US – Researchers at New Mexico State University are carrying out field and lab trials on a glandless variety of cotton whose seed meal has potential as a feed ingredient because of its low gossypol content.
What if cotton production was not all about the lint, the fibre we use so extensively for clothing and other products? What if the seeds, which form a significant part of the boll, could, like sunflower seeds, be used in human foods and in feed for a wide range of domesticated animals?
El Paso Times reports that, in such a world, cotton producers would make more money on their crop because more of the plant would be of value; livestock producers and aquaculturalists would have another, and perhaps less expensive, feed option for their animals; and consumers would have new food products. Think cottonseed oil for salads; baking and frying; cottonseed butter for individuals with peanut allergies; cottonseed granola bars; or cotton-based ice cream.
The main impediment to realising this scenario is the presence of high levels of gossypol in cottonseed. Gossypol is a natural toxin, found in most varieties of cotton that makes all of the plant’s tissue, including the seeds, inedible by humans and most animals. It acts as a natural defence, helping to limit damage from chewing insects.
Currently, cottonseed by-products are used in some cattle feed, since ruminants, with their special digestive system, can tolerate limited amounts of gossypol. Using gossypol-laden cottonseed oil or meal in food for humans or in feed for poultry, hogs, shrimp or catfish is out of the question.
Gossypol is produced by small glands found throughout the above-ground tissue of most cotton plants, and therefore varieties without those glands, and which therefore do not produce the toxin, are referred to as ‘glandless’ cotton. Gossypol-producing varieties are frequently referred to as ‘glanded’ cotton.
Several New Mexico State University researchers are involved in field and lab trials of a glandless variety of cotton, Acala-GLS. The research trials, which include agronomic and insect resistance evaluation, are funded by Cotton Incorporated, a national organization that supports the cotton industry.
Acala is one of the leading varieties of cotton, due to its combination of high fibre quality and productivity. In this research, the glandless Acala is being compared to two other Acala varieties, Acala 1517-99 and 1517-08, in terms of productivity and of susceptibility to insect pests.
The principal investigators on CI grants involving glandless cotton are John Idowu, Extension agronomist in the Department of Extension Plant Sciences; Jane Pierce, Extension entomologist in EPS and associate professor in the Department of Entomology, Plant Pathology and Weed Science, who is based at NMSU’s Agricultural Science Center at Artesia; and Tracey Carrillo, assistant director of campus farm operations and superintendent of NMSU’s Leyendecker Plant Science Center and Fabian Garcia Research Center.
Also participating in various aspects of the glandless cotton research are Jinfa Zhang, associate professor in the Department of Plant and Environmental Sciences, who heads up NMSU’s long-standing Cotton Breeding and Research program; Scott Bundy, associate professor and entomologist in EPPWS; and Robert Flynn, associate professor and Extension agronomist in EPS and superintendent of the Artesia science centre.
This idea of expanding the use of cottonseed meal and oil is not new but actually implementing the dream has yet to prove commercially viable. With glanded cotton, the additional processing required to remove gossypol from the seed products makes the meal and oil more costly than other widely available oil and protein sources. With glandless varieties, the pest pressure, lower yield and lack of a robust market for the gossypol-free seed have deterred producers.
Varieties of gossypol-free cotton have existed for a long time – a variety of such cotton, with variable density of gossypol glands, was raised by the Hopis of Arizona more than 100 years ago. Seeds from that variety, dubbed Gossypium hopi, were actually used in US Department of Agriculture upland cotton breeding projects beginning as early as 1905. However, the issue back then was not the lack of gossypol but rather Hopi cotton’s early maturation and its viability in arid environments. Introducing those characteristics into upland varieties, with their larger bolls and longer, thicker lint, was the breeding goal.
According to Dr Zhang, it was not until the late 1950s that there was discussion of developing glandless cotton for food and feed applications. He said that glandless cotton was raised extensively in both Africa and China in the 1990s with the idea of using the seed products more widely for food and feed but the economic forces at work did not support the enterprise.
The Acala-GLS in the NMSU study was originally developed and tested in California, where it faced higher pest pressure and produced lower yield than other Acala varieties. NMSU researchers hope that New Mexico will prove more hospitable for growing glandless cotton than many other locations, since the two most serious cotton pests, pink bollworm and boll weevil, have been largely eradicated and pest pressure from other insects is relatively low.
"Right now, here in New Mexico, there have been major eradication initiatives of the major cotton pests, like pink bollworm and boll weevil, and the lygus pressure is very low, so we are thinking that this cotton might be able to do well," said Dr Idowu in a recent interview at his Leyendecker test plot.
"This is the second year of our study. Last year we tested it, and we saw that we were able to get reasonable, significant lint yield and seed yield from the glandless cotton. So far it’s looking good, we have not had any major pest attack on the crops. The cotton at this stage is looking better than even last year so we are expecting a higher yield this year."
According to Dr Idowu, what was unclear after the first year was whether the somewhat lower yield in both lint and seed from the Acala-GLS, compared to the other Acala varieties, was due to differences in pest pressure or other factors, perhaps genetic productivity differences among the three varieties. El Paso Times adds that the next step was to monitor the insects and try to assess their impact on the glandless cotton.