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

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.