Seedborne pathogens Minimize

May 2011. An email on the cocount list (coconut@googlegroups.com) mentioned the recently reported outbreak of a phytoplasma disease of cocounts in Madang, PNG. In that email the writer mentions a report by Dwyer (1938) (http://cocos.arecaceae.com/Dwyer_1938.pdf). In this report Dwyer tells of an epidemic disease that killed many palms on the Witu (or Vitu) Islands in the late 19th or early 20th century. He also states that during the German administration, Witu was a source of desirable plantign materiial, and the Neew Guinea Company sent seednuts to its plantations all around the territory, including Madang.

There is no way of knowing what epidemic hit Witu Island in the early 1900s and it may only be a coincidence that the coconuts at Baracoa in Cuba were decimated, almost certainly by LY disease, in 1905-1910. So, should the powers-that-be in PNG (and elsewhere in the Pacific) be concerned that history may be repeating itself?

In response a member (and moderator) said that movement of coconuts has always been associated with risk or at least unease by some people. In the 1990s there was concern in some quarters about the threat posed by viroids, especially those related to the cadang-cadang viroid. There were some who believed movement of coconuts from areas where these cadang-cadang-like viroids existed should be put on hold until indexing procedures were put in place; there were others who believed the opposite, that the viroids presented little risk, and germplasm was needed for breeders or for replanting schemes. The latter won the day.

It was pointerd out that whereas there is no evoidecne that phytoplasma diseases are seedborne in any crop, there is evidence that those diseases caused by viroids may be.

There was further clarifcation of the situation in coconuts by another member. There has been limited evidence of CCCVd transmitted through nuts in the Philippines to a few experimental palms, and the viroid can be detected in isolated embryos. Variants of CCCVd have now been sequenced from oil palms in association with "genetic" orange spotting, these are definitely seed transmitted at a rate higher than the Mendelian 50%. Some of the countries concerned are again looking at the issue in oil palm. 

Original:
tech.groups.yahoo.com/group/pestnet/message/8041

Replies:
tech.groups.yahoo.com/group/pestnet/message/8044
tech.groups.yahoo.com/group/pestnet/message/8046
tech.groups.yahoo.com/group/pestnet/message/8047