Endophytic bacteria are an immense constraint in date palm micropropagation but their abundance is a good plant health indicator

Two strains of endophytic bacteria hampering date palm micropropagation were isolated from two cultivars (‘Deglet Nour’ and ‘Barhee’). Significant differences in bacterial population densities were observed in the cultures of the two genotypes and in cultures established from healthy and brittle leaf disease-affected plants. Indeed, the percentage of contaminated recipients in 3-year-old in vitro tissue cultures established from ‘Deglet Nour’ and ‘Barhee’ were 15 and 30%, respectively. Moreover, we found that percentage of contaminated recipients in 3-year-old in vitro tissue cultures established from healthy and BLD-affected ‘Deglet Nour’ palms were 15 and 2%, respectively. Embryogenic and organogenic cultures were seriously damaged by these fastidious bacteria. They slowly turned yellow and brown and then died within three months. On the other hand, the two bacteria were not toxic for vitro-plants as growth rates were similar in vitro-plants growing with and without bacteria.