CAAREA Activities & Key postharvest solutions for aflatoxin control Said M.S. Massomo Open University of Tanzania Morogoro Regional Centre www.out.ac.tz Email: [email protected] [email protected] Aflatoxin Stakeholders Workshop. Dar es Salaam December 3-4, 2012 Massomo, SMS 1 CAAREA Objectives 1. Establish aflatoxin diagnostics platform at BecA-ILRI, and develop novel aflatoxin diagnostics 2. Characterize maize fungi from around Kenya and Tanzania: information, biobank and inoculum. 3. Identify maize germplasm resistant to aflatoxin accumulation (G x E). 4. Test modelling as a potential predictive tool and to contextualize findings regionally (risk map). 5. National breeders will affect subsequent changes to maize breeding programs in Kenya and Tanzania. Introduction • Aflatoxins are primarily produced by the fungi – Aspergillus flavus Link – A. parasiticus Speare • Optimal conditions for fungal development are – high temperatures 36 to 38 C – high humidity >85% A. flavus image from: http://www.pfdb.net/photo/mirhendi_h/box020909/ Factors influencing Aflatoxin Production Fungal growth and aflatoxin contamination are the consequence of interactions among the fungus, the host and the environment Pathogen Aggressiveness Other factors Favourable Environment Host Plant Susceptibility Interaction vary with • Geographic location, agricultural and agronomic practices, • The susceptibility of commodities to fungal invasion during preharvest, storage, and/or processing periods CAAREA objective II • To characterize the diversity, distribution and toxigenicity of Aspergillus flavus (and to a limited extent, other relevant fungi) in Kenya and Tanzania • Determine relation to maize contamination by aflatoxins across AEZs/regions • Mainly focused on pre harvest with some post harvest component Country Wide Survey • Work with and through the NARs • Activity I: Field trials – 20 sites of 10 varieties will be planted across Agro Ecological Zones – Data/item to be collected • Maize phenotypic characters • Insect abundance, Weather … • Collection of maize cob samples • Activity II: Interviews of farmers • Activity III: Collection of maize samples from farmers • Biophysical data • Management data • Maize Genotyping (maize map) • Area planted to maize • Planting density • Integrated index of insect load • Maize sample aflatoxin concentration Isolation & Characterization of A. flavus • Isolation of fungi from seeds at ARI-Mikocheni & at BECA-ILRI • Characterization work at BECAILRI lab • Characterization of A. flavus isolates: – Morphology (S or L strain) – Toxigenicity (extent & type(s) of toxin produced) – Microsatellite genotyping – Other Molecular tools • Grouping of A. flavus basing on vegetative compatibility groups Isolation & Identification Characterization Strain selection for Inoculum production &Field inoculation (screening for resistance) Biobank for future studies Fungi survey data from 11 sites in two zones Activity Aspergillus flavus isolates Mid and highland Tanzania 19 Lowland in Tanzania 57 Total Tanzania 76 16 genera identified Fungal isolations/training, ARI Mikocheni , Dar Tanzania AF KBK02 AF KBK12 AF KBK05 Distribution and diversity of toxigenic A. flavus strains in Kenya AF KBK10 AF KBK11 AF KBK24 KAT05 KAT03 KAT06 AF KBK20 AF KBK19 KAT07 AF KBK18 KAT04 AF KBK17 KAT02 KAT11 KAT10 KBK13 KAT12 PK08 PK02 PK04 AF KBK08 AF KBK07 AF KBK13 AF KBK04 AF KBK16 AF KBK09 AF KBK06 PK07 PK03 PK06 PK05 PK01 PK09 AF KBK03 AF KBK01 AF KBK14 MTW 1A KK1A KAT01 AF KBK21 AF KBK26 AF KBK22 AF KBK23 MTW 4A MTW 2A MTW 3A AF KBK25 AF KBK15 Fungal survey: postharvest component • PCR assay being used to determine prevalence of Aspergillus flavus and A. parasiticus in post harvest samples. • This will ensure that pre harvest prevalence data does not “miss” part of the problem in some areas. Major Drivers: Pre Harvest Pathogen abundance • Basal inoculum load & prevalence of toxigenic strains and microbiological interactions – Continuous cropping, double cropping & Soil etc. Stressful Environment • Untimely planting Water stress or wetness at harvest • High-temperature stress • Low input farming practice stressed plants – high crop densities, low fertility and weed competition Low host plant resistance Other factors • Insect damage of the host plant • Growth of other molds or microbes Major Drivers: Post Harvest Environment • High-temperature & High humidity Host • Resistance factors – (i.e. Grain texture, resistance to Aspergillus & insect infestation) Pathogen • Basal inoculum density in & around the store Other factors • Pest infestation & microbe interactions & endophytes Interventions: Post Harvest, Pre processing • Public education and awareness to sensitize the population on aflatoxin risk and its management – Across all the relevant industry sectors – Using effective communication strategies • e.g Mobile phone sms & Community radios • Timely harvesting • Moisture control/Drying of crop – Rapid and proper drying – Avoid drying on bare ground (Use of drying platforms and drying on mats) Interventions: Post Harvest, Pre processing cont.. • Sorting (infected and insect damaged cobs) • Improved farm storage and drying methods – e.g Hermetic storage (sealed/air tight containers) • Proper transportation and packaging (dry & aerated) • Pest Management – Cleaning of store before introduction of new produce – Reduce pest infestation Interventions: Post Harvest, Pre processing • Good food regulatory systems – To regulate quality & safety of food • Efficient monitoring and surveillance with rapid, cost-effective sampling and analytical methods • Finding alternative uses for contaminated grain • Behavioural changes on food supplementation • Dietary change? Interventions: Post Harvest, Pre processing cont.. • Other strategies – Mould inhibitors – Detoxification of aflatoxins • Physical (Sorting, Flotation & Physical segregation) • Chemically (e.g. Ammonia & Calcium hydroxide) • Microbiologically (e.g. Fermentation, pro-biotics or lactic acid bacteria into the diet) – Alteration of Bioavailability by Aflatoxin • Enterosorbents in human diets • Chemisorbents in livestock Interventions: Post Harvest, Processing period • Practising food processing procedures that may involve processes such as • Grain cleaning, dehulling, washing, wet and dry milling, roasting, baking, frying etc. Integrated suite of intervention measures should be advocated Challenges • Existence of favourable climatic conditions for fungal development & aflatoxin accumulation • Difficult to accurately estimate aflatoxins concentration – When large quantity of material are involved – Variability associated with testing procedures • Cost-effectiveness of the control methods • Food insecurity and drought • Limited resources at Household level Thank you! Thank you!