By Zhonghu He, Garry Rosewarne and Wuyun Yang
Genes found in million-year-old grass species are helping scientists multiply the genetic diversity of wheat and generate varieties that yield more than eight tons of grain per hectare in southwestern China, where rain-fed wheat grows in low temperatures after sowing and winter droughts can hold back productivity.
Many wheat x grass crosses – known as “synthetic” wheats – were developed 25 years ago by a CIMMYT research team, and have since been used in breeding programs worldwide. The first synthetic variety to reach Chinese farms, Chuanmai 42, arrived in the Sichuan Basin in 2003, and allowed wheat farmers there to boost yields by as much as 20 percent – the most significant increase in the region for decades.
“Despite major research and breeding efforts, on-farm wheat yields in southwestern China had stagnated below eight tons per hectare,” said Dr. Zhonghu He, CIMMYT distinguished scientist and wheat breeder. “Chuanmai 42 and more recent synthetic-derived varieties changed that. It has been the leading variety in the Sichuan Basin for a decade.” Chuanmai 42 was developed by Professor Wuyun Yang, senior wheat breeder at the Sichuan Academy of Agricultural Science (SAAS) and a CIMMYT wheat training graduate. “In 2011, the China State Council gave SAAS the scientific progress award for the creation of Chuanmai 42 and the exploration of genetic diversity from synthetic wheat,” He said.
A new report in the journal Crop Science (1) has shed light on the physiological differences that give Chuanmai 42 and other synthetic derivatives better yields. “In our three-year study, the synthetic crosses were more vigorous in early growth stages, and grew more above ground at flowering time than non-synthetic varieties,” said Dr. Garry Rosewarne, CIMMYT wheat scientist and co-author of the report. “At maturity, more dry matter was partitioned to grain in the synthetic varieties and the plants were more erect and compact,” he added. These differences gave the synthetics a nearly 12 percent yield advantage, according to Rosewarne. “It’s very encouraging to see the newer synthetic derivatives significantly out-performing Chuanmai 42,” he said.
A report published in the journal BMC Plant Biology (2) in May describes a study that combines digital imaging of grain and molecular markers to analyze grain size and shape and their effects on yield in synthetic-derived wheat. This work was accomplished under the Valilov-Frankel Fellowship, involving scientists from institutes in Australia, China and Pakistan, as well as CGIAR Centers Bioversity International and CIMMYT. The study found that parts of the synthetic genome originating from a wild grass might carry genes that enhance grain weight, a key component of higher yield in wheat. “This study involved 231 synthetic derivatives,” said He, a co-author of the report. “It confirms the great potential of this type of wheat to help low- and middle-income countries meet the rising demand for wheat-based products, as their populations grow and urbanize.”
Dr. Abdul Mujeeb-Kazi, retired CIMMYT distinguished scientist who led the team that performed the original wheat x grass crosses 25 years ago, is also a co-author of the study.
1. Tang, Y., G.M. Rosewarne, C. Li, X. Wu, W. Yang, and C. Wu. 2014. Physiological factors underpinning grain yield improvements of synthetic derived wheat in South Western China, accepted paper, Crop Science, posted 07/29/2014. doi:10.2135/cropsci2014.02.0124.
2. Rasheed, A., X. Xia, F. Ogbonnaya, T. Mahmood, Z. Zhang, A. Mujeeb-Kazi, and Z. He. 2014. Genome-wide association for grain morphology in synthetic hexaploid wheats using digital imaging analysis. BMC Plant Biology 2014, 14:128 doi:10.1186/1471-2229-14-128