Improvement of tomato through GE

THE AGRICULTURE must be looked after seriously being the backbone of our economy and life must be ordained for the poor masses. There is dire need for the developing countries like Pakistan to focus on developing their own technologies especially in food security because the cultivated land is decreasing day by day due to urbanization. Hence the need of the hour is that to develop such varieties that can give maximum production on the smallest pieces of land. Plant biotechnology can fulfill these requirements. As for example in Sri Lanka tissue culture labs had been established at cottage levels producing excellent results.

Tomato is the second most popular vegetable crop next to potato in the world. It is considered as one of the most important vegetable crops of Pakistan and is used throughout the year. From the nutritional point of view, it contains vitamins A and C, calcium, phosphorous and iron and also mineral salts that are helpful to accomplish the needs of human body. It is also cholesterol free. It contains approximately 20-50 mg of lycopene per 100 g of fruit weight. Lycopene is the powerful antioxidant and it protects humans from free radicals that degrade many parts of the body. Lycopene is also known to prevent cancer. Tomato is generally used in preparing “Catchup Chatni”, “Paste” and can become a source of foreign exchange. In Pakistan, due to difference in climate and land etc, it is cultivated round the year. At present, tomatoes are consumed at a higher rate in the developed countries than in the developing countries and hence it may be referred to as a luxury crop. At present in Pakistan, tomato has been cultivated on an area of about 31,822 hectares with annual production of about 379653 tones. Its average yield on hectare basis is 10,000-12,000 Kg/hectare.

Cultivation of tomato is closely related with climate. It can neither tolerate too high nor too low temperature. Normally 20-25°C temperature is best for its optimum growth and reproduction. In Pakistan, the quality and quantity of tomato is very low as compared to other countries of the world. The major reasons for low productivity includes lack of disease free seeds, lack of proper cultural practices, biotic and abiotic stresses. It is very sensitive vegetable that becomes spoil due to severity of weather. The abiotic stresses especially cold, drought and salinity are the major threat to tomato in Pakistan as well as in the world. Genetic engineering plays an important role to overcome these problems. This technique can be used for the transformation of DREB1A and OsNAC6 genes in tomato against these stresses (cold, drought and salinity).

Genetic engineering involves the insertion of desired gene or group of genes into a suitable vector system chosen for its ability to eventually transfer DNA to plant cells. Transformation refers to procedures of delivering foreign DNA into a living cell. Using these gene transfer systems, the desired DNA can be introduced into single cells of the plants. These single cells containing the new gene in one of their chromosomes are multiplied and subsequently persuaded to regenerate a complete healthy plant, in which each cell of very tissue contains the new genes. This whole process is called genetic engineering (GE). The most commonly used technique for genetic transformation in our country is Agrobacterium-mediated genetic transformation. The soil bacterium Agrobacterium tumefaciens – a natural genetic engineer is capable of transforming a range of dicotyledonous plants by transferring plasmid encoded genes into recipient plant genome. But recently specific phenolic compounds (Acetosyringone and Hydroxyacetosyringone) are used for transformation of monocotyledonous plants.

DREB1A and OsNAC6 genes encode a small family of transcriptional activators that have been described as playing an important role in freezing tolerance. As frost causes substantial agricultural yield losses, particularly if a freezing event occurs during reproductive development. Low temperature also substantially limits the geographic locations where crops can be grown. Both of these genes also play an important role in drought and high salinity. In Pakistan rice and wheat cultivars have been successfully transformed by using DREB1A and OsNAC6 genes against cold, drought and salinity stresses. The Xa-21 gene has also been successfully introduced into tomato cultivars such as Riograndae and Roma against bacterial wilt by using Agrobacterium-mediated genetic transformation.

Those areas of Pakistan where there are problems of cold, water shortage (drought) and high salinity, the transgenic tomatoes containing DREB1A and OsNAC6 genes would have the ability to tolerate all these stresses because the transformed genes would be expressed and activate the transcriptional factors that help in their expression pathway.

Both conventional and modern agriculture play their role in improving the quality and quantity of crop but conventional agriculture takes nearly 7-10 years in releasing desired genotypes. While by modern agriculture (Plant Biotechnology), we can achieve our target genotype within one year. In conventional agriculture, gene pool is limited i.e. we make crosses within the species but plant biotechnology solves this problem. We can take gene from any species and put it into our desired crop. The conventional agriculture is very laborious but modern agriculture is not that much labor intensive. In conventional methods such as hybrid seed production; the desired genetic characters are not transferred to next generations but in plant biotechnology desired characters are transferred from generation to generation. Same like, in conventional breeding, there is uncontrolled integration of genes while in plant biotechnology; there is a direct integration of genes.

All agricultural universities and agricultural research centres in Pakistan have been doing experiments in biotechnology on priority basis to make conspicuous the importance of biotechnology.

http://www.technologytimes.pk/mag/2011/feb11/issue01/improvement_of_tomato.php