Location: Crop Genetics Research
2020 Annual Report
Objectives
Objective 1: Identify sources of resistance to newly emerging soybean cyst nematode populations, develop new soybean germplasm with resistance, and develop methods for managing soybean cyst nematodes in soybeans using traditional and marker assisted breeding methods.
Subobjective 1a. Phenotype Glycine max accessions available in USDA soybean germplasm collection for reaction to SCN populations. Identify new/additional sources of resistance, characterize for unique resistance genes and develop molecular markers associated with resistance.
Subobjective 1b. Pyramid nematode resistance genes into elite backgrounds of maturity groups IV and V in combination with resistance to charcoal rot and Frogeye leaf spot to develop new germplasm/cultivars.
Subobjective 1c. Determine the effect of soybean cyst nematode in combination with other plant-parasitic nematodes on crop damage in Mid South soybean production fields.
Subobjetive 1d. Evaluate entries in USDA Uniform Soybean Tests for Southern States and ARS breeding lines for reaction to SCN.
Objective 2: Determine mechanisms underlying host-pathogen interactions in soybean for the fungal diseases charcoal rot and frogeye leaf spot, identify new sources of resistance in soybean to these diseases using improved screening methods, and develop methods for managing these fungal diseases using traditional and marker assisted breeding methods.
Subobjective 2a. Evaluate and identify new sources of germplasms, breeding lines, and cultivars for charcoal rot and frogeye leaf spot resistance in stress and non-stress environments for use in breeding programs.
Subobjective 2b. Evaluate the effects of cultural practices on charcoal rot and frogeye leaf spot severity and yield and develop alternate management practices for control of these diseases in soybean.
Approach
Identify new sources of resistance to nematode populations in soybean that will potentially broaden diversity among resistance genes in soybean cultivars and may provide more durable resistance. New soybean germplasm line or lines will be developed in two different maturity groups IV and V with resistance to soybean cyst nematode, frogeye leaf spot, and charcoal rot, as well as other fungal pathogens, nematodes and insect pests. Nematodes will be found in soybean fields, especially those with corn and/or cotton in the rotation. Valuable data for the reaction of breeding lines to nematode populations will be available to be utilized by the breeders for potential release to public and private sectors. New accessions and germplasm lines with resistance to charcoal rot and
frogeye leaf spot will be identified and released.
Progress Report
Progress was made on both objectives of this long term research project. We continue to work to identify new sources of resistance to soybean cyst nematode populations and the fungi that cause the diseases frogeye leaf spot and charcoal rot, and to incorporate the resistance into new varieties of soybean for growers in Tennessee and other southern states. We also are evaluating the impact of cultural practices such as tillage and planting date on disease severity and yield losses. This information will be used to improve crop management recommendations to better manage these diseases.
ARS researchers in Jackson, Tennessee, are making progress related to developing soybean with resistance to one or more diseases, which is related to Sub-objective 1b. We previously developed and released soybean JTN-5203 for its broad resistance to soybean cyst nematode populations, reniform nematode and major fungal diseases combined with high yield potential. Several major commercial seed companies are using JTN-5203 as a parent material in their crosses to further improve yield and provide herbicide tolerance, especially in Argentina. Due to the high cost of commercially available herbicide tolerant soybean seed for planting, some of the growers in Arkansas, Missouri, North Carolina and Kentucky continue to plant JTN-5203 in their fields. ARS researchers in Jackson, Tennessee, are making progress for evaluation of 200 plant introductions from USDA soybean germplasm collection for nematode resistance. This progress is related to Sub-objective 1a.
We evaluated progenies from 10 different specific soybean crosses in the field and 300 selections and 217 single plant selections. These selections were made based on phenotype, primarily for their desirable agronomic traits under field conditions. Over the winter, all selected breeding with lines were evaluated with live soybean cyst nematode populations in the greenhouse for resistance. These lines are considered unique because they have new sources of resistance from China, Japan and South Korea, which were not used previously. Concurrently the DNA (genetic material) from leaves of these greenhouse grown seedlings was collected and laboratory tests were conducted using 13 known DNA markers linked to nematode resistance. This methodology is called marker assisted selection (MAS) and is intended for further confirmation of resistance.
Work to combine resistance to multiple diseases into a single soybean line continued in 2020 (Sub-objective