Conditioning effects of Striga hermonthica seed on field performance of maize

Seeds of the obligate parasite Striga hermonthica, germinate in response to stimulants in the root exudate of maize and other host crops. Under labora tory conditions, conditioning (defined as treatment with moisture) of Strig a seeds for one to three weeks before exposure to germination stimulant is required for optimum germination. The objective of this study was to determ ine if maize performance and Striga emergence, both indices of resistance, were influenced by the interval between Striga seed infestation and maize p lanting, under high parasite inoculum (3000-6000 germinable seeds) as pract iced in maize resistance breeding field nurseries. Four conditioning treatm ents were investigated: maize planted immediately after Striga seed infesta tion, and maize planted after one, two and three weeks after infestation. E xperimental design was randomized complete block with four replications. Di fferences among the four conditioning treatments were not significant for m aize damage score, height, stalk lodging, number of ears harvested, grain y ield and number of emerged Striga plants. Thus, maize planted on the same d ay as Striga infestation showed similar response as maize planted one to th ree weeks after infestation. Using high seed inoculum, maize can be planted immediately after Striga infestation in maize breeding nurseries. Combinin g Striga seed infestation and maize planting into a single field operation is convenient: and reduces cost of screening. (C) 2001 Elsevier Science Ltd . All rights reserved.