Improving wheat yields by increasing grain size, weight

South Dakota State is one of seven universities nationwide to receive funding to develop new wheat varieties as part of the National Institute of Food and Agriculture's International Wheat Yield Partnership (IWYP) Program. The program supports the G20's Wheat Initiative, which seeks to enhance the genetics related to yield and develop varieties adapted to different regions and environmental conditions.

The goal of IWYP, which was formed in 2014, is to increase wheat yields by 50 percent in 20 years. Currently, the yearly yield gain is less than 1 percent, but to meet the WYYP goal wheat yields must increase 1.7 percent per year. "It's a quantum leap," he said. "We need a lot of work to reach this."

Humans consume more than 500 million tons of wheat per year, according to Li. However, United States wheat production is decreasing, because farmers can make more money growing other crops. He hopes that increasing the yield potential will make wheat more profitable.

First, the researchers will identify genes that control grain size and weight in bread wheat using the rice genome as a model.

The CRISPR editing tool allows the researchers to knockout each negatively regulating gene and thus study its function, according to Li. "CRISPR is both fast and precise," he added. "It can produce very accurate mutations."

This technique will be used to create 30 constructs that target 20 genes that negatively impact wheat grain size and weight. From these, the University of California Davis Plant Transformation Facility, through a service contract, will produce 150 first-generation transgenic plants and the SDSU researchers will then identify which ones yield larger seeds. One graduate student and a research assistant will work on the project.

"The end products are not genetically modified organisms," Li emphasized. "When we transfer one of the CRISPR genes to wheat, it's transgenic. That then produces a mutation in a different genomic region. When the plants are then self-pollinated or backcrossed, the transgene and the mutation are separated."

The researchers then screen the plants to select those that carry the desired mutations. "This is null transgenic," Li said, noting USDA has approved this process in other organisms. Yang used this technique to develop bacterial blight-resistant rice.

As part of the project, the researchers will also transfer the mutations into durum wheat. Ultimately, these yield-increasing mutations, along with the markers to identify the traits, can be transferred to spring and winter wheat.