Diversity of culturable bacteria and occurrence of phytopathogenic species in bean seeds (Phaseolus vulgaris L.) preserved in a germplasm bank

Genetic Resources and Crop Evolution (Impact Factor: 1.46). 08/2012; 59:1597-1603. DOI: 10.1007/s10722-012-9902-y


The preservation of plant genetic resources involves the conservation of the microbial biota associated with them. The presence of culturable bacteria in a series of 16 bean seed batches, corresponding to nine local bean varieties, stored in a germplasm bank was studied by amplifying and sequencing the 16S rDNA. Microorganisms identified in seed lots were classified into three groups: environmental biota (present in all samples), biota characteristic of humans and animals (present in 53 % of samples) and phytopathogenic biota (present in 19 % of samples). Genus diversity ranged between 0.6931 and 2.0942 according to the Shannon–Weaver Index (H’), the sample presenting the highest number of plant pathogenic bacteria being the most diverse. This result suggests that contrary to common practice in diagnostic laboratories, it is necessary to identify all culturable bacteria isolates from each sample. In addition, the fact that potentially phytopathogenic bacteria have been preserved in a genebank should emphasize the importance of rigorous sanitary controls for plant genetic resources.

1 Follower
14 Reads
  • Source
    • "A previous study provided 16S rRNA gene sequence (Trapiello & González, 2012). This sequence shows 99 % similarity with those deposited in databases corresponding with strains of C. michiganensis. "
    [Show abstract] [Hide abstract]
    ABSTRACT: A yellow Gram-positive bacterium isolated from bean seeds (Phaseolus vulgaris L.) was identified as Clavibacter michiganensis by 16S rRNA gene sequencing. Molecular methods were performed in order to identify the subspecies. Such methods included the amplification of specific sequences by PCR, 16S-ARDRA, RFLP and MLSA as well as the analysis of biochemical and phenotypical traits including API 50CH and API ZYM. Results showed that strain LPPA 982T did not match any known C. michiganensis subspecies. Pathogenicity tests revealed that the strain is a bean pathogen causing a new bacterial disease that we name bacterial bean leaf yellowing. On the basis of these results, strain LPPA 982T is regarded as belonging to a new subspecies for which the name C. michiganensis subsp. phaseoli is proposed. The type strain is LPPA 982T (= CECT 8144T = LMG 27667T).
    Preview · Article · Feb 2014 · International Journal of Systematic and Evolutionary Microbiology
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Since the ability to genetically engineer plants was established, researchers have modified a great number of plant species to satisfy agricultural, horticultural, industrial, medicinal or veterinary requirements. Almost thirty years after the first approaches to the genetic modification of pulse crops, it is possible to transform many grain legumes. However, one of the most important species for human nutrition, Phaseolus vulgaris, still lacks some practical tools for genomic research, such as routine genetic transformation. Its recalcitrance towards in vitro regeneration and rooting significantly hampers the possibilities of improvement of the common bean that suffers from many biotic and abiotic constraints. Thus, an efficient and reproducible system for regeneration of a whole plant is desired. Although noticeable progress has been made, the rate of recovery of transgenic lines is still low. Here, the current status of tissue culture and recent progress in transformation methodology are presented. Some major challenges and obstacles are discussed and some examples of their solutions are presented.
    Full-text · Article · Nov 2014 · Biotechnology Advances
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The genus Clavibacter contains one recognized species, Clavibacter michiganensis. Clavibacter michiganensis is subdivided into subspecies based on host specificity and bacteriological characteristics, with Clavibacter michiganensis subspecies michiganensis (Cmm) causing bacterial canker of tomato. Cmm is often spread through contaminated seed leading to outbreaks of bacterial canker in tomato production areas worldwide. The frequent occurrence of non-pathogenic Cmm-like bacteria is a concern for seed producers because Cmm is a quarantine organism and detection of a non-pathogenic variant may result in destruction of an otherwise healthy seed lot. A thorough biological and genetic characterization of these seed-associated Cmm-like strains was performed using standard biochemical tests, cell wall analyses, metabolic profiling using BIOLOG, single-gene and multilocus sequence analyses. Combined, these tests revealed two distinct populations of seed-associated Clavibacter that differed from each other, as well as all other described Clavibacter michiganensis subspecies. DNA-DNA hybridization values are 70% or higher, justifying placement into the single recognized species, C. michiganensis, but other analyses justify separate subspecies designations. Additionally, Clavibacter strains isolated from pepper also represent a distinct population and warrant separate subspecies designation. On the basis of these data we propose subspecies designations for separate nonpathogenic subpopulations of Clavibacter michiganensis: Clavibacter michiganensis subsp. californici californiensis subsp. nov. and Clavibacter michiganensis subsp. chiloensis subsp. nov. for seed-associated strains represented by C55T (=ATCC BAA-2691T, =CFBP 8216T) and ZUM3936T (=ATCC BAA-2690T, =CFBP 8217T), respectively. Recognition of separate subspecies is essential for improved international seed testing operations.
    Full-text · Article · Dec 2014 · International Journal of Systematic and Evolutionary Microbiology