Detection of the coconut cadang-cadang viroid sequence in oil palm by ribonuclease protection assay
2007
Vadamalai, G. | Lau, W.H. | Tan, Y.H., Universiti Putra Malaysia, 43400 Serdang, Selangor (Malaysia). Dept. of Plant Protection
A ribonuclease protection assay (RPA) has been developed for detecting the 246nt sequence of coconut cadang-cadang viroid (CCCVd). Nucleic acid extracts from CCCVd-infected coconut palms protected three major fragments of the complementary RNA viroid probes, ca250, 125 and 50nt in length, as well as a variable number of minor fragments. While smaller than full length components alone cannot be considered as specific markers of infection, the protection of full length ca250 nt probe was shown to be diagnostic for the presence of the minimal infectious 246 nt unit of CCCVd in inoculated oil (Elaies guineensis) palms. Coconut and oil palms growing outside the known geographical range of CCCVd have previously been reported to contain CCCVd-related RNA. RPA was used to show that the sequence of CCCVd (to an estimated accuracy of 99%) was present in twelve out of eighteen commercial oil palms sampled in Malaysia. Signal intensity varied between the positive oil palms, was generally lower than in CCCVd affected coconut palms, and a comparison of fronds of one oil palm showed it was strongest in the oldest frond assayed. Detection of the sequence was not exclusively associated with the orange leaf spotting syndrome of oil palm. Apart from allowing to conclude that the CCCVd sequence occurs outside the known cadang-cadang area, RPA has potential as a sensitive, simple, robust and specific diagnostic method for studying the pathology, epidemiology and control of CCCVd.
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