Fusarium Species and Fumonisin in Atoxigenic Aspergillus Flavus (Aflasafe Ke01) Treated Maize Fields in Lower Eastern Kenya University of Nairobi

Abstract

Contamination of crops with fumonisin leads to huge losses in cereals and negatively impacts on human health, animal productivity and international trade. Management of fumonisin contamination in maize has been a challenge since there are no effective management measures for Fusarium ear rots and lack of resistant maize varieties. This study was conducted with the objective of determining the efficacy of Aflasafe KE01 on the population of Fusarium species and fumonisin contamination of maize. The study was carried out in Wote, Kaiti, Kathiani and Nzambani sub counties of Makueni, Kitui and Machakos Counties, respectively. Twenty four maize fields were selected in each of the sub county where 12 fields were treated with Aflasafe KE01, while 12 fields comprised the untreated controls. The formulation comprised of four atoxigenic Aspergillus flavus on sterile sorghum seeds. Aflasafe KE01 was applied at a rate of 5 kg/ha and 10kg/ha by hand broadcasting in the maize fields two to three weeks before tussling of the maize. Soil samples were collected from each field prior to application of Aflasafe while maize grain samples were collected at harvest. Fusarium species were isolated from the ground maize and soil samples using pour plate method following serial dilution on low strength potato dextrose agar (PDA) and Spezieller Nahrstoffarmer Agar (SNA). Fusarium species growing were identified based on their cultural and morphological characteristics such as septation and sporophores, spore shape, pigmentation, mycelia color and colony pigmentation. Fumonisin in the maize samples was determined using Accuscan Pro-reader enzyme-linked immunosorbent assay (ELISA). The Fusarium species isolated from soil and maize samples at high frequency were F. verticillioides, F. proliferatum, F. chlamydosporum, F. merismoides, F. semitectum and F. oxysporum. Fusarium verticillioides was isolated at highest frequencies across the four sub counties. Maize samples from Aflasafe KE01 treated maize fields had significantly lower xiv population of the Fusarium species compared to untreated maize fields across all the four sub counties. The mean incidence of F. verticillioides was 43% and 40.9% in the maize grains sampled from fields treated with Aflasafe KE01 at the rate 5 kg/ha and 10kg/ha, respectively; while the control fields corresponding to the 5 kg/ha and 10kg/ha application rates had mean incidences of 63% and 54.8%, respectively. There was significant reduction of up to 68.7% in the fumonisin levels in maize samples from Aflasafe KE01 treated compared to the untreated maize fields. The population of Fusarium species and fumonisin levels were significantly different among the study areas following Aflasafe KE01 application. About 62.5% of the maize fields treated with 5kg/ha of Aflasafe KE01 met the European commission regulatory threshold of ≤2ppmfor total fumonisin as compared to about 45% from the control fields. The results showed that application of Aflasafe KE01 effectively displaced the toxigenic Fusarium species in maize resulting in reduction of fumonisin in the maize from the Aflasafe KE01 treated fields by up to 68% compared to samples from untreated fields. This indicates that Aflasafe KE01 is a potential biopesticide for the biocontrol of Fusarium species and fumonisin production in maize. Efficacy of Aflasafe KE01 on reducing fumonisin contamination of other key staples in Kenya should be evaluated. Key words: Fusarium species, fumonisins, Aflasafe KE01, maize, atoxigenic Aspergillus sp. Key Words: Aflasafe, atoxigenic, Fumonisin, Fusarium, maize