3 August 1998

Mangoes and papayas could have a longer shelf life without refrigeration following a $1 million project involving Australian, Filipino and Malaysian researchers.

The Australian Centre for International Agricultural Research-funded project is investigating molecular approaches to controlling fruit ripening.

The project is led by Dr Jose (Jimmy) Botella, head of the University of Queensland's Plant Genetic Engineering Laboratory. It also involves the University of the Philippines at Los Banos, and the Malaysian Agricultural Research and Development Institute (MARDI) at Kuala Lumpur.

Dr Botella said most research in controlling fruit ripening had been conducted on tomatoes. Now that tomato plants could be genetically engineered to produce fruit that remained firmer for longer, research needed to expand into other fruits which rapidly spoiled, especially tropical fruits.

Genetically engineered fruits with slower rates of ripening could have extended shelf lives beyond those of current cultivars, allowing fruit to be shipped longer distances without spoilage. The quality of such fruit could be enhanced since fruit could remain longer on the tree before harvest, he said.

Dr Botella said papaya and mango were important fruit for domestic and export markets in ASEAN countries. However, in some countries where farmers did not always have access to electricity or refrigeration, there were "immense" losses through spoilage, sometimes reaching up to 80% of the harvest.

"One project aim is to find the genes responsible for ripening in papaya, and knock them out using antisense technology," Dr Botella said.

"We extract the gene from the plant, flip it around, and put it back in the new antisense construct which can reduce or block the expression of the original ripening gene.

"We are aiming to produce a range of plants - some which do not show any delay in ripening, some with a little delay, and some with major delays. Even fruits which never ripen could prove valuable, as we can artificially treat them with ethylene, a routine agricultural practice to stimulate ripening."

"The plants will be grown out in our containment glasshouses, then tested in field trials under GMAC supervision. If they receive GMAC approval, the most promising candidates should be available to farmers within the next five to seven years."

Dr Botella has used the technology in vegetable research at Pennsylvania State University, where he was formerly a postdoctoral fellow. Transgenic vegetables developed by another team at the Plant Gene Expression Center in Berkeley, California, included tomatoes with antisense genes. These were significantly firmer after harvest, had delayed ripening, and a reduced rate of fruit spoilage.

The ACIAR research project also aims to establish transformation methods for some mango varieties. Only one laboratory in the world, at the University of Florida, which has worked with mangoes for 25 years, has succeeded in any mango genetic transformations. Dr Botella said mangoes were "notoriously difficult and complex" plants with which to work.

He has appointed Dr Andres Cruz, a Mexican scientist awarded a PhD for his work on the Florida mango project, to the ACIAR team.

"Every transformation experiment lasts two to three years, a long time to wait before you know whether it has worked," he said.

"We are looking at ways to optimise success and reduce the experimental time to one year. The establishment of efficient mango transformation procedures will be a quantum leap in mango improvement since traditional breeding is excessively slow"

The project is using genes developed by the Plant Genetic Engineering Laboratory and patented by UniQuest, the University of Queensland's technology transfer company. The ACC synthase genes, known as CAPACS-1 and CAPACS-2, which play a key role in the fruit ripening process, have been isolated and cloned over the past few years.

Filipino researchers Dr Tony Larena and Dr Pablito Magdalita are working in the University's laboratory in the Botany Department. An important project component is to interact with scientists from the collaborating countries and provide training in advanced molecular biology techniques which can be used in their home countries.

In conjunction with other University departments, researchers are developing a proposal for extra containment glasshouses under the Federal Government's Research Infrastructure and Equipment Facilities Program.

For further information, contact Dr Botella, telephone 07 3365 1128, email: j.botella@botany.uq.edu.au