Location: Peanut and Small Grains Research Unit
2023 Annual Report
Objectives
The long-term goal of this project is to improve integrated pest management (IPM) practices for cereal aphids in wheat, barley, and sorghum in the United States. To achieve this goal, we will increase the knowledge of aphid host plant resistance and natural enemies for IPM programs and provide fundamental knowledge of cereal aphid biology and ecology. Over the next 5 years we will focus on the following objectives:
OBJECTIVE 1: Determine regional distribution and significance of invasive aphid species on cereals and alternate grass hosts, discover changes or shifts in the populations, generate relevant phenotypic information, and work with breeders or geneticists to map and pyramid resistant genes.
Subobjective 1A: Determine the biotype diversity of the S. Maydis known as the hedgehog aphid (HGA) in cereals and native grasses in advance of discovering and utilizing resistant sources used in breeding for resistance.
Subobjective 1B: Identify wheat germplasm resistant to HGA, as well as wheat accessions resistant to all U.S. RWA biotypes.
Subobjective 1C: Characterize RWA and HGA resistance genes and develop molecular markers for their introgression into locally adapted breeding lines and cultivars.
OBJECTIVE 2: Determine the biological differences and interactions among available sugarcane aphid resistance genes, including comparisons of cross-resistance genes, elucidate resistance mechanisms, and work with breeders and geneticists to map, pyramid, and deploy resistant genes.
Subobjective 2A: Develop forage sorghum germplasm resistant to sugarcane aphids.
OBJECTIVE 3: Develop effective multi-scale aphid infestation monitoring and sampling technology, develop geographically explicit cereal aphid pest infestation risk models, and elucidate and integrate field and landscape-level components of the natural enemy populations into improved management systems for invasive cereal aphids.
Subobjective 3A: Use field research methods and statistical modeling and hypothesis testing to develop a detailed understanding of spatial and temporal factors that determine colonization, population dynamics, and community development of aphid natural enemies in grain sorghum fields and their importance for sugarcane aphid biological control.
Subobjective 3B: Develop and disseminate new, time-efficient, and statistically accurate and precise methods for sampling aphid natural enemies in sorghum.
Approach
The combined annual economic value of wheat, sorghum, and barley within the United States is over $16 billion. Cereal aphids are major pests of world agriculture that vector numerous plant viruses and remove photoassimilates by inserting their mouthparts into the sieve elements of the phloem tissue. The direct loss from feeding and the transmission of viral diseases during the process of feeding make cereal aphids the most significant threat to U.S. cereal crop producers. Although aphids in general are small in size, the reproductive potential is at the higher end of the spectrum when compared to all arthropods, with exponential increases and short generation times. Significant yield reductions occur from the direct effect of endemic or epidemic aphid populations. New information on the factors affecting insect populations and new integrated pest management (IPM) tools, control technologies, and aphid-resistant germplasm are needed in order to advance sustainable IPM programs for cereals. The objectives of this project that will deliver the associated products to the consumer are to: 1) determine the biotypic diversity in aphid populations which threatens deployment of aphid-resistant cereals; 2) identify new sources of resistance to aphids in wheat and sorghum and barley; 3) determine the extent and severity of new aphid pest species attacking cereal crops; and 4) develop or refine methods for detecting and monitoring aphid infestations to optimize biocontrol in cereals. The specifically designed research provided in this plan will increase our knowledge on the genomics of virulent cereal aphid biotypes within the U.S. and increase the knowledge of available genetic sources of resistance in wheat, barley, and sorghum. Once identified these resistant sources will be introgressed into available breeding lines. In addition, the benefits and ecological associations of beneficial insects in the agricultural landscape will be better understood and utilized as a result of areawide studies on these organisms.
Progress Report
Under Objective 1, Subobjective A; ARS scientists from Stillwater, Oklahoma, and Tifton, Georgia, identified the host plants, the geographical distribution and if differing biotypes of the hedgehog grain aphid (HGA) exists in the U.S. Only a single clone of the HGA exists within the U.S. and the distribution of HGA is diminishing. The threat of this particular aphid species as a pest of small grains appears to be shrinking. This is a positive for the U.S. small grains producer.
