Abstract:
The root parasitic weed Striga hermonthica constitutes a major constraint to cereals production in sub-Saharan Africa. Several control measures have been recommended, however, incompatibility with the prevalent low inputs production systems precludes their adoption. Resistant genotypes could provide an ideal solution; however, durable resistance necessitates pyramiding of resistance mechanisms. The present investigation was undertaken at the College of Agricultural Studies Sudan University of Science and Technology to study in situ germination of S. hermonthica seeds, seedlings attachment and subsequent development, over a three weeks duration, on three sorghum genotypes, Wad-Ahmed, Striga tolerant, and Tetron and Hakika Striga resistant, using an in vitro system (the Rhizotron technique) for sorghum and Striga co-culture. Striga germination progressively increased with time and was 66.9-92.1%, 61.1-85.5% and 52.6-74.1% for Wad-Ahmed, Tetron and Hakika, respectively. Striga seedlings affected comparable attachment (53.6-68.8%) to the roots of the three genotypes. However, development and survival of the seedlings were genotype dependent. At 1-3 weeks post-inoculation Striga seedlings at stage 3 were 19.1-24.7%, 2.9-7.1% and 6.3-12.6% on Wad-Ahmed, Tetron and Hakika, respectively. Seedlings mortality was 0-1.2%, 3.0-8.1% and 2.5-29.6% on Wad -Ahmed, Hakika and Tetron, respectively. The strong developmental arrest noted beyond stage 2, where xylem-to-xylem connection between the parasite and the host was established, coupled with the notable seedling mortality on Tetron and Hakika suggest that Striga resistance in these genotypes is attributed, in part, to impairment of diversion of nutrients, water and carbon compounds from the host to the parasite.
