A new study published by Chinese researchers has shown that genetically engineered papaya trees are increasingly spreading beyond the plantations. This has also been observed on the island of Hainan. The trees were originally genetically engineered to be resistant to a virus that causes considerable problems in cultivation, i.e. papaya ringspot virus (PRSV). However, this resistance has been declining for several years, and another virus, very similar to PRSV, is spreading.
Until now, the transgenic, virus-resistant papaya trees were thought to be very successful in combating PRSV. In order to achieve resistance, parts of the genetic material of the virus were permanently integrated into the papaya plants. The trees were first approved in Hawaii in 1998. In 2006, Chinese researchers developed other variants, which have since then been cultivated in China.
The transgenic trees have already been found several times growing outside the areas of cultivation. Seeds from the fruits are one route of dispersal. Chinese researchers have now taken a closer look at the feral trees growing on the island of Hainan, as a very similar virus, the papaya leaf distortion mosaic virus (PLDMV), seems to be increasingly causing problems in this region. PLDMV is also present in other papaya cultivation regions and spreading rapidly in Hainan since a few years.
According to the publication, the transgenes were found in more than half of the samples stemming from the feral trees. Many of the genetically engineered trees were infected with PRSV. In some cases, the researchers found the trees had a combination of both infections, i.e. PRSV and PLDMV.
Testbiotech is concluding that the feral transgenic papaya plants can act as a reservoir for both, transgenes and viruses, at the same time. Such a situation can promote the emergence of new virus variants. Recombinations between different viruses also may occur.
The Chinese researches found the evolution of the viruses in Hainan to differ from developments in other regions, such as Japan or Taiwan: It appears that the high level of genetic diversity in PRSV and PLDMV together with signs of accelerated adaptation of PLDMV viruses, could lead to these viruses spreading faster.
This particular development could be promoted by the partial isolation of the Chinese island. In addition, it may also play a role that different gene segments of the virus were used in the transgenic trees in China to the ones in Hawaii. However, the problem is by no means limited to Hainan. Some of the virus variants occurring there have also been found on the mainland, and the possible routes of spread extend as far as Thailand.
According to the Chinese researchers, further research is needed to investigate the actual causes of the problem and how it can be contained.
Contact:
Christoph Then, info@testbiotech.org, Tel + 49 151 54638040
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