Journal of Applied Biosciences (J. Appl. Biosci.) [ISSN 1997 - 5902]
Volume 38: 2540 - 2550. Published February 9, 2011.
Diversity of pectinolytic bacteria causing soft rot disease of vegetables in Ibadan, Nigeria
Wakil, Sherifah Monilola and Oyinlola, Kubrat Abiola
1Department of Microbiology, University of Ibadan, Ibadan, Nigeria.
*Corresponding author: E-mail: Shemowak@yahoo.comABSTRACT
Abstract: Pectinolytic organisms are a constant threat with regard to spoilage of vegetables because of their extensive host range and widespread distribution. It is estimated that between 10 and 30% of fresh vegetables are wasted, mainly due to three factors: mechanical injuries, physiological decays and microbial spoilage. The role of microorganisms in this wastage is significant, hence the need to better understand the microbial diversity responsible for soft rot spoilage in vegetables.
Methodology and results: Mineral medium described by Jayasankar and Graham (1970) was used to isolate and enumerate pectinolytic organisms. Shannon-Weaver indices of general biodiversity and equitability were used to analyze their diversity and evenness. A total of seventy-six (76) strains of bacteria were isolated from carrot, tomato, onion, pepper and potato. They were identified as Erwinia carotovora, E. chrysanthemi, E. herbicola, E. atroseptica, E. amylovora, Pseudomonas flourescens, P. syringae, P. cichorii and Xanthomonas campestris isolates. Most of the organisms grew well on the mineral medium and showed pectinolytic activity at pH 6.0. Erwinia species were the most isolated (64.44%) with E carotovora having the highest frequency of occurrence (21) and the greatest diversity index of 0.36 among the samples analyzed. This was closely followed by Pseudomonas species (31.58%) with P. syringae having an occurrence frequency of 14 and index of 0.31. The least occurrence (3) and diversity (0.13) was recorded for X. campestris. Among the samples, onion had the greatest diversity of organisms with a total index of 0.98, followed by tomato (0.91) and the least was from carrot (0.69). Ojoo market had the greatest diversity among the sampled locations. Statistical analysis of the biodiversity index indicated that carrot, tomato and pepper (from Bodija), onion and potato (from Ojoo) as well as carrot and onion (from Oja oba) had no significant differences (p³0.05) in the diversity of the organisms isolated. Also, no significant difference (p³0.05) was recorded in onion and potato (from Bodija), carrot, tomato and pepper (from Ojoo) as well as tomato and pepper (from (Oja oba).
Conclusion and application of results: The results of this work showed that diverse pectinolytic organisms cause soft rot in various vegetables and pectinolytic organisms varied with different vegetables and locations of purchase. Therefore, there is the need for good hygiene, proper handling and sorting during transportation of retail vegetables to ensure good quality and safe vegetable.
Key words: Vegetables, soft rot, pectinolytic organisms, biodiversity index
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