When the world is facing a food crisis, land salinization has become one of the important reasons that threaten food production. Up to now, about 20% of the agricultural land in the world has high salt content, which has seriously reduced production. However, this problem is not hopeless. On March 12, 1 1 Sunday, a team led by Matthew Gilliham of the University of Adelaide, Australia, published a paper in the journal Nature Biotechnology, announcing the cultivation of a new salt-tolerant wheat variety, which can increase the grain yield in saline-alkali land by as much as 25%. ( 1)

Most crops planted by human beings are not salt-tolerant. Among them, durum wheat, which is common in Europe and America, is particularly sensitive to salt concentration in soil. In saline-alkali land, many crops have died before they are mature, and even if they can be harvested, the output will be reduced a lot.

Why are these crops not suitable for growing in saline-alkali land? There are two main reasons. First of all, in salt fields, it is more difficult for plants to absorb water and grow more slowly. In addition, salt ions entering the transpiration system of plants will also damage leaf cells. Sodium ions can accumulate in cytoplasm and cell wall, inhibit enzyme activity, dehydrate cells and eventually lead to leaf cell death. (2)

Wheat and rice, barley and corn all belong to Gramineae, and there are more than 10000 plants in this family. Its pollen is nearly round and there is a germination hole on its surface. On the left is the pollen of Gramineae, and on the right is the electron microscope image of artificially colored pollen grains with different shapes and sizes. What is circled is Gramineae pollen. wheatbp

However, some plants are born with salt tolerance. In 2006, Australian and British scientists discovered that in a fairly old diploid wheat variety Triticum monococcum, there are two gene loci that can express protein molecules that can improve plant salt tolerance. A grain of wheat is the ancestor of modern wheat and the earliest wheat variety planted by human beings. A processed wheat was found in the intestine of Oates, the famous mummy Iceman. However, a grain of wheat has long been excluded from modern people's diet, and the salt-tolerant gene it carries has disappeared in the long process of artificial breeding. Graham and his colleagues first identified a key salt-tolerant gene TmHKT 1 in wheat. 5a. Graham let tmhkt1; 5-A was expressed in yeast cells and Xenopus eggs respectively. It is found that this gene encodes a sodium ion channel whose function is to expel sodium ions from cells.

Further research shows that in wheat, tmhkt1; 5-A mainly acts in xylem cells of roots. The water absorbed by roots must pass through xylem to reach leaves, and if xylem cells are equipped with such a "salt discharger", the water absorbed from roots will lose quite a lot of sodium ions during transportation. In this way, the salt concentration will be reduced to a safe level before the water in the conduit reaches the blades. This has become the secret of salt tolerance of wheat.

Graham and his colleagues obtained a salt-tolerant gene TmHKT 1 from artificially planted durum wheat through hybridization. 5a. If it grows in saline-alkali land, the salt content of the leaves of this newly cultivated salt-resistant wheat is indeed lower than that of ordinary durum wheat. Although researchers have adopted many molecular breeding techniques, this salt-tolerant hybrid wheat is not a transgenic crop, so in the future marketing, planting and sales process, the new hybrid wheat will not be subject to some policy restrictions.

Compared with previous studies, Graham's results are more beautiful. Because his research has not only been successful in the laboratory, but also achieved good results in the actual cultivated land. Field experiments in various parts of Australia show that this new salt-resistant wheat can really increase the yield, which can not only increase the grain yield of Yantian by up to 25%, but also will not reduce the yield on ordinary cultivated land.

In this study, Graham and his colleagues used tetraploid durum wheat, which is common in Europe and America, as materials to cultivate a new hybrid wheat, which is also tetraploid wheat. However, in developing countries, people mostly grow hexaploid common wheat. Therefore, if the salt-tolerant gene can also be introduced into hexaploid common wheat, it will better help developing countries to increase food production and alleviate global hunger more effectively. In an interview with Shell. Graham said that they have successfully transferred the salt-tolerant gene into hexaploid wheat through cross breeding technology. The leaves of this hexaploid hybrid wheat variety with new genes can also be well protected from high-salt soil, making the whole plant salt-tolerant. However, Graham and his colleagues are still conducting field experiments to test whether this new salt-tolerant hexaploid hybrid wheat can really increase the yield.

Some people will worry that the newly cultivated salt-resistant hybrid wheat will further aggravate the degree of land salinization. For this reason, Graham told Shell.com that the newly cultivated salt-tolerant hybrid wheat would not worsen the soil quality more than other crop varieties. Under natural conditions, the main reason of soil salinization is still the leaching of rain.

This study not only cultivated new crop varieties, but also showed once again that the wild relatives of human crops are probably the treasure house of genes. In the long process of breeding, human crops have lost many genes, and their resistance to environmental stress is getting worse and worse. It is a feasible breeding method to try to retrieve the lost excellent genes from the wild counterparts of these crops.