Clemson researchers modify cotton genes to improve productivity

May 24, 2023May 24, 2023

Clemson University researchers are determining how to develop higher-yielding, better-quality cotton by altering the growth habit and shape of plants.

Led by molecular biologist Sachin Rustgi, the researchers are examining how regulating certain genes can transform cotton from a perennial to an annual plant, as well as genes that control the number of bracts, small leaf-like structures that protect flower buds. of plants , or squares, against bollworms and other pests.

Right now, cotton is planted and grown as an annual but is actually a perennial, said Rustgi, an Advanced Plant Technology Program scientist at Clemsons Pee Dee Research and Education Center (REC) near Florence. , South Carolina. If we can develop an annual variety for cotton, we believe farmers in South Carolina will benefit by seeing higher yielding cotton with higher quality fibers.

The United States is the world’s top exporter of cotton, supplying about 35% of world cotton exports in recent years. Data from the United States Department of Agriculture shows that nearly 18 million bales of cotton were produced in the United States in 2021. Other than South Carolina, other major cotton-producing states are Alabama, Arizona, Arkansas, California, Georgia , Louisiana, Mississippi , Missouri, New Mexico, North Carolina, Oklahoma, Tennessee, Texas, Florida, Kansas and Virginia.

Cotton takes 130 to 160 days to grow. During this time, plants go through several stages from seed to emergence, emergence to first square (bud), square to flower, flower to capsule opening, and harvest.

The growth habit and structure of cotton plants determine its productivity and influence production management strategies, said Salman Naveed, a Clemson doctoral student who works with Rustgi.

Researchers are examining how plants use environmental and hormonal signals to switch from vegetative growth to reproduction. Reproductive development begins 4-5 weeks after sowing when squares are formed. During this stage, bracts surround the squares.

Typical cotton plants include three bracts. A fourth bract can form on some cultivars under certain conditions. This extra bract is undesirable because it can provide openings and allow thrips and other pests access to the squares.

During this study, the researchers injected tobacco rattle virus into cotton plants to fine-tune the balance between vegetative and reproductive growth. The virus has been used to manipulate a cotton gene associated with bract development to help prevent the appearance of a fourth bract.

When injected into a cotton plant, the tobacco rattle virus knocks down the gene associated with the fourth bract and only three bracts are produced, Rustgi said. The compact bracts make it more difficult for insects to attack the capsules.

The tobacco rattle virus has also been used to manipulate a cotton gene associated with plant growth.

Perennial crops usually grow in environments that may have limitations such as short growing seasons or dry climates, or where plants’ ability to access resources may be limited. Perennials store reserves such as carbohydrates, fats and proteins to use for regrowth. In many plant species, this process produces roots and shoots that can grow into new plants. This is called vegetative reproduction.

Because of its growth habit, cotton continues to add vegetative growth at the same time as reproductive development, diverting plant energy away from the production of fluff and seeds. Researchers believe that an annual cotton variety will help cotton plants use more energy to produce higher quality lint, resulting in higher profits for growers.

The hope is that the results of this study lead to breeding methods for developing annual-type cotton plants.

The upland cotton cultivars used in this study are Coker 201, CABD3CABCH-1-89, ARKOT 8102, HOPI MOENCOPI, SPNXCHGLBH-1-94, CAHUGLBBCS-1-88, TAMCOT SP-23, and GSA 74.

In addition to Naveed, other researchers collaborating with Rustgi on this project include Clemson graduate student Seyi Toyinbo and Clemson engineers Nitant Gandhi and Sarah Rawlins. Also involved are Mike Jones, a cotton specialist at Clemson Extension, and Todd Campbell, a research geneticist at the USDA-Agricultural Research Service.

This research is supported by the South Carolina Cotton Board and Cotton Incorporated.

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