The value of cotton extends well beyond the plant's fibres. The plant's thick green leaves and thin, yet sturdy, stems not only nourish and support the cotton bolls (the plant's oval-shaped fruit), but are also used for mulch and animal feed. In addition, cotton seeds are crushed and distilled into one of the world's most popular vegetable oils, used for soap, cosmetics, pharmaceuticals and plastics.
"There's nothing like cotton," says Ibrokhim Y. Abdurakhmonov, a professor at the Institute of Genetics and Plant Experimental Biology, which is part of the Uzbekistan Academy of Sciences. Abdurakhmonov shared the TWAS Prize in Agricultural Sciences for 2010 for his research examining the molecular biology of cotton.
As Abdurakhmonov notes, cotton is at risk. While troublesome and destructive, it's not the pests – caterpillars, aphids and flies – that pose the most serious long-term risk, he says. Nor is it a loss of land to development or the depletion of top soil that is at the heart of the problem.
Instead, Abdurakhmonov points to the use of a limited number of cultivars, each with the same germplasm, as the key threat to future cotton yields. "It's narrowing the genetic diversity," he says. "That makes cotton plants highly vulnerable to pathogens and insects."
"Over the past half century, Uzbek cotton farmers have repeatedly planted the same cultivar, 'Tashkent'," says Abdurakhmonov. Drawing on seeds from the same gene pool has not only compromised the size and quality of cotton yields; it has also placed the health of cotton plants at risk since genetic diversity makes the plants stronger and more resilient.
Abdurakhmonov and his colleagues use molecular biological techniques to examine the germplasm of Uzbekistan's cotton. They do this to uncover the precise location of individual genes in the DNA. In the language of molecular biology, Abdurakhmonov and his colleagues map QTLs (quantitative trait loci) to identify specific genes that govern, for example, fibre quality, the timing of flowering and leaf defoliation, and the structure and strength of stems and roots.
"As you might expect," Abdurakhmonov notes, "this is a demanding task." First of all, it requires access to state-of-the-art molecular biological equipment and advanced scientific knowledge to appreciate and understand what is revealed. He and his colleagues, for instance, apply RNAi (RNA interference) to "knock out" or "silence" (that is, disable) a specific gene by blocking the corresponding RNA – the messenger molecule that carries the information stored in the DNA to the protein-making machinery within the cell.
By "silencing" a specific RNA gene, scientists can explore the proteins' functions and examine the consequences of the gene's absence. This is especially important because, as researchers have learned, there is not a one-to-one relationship between a gene and its biological and chemical function. Instead, biological and chemical function results from an intricate series of interactions among multiple proteins. Environmental impacts, moreover, can alter these interactions in ways that scientists do not yet understand.
With nearly 1.5 million hectares of cotton under cultivation, Uzbekistan is the world's third largest cotton exporter. Only the United States and Australia export more. The research being conducted by Abdurakhmonov thus has important implications for both the nation's farmers and overall economy.
"If Uzbekistan's cotton crop is to remain sustainable over the long term," Abdurakhmonov maintains, "we will have to broaden the genetic diversity of commercial cotton crops. That's the best insurance policy we have to protect cotton from pathogens and pests."
Genetic diversity depends first and foremost on an understanding of the makeup and behaviour of proteins, and the way in which proteins work together to create specific biological and chemical traits. The study of cotton's genetic makeup is a fascinating research challenge, says Abdurakhmonov. "But it also has significant implications for broad segments of Uzbekistan's society and economy."