Date of Award

Fall 1989

Document Type


Degree Name

Master of Science (MS)


Biological Sciences



Committee Director

Lytton J. Musselman

Committee Member

Kneeland Nesius

Committee Member

Robert Ratzlaff

Call Number for Print

Special Collections LD4331.B46 K64


Of the seven species of Striga found in Zimbabwe, S. forbesii Benth. is currently the most destructive in terms of crop damage. Owing to its limited occurrence worldwide as a pest of crops, relatively little work has been done on this species.

Striga forbesii has been found to be a consistent problem on both maize and sorghum in the Hunter's Road District of KweKwe, Zimbabwe. Results of a pot study and field observations, indicate S. forbesii can successfully parasitize Urochloa panicoides Beauv., Sorghum arundinaceum (Desv.) Stapf, and Rottboellia cochinchinensis (L.) L.f., all of which are widespread weeds of arable land.

A population of S. forbesii in KweKwe was found to have an unusual floral form with a strongly exserted style and stigma. The possibility of outcrossing in this predominantly autogamous population is examined.

The seeds of the giant mealie witchweed germinated in the presence of the strigol analogue, GR-24, only after a period of after-ripening.

Sorghum cultivars were field-screened for resistance to S. forbesii using the Observation Nursery and Advanced Screening procedures developed at the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), in India. Striga asiatica-resistant (SAR) cultivars 19, 29, 33, 35, and SAR 37 were found to have higher levels of tolerance to S. forbesii than the traditional sorghum cultivars of the communal farmers.


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