Using biotechnology to: Alter cotton's lint/oil production

You can take the cotton extension specialist out of the San Joaquin Valley, but you cannot take the San Joaquin Valley out of a former cotton Extension specialist.

Tom Kerby left the University of California 13 years ago after a decade-long stint in California, yet he still harkens back to a treasure chest of information he and an outstanding crew of UC and USDA scientists and UC Cooperative Extension farm advisors developed during a decade of field research.

It was so significant, Kerby said it has impacted cotton production worldwide. He ought to know. Until recently, he headed a Delta and Pine Land Co. agronomy staff of 40 people stationed worldwide working in cotton production.

He stepped down from that post Sept. 1, becoming vice president of technical products for the company. He now lives in Utah.

What Kerby and the others discovered about the energy production and consumption of a cotton plant has crossed into the fascinating world of cotton biotechnology.

Biotechnology has given cotton growers revolutionary tools to control weeds and lepidopterous pests, but as cotton growers have heard that is only the tip of the tantalizing iceberg of what the potential is for biotechnology; drought tolerance; cotton plant tolerance to a host of herbicides other than glyphosate; transgenic crops resistant to nematodes and improved fiber properties and the list goes on.

Kerby at the Central Coast Cotton Conference in Monterey, Calif., put the ultimate carrot before growers and consultants when he said Deltapine is developing a biotech cotton plant that can redirect its energy from the oil and seed production to significantly more lint production.

“Why do we grow cotton? For the oil or the lint?” Kerby said. “It's the lint.”

From Kerby's work in California and earlier as a graduate student at the University of Arizona, cotton physiologists and agronomists learned that about the time a cotton plant starts flowering, it basically starts a downward vegetative cycle. The fruit a cotton plant sets basically cannibalizes the energy from the photosynthesis process of the vegetative growth.

The more fruit, less growth and, therefore, reduced long-term yield potential.

Fortunately, Kerby said a cotton plant is very responsive to inputs, and growers have been able to successfully mitigate this process by manipulating the plant by reducing or increasing inputs like fertilizer and water and using plant growth regulators.

Development of more indeterminate cottons, as well as different shaped cottons like columnar types, also has allowed growers to better “apply the gas or put on the brakes of a cotton plant” to improve yields.

Monitoring techniques to record nodes above white flower and internode distances gives growers clues as to what manipulative tools to use get the desired response.

“Cotton is extremely responsive to management,” and growers can make decisions based on what they consider the needs of the plant.

However, because of the huge energy drain on the plant as it sets for mature fruit, management can go only so far. Kerby implied biotechnology can be the next major step to higher lint yields.

Kerby would not say too much about this tantalizing new cotton biotechnology path, other than Deltapine has been working on it for a “few years” and is growing these modified plants in greenhouses. They have exhibited higher yields and “substantially higher turnouts” with little added nitrogen to compensate for higher yields.

A clue to pursue this low oil/high cellulose biotech cotton came from one of Deltapine's most successful conventional cotton introductions, Deltapine 555, an indeterminate variety that Kerby called “a different kind of plant…it did not slow down after first flowering.”

A clue to why this happened was revealed in the oil content of 555. Where most other cottons have oil contents of 18 percent to 20 percent, 555's oil content is only 15 percent.

Kerby said that difference in a 555 oil content and what he had learned about the energy cycle of cotton were two clues that created the hypothesis that if more energy was put into making lint rather than oil and seed, yields could be substantially higher.

Obviously, there are some issues yet to resolve. One is reduced oil and seed content. This would reduce the value of the seed and oil in cotton, but Kerby contends this could be more than compensated for with significantly higher yields.

The seed would be smaller and not as viable as conventional seed. Kerby acknowledged the problem, but hinted that the transgenic trait in this high cellulose cotton would be triggered after emergence of conventionally planted cotton.

If Deltapine or another company commercializes these racehorse cotton varieties that produce far more lint and considerable less oil than current cottons, its genesis can be traced to the years Kerby spent in the San Joaquin Valley.

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