Wheat Reaches its Limit
Voice of America
August 24, 2010
The world’s population keeps growing, but the amount of wheat farmers worldwide are able to grow per hectare has leveled off.
According to a new study, that’s because breeders and researchers have reached the limit of how much grain the wheat plant can produce.
“In the 50 years of breeding history, we’ve essentially almost doubled our genetic potential for yield,” says wheat geneticist Bob Graybosch with the U.S. Department of Agriculture and the lead author of the new
study in the journal Crop Science.
Unfortunately, Graybosch says, “There’s got to be an upper limit on how much they can do, and it maybe looks like we’re approaching that upper limit.”
“The farmers that are growing dry-land wheat may see the same yields from now on,” he says. “They may not see increases in yield under dry-land conditions because we simply are shuffling the same genetic
deck out there.”
Robert A. Graybosch and C. James Peterson
doi:10.2135/cropsci2009.11.0685 Crop Science 2010 50:1882-1890
Data from USDA-coordinated winter wheat (Triticum aestivum L.) regional performance nurseries collected over the time period 1959 to 2008 were used to estimate genetic gain (loss) in grain yield, grain volume weight, days to heading, and plant height in winter wheats adapted to the Great Plains of North America. In both the Southern Regional (SRPN) and Northern Regional Performance Nurseries (NRPN), linear regression revealed significant positive relationships between relative grain yields of advanced breeding lines and calendar year of
the nursery trial. The estimated genetic gain in grain yield potential since 1959 was approximately 1.1% (of the control cultivar Kharkof) yr-1 for all entries in the SRPN, and 1.3% yr-1 if only the most productive entry was considered. For the NRPN, the estimates of genetic gain in grain yield were 0.79% yr-1 for all entries, and also 0.79% yr-1 for the most productive entry. Linear regressions of relative grain yields vs. year over the time period 1984 to 2008, however, showed no statistically significant trend in the SRPN. For the same time period in the NRPN, a statistically significant positive slope of 0.83 was observed, though the coefficient of determination (R2) was only 0.28. Relative grain yields of Great Plains hard winter wheats may have peaked in the early to mid-1990s, and further improvement in the genetic potential for grain yield awaits some new technological or biological advance.