Culturing Bursaphelenchus cocophilus in vitro and in vivo.

Abstract

Red ring disease (RRD) is of particular importance in many African oil palms- and coconut-producing regions in Central and South America and the Caribbean. Its causal agent, the nematode Bursaphelenchus cocophilus (Cobb) Baujard, causes extensive damage to tissues in the plant trunk that typically leads to plant death within months. Nearly 100 years after its first report RRD remains understudied largely because the nematode cannot be cultured in vivo or in vitro, what hinders sustained research efforts on basic and applied aspects of the pathosystem. To overcome this problem we attempted in vivo culturing in coconut seedlings, paying attention to aspects that had been overlooked in previous trials. We also attempted in vitro culturing on several fungi endophytic to healthy and RRD-affected coconut trees. In the two in vivo assays performed we were able to recover hundreds of nematodes from the seedlings up to 60 days after inoculation, but the nematodes seemed unable to sustain parasitism in most seedlings. No nematode was recovered from the endophytic fungal cultures in neither of the two assays performed. Hence B. cocophilus continues to stand as the only obligatory plant-parasitic species of the speciose genus Bursaphelenchus and a somewhat intractable plant-parasitic nematode to study on.