Resistance screening of sorghum and effects of varieties and herbicide application on reproduction of Striga hermonthica

Abstract

The obligate parasitic witchweed, [Striga hermonthica (Del.) Benth] is the greatest biological constraint to cereal production in sub-Saharan Africa. Sorghum [Sorghum bicolor (L.) Moench], a widely grown cereal in the region is an important host crop that has coevolved with the parasite. Several methods to control striga have been proposed, but with limited success. Genetic control of striga is effective, although sources of resistance are limited in most crops. Studies were initiated on striga–infested fields in view to identify sources of resistance to Striga hermonthica and to investigate the response of selected sorghum cultivars and some herbicides on the emergence of striga. In one experiment, eleven sorghum cultivars were screened for resistance to Striga hermonthica. Cultivars of sorghum differed significantly with respect to number of emerged striga plants at 60 days after planting and at harvesting. The varieties S 35 and CS 54 constantly recorded low number of striga plants than the popular resistant variety Framida. In the herbicide application trials, the numbers of emerged striga per square meter were much reduced following spraying with 2,4-D. Although the urea treatment
had high grain yield, the number of emerged striga plant per unit area was also very high. Application of the appropriate herbicide at the right stage of striga emergence and growth, combined with the use of resistant/tolerant varieties may inhibit striga development. The results reported in this study offer promise in simultaneously sustaining high grain yields and suppressing the development of striga in farmers’ fields.

Key words: Herbicides, Sorghum bicolor, host resistance, Striga hermonthica, sustainable production