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BACTERIAL SOFT ROT OF TUBERS INDUCED BY ERWINIA SPP. (JONES)
Abstract:
The incidence of bacterial soft rot was investigated in three markets in Zaria area namely: Samaru, Wusasa and Sabon Gari markets. Examination of symptoms on tubers (both wounded and unwounded), were done on tubers stored under different environmental conditions in order to determine the factor(s) that might predispose them to attack by the soft rot pathogen. High populations of Erwinia spp. were isolated from the samples collected from various markets, which was an indication of high inoculum level from the various soils of origin or storehouses. Tubers without symptoms were frequently contaminated, usually at eye, lenticels and heel end, suggesting contamination from mother tuber to progeny. Aqueous extracts of neem (Azadirachta indica A. Juss), Eucalyptus leaves (Eucalyptus citrodorus (L)), Lemon grass (Cymbopogon citratus (stapf)), Garlic bulb (Allium Sativum (Linn)), Ginger (Zingiber officinale) (Roscoe)) and Aloe vera were evaluated for the management of bacterial soft rot. Two methods were used, namely in vitro methods and on the tubers both whole and sliced. Lemon grass had the greatest inhibitory effect and it’s statistically comparable with garlic, Aloe vera, borax and neem extracts. Eucalyptus had the least inhibitory effect and statistically similar to ginger extract. Two methods (Tuber slice assay and point titration assay) were used to screen yam (Dioscorea rotundata), sweet potato (Ipomoea batatas), Irish potato (Solanum tuberosum), cocoyam (Xanthosoma sagittifolium), cassava (Manihot esculenta) and carrot (Daucus carota) for susceptibility to soft rot bacteria. Irish potato ranked the most susceptible followed by carrot, sweet potato, yam, cocoyam and cassava. The two methods examined were considered to be effective for screening tubers for bacterial soft rot. However, with the single site titration assay, it is possible to determine not only the extent of tissue maceration but also the bacterial population necessary for initiation of lesions. Tuber Slice assay on the other hand, has the advantage of being faster than the single site titration assay.
BACTERIAL SOFT ROT OF TUBERS INDUCED BY ERWINIA SPP. (JONES)
