Variability and host specificity of witchweed [Striga hermonthica (Del.) Benth.] populations on millet [Pennisetum glaucum (L.) R. Br.]

Awadallah B. Dafaallah, Abd Elgabar T. Babiker, Mohammed H. Zain El Abdeen

Abstract


Field surveys and greenhouse experiments were conducted during season 2009/10 in the Sudan to investigate variability and host specificity of witchweed [Striga hermonthica (Del.) Benth.] populations. Field surveys were conducted in S. hermonthica endemic areas in Gadarif, Gezira and Kordofan to collect seeds from Striga plants growing under their respective hosts. A total of fifteen S. hermonthica populations were collected. Twelve S. hermonthica populations, one each, were collected from under sorghum and three S. hermonthica populations, one each, were collected from under millet. A greenhouse experiment was undertaken at the horticulture nursery, Faculty of Agricultural Sciences, University of Gezira, Wad Medani, Sudan, to test the infectivity of seeds of witchweed populations on millet, cultivar Ashana, which is known for its differential response and to study virulence of parasitism on this cultivar. The fifteen S. hermonthica populations were arranged in a randomized complete block design with three replicates. Growth and harvest attributes on the parasite and crop were measured. Data were collected and transformed as necessary to √x+0.5 and subjected to the analysis of variance procedure. Means were separated for significance using Duncan's Multiple Range Test (at p £ 0.5). The greenhouse experiment showed that emergent S. hermonthica, capsules per plant and shoot dry weight were highest on the respective host. It is noteworthy that some of the Striga, sorghum populations, displayed limited emergence on millet and produced seeds. S. hermonthica populations significantly reduced growth and yield of millet. However, the magnitude of the damage attained, by each

 

population was highest on the respective host. These findings suggest the existence of inter-crop specialization. Moreover, the results confirmed the existence of two strains of S. hermonthica, one specific to sorghum and the other to millet. These findings showed clearly the complexity of obtaining millet cultivars with high and durable resistance across locations.


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