Biocontrol of Cereal Pathogens

Abstract

Septoria leaf blotch has been the major disease of wheat in Britain and much of the rest of Europe. It has been reported that the disease causes serious yield losses to range from 31 to 53%. Mycosphaerella graminicola (anamorph: Septoria tritici) is the pathogen which causes Septoria leaf blotch. The disease can be controlled by various methods such as cultural practices, chemical control, using resistant varieties and biological control. In plant pathology, the term biological control leads to the introduction of microbial antagonists or host specific pathogens to suppress diseases and populations of one or more plant pathogens. This study investigated the microbial community on and within wheat leaves which can suppress Septoria leaf blotch by reducing the inoculum level of the causative pathogen M. graminicola. Plate count and DGGE analysis techniques were used to assess the microbial community. The changes in the microbial populations of healthy, senescent and M. graminicola infected i.e. diseased wheat leaves were investigated in vitro on agar plates using plate colony count method. It was found that method was successful in assessing both bacterial and fungal population sizes showing distinct colonies. DGGE is a rapid method which can analyze large number of samples simultaneously. The bands appearing in DGGE profile represent different species present in the microbial population. The DGGE technique was successfully used in this study to assess bacterial community. Bioinformatics tools have also played a vital role in this study for identifying bacterial and fungal species. A total of five bacterial species and five fungal species were identified by bioinformatics tools. The antagonistic abilities of identified bacterial and fungal species were tested against a Septoria isolate in vitro on dual culture PDA plates. Four microorganisms (Fusarium sp., Verticillium sp., Penicillium sp., Sporobolomyces sp. and Microbotryum sp.) in the dual cultures vary in their colony length, width, ratio of length and width and distance bwtween them. But after statistical analysis all the values are insignificant observations of dual culture plates indicated that the microorganisms might inhibit Septoria by competing for space. These microorganisms after testing might be good candidates for further in vivo testing of Septoria inhibition. A thorough knowledge of wheat leaf microbial communities is required for further use of biocontrol in the future.