Under Objective 1, Subobjective B; ARS scientists in Stillwater, Oklahoma, continued to evaluate wheat germplasm for resistance to Russian wheat aphid (RWA) biotype 2, leading to the identification of two new resistance sources. Two F2:3 populations from crosses PI 625139 × OK11D25066 and PI 626575 × Jagalene were evaluated for responses to RWA biotype 2, and a subset of plants from each population are currently genotyped using the “genotyping by sequencing” (GBS) approach. The RWA resistance genes in PI 625139 and PI 626575 are expected to be revealed in FY2024.
Under Objective 1, Subobjective C; ARS scientists in Stillwater, Oklahoma, continued to work on Hedgehog grain aphid (HGA) in FY2023. However, the lead scientist’s recent study indicated that HGA is unlikely a pest of wheat. Therefore, the HGA-related objectives and milestones no longer apply. We will discontinue related studies from FY2024.
Under Objective 2, Subobjective A; ARS scientists in Stillwater, Oklahoma, and Lubbock, Texas, incorporated host plant resistance from grain sorghum sources in to forage sorghum resistance and released forage sorghum lines to the public.
Under Objective 3, Subobjective 3C; ARS scientists in Stillwater, Oklahoma, continued to evaluate the population dynamics and biological control potential for sugarcane aphid in grain sorghum. In total aphid and natural enemies have been studied throughout the growing season in over 60 grain sorghum fields. These data are being combined with weather and landscape data, which along with natural enemy data will serve as predictors of sugarcane population dynamics in grain sorghum.
ARS scientists in Stillwater, Oklahoma, continued field studies to determine the most efficient and most accurate sampling methods for natural enemies for use in operational pest management programs for sugarcane aphid in grain sorghum.
Accomplishments
Review Publications
Brewer, M.J., Elliott, N.C. 2023. Recent advances in agroecological research for increasing scope of areawide pest management of arthropods in cropping systems. Current Opinion in Insect Science. 56. Article 101019. https://doi.org/10.1016/j.cois.2023.101019.
Lee, S., Vitale, J., Lambert, D., Vitale, P., Elliott, N.C., Giles, K. 2023. Effects of weather on sugarcane aphid infestation and movement in Oklahoma. Agriculture. 13(3). Article 613. https://doi.org/10.3390/agriculture13030613.
Mornhinweg, D.W., Armstrong, J.S. 2023. Resistance to bird cherry-oat aphid, Rhopalosiphum padi (L.), in barley, Hordeum vulgare (L.). Southwestern Entomologist. 48(1):75-82. https://doi.org/10.3958/059.048.0107.
Carey, C., Hoback, W., Armstrong, J.S., Hayashida, R., Zarrabi, A. 2023. Survival and fecundity of single and grouped clonal sorghum aphids and a novel aphid marking technique. Southwestern Entomologist. 48(2):303-311. https://doi.org/10.3958/059.048.0202.
Xu, X., Mornhinweg, D.W., Bai, G., Li, G., Bian, R., Bernardo, A.E., Armstrong, J.S. 2022. Characterization of Rsg3, a novel greenbug resistance gene from the Chinese barley landrace PI 565657. The Plant Genome. 16(1). Article e20287. https://doi.org/10.1002/tpg2.20287.
Xu, X., Li, G., Bai, G., Carver, B.F., Bian, R., Bernardo, A.E., Armstrong, J.S. 2023. Genomic location of Gb1, a unique gene conferring wheat resistance to greenbug biotype F. The Crop Journal. https://doi.org/10.1016/j.cj.2023.02.002.
Xu, X., Li, G., Cower, C., Bai, G., Carver, B.F., Bian, R., Bernardo, A. 2023. Identification of a novel Pm65 allele conferring a wide spectrum of resistance to powdery mildew in wheat accession PI 351817. Phytopathology. https://doi.org/10.1094/PHYTO-01-23-0032-R.
Xu, X., Li, G., Lhamo, D., Carver, B.F., Wulff, B., Gu, Y.Q., Xu, S.S., Armstrong, J.S. 2023. Identification of bird-cherry oat aphid and greenbug resistance sources from Ae. tauschii for wheat improvement. Crop Science. 36(5):2913-2924. https://doi.org/10.1002/csc2.21042.
