Aflatoxin Stakeholders Workshop. Dar es Salaam December 3-4, 2012 Massomo, SMS 1

CAAREA Activities & Key post-harvest solutions for aflatoxin control

Said M.S. Massomo Open University of TanzaniaMorogoro Regional Centrewww.out.ac.tzEmail: said.massomo@out.ac.tz

smsmassomo@yahoo.com

CAAREA Objectives1. Establish aflatoxin diagnostics platform at BecA-ILRI, and

develop novel aflatoxin diagnostics2. 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

Interaction vary with • Geographic location, agricultural and agronomic

practices, • The susceptibility of commodities to fungal invasion

during pre-harvest, storage, and/or processing periods

Pathogen Aggressivenes

s

Host Plant Susceptibility

Favourable Environment

Other factors

Fungal growth and aflatoxin contamination are the consequence of interactions among the

fungus, the host and the environment

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 BECA-ILRI 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

Characterization

Strain selection for Inoculum production

&Field inoculation (screening for resistance)

Isolation & Identification

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 57Total Tanzania 76

16 genera identified

Fungal isolations/training, ARI Mikocheni , DarTanzania

AF KBK02

AF KBK12

AF KBK05

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

MTW1A

KK1A

KAT01

AF KBK21

AF KBK26

AF KBK22

AF KBK23

MTW4A

MTW2A

MTW3A

AF KBK25

AF KBK15

0.05

Distribution and diversity of toxigenic A. flavus strains in Kenya

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 HarvestPathogen 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 competitionLow host plant resistanceOther factors• Insect damage of the host plant• Growth of other molds or microbes

Major Drivers: Post Harvest

Environment• High-temperature & High humidityHost • Resistance factors

– (i.e. Grain texture, resistance to Aspergillus & insect infestation)

Pathogen• Basal inoculum density in & around the storeOther 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 suiteof 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!