Detection of coconut cadang-cadang viroid-like sequences in oil and coconut palm and other monocotyledons in the south-west Pacific

Fractionation, electroblotting and molecular hybridisation of nucleic acids extracted from tissue of African oil palm and coconut palm and some other monocotyledonous species, collected in several areas of the south-west Pacific region, demonstrated the presence of small nucleic acids with nucleotide sequences and secondary structure similar to coconut cadang-cadang viroid (CCCVd). The oil palms which contained CCCVd-related molecules showed orange leaf spots resembling those described for oil palm naturally infected with CCCVd in the Philippines, and also characteristic of a condition known as "genetic orange spotting" (GOS). We provide preliminary evidence that GOS is an infectious disorder caused by a viroid. The coconut palms did not show symptoms typical of cadang-cadang disease, but sometimes were chlorotic, stunted, or had a reduced yield. The possibility that the isolates represent variants of CCCVd is discussed. The data suggest that viroids with nucleotide sequences similar to CCCVd occur widely in palms and other monocotyledons outside the Philippines.