Muscat: A research team from Sultan Qaboos University (SQU) has detected a new strain of the damaging citrus tristeza virus in Oman, according to a press release issued by the state-funded university on Saturday.

The university said that citrus tristeza is associated with some of the most severe viral diseases of citrus trees worldwide and threatens Omani lime, grapefruit, oranges and many other citrus cultivars.

The virus is believed to have killed over 100 million citrus trees in Spain, Brazil and Argentina, especially those which are grafted on sour orange rootstocks.

Dr Abdullah Mohammad Al Sa’adi, an assistant professor at the College of Agricultural and Marine Sciences at SQU, and his research team carried out a two-year study to assess the incidence of the virus in different regions of the country.

The study revealed that the virus had spread over a wide area in Oman, from Musandam to Dhofar. The researchers identified tell-tale signs of the virus such as sudden death of trees, weak growth and low yield across many regions. Studies on the ribonucleic acid (RNA) of the virus isolated in areas like Barka, Sohar, Madha and Dibba point to a category considered one of the most severe strains of the virus worldwide.

However, RNA analysis on two samples detected in Suwaiq revealed that they do not belong to any of the seven identified strains of tristeza virus, but suggest an entirely new mutation reported for the first time from Oman.

One of the main participants in the research, Shamsa Abdullah Al Hilali, noted that many citrus seedlings, particularly oranges, mandarins, grapefruit and others are usually imported. On examining imported seedlings closely, she found more than 40 per cent of the tested stock from India, Pakistan, Egypt, Syria and Lebanon to be infected with citrus tristeza virus. “Unless strict quarantine measures are applied, many of the seedlings imported from abroad may pose a threat to citrus cultivation in the sultanate and introduce serious diseases,” she said.

The study was funded by the Sultan’s Strategic Research Trust Fund for projects at Sultan Qaboos University.

The study recommends future investigations on symptoms that could be induced by the new strain of the virus, besides further studies on the spread of the new strain and other strains in different parts of the country.