A study on microbial diversity in different cultivars ofBrassica napusin relation to its wilt pathogen,Verticillium longisporum

Abstract

Oilseed rape (Brassica napus) is one of the major oilseed crops in the world but is vulnerable to attack by many pathogens and insect pests. In addition to the host plant genotype, micro-organisms present in the rhizosphere and within plant tissues affect the susceptibility to plant pathogens. While rapid progress has been achieved concerning the concept of plant resistance genes, information on the role of the microbial community in plant protection is less apparent. We have studied the endophytic bacterial populations present in different tissues of oilseed rape and also analysed several cultivars (Express, Libraska, Maluka and Westar), which differ in their susceptibility to the wilt pathogen Verticillium longisporum. The population diversity was studied using agar plating assay, fatty acid methyl ester analysis and functional characterisation of isolated strains. Our work shows that already in the seeds there exists diversity in populations as well as in the total microbial load between two of the four tested cultivars. About 50% of the strains isolated from cultivars Express and Libraska showed moderate to strong direct inhibition of V. longisporum. The diversity of the endophytic flora isolated from oilseed rape and its implications in crop protection are discussed.

LasI/R and RhlI/R Quorum Sensing in a Strain ofPseudomonas aeruginosaBeneficial to Plants

“…This close relationship between clinical and environmental strains implies that the environment can be a reservoir for opportunistic human pathogens, especially the rhizosphere, where the characteristics that make a bacterial strain an efficient plant growth promoter (e.g., antagonistic properties, colonization ability) could also make it a threatening human opportunistic pathogen (4). P. aeruginosa has been isolated from roots of different plants, such as oilseed rape, potato, and rice (17,27,38,55). However, few studies have specifically tested the abilities of these strains to act as root colonizers and plant growth promoters (13).…”

Impact of Plant Species and Site on Rhizosphere-Associated Fungi Antagonistic to Verticillium dahliae Kleb

“…Several studies have identified different biotic and abiotic factors influencing the structural and functional diversity of bacterial communities: (i) the plant species or genotype, (ii) the plant development stage or vegetation time, (iii) colonization with pathogens as well as the physiological state of the plant, (iv) the quality of the soil, (v) crop rotation, (vi) treatment with pesticides or fertilizers, and (vii) the geographical region (12,14,16,20,26,27,29). However, relatively little is known about how these factors influence fungal communities in rhizosphere and bulk soil.…”

Distribution and Identification of Endophytic Streptomyces Species from Schima wallichii as Potential Biocontrol Agents against Fungal Plant Pathogens

“…Microbial metabolites may have an active role in resistance development by functioning as signals mediating cross-talk between the endophytes and their host (Graner et al, 2003). Since the endophytic actinomycetes were isolated from medicinal plant and that strains expected to produce a wide variety of antifungal and plant growth regulatory bioactive metabolites (Bredi, 1989;Franco and Cautinho, 1991), they can be exploited as novel sources of natural products and novel biocontrol agents as well.…”