Effectiveness of arbuscular mycorrhizal fungi in protection of maize (Zea mays L.) against witchweed (Striga hermonthica Del Benth) infestation

Abstract

Striga hermonthica is one of the most important obligate root hemiparasitic weeds of cereals such as maize and sorghum. This study investigated the impact of arbuscular mycorrhizal fungi (AMF) on the Striga-maize host interaction and its potential application in management of Striga infestation. Two maize varieties: Striga-susceptible Nyamilambo and Striga-tolerant KSTP94; three species of AMF; Glomus etunicatum, Scutellospora fulgida, Gigaspora margarita and Striga hermonthica seeds were used in a greenhouse experiment. Colonization of maize roots was fastest with Glomus spp. (51.98%) than other AMF species; however, Striga infestation reduced root colonization but conversely increased relative mycorrhizal dependency (Glomus spp. = 6.12%) in both maize cultivars. Inoculation of Nyamilambo maize cultivars with AMF reduced Striga plant incidence (9.50) and biomass (5.40 g) to significantly lower (4.90 and 3.82 g) levels. Mycorrhizal Nyamilambo and KSTP94 had higher nitrogen (154.01 and 116.88 mg) and phosphorus (25.33 and 31.07 mg) content compared to non-mycorrhizal cultivars (63.37 mg N and 16.81 mg P) in absence and presence of Striga infestation. While mycorrhizal maize had increased height (100.50 to 135.20 cm) and biomass (75.70 to 87.54 cm), their Striga damage score (4.07) was significantly lower than with non-mycorrhizal maize (8.10). Glomus spp. had most significant positive effect compared to both Gigaspora and Scutellospora spp. In conclusion, AMF inhibits germination and reduces growth of Striga hermonthica while enhancing maize host growth and development.