique, 45% du territoire est situé dans des régions où l’agriculture pluviale est fragilisée par les sécheresses récurrentes. Au Burkina Faso, la dégradation des sols peut être limitée grâce à la technique du Zaï, technique manuelle traditionnelle très exigeante en main d’œuvre (300h/ha). La mécanisation de l'opération permet de passer à 40h/ha. L’amélioration de la technique touche aujourd’hui plusieurs centaines de fermes et d’artisans dans une vingtaine de villages du nord du Burkina Faso. Une cactée (Opuntia ficus-indica Mill) originaire du Mexique a été introduite accidentellement il y a moins de 20 ans en dans la province aride du Tigray au le nord de l’Ethiopie. Dans un délai très court, des modes de culture, d’utilisation et de transformation des différents produits de Opuntia ont fait l’objet d’améliorations techniques permettant d’améliorer l’alimentation humaine et animale et les revenus en période de soudure (juillet-septembre). Ces progrès ont été, au départ, initiés par la recherche agricole locale mais une rapide montée en puissance a été opérée grâce à une collaboration multi acteurs impliquant notamment les utilisateurs de ces techniques notamment les agriculteurs eux mêmes. Les deux expériences ont été présentées à la conférence AIDA : « Agricultural Innovation in Dryland Africa » (http://inco-aida.cirad.fr ) tenue à Accra (Ghana), 22-24 janvier 2007, qui a permis un premier inventaire d’études de cas d’amélioration agricole en Afrique sahélienne. Le principal enseignement de la conférence, illustré par ces deux études de cas, est que dans les conditions d’une grande variabilité spatiale et temporelle des facteurs environnementaux et humains, l’innovation agricole est un processus dynamique, complexe et interactif, en rupture avec les démarches linéaires de transfert de technologie majoritairement pratiqués depuis 40 ans. Les méthodes et les approches qui permettent d’intégrer cette complexité sont aujourd’hui au centre des débats afin de permettre l’appropriation par les acteurs donc accroitre l’impact des améliorations technologiques et leur pérennisation dans des contextes où les marges de manœuvre économique et climatiques sont très réduites.

Carmine cochineal, Dactylopius coccus Costa, was introduced to northern Ethiopia to addconsiderable value to existing cactus pear vegetation that in places like the southern Tigraywas becoming an invasive plant. It became an investment opportunity where Foodsafe, aChilean company was involved. Company was granted 300 ha at the cactus pear infestedplains of southern Tigray. Foodsafe was also expected to expand cochineal productionthrough an outgrower scheme. It created employment opportunity for the locals and startedexporting dried cochineal to Mexico and Germany bringing in foreign currency. As cactuspear grows in communal lands, conflict of interest arose and it polarised the community. Thecompany was forcibly closed and it was a tragedy that a one time commercial insect becamea full-fledged invasive insect pest. Attempts to contain the insect with mechanical andchemical control were not successful. So far more than 16,000 ha of cactus pear land wasinfested with carmine cochineal. 13,000 ton of dried cochineal could have been harvested ina single year, generated USD $52 million, and part of that money could have been used forits management.

The Russian wheat aphid, Diuraphis noxia (Mordvilko), is a serious worldwide pest of wheat and barley. Russian wheat aphid populations from Hungary, Russia, and Syria have previously been identified as virulent to D. noxia (Dn) 4, the gene in all Russian wheat aphid-resistant cultivars produced in Colorado. However, the virulence of Russian wheat aphid populations from central Europe, North Africa, and South America to existing Dn genes has not been assessed. Experiments with plants containing several different Dn genes demonstrated that populations from Chile, the Czech Republic, and Ethiopia are also virulent to Dn4. The Czech population was also virulent to plants containing the Dnx gene in wheat plant introduction PI220127. The Ethiopian population was also virulent to plants containing the Dny gene in the Russian wheat aphid-resistant 'Stanton' produced in Kansas. The Chilean and Ethiopian populations were unaffected by the antibiosis resistance in Dn4 plants. There were significantly more nymphs of the Chilean population on plants of Dn4 than on Dn6 plants at both 18 and 23 d postinfestation, and the Ethiopian population attained a significantly greater weight on Dn4 plants than on plants containing Dn5 or Dn6. These newly characterized virulent Russian wheat aphid populations pose a distinct threat to existing or proposed wheat cultivars possessing Dn4.

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