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Wageningen Universiteit (2005)

The role of sorghum genotype in the interaction with the parasitic weed Striga hermonthica

Rodenburg, J.

Titre : The role of sorghum genotype in the interaction with the parasitic weed Striga hermonthica

Auteur : Rodenburg, J.

Université de soutenance : Wageningen Universiteit

Grade : Doctor Thesis 2005

Résumé
This thesis presents a study on the interaction between the parasitic weed Striga (S. hermonthica [Del.] Benth.) and the cereal crop sorghum (S. bicolor [L.] Moench). Its main objective was to find suitable measures for the selection of breeding material (crop genotypes) with superior levels of resistance or superior levels of tolerance to Striga. To meet this objective the physiological background of tolerance, the relation between Striga infestation, infection and yield loss and the effect of host genotype on Striga parasitism and reproduction were studied. These host-parasite interactions were studied with 4-10 different sorghum genotypes differing in level and mechanism of defence against Striga. Field experiments carried out in Mali were used for yield assessments and development and validation of selection measures. Through pot and agar-gel experiments, aboveground resistance measures were validated with observations on belowground stages. Pot experimentation was also used to create infection response curves and to measure photosynthesis and chlorophyll fluorescence to develop tolerance measures. Striga parasitism and reproduction, and the detrimental effect of Striga on crop yield can significantly be reduced through crop genotype choice. Maximum aboveground Striga number is a reliable selection measure for resistance. Striga flowerstalk dry weight can be used to identify genotypes that reduce Striga reproduction. The maximum relative yield loss is a suitable selection measure for tolerance in susceptible genotypes, while for more resistant genotypes the relative yield loss per Striga infection seems more appropriate. For these tolerance measures, yield assessment of nearby uninfected controls is indispensable. Chlorophyll fluorescence, more precisely photochemical quenching and electron transport rate, may enable screening for tolerance without this requirement.

Mots clés : SORGHUM BICOLOR / SORGHUM / STRIGA HERMONTHICA / PARASITIC PLANTS / GENOTYPE ENVIRONMENT INTERACTION / GENETIC PARAMETERS / SELECTION METHODS / GENETIC RESISTANCE / PLANT BREEDING / VARIETAL SUSCEPTIBILITY

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Page publiée le 17 mars 2006, mise à jour le 3 juin 2022