Evaluation of maize (Zea mays L.) genotypes with multiple resistance to striga hermonthica (Del.) benth and striga asiatica (L.) kuntze

Abstract

Striga asiatica is a noxious, obligate hemi-parasite of cereal grasses that causes grain yield losses in susceptible maize genotypes in Southern Africa. The development of host plant resistance is one of the most practical Striga control strategies. A study was carried out to identify genotypes that were resistant to Striga asiatica, and to investigate the mechanism of resistance of selected genotypes of maize to Striga asiatica. A total of 14 maize genotypes comprising of 12 developed by IITA with resistance to Striga hermonthica (causes grain yield losses in susceptible maize genotypes in West Africa) and two locally grown maize genotypes with unknown reaction to Striga hermonthica were assessed through field and laboratory experiments. The field experiment was conducted at Lundazi, Katete and at the UNZA field station during the 2013/14 farming season; while the laboratory experiment was conducted at the IITA biosciences laboratory. Grain yield, Striga Damage Rating (SDR) representing the reaction to Striga in the field, Striga count, plant height, cob length and cob diameter, days to 50% flowering and days to maturity were measured or derived from the field. Significant differences (p<0.05) were detected among the genotypes for grain yield with the highest yield being obtained from genotype 1113-13STR (8.68 T/ha) and the lowest for genotype 8338-1 (5.64 T/ha). Genotypes were not significantly different for SDR across locations. A highly significant and negative correlation was observed between grain yield and SDR (r= -0.29**). A non-significant and negative correlation was also observed between grain yield and Striga counts at 14 weeks after planting (WAP) (r= -0.056). Positive correlations were observed between grain yield and cob diameter (r= 0.908***), cob length (r= 0.55***), days to 50% flowering (r= 0.4***) and days to maturity (r= 0.4***). A significant positive correlation for Striga counts was observed between sampling stage 10 WAP and 12 WAP (r= 0.85***) and also between sampling stage 12 WAP and 14 WAP (r= 0.93***). A negative correlation was observed between SDR and plant height (r= -0.37***) Maize genotypes 1113-13STR, 1113-3STR and 1113-2STR were identified as the most resistant genotypes based on the fewer Striga numbers per plant produced, lower SDR scores (scores of 1-4) and were higher yielding. These genotypes also produced lower germination stimulants which did not favour Striga germination. The three genotypes can be used in the improvement of resistance to S. asiatica in maize genotypes.