NCDC237: Regional Wheat Virus Research Initiative
(Multistate Research Coordinating Committee and Information Exchange Group)
NCDC237: Regional Wheat Virus Research Initiative
Duration: 03/08/2023 to 09/30/2025
Statement of Issues and Justification
States with identified (and potentially) interested faculty:
- NC – KS, NE, SD (ND)
- S – OK (TX)
- W – CO (MT)
The emergence and reemergence of plant viruses has threatened food security and farmer profitability globally and their incidence is increasing. Hence, early detection and characterization of the emerging and reemerging viruses is necessary for developing effective control strategies and to prepare for potential outbreaks that may occur in the near future.
Wheat (Triticum aestivum L.) is one of leading staple crops in the world, responsible for ~ 20% of the daily human nutrition needs (Hawkesford et al. 2013). With a rapidly growing world population expecting to be at 9.7 billion by 2050 (FAO, 2017), wheat yield production needs to be increased by 50% over the next few decades to meet the rising food demand (Ray et al. 2013).
Pests and pathogens are considered as key yield-limiting factors globally, and among pathogens, viruses, especially vector-borne viruses are an increasing threat to the wheat production and food security. Wheat documented viruses including Wheat streak mosaic virus (WSMV), Triticum mosaic virus (TriMV), High Plains wheat mosaic virus (HPWMoV), Barley yellow dwarf virus (BYDV), Cereal yellow dwarf virus (CYDV), and Soil borne wheat mosaic virus (SBWMV) cost substantial losses in crop yields every year. Wheat streak mosaic (WSM) which is one of the most economically important wheat diseases is a complex consisting of three documented viruses: WSMV, TriMV, and HPWMoV with WSMV as the major causal agent. Synergistic interaction between WSMV and TriMV has been reported in wheat (Byamukama et al. 2013; Tatineni et al. 2019). All three viruses are transmitted by wheat curl mites (WCM), Aceria tosichella Kiefer (Slykhuis 1955; Seifers et al. 1997; Seifers et al. 2009).
To date, only 3 resistant genes, Wsm1, Wsm2, and Wsm3 have been identified (Friebe et al. 1991; Haley et al. 2002; Lu et al. 2011; Liu et al. 2011) and introduced into cultivated wheat lines from perennial relatives. Both Wsm2 and Wsm3 genes are resistant against WSMV and TriMV, while Wsm1 is only resistant against WSMV isolates (Kumssa et al. 2019). Wsm1 and Wsm2 genes are applied in different wheat varieties and deployed in fields cross the Great Plains, but unlike Wsm3, these resistant genes are temperature-sensitive and have been proven to be ineffective in temperatures above 25 ͦ C (Seifers et al. 2006, 2007; Haley et al. 2002). Wheat varieties containing Wsm3 are evaluating in research fields and they are not commercially available yet. Although the use of these resistant varieties is promising, a WSMV isolate overcoming the Wsm2 resistance and several potential WSMV and TriMV isolates overcoming resistance have been recently reported in Kansas (Kumssa et al. 2019; Fellers et al. 2019; Redila et al. 2021). Therefore, wheat viral diseases are still major issues for farmers. WSM alone caused a total of $76 million in yield loss to Kansas farmers in 2017 (Hollandbeck et al. 2017). Mixed infections of viruses in the field, evolving resistance-breaking isolates in viral populations, different populations of the vector with different transmission efficiencies, and emerging new viruses are the main challenges.
To have a better understanding of the genetic structure of these documented wheat viruses and their molecular evolution in the field, we conducted a full genome evolutionary study of WSM-associated viruses mainly in KS fields and fields in some other parts of the Great Plains using Hight-Throughput sequencing (RNA-seq) in 2019 and 2020 (Redila et al. 2021a). Field survey results showed WSMV as the predominant virus followed by mixed infections of WSMV + TriMV. Recombination was identified as the major evolutionary force of WSMV and TriMV variation in KS fields, and positive selection was detected in some encoding genomic regions in the genome of both viruses (Redila et al. 2021a). We also identified previously unknown WSMV isolates in KS and NE fields sharing clades and high nucleotide sequence similarities with Central Europe isolates. It still remains unclear about whether or not these European isolates were brought to the Great Plains directly from seed exchange with Central Europe or indirectly from the APNW, which first reported the presence of WSMV Central Europe isolates in the U.S. (Robinson and Murray, 2013). This needs to be studied further using more virus field isolates from KS and other parts of the Great Plains.
Additionally, our phylogenetic study of TriMV suggests that natural populations of TriMV may be under pressure to evolve due to the widely use of resistant wheat varieties in the field (Redila et al. 2021a). However, the analysis of a greater number of TriMV isolates would be needed to validate that claim.
In addition to the documented wheat viruses including WSMV, TriMV, HPMoV, BYDV, and CYDV, our metagenomics study identified at least two novel putative viruses (Redila et al. 2021b). Discovering these viruses in wheat fields has raised this question/concern whether these newly identified viruses have potentials to be a new threat for wheat production and food security in the near future.
We are currently characterizing these new viruses. This includes the distribution and genetic diversity in Great Plains fields, potential hosts other than wheat, their interactions with other wheat viruses and the impact of this relationship on disease outcome, and the last but not the least, the natural potential vector(s).
On December 16, 2022, the Kansas wheat virus working group, including both Kansas State and USDA-ARS researchers, gathered and provided updates on breeding, surveys, current activities and to set priorities for future work. The USDA-ARS lab reported the presence of three other documented viruses including BMV, WSSMV and SBWMV in KS fields (Ranabhat et al., unpublished) from their survey in 2019 and 2020. The wheat virus working group came to several conclusions. First, more needs to be known about what viruses are present in the field. Second, work needs to be done to improve the ease and accuracy of detection. Third, a coordinated regional effort is necessary to see if we can leverage research synergies in the areas of resistance, diagnostics/detection/characterization of the documented and novel potential viruses, and have a better understanding of the virus molecular evolution and what constitutes current field virus populations. Initiating this bigger regional wheat virus working group including States` virologists, wheat pathologists, entomologists and breeders is the first step for developing and conducting comprehensive research about wheat viruses and their control. A workshop is being planned during the upcoming McFadden Wheat conference, April 24, 2023, to start the conversations.
The objective of NCDC237 is to convene a writing team to prepare a full, five-year multistate committee in NIMSS.