Inactivation of pathogenic organisms of cassava (Manihot esculenta Crantz) by heat and other treatments

Abstract

CIAT`s contribution to this joint research program was (1) to develop a technique for the production of bacteria-free planting stocks of cassava and (2) to study the effect of physical therapeutic agents on vegetative material used for propagation. The propagation technique developed to produce CBB-free cuttings is described. Guidelines are given for eradicating CBB from infected plantations. Hot water, microwave and ultraviolet (UV) light treatments of cuttings were evaluated. It was found that hot water or microwaves can seriously reduce germination of cuttings, whereas UV light for 7 h had no effect on germination. The optimum hot water treatment for cuttings was 52 degrees Celsius/30 min; the optimum microwave treatment, 75-90 sec of exposure. CBB, a vascular pathogen, was not controlled by these treatments. Its inactivity or inhibitory point, when associated with its host, is higher than the optimum point of sensitivity of the cuttings to these treatments. Botryodiplodia sp., Glomerella sp. and the causal agent of the superelongation disease (a lower ascomycete) were controlled by hot water or microwave treatments only in the case of early infection.UV light exposure did not control these pathogens. Since green cuttings are very sensitive to hot water and microwaves, these treatments are unsuitable for this type of cutting. (CIAT)