Gene transfer yields pest resisting rice strain
THE International Rice Research Institute (IRRI) is located very picturesquely amidst emerald green paddy fields against a backdrop of hills in Los Banos, Philippines. The institute has generated many controversies and has even been accused of stealing germplasm from rice-growing countries. Hybrid rice varieties developed at IRRI in the 1960s and 1970s require heavy inputs of expensive fertilisers and pesticides and they are blamed today for both degrading the land and marginalising poor farmers. But IRRI scientists are quick to defend their institute. Said a spokesperson, "Our gene bank is a means of conserving germplasm, not of controlling it. Today, the raison d'etre of our research is to grow about 75 per cent more rice on the same amount of land and to do it in a sustainable way." To find out about some of IRRI's new breakthroughs in rice research, Down To Earth spoke to Darshan S Brar, an associate plant breeder at the institute, who has been working for years on rice hybrids.
What would you say are the most outstanding recent breakthroughs in the field of rice research?
A major breakthrough is the development of transgenic rice. Here, you transfer a gene from another rice or non-rice source like a bacteria, into a particular strain of rice. Earlier, it was not possible to produce transgenic rice, particularly in Indica rice strains. Indica, by the way, is one of two kinds of rice -- the other is Japanica rice. Indica rice is predominantly grown in tropical countries, while the other grows in cooler climates like that of Japan or some parts of Korea.
How will this transfer of the gene help?
An example illustrates this best. It is possible to transfer a gene from a bacteria known as Bacillus thuriengiensis (BT) into rice. When you do this, the rice plant develops resistance to insects, particularly to the Yellow Stem Borer, which is a worldwide problem and has caused a lot of damage to rice crops. We have not been successful in developing rice plants that are resistant to this pest through conventional methods.
Then there is case of the tungro virus, which attacks rice plants. In the last two years, scientists have also been successful in cloning the coat protein gene that can be transferred to the rice plant to make it resistant to tungro disease, which is a particularly virulent infection. In fact, this approach has been so successful that recently scientists were able to put the BT gene into cotton, making it more resistant to the boll-weevil, a notorious pest that attacks cotton and usually needs at least 15 sprays of pesticides to control.
We also have another major programme on a technique known as gene tagging. Here, a particular gene is tagged to molecular markers. This will help breeders in future to make a selection of characters -- something that's not possible at the moment. If, for instance, you want to breed rice for saline soils or for drought conditions, you can tag the genes for salinity or for drought and it will be much easier to do so.
There seems to be a radical change in approach here. Instead of changing the environment, are you changing the structure of the cell?
Yes. But although we are working at the cell level, or the protoplast level or the tissue level, the products that we are going to develop will have a very strong impact on the environment. They will help protect the land from the dangers of insecticides, herbicides and excessive fertilisers. We are looking for ways to minimise the use of these expensive yet toxic inputs.
But aren't there any dangers in this kind of experimentation? You are, after all, working in a new frontier and probably don't know the ecological effects of what you are doing.
The work we are doing is being undertaken under very controlled conditions. We do not release any material or any germplasm until it is thoroughly tested. Besides, every bit of research has to follow certain stipulated rules. Today, there is a very high level of public awareness about the hazards of biotechnology and each country has evolved its own set of regulations concerning it.
How long does it take for a transgenic rice plant to make its way from the lab to the market?
This varies a great deal and depends on the kind of improvement or character you're looking for. For instance, if you are transferring a character like resistance to insects using the BT gene, it will be a little easier because this gene has already been cloned. But if you are looking for characters like drought or flood tolerance or salinity resistance, it is more difficult as these are complex characters affected not just by one gene but by many. So experimentation to develop even the germplasm may take a longer time and then there is the period of testing and evaluation before its final release.
What do you think will be the next jump in rice biotechnology?
You could say that the first era was characterised by the breakthroughs in developing dwarf and semi-dwarf strains, like the IR varieties developed at IRRI. They were very good plant types and yield very well but required a lot of inputs and took a long time to mature. As a result, farmers were not able to grow more than one crop annually.
In the second era, we reduced the maturity period of rice so that two and even three crops could be grown a year, increasing yields very dramatically.
But we found that the earlier varieties had 20 or 25 tillers (a shoot of the plant springing from the bottom of the original stalk) and many of them had panicles (loose, branching cluster of flowers) that were weak or didn't sufficiently fill up with seeds. So the plant was wasting energy on these useless tillers. What we are hoping to develop now is a new plant variety that will have six to eight, or eight to ten tillers, but all of them well-filled with seed so that the total energy of the plant is put to optimum use.
Is it true that in some parts of Asia farmers have been successful in growing four rice crops a year?
Getting too many crops from the land is not advisable. It brings too many insects and other pressures on it. The soil is not allowed to regenerate. It is our concern that we do not impair the fertility or structure of the soil. Getting two crops has now become routine in many parts of Asia. Even three crops is possible, provided there are irrigation facilities and good fertilisers. But four crops would be putting too much strain on the soil.
But, surely, even three crops can be possible only if you have quick-maturing strains?
We already have varieties that can mature in 90 to 95 days, as against those that take 130 days.
Fears have been expressed that once a particular flavour of a rice, say, a basmati strain, is replicated in the lab, the farmer will lose control over the strain and later may not have access to it.
Yes, I've heard such fears being expressed. They may be valid as far as private seed companies are concerned, because they are governed by the laws of the market. But at IRRI, our mandate dictates that all germplasm developed here should be freely distributed to the countries participating in our programme.
Take the case of basmati. The germplasm of Dehra Dun basmati is already available in our germplasm centre, which has the germplasm of about 80,000 rice varieties from all over the world. Anybody can get this material from us. At the moment, Dr Gurdev Khush, the principal plant breeder at IRRI, is working on improving the basmati strain so that it has yields comparable to other modern rice varieties while still retaining the aroma. If this material becomes available in the next two to three years, then it will go back to all the national programmes associated in IRRI's work. It will then be the responsibility of the country concerned to make sure that the material reaches the farmer.
This is precisely what happened in the case of the dwarf and semi-dwarf varieties. The maximum benefits from these strains went to countries like India, China, Indonesia and Pakistan. This is the practice that has been followed over the last 30 years and it will continue to be followed. In fact, we expect in another four years to have some good material ready for distribution to the rice-consuming countries in this part of the world.