Abstract
Sorghum (Sorghum bicolour (L.) Moench), the second most important staple crop in Sub-Saharan Africa (SSA) after maize, is well adapted to marginal environments of drought stress and high temperatures. But besides drought stress, the obligate root-parasitic flowering plant Striga hermonthica is an equally economically important biotic stress in agro-ecological zones where soils are marginal. Notwithstanding widespread and intense Striga infestation, genetic variations in defence mechanisms against the parasite have been reported. Sorghum variants, producing low levels of chemical stimulants such as sorgolactones that deter the advance of Striga seed germination and are therefore deemed resistant to the parasite, have been also reported in a few studies. But the existence of sorghum genetic variation for this resistance especially among farmers’ landraces is yet to be demonstrated. The objective of this study was therefore to determine the levels of Striga germination stimulants in response to each of the 111 collected sorghum landraces and their progenies from Eritrea. The ability of a sorghum genotype to cause germination of a Striga seed as a measure of the amount of the germination stimulant produced was used to assess the resistance of these accessions. The data were recorded as Striga germination percentage by counting the number of germinated Striga seeds. Landraces EG47, EG1261, EG830, EG1076, EG54 and EG746 with 14.68%, 15.32%, 11.85%, 13.05%, 15.74% and 16.5% germination percentages respectively were found to stimulate low levels of Striga germination percentage compared to commercial checks, IS9830, SRN39, Framida, with 22.46%, 22.67%, 23.27% germination respectively. While these variants did not show complete resistance against Striga seed germination, the low level production of stimulant indicated their high level of resistance to Striga . These results implied that these accessions are likely potential sources of resistance against Striga infestation in SSA sorghum breeding programs.
Highlights
Sorghum (Sorghum bicolour (L.) Moench) is an important staple crop in Sub-Saharan Africa (SSA) that can meet the increasing demand of food [1]
This enabled the harvesting of at least 1gram of root from each accession which was required as source of Striga germination stimulant in the study
Analysis of variance for Striga germination revealed that highly significant differences (P < 0.001) were observed among the sorghum accessions tested for their ability to cause Striga germination with a range of 11.8 to 40.6% (Table 2)
Summary
Sorghum (Sorghum bicolour (L.) Moench) is an important staple crop in Sub-Saharan Africa (SSA) that can meet the increasing demand of food [1]. Striga causes 75% of its damage before it emerges above the ground making its control more difficult [5]. Mechanical and chemical control options are less effective because they affect Striga after it has already attached and damaged the host [5]. Different control measures such as hand weeding, crop rotation trap crop, catch crops, intercropping, fertilizers and herbicides have been suggested but with limited success. The many herbicides that have been tried have not been effective, and are costly and in most cases may not be available to resource-poor farmers in SSA
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