Cotton breeders are using genetic insights to make this global crop more sustainable :: InvestMacro

By Serena TalugaAnd the Texas A&M University

Products derived from the cotton plant appear in Many items that people use dailyIncluding blue jeans, bed sheets, paper, candles, and peanut butter. In the United States cotton Annual yield of 7 billion US dollars It is grown in 17 states from Virginia to Southern California. Today, however, it is in danger.

Cotton plants from fields in India, China and the United States – the three largest producers in the world – all grow, flower and produce cotton fibers very similarly. This is because they are genetically similar.

This can be a good thing, as breeders select the best performing plants and breed them to produce better cotton each generation. If a variety produces the best quality fiber that sells at the best price, then farmers will grow that variety exclusively. But after many years of this cycle, The grown cotton begins to look the sameHigh yielding and easy for farmers to harvest with machinery, but largely ill-equipped to combat disease, drought, or insect-borne pathogens.

Breeding alone may not be enough to combat the low genetic diversity of the cultivated cotton genome, because breeding works with what is there, and all that is there looks the same. Genetic modification may not be a realistic option to produce beneficial cotton for farmers, because obtaining approval for engineered crops is expensive and heavily regulated. my research It focuses on the possible solutions that lie at the intersection of these tools.

Harvesting and mechanical processing takes the cotton from the field to the fibers and seeds.

How to reprocess cotton

In an ideal world, scientists can Change only some of the main components of the cotton genome to make plants more resistant to stresses such as pests, bacteria, fungi and water restrictions. The plants will still produce high quality cotton fibres.

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This strategy is not new. some 88% of the cotton grown in the United States It has been genetically modified to resist caterpillar pests, which are expensive and difficult to manage with conventional insecticides. But as new problems emerge, new solutions will be needed that require more complex changes to the genome.

Recent advances in plant tissue culture and regeneration have made it possible to develop a whole new plant from a few cells. Scientists can use good genes from other organisms to replace defective genes in cotton, resulting in cotton plants with all resistance genes and all genes of agricultural value.

The problem is that obtaining regulatory approval for a genetically modified crop to be brought to market is a long process, often between eight to ten years. It is usually expensive.

But genetic modification is not the only option. Today researchers have access to a huge amount of data about all living things. Scientists have Complete genome sequencing of many organisms And they annotated many of these genomes to show where the genes and regulatory sequences were located within them. Different Sequence comparison tools Allowing scientists to match one gene or genome against another and quickly locate differences.

Map showing US states where cotton was harvested in 2017.
Cotton is grown in 13 states across the southern United States, and the western half of this belt has been experiencing drought since 2000.
US Department of Agriculture

Plants have very large genomes with lots of repetitive sequences, making them very difficult decode. However, a team of researchers changed the cotton genetics game in 2020 with its release Five updated and annotated genomes Two of the cultivated species and three of the wild species.

Assembling wild genomes makes it possible to begin using their valuable genes to try to improve the cultivated cotton species by breeding them together and looking for those genes in the offspring. This approach combines traditional plant breeding with detailed insights into the cotton genome.

We now know the genes we need to make grown cotton more resistant to disease and drought. We also know where to avoid making changes to important agricultural genes.

Hybrid Cotton Analysis

These genomes also allow the development of new screening tools to characterize interspecific hybrids – the offspring of two cotton plants of two different species. Before this information was available, there were two basic types of Hybrid characterization. Both were dependent on Single nucleotide polymorphisms, or SNPs Differences between species in one husband baseThe individual building blocks of DNA. Even plants with small genomes have Millions of base pairs.

Bases are the parts of DNA that store information and give DNA the ability to encode visible features of an organism. There are four types of bases in DNA: adenine (A), cytosine (C), guanine (G), and thymine (T).
National human genome research instituteAnd the CC BY-ND

SNPs work well if you know exactly where they are in the genome, if there are no mutations that alter the polymorphism, and if there are a lot of them. While cotton contains SNPs that have been identified and verified in specific regions of the genome, they are few and far between. So the characterization of cotton hybrids by focusing exclusively on the polymorphism would produce incomplete information about the genetic makeup of those hybrids.

These new genomes open the door to evolution Sequence-based screening Hybrids, something I have included in my work. In this approach, scientists still use SNPs as a starting point, but they can also sequence the surrounding DNA. This helps fill in loopholes and sometimes detect new previously undocumented polymorphisms.

Sequence-based screening helps scientists make more informed and robust maps of the genomes of hybrids. Determining which parts of the genome belong to both parents can give breeders a better idea of ​​which plants must cross together to produce better and more productive cotton in each generation.

What does cotton need to grow?

With the world population rising towards a It is expected to reach 9.8 billion by 2050The demand for all agricultural products will also rise. But making the cotton plant more productive is not the only goal of genetic improvement.

Outside the United States, much of the world’s cotton is grown in low- and middle-income countries.

Climate change Raising average global temperaturesand some important cotton-producing regions such as the southwestern United States become drier. Cotton is a crop already accustomed to heating—our research plots can thrive in temperatures of up to 102°F (39°C)—but a single cotton plant requires about 10 gallons (38 liters) of water over a four-month growing season for maximum yield potential.

Researchers have begun searching for cultivated cotton that can withstand drought in seedling stageas well as in Hybrid lines And the genetically modified lines. Scientists are optimistic about their ability to develop plants with higher drought resistance. Along with many other cotton breeders around the world, my goal is to produce more sustainable and genetically diverse cotton so that this essential crop can thrive in a changing world.Conversation

About the author:

Serena Taloga, Ph.D. candidate in genetics and genomics, Texas A&M University

This article has been republished from Conversation Under a Creative Commons License. Read the original article.

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