**5. Selection and efficacy of fungicides**

Some fungicides commonly used to control plant culture contaminations during the *in vitro* culture include Benomyl, Captain and several others (Table 1). Utilization of these fungicides and other sterilants and disinfectants largely depends on their availability and the costs, especially in some Africa countries where these fungicides, sterilants and/or disinfectants are imported. Generally, they are not locally available in many African countries for use in plant culture laboratories.

The fungicides and disinfectants can be in the form of powder or liquid. Generally, the quantity of fungicides normally used per decontamination is very little. For instance, a low amount of Benomyl such as 0.14g per litre of water could be used to decontaminate some stock plants. Fungicides and disinfectants are harmful to human beings when swallowed or inhaled. Therefore, proper handling of all fungicides must be a priority.

#### **5.1 Selecting fungicides**

In many plant culture laboratories, systematic fungicides (such as Benomyl) are preferred in case of endogenous fungi. Selection of a particular fungicide depends on the nature of fungal contaminants as some are hard to eliminate (e.g. endogenous fungi). The use of systemic fungicides (such as Benomyl) has often been recommended. In some cases, stronger disinfectants or fungicides have been used to remove culture contaminants, especially those which are hard to decontaminate. For instance, mercuric chloride (HgCl2) has been effective in decontaminating pre-conditioned mature *U. kirkiana* stock plants (Mng'omba et al., 2007) where sodium hypochlorite (NaOCl) and Calcium hypochlorite (Ca (OCl2)2) have not been effective in decontaminating the above stock plants. There have been no aseptic cultures obtained regardless of the type and concentration of such disinfectants used on *U. kirkiana* stock plants. These fungi were suspected to be endogenous.
