Seed sharing rescues a crop and leads to new pest-resistant technology

Haitian sorghum crop now viable due to molecular marker discovery supported by 50 years of research

A research team supported by the Feed the Future Innovation Lab for Collaborative Research on Sorghum and Millet (SMIL) helped rescue the cereal crop sorghum with fifty years of global research and new technology.

This research is reported in the February 11 issue of Science Advances as “The recent evolutionary rescue of a staple crop depended on over half a century of global germplasm exchange.”

Saving a Staple Crop From Elimination
In Haiti, smallholder farmers saw the devastation that the sugarcane aphid can cause when it almost eliminated their sorghum crop in 2017. This was only two years after the aggressive new form of sugarcane aphid, M. sacchari, had been rapidly expanding and putting more than 90% of sorghum-producing areas of North America at risk.

A new form of sugarcane aphid was putting more than

90%

of sorghum-producing areas in North America at risk

To assist the Haitian farmers, the SMIL research team, led by Geoffrey P. Morris, partnered with the extensive and already established in-country sorghum-breeding program to develop a global germplasm exchange.

“We were able to identify this molecular marker to combat the aphid desolation rapidly thanks to a half a century investment in sharing sorghum germplasm worldwide,” said Morris, a professor at Colorado State University and principal investigator for the research. “The focus of SMIL and its predecessor, INTSORMIL, to push for the global exchange of sorghum-breeding research is essential in this approach and discovery.”

Figure 1.d Source: The recent evolutionary rescue of a staple crop depended on over half a century of global germplasm exchange

Timothy J. Dalton, SMIL director and professor of agricultural economics at Kansas State University, reiterates the importance of the sorghum-breeding global exchange network as a backbone for this solution for the current aphid problem and for future pests. “We started this research back in the 80s with greenbug, which was the priority pest at the time, but have seen through this public exchange of information across the globe that we were able to solve the latest pest issue more rapidly. We believe this truly helped save sorghum’s viability for so many smallholder farmers in Haiti that depend on it for the base income and food source for their family’s survival.”

Global Sorghum-Breeding Platform Provides Backing for Scientific Discovery
During the research, the team discovered a single gene naturally responsible for aphid resistance. When researchers combined the genomic scan technology with the research previously done, they were able to validate that the marker resistance to Melanaphis sacchari-1 (RMES1) gene was indeed a sugarcane-aphid-resistant locus and found throughout the global sorghum-breeding network.

The RMES1 gene variant, originally discovered in China, is a global rarity. However, RMES1 originated in Ethiopian sorghum lines, and through the research, it was understood that sorghum breeders across the globe prefer this germplasm. It was also discovered that the identified gene with sugarcane aphid, over time, had already been distributed across the sorghum-breeding platforms in three continents.

Dr. Geoffrey Morris, Principal Investigator

“As we pulled on the thread of history, we found a whole tapestry of how this success had come through the work of so many different scientists over the last 50 years. Fifty years of breeders, geneticists and entomologists were tracing it all the way back to farmers in Ethiopia, where this resistance likely originated a few hundred years ago,” said Morris. “This research allowed us to understand the history behind the genetic evolution of the natural resistance to build the foundation for the use of today’s genomic tools.”

The molecular markers developed through this research for RMES1 facilitate the rapid conversion of existing farmer-preferred varieties to aphid-resistant varieties. However, that does not mean this gene will always be effective, as pests like the aphid evolve and create new variants. New discoveries are needed to stay ahead of genetic evolution of the aphid. “With the previous research on greenbug aphid, we know that pests can and will evolve to the products we use. With these genetic markers, we can continue to advance resistant varieties and hope to stay ahead of the natural evolution of the aphid,” Morris said.

Figure 6.A, Source: The recent evolutionary rescue of a staple crop depended on over half a century of global germplasm exchange

New Molecular Markers Help Sorghum Farmers Globally and in the United States
As a final step in the research, the sugarcane-aphid-resistance molecular markers were tested with four U.S. commercial seed breeding programs and three U.S. public sector breeding programs. This step confirmed that there was a match between the phenotype-based breeder classification and the molecular marker genotypes.

Now with the molecular marker tool developed, breeders can efficiently convert the current farmer-preferred varieties to aphid-resistance varieties.

Sorghum is one of the most important crops in Haiti and worldwide because it is one of the most drought-tolerant cereal crops. Partnerships with researchers in Africa and Haiti were made possible with SMIL and funding from USAID. Success has translated into resilient seeds for low-income farmers in Africa and the Caribbean and improved profits for farmers in the United States.

Tim Lust, chief executive officer of National Sorghum Producers, said, “The work of SMIL certainly benefits the United States. Sorghum is a small industry worldwide and leveraging those dollars and the research and human talent is so important. With this project, when we look at sugarcane aphid and some of the challenges with it, the lessons we learned from this project are critical, from both a germplasm and plant viability standpoint. With this new molecular marker, we can quickly look at how that can be applied, and practical, hands-on research can be done in a timely manner that can get results. In all reality that would take us years and years to accomplish domestically by ourselves. And so, it's something that really allows us from a partnership role to evaluate new technologies and how those can be implemented quickly and what those opportunities really allow.”

“These findings reiterate why we will continue to focus on ensuring sorghum production grows and evolves in our focus countries such as Haiti to support this vital crop to so many smallholder farmers,” Dalton said. “But it also reiterates why we will continue to stress the need for sharing and learning across countries, continents and generations of researchers with the global exchange of sorghum research. This exchange benefits sorghum farmers small and large and maximizes the research time and dollar investment.”

To learn more about this research project and aphid resistance in sorghum, you can find the research paper here: https://www.science.org/doi/10.1126/sciadv.abj4633.

This project was funded and supported by the United States Agency for International Development (USAID) through the Feed the Future Innovation Lab for Collaborative Research on Sorghum and Millet (SMIL). It was a joint effort led by Dr. Geoffrey P. Morris and included a team of students and scientists from Kansas State University, Colorado State University, Université Quisqueya in Haiti, University of California-Berkeley, the HudsonAlpha Institute for Biotechnology, the Donald Danforth Plant Science Center, the United States Department of Agriculture, and the United States Department of Energy.

“We were able to identify this molecular marker to combat the aphid desolation rapidly thanks to a half a century investment in sharing sorghum germplasm worldwide. The focus of SMIL and its predecessor, INTSORMIL, to push for the global exchange of sorghum-breeding research is essential in this approach and discovery”

Dr. Geoffrey Morris, Colorado State University