Potential of the coffee endophytic <i>Bacillus cereus sensu lato</i> strain CCBLR15 to control the plant-parasitic nematode <i>Radopholus duriophilus</i>

<i>Bacillus cereus sensu lato</i> strain CCBLR15 is highly efficient in inducing <i>in vitro</i> the mortality of coffee-parasitic nematodes, including <i>Pratylenchus coffeae</i> and <i>Radopholus duriophilus</i>. In the present study, this strain was further characterised to investigate (1) its taxonomic position, (2) the secreted/non-secreted nature of its nematicidal compounds, and (3) its in <i>planta</i> biocontrol capacity towards <i>R. duriophilus</i>. Firstly, analysis of 16S rRNA gene sequences and motility test indicated that CCBLR15 was closely related to <i>B. cereus sensu</i> stricto. Secondly, nematodes separate expositions <i>in vitro</i> to CCBLR15 culture filtrate and cell lysate revealed that nematicidal activity was attributed to compounds released after bacterial cell lysis. Thirdly, CCBLR15 nematode biocontrol capacity was studied using three <i>Coffea arabica</i> cultivars, either seed- or cutting-propagated. Plants were therefore characterised by different developmental stages, referred to as ‘early' and ‘advanced', with respectively 2-3 and 6-8 leaf pairs. Additionally, plants were grown in unsterilised soil, with a one-month delay between inoculations of bacteria and nematodes to assess the persistence of the nematicidal effects. The presence of <i>R. duriophilus</i> in roots decreased plant growth only in one cultivar whose plants were inoculated at the ‘early' stage. Nonetheless, CCBLR15 pre-inoculation significantly reduced the number of nematodes in roots of all cultivars and inhibited the negative effects of nematodes in ‘early’-inoculated plants. These results demonstrate the capacity of CCBLR15 to control <i>R. duriophilus</i> and constitute an important step before studying the persistence of its biocontrol effects on a longer period or after plants establishment in the field.