For many years, farmers have sought to improve their crops by a process called cross-pollination. The aim is to breed plants selectively to produce superior strains. Individual plants with desired traits are selected and artificially cross pollinated, in the hope of producing offspring that shares those traits. For example, new strains have been developed to resist specific bacterial and viral attacks, to tolerate adverse environments such as drought or salty soil and to increase yields.
As the knowledge of classical genetics has increased, so has the ability to predict the outcome of particular cross-breeding strategies. Despite this knowledge, cross-breeding remains a somewhat hit-or-miss affair and it is expensive in both time and money.
Modern biotechnology makes plant-breeding programs more effective in two important ways. Firstly, it allows breeders to choose specific genes, incorporating into the new plant only those traits they want like salinity-tolerance plants. This makes the process of trait transfer faster, more exact, cheaper and less likely to fail than traditional cross-breeding methods. Secondly, it gives breeders the freedom to incorporate genes from unrelated species into the plant they are trying to improve. In classical cross-breeding, only plants that are similar may be cross-bred. However, the genetic engineering techniques of modern biotechnology allow genes to be swapped between unrelated species, so that plant breeders can incorporate new features that would normally not be available.
Since the 1960s a number of international bodies are helping Pakistan to improve the problem of rising water tables that cause waterlogging and salinity. Some of the most hard-hit areas are on the left side of the Indus River, in the arid zones of the Sindh province, like Nawabshah, Mirpurkhas and Sanghar. Salinity is one of Pakistan's top environmental challenges and the principal threat to Pakistan's vitally important irrigated agriculture. Each year, Pakistan loses about 25 percent of its potential crop production equivalent to US$ 2.5 billion due to salinity.
Some 50 to 60 years ago, the water table area was a minimum of 12 feet below the ground level. By 1984, the water table was less than 5 feet. Since the annual rainfall in Sindh is low, irrigation water has been primarily responsible for the rise in the water table and for build-up of salts in the soil, which chokes off potential for cropping. Because there was no natural route for groundwater to drain, an estimated one ton of salt was added to every irrigated acre in Sindh each year. Over the last decade, many farmers in this region are unable to cultivate, were forced to abandon their lands and ancestral homes in search of labor when their farmlands became saline and waterlogged. Vast tracts lay completely barren, and the salty soils give the appearance, from the air, of having received a recent snowfall.
Saline agriculture has provided hope for regenerating and vegetating the salinity-affected soils. This means managing soil and water and introduction of such crops that are more tolerant to the prevailing harsh environment marked by high salinity and water-logging. According to a research report, a great breakthrough has been made in re-vegetation of the saline-affected and degraded soils. "In Western Australia, farmers are getting yield increase between 30 to 50 percent on water-logged soils under crop such as cereal and canola as compared to the conventional plantation."
This year researchers have genetically engineered the world's first tomatoes that can grow in salty water - a potentially important discovery that could be used to grow other crops on irrigation-damaged and marginal land. Salty water is generally toxic to plants, but we have found a way to increase tomato's ability to transport it away and isolate it from the rest of the plant cell. Eduardo Blumwald from the University of California, Davis, said that "the sodium is taken up and kept in the leaves, away from the tomato itself."
Blumwald said that the tomato's taste no different from conventional varieties, but cautioned that was a personal rather than a scientific conclusion. He added that the genetically engineered tomato can grow in soil irrigated by water that is about 50 times saltier than normal. He said that although his research was on tomatoes growing in water made salty through irrigation, the technology would theoretically apply to naturally brackish water as well. Researchers used a gene from the plant Arabidopsis thaliana, relative of the cabbage, to transform their tomatoes. With the new gene spliced in, the modified tomatoes had a greatly increased ability to move the sodium portion of salt into storage cavities in the leaves.
In the U.S. there is now active academic and corporate research into the fields of salt tolerance and water use in plants. This research has very clear and enormous potential in a country where water is a big issue in agriculture, this technology, which allows the plants to use water more efficiently, could have great benefits.
Genetic modification that allowed the tomatoes to grow in salty conditions could have positive implications for making other crops salt resistant and for understanding how plants use water generally. The history of genetically - transformed tomatoes has been mixed. The first genetically engineered food approved by US federal regulators was the Flavr Savr tomato, which had been engineered to stay ripe for a longer time after being picked from the vine. The product had an initial success, but later was pulled from the market for commercial reasons. In the Nature Biotechnology article, the authors reported that "their tomatoes did have slightly increased levels of sodium and chlorine, which together make salt, and that the tomatoes were somewhat smaller than the conventional varieties."
Source: Financial Times
