Tomatoes and Conventional Plant breeding

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    Tomatoes taste much better than before due to the proper plant selection and conventional plant breeding - a technology where scientists crossbreed plants to introduce genes from one variety into a new genetic background. You may not be surprised to find that the tomatoes you get from the market near your house are sweeter and juicier than the ones you have in your granny's garden twenty years ago. According to a European Union study cited in “You Say Tomato” from Nature magazine, nowadays tomatoes contain more sugar and acids that make up the flavor than those before. Tomatoes’ genes are developing to get closer and closer to human desire. However, due to the uncertainty of the different gene foundations, proper plant selection becomes more and more difficult, which causes conventional plant breeding to make minimal progress. By further researching tomato genetics, including mapping its genome, scientists will spur huge developments in conventional plant breeding not only in tomatoes, but also many other crops, causing that ancient task to finally replace the currently popular mutation breeding.

Photo by Iynn. gardner

    A report in Nature website presents both domesticated tomato Heinz 1706’s and its wild ancestor Solanum pimpinellifolium’s high-quality genomic sequences; thus emphasizes that through the comparison between the two plants’ genome sequences, scientists can better understand the limitation in conventional plant breeding. Heinz 1706 was generated by Heinz Company and named after the company’s founder Henry Heinz. It was firstly cultivated by the conventional plant breeding of different tomatoes from all over the world and finally became an ideal type of tomato for making tomato ketchup. Therefore, different from its ancestor Solanum pimpinellifolium, “Heinz 1706” has many more developed traits which humans prefer. In this way, by comparing Heinz 1706’s genome with that of its ancestor, scientists can have a basic idea about what tomato genomes have been changed. As a result, they will be able to figure out which genomes have been well developed according to human desire and which have not. In other words, focusing on those undeveloped genomes, scientists may introduce new ways to carry out conventional plant breeding.

   
    After understanding the scientific value of genomic sequence, scientists then applied the discovery to tomato genetics studies into conventional plant breeding and formed a new technology - molecular plant breeding. This technology will then bring breeders a clearer guide about how to choose the types of tomatoes they are going to breed in order to get the desirable result. This is because under the help of genomic information, breeders now are more familiar with the function of different genomes. In this way, instead of trying all kinds of tomatoes in order to see which combination is the best, now the breeders can easily choose two types of tomatoes by checking if they have the genomes that are in need. Therefore, the plant breeding will be faster and more efficient. 

 
    Furthermore, that progress made in tomato cultivation will also enhance the plant breeding of other crops. There are two reasons, the first one is because tomatoes belong to one of the planet's most diverse plant genera - Solanum. There are more than 1,000 members in this family, including potatoes, tobacco plants, peppers, eggplant and nightshade. They spread all over the world and can be easily found. By studying tomato’s genome sequence, it will be easy for scientists to apply their knowledge about tomatoes to the cultivation of other crops in its family.  In “The time is ripe for tomato genetics”, because tomato is closely related to a large family, studying the tomato genome can increase the knowledge base around many different plants. (Howell, Whitney L.J.)

    Another reason for the application into other crops is the combination of the genomic knowledge, cloning technology and conventional plant breeding. Presented in “Genome analysis and genetic enhancement of tomato” (Gupta et al.), different genes are responsible for many different traits in plants and the map of genes is helpful for scientists to clone them. Therefore, after successfully cloning those ideal traits, scientists can help breeders to make further progress in the conventional plant breeding - breeders then will not have to wait for a long time for the bred plants to grow together and share the genomes. Instead, the specific genomes which control certain desirable trait will be able to be directly introduced into crops. This may not sound like conventional plant breeding, but it actually removes the biggest drawback - time consumed using from the conventional plant breeding and all the other good characteristics are maintained. In this way, the research on tomato genomes will bring the revolution to the conventional plant breeding of both crops in Solanum genera and all kinds of other plants. 

    Compared to huge potential improvements in conventional plant breeding, another population breeding type - mutation breeding has many more disadvantages. For conventional plant breeding, breeders mainly utilize the natural combination of two or more plants’ genes - even the combination of cloning technology only introduces new genomes to plants but never changes the existing genomes.  However, mutation breeding differs from conventional plant breeding by exposing plants to X-rays and using chemicals to cause mutations on existing genes. In this way, breeders completely lose control on the variations because there are thousands of possibilities that genomes can change under the influence of chemicals and ultra-rays and no one is sure what will happen. Also, exposing plants directly under those physical and chemical substances may cause the variation of the desirable genomes like those leading to high sweetness and strong disease-resistance. Therefore, although up to now, due to its convenience and fast speed, mutation breeding is still more popular than the conventional plant breeding, the application of genomic knowledge into the plant breeding will improve this ancient task in many ways and finally help it replace that uncontrollable mutation breeding.

    In general, through the tomato genomics study, scientists will have further understanding of plant genetic diversity and a huge development on the conventional plant breeding will be spurred. In spite of the immaturity of the molecular plant breeding, it is still a potent and powerful tool to improve the conventional plant breeding. In the future, crops may grow faster and become more resistant to diseases while also tasting better. Therefore, we will be able to enjoy delicious food whenever we want.













Bibliography:
- Gupta, Vikrant. Mathur, Saloni. Solanke, Amolkumar U. Sharma, Manoj K. Kumar, Rahul. Vyas, Shailendra. Khurana, Paramjit. Khurana, Jitendra P. Tyagi, Akhilesh K. Sharma, Arun K. “Genome analysis and genetic enhancement of tomato”. Critical Reviews in Biotechnology.Vol. 29.2 (2009): 152-181. Web. Feb.6.2013. <http://ehis.ebscohost.com/ehost/detail?vid=9&sid=77ff9587-e567-4e33-8758-0db495091d08%40sessionmgr115&hid=101&bdata=JnNpdGU9ZWhvc3QtbGl2ZSZzY29wZT1zaXRl#db=a9h&AN=43448167>

- Howell, Whitney L.J. “The time is ripe for tomato genetics” Whitney Howell. July 16, 2012. Web Feb.6, 2012 <http://wljhowell.wordpress.com/tag/heinz-1706-tomato-variety/>

- “The tomato genome sequence provides insights into fleshy fruit evolution” Nature, 30 May 2012, Mon. 18 Feb 2013. <http://www.nature.com/nature/journal/v485/n7400/full/nature11119.html>

- “You say tomato”, Nature, 30 May 2012. Mon. 18 Feb. 2013 <http://www.nature.com/nature/journal/v485/n7400/full/485547a.html>