Response of IITA maize inbred lines bred for Striga hermonthica resistance to Striga asiatica and associated resistance mechanisms in southern Africa

Striga spp. is endemic in sub-Saharan Africa causing up to 100% yield loss equating to US$ 7 billion. Striga asiatica (with red flowers) is found in southern Africa while Striga hermonthica (with purple flowers) is found in east and west Africa. At the International Institute of Tropical Agriculture, resistance to S. hermonthica was introgressed from wild relatives into commercial maize. This study aimed at ascertaining resistance to S. hermonthica and associated mechanisms that could effectively control S. asiatica. Thirty maize inbred lines were evaluated for S. asiatica resistance using the pot culture and agar gel technique. The pot experiment was arranged in a 10 x 6 alpha-lattice design with three replications and the gar gel experiments were conducted in complete randomized design with four replications. Maize inbred lines were significantly different (P < 0.001) for Striga seed germination stimulant production. Inbred lines 2, 32, 28, 29, 27, 33, 7, and 14 recorded less than 10 mm in furthest Striga seed germinated and were identified as resistant with a mechanisms of reduced amounts of germination stimulants. Significant differences (P < 0.05) were also noted for plant height, stem, root, leaf and total biomass, the number of Striga root attachments and emerged Striga for the pot experiment. Inbred lines 18, 27, 20 and 32 had low Striga haustorial attachments. Identified resistant lines could be used in either genetic studies or genetic improvement for S. asiatica resistance by making sure that different mechanisms are stacked in a given variety.