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sur le développement des zones arides et semi-arides

Titre : The tripartite interaction between sorghum, Striga hermonthica, and arbuscular mycorrhizal fungi

Auteur : Lendzemo, V.W.

Université de soutenance : Wageningen Universiteit

Grade : PhD thesis 2004

Résumé
Striga hermonthica is a major biological constraint to cereal production inAfrica. The intricate association between this phytoparasite and the cereal host makes management difficult. Damage to the host begins before Striga comes out of the soil. Also, infestation correlates negatively with soil fertility. Arbuscular mycorrrhizal (AM) fungi have a variety of ecological functions ranging from improved uptake of immobile nutrients, protection of host from pathogens, to soil aggregation. The question whether these beneficial micro-organisms could play a role within the Striga -cereal (patho)systemwas addressed. Inoculating Striga -infested sorghum with AM fungi in pots or in the field resulted in a significant reduction in the performance of Striga in terms of numbers attached to the roots, relative time of emergence, numbers emerged and dry weight of Striga shoots at sorghum harvest. AM effects on Striga were more pronounced with the Striga -tolerant S-35 sorghum cultivar compared to effects with the Striga -sensitive CK60B. Inoculation with AM fungi compensated for damage by Striga in the S-35 cultivar. This compensation was independent of AM inoculum density and was not affected by P application. Germination of preconditioned Striga seeds after exposure to root exudates from sorghum colonized by AM fungi was significantly reduced, with effects more prominent with exudates from S-35 plants. AM fungi have the potential to affect Striga during germination, attachment, emergence, and possibly subsequent growth and development. It is important to understand the kind of management practices that farmers can apply to enhance mycorrhizal performance in an integrated management system.

Mots clés : striga hermonthica - striga - mycorrhizas - sorghum bicolor - sorghum - plant interaction - weed biology - cameroon

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