Writer: Kathleen Davis Phillips, (979) 845-2872, ka-phillips@tamu.edu
Contact: Dr. Andrew Paterson, (979) 845-3773, ahp0918@acs.tamu.edu
COLLEGE STATION — Millions of years ago, two different types of cotton evolved independently of each other, on different continents — one with fibers on its seeds, the other without.
“These two types joined together about 1 million years ago, leading to the cultivated cottons of today that are superior to each of their ancestors,” says Dr. Andrew Paterson, director of the Plant Genome Mapping Laboratory at Texas A&M University.
Molecular research at the Texas Agricultural Experiment Station now has found where many of the positive attributes from each cotton reside in the DNA. And that is helping breeders develop higher yielding, better fiber cotton in Texas, according to Paterson.
“For farmers, this means that we have identified a subset of genes that regulate the quality of cotton yield and fiber,” Paterson said. “Already this subset has been used to breed potential new varieties which will soon be tested in the field and will be further developed commercially in two or three more years if they do well there.”
The finding was published in the Proceedings of the National Academy of Sciences.
Paterson explained that about 10 million years ago, cotton derived from one plant of an unknown genotype. Through evolution, that plant spawned type “A” plants that “learned” how to make spinnable fiber, and “D” plants that could only make short fuzz on its seed,” he said.
“A” cottons come from the Old World, Asia and Africa, Paterson noted, while “D” cottons are from the New World, Central and South America.
“Then about 1 million years ago, A and D somehow came together,” he said. “We don’t know how that happened since they were on different continents, but the AD plant emerged, this time with fiber- producing quality from A.
“Over time, both natural selection and scientific plant breeding led to AD types that have both higher yield and quality of fiber than A types. This suggests that genes from D are making a contribution to fiber yield and quality, despite the fact that the D ancestors do not make fiber,” Paterson added.
To identify the genes, Paterson and colleagues Chun-Xiao Jiang, Robert Wright and Kamal El-Zik crossed two genotypes and then measured the fiber characteristics in more than 270 of the progeny.
“Fingerprinting tools for a cotton (gene) map didn’t exist when we started this project, so we developed them” Paterson said. “Then we did the DNA fingerprint for the entire chromosomal complement on all 271 of them, and lastly we scanned the chromosomes for the association of particular traits such as fiber strength, yield, number of bolls and others.”
Their first experiment led to the identification of 14 genes associated with fiber yield and quality. Their recent work has added at least 30 additional genes, and Paterson believes that more are likely to be found. The trick for cotton breeders, he said, is finding which of the genes have positive offerings and which do not.
“Perhaps with one of the genes breeders will see an improvement in fiber quality but a reduction in yield. That would not be a good gene to use in the breeding program,” he said.
Dr. John Gannaway, Texas Agricultural Experiment Station cotton breeder in Lubbock, said the mapping efforts of Paterson and his colleagues will enable cotton breeders to make significant improvements in yield, quality and other desirable traits that are in demand by producers, textile manufacturers and other segments of the cotton industry.
“Identification of the desired genes in concert with marker assisted selection will enable us to more easily identify the plants that contain the superior traits and then make them available to commercial seedsmen for production of superior varieties,” Gannaway said. “Dr. Paterson’s research efforts will reduce our varietal developmental time frame and improve our efficiency.”
This research is vital for Texas because about one-fourth of the U.S. crop is produced in the state, bringing in about 5.2 million bales valued at $1.6 billion in 1997, according to the Texas Agricultural Statistics Service.
“There is huge interest in the cotton gene map,” said Paterson. “We are continuing to look for more genes to incorporate the subset into Texas germ plasm. We are looking for avenues to isolate specific genes to look for still better cottons.
“Our goals were to look for more genes which we have, incorporate them which we are, and identify all of them which will be done within five to 10 years,” he said. “Cotton plants have more than 50,000 genes, but perhaps as few as 50 or so are the key players in determining fiber yield and quality.”
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