**3. Management strategies against aflatoxins**

Aspergillus infection increase with high temperature, high humidity, insect damage and ni‐ trogen deficiency. Temperature and humidity are therefore important in aflatoxin manage‐ ment. A. flavus and A. parasiticus are unable to grow or produce aflatoxin at water activity of less than 0.7 (relative humidity below 70% or temperature below 100C, however under stress condition such as drought, aflatoxin contamination can be higher [17]. Various strat‐ egies have been suggested in management of aflatoxins. The strategies should adhere to the following: a) aflatoxin must be transformed to non-toxic products, b) fungal spores and my‐ celia should be destroyed to prevent formation of new toxins, c) the food or feed material should retain its nutritive value and palatability, d) the physical properties of raw material should not change significantly d) it must be cost efficient [5, 16, 64].

mushroom) is known to promote health effects in animals and human and have ability to inhibit aflatoxin biosynthesis by stimulating the antioxidant defence of the toxigenic fungus. Oxidative stress induced using paraquatenhanced the expression of β-glucan synthase gene and stimulated effect of β-glucans production that leads to a higher afla‐ toxin inhibiting capacity. Efficient inhibition could be due to higher content of β-glu‐ cans [60]. Utilization of microorganisms or their enzymatic metabolites to detoxify mycotoxins in food and feed has advantages such as mild reaction conditions, target

Species by RNA Silencing Technique http://dx.doi.org/10.5772/51440 45

A New Approach in Aflatoxin Management in Africa: Targeting Aflatoxin/Sterigmatocystin Biosynthesis in Aspergillus

**f.** Resistant hybrids could be very promising but commercial hybrids are not always available [1]. However, availability of resistant varieties is the best solution for farmers so long as they are available and affordable. Some high yielding yellow maize varieties with good resistance to Aspergillus have been identified. This includes AO901-25 that has a grain yield of 7115kg/h and low aflatoxin level (IITA). However there is still a lot to be done in order to consider consumer prevalence as most people in Africa have prevalence to white maize. Furthermore, reduction in aflatoxin level is still required. Menkiret al. [51] registered tropical maize germplasm with resistance to aflatoxins. These varieties have been distributed to National programs for the development of lo‐

**g.** Biological control is use of one microorganism to control another microorganism such as Pseudomonas strains [55]. It has been noted that Aspergillusflavus strains differ in aflatoxin production and this influences crop contamination. There are strains that pro‐ duce a lot of aflatoxins and also produce numerous small sclerotia (<400µm). These are the 'S' strains (toxigenic strain). Another strain the 'L' strain produces low aflatoxin lev‐ els and a few large sclerotia that are about >400µm and are atoxigenic [18]. There is competitive exclusion when one strain competes to exclude another in the environment. This implies that a shift of strain profile from toxigenic to atoxigenic is a viable biologi‐ cal control strategy. Atoxigenic strains of A. flavus from Nigeria have been combined as a bio-control product and registered as AflaSafe. It is used on sorghum as a carrier at the rate of 10kg/ha applied 2-3 weeks before flowering. Native strains have been identi‐ fied and are being used in African countries. In Diourbel (Senegal) peanuts treated with AflaSafe had aflatoxin level of 1.9ng/g while control had 29.7ng/g giving a reduction in aflatoxin level of 93%. In Ibadan (Nigeria), crops in treated plots had Aflatoxin level of 11ppb while control had 42ppb giving 73% in reduction of aflatoxin. Stored products had 105ppb in treated samples while untreated samples had 2408ppb giving a reduc‐ tion of 96% in Aflatoxin level [7, 18]. Due to good performance of atoxigenic strains, peanut producers in Senegal and Gambia are willing to adopt competitive exclusion

Reduction of moisture in grains is very important. There are a number of technologies that could be used to dry maize fast. Such technologies have extensively been reviewed by Lut‐

specificity, efficiency and environmental friendly.

technology for aflatoxin control in peanuts.

**5. Post-harvest management**

cally adapted hybrids.

The Physical and chemical treatment of contaminated commodities include detoxification of aflatoxins using physical means such as removal of contaminated commodities or inactiva‐ tion of the toxin in the commodity. These methods include mechanical sorting and separa‐ tion, washing, density segregation, solvent extraction, irradiationand oxidation [5]. However,efficiency of these techniques will depend on level of contamination. Furthermore, results obtained are often uncertain and relatively costly and could remove or destroy essen‐ tial nutrients in feed [41]. Also some of the methods have disadvantages such as nutritional loss, toxic, limited efficiency and high cost therefore limiting practical application. Various natural and synthetic agents could prevent growth of toxigenic fungi and formation of my‐ cotoxins and these have been reviewed by Mahoneyet al. [47]. Chemical methods of deacti‐ vating mycotoxins in feeds and also clay products that could be used in deactivating mycotoxins have been extensively been reviewed by Kolosova and Stroka [41]. Management strategies can be divided into Pre-harvest and Post-harvest strategies.
