Cassava improvement strategies for resistance to major economic diseases and pests in Africa

Abstract

The cassava diseases of major economic importance in Africa are cassava mosaic, bacterial blight, and anthracnose, and the major cassava pests are cassava mealybug and green spider mite. Methods of screening cassava breeding material for resistance to the diseases and pests in the light of factors determining the disease and pest incidence and their effect on efficiency of screening have been discussed. The role of the presence of pathogenic variation and biotypes of pe.tr in determining the durability of resistance over localities and time has been considered, and the optimum conditions for efficient screening of the breeding materials have been suggested.

En Afrique, les maladies et ennemis du manioc d'une grande imponance economique sontrespectivement la br0lure bacterienne, I'anthracnose et la mosai,que dans le premiercas et la cochenilledans le second. Des discussions ont eu lieu sur des m6thodes de s6lection du materiel genetique demanioc i la lumilre des facteurs determinant la maladie et l'apparition des insectes et sur Ie r6le que cesfacteurs jouent dans I'efficacit6 de la selection. On a eniisage I'existence possible de variationpathogenique et de biotypes d'insectes qui determineraient Ia durabilite de la resistance selon le temps oule. lieu. L'etude sugglre les conditions optimales requises pour selectionner efficacement le materiel genetique du manioc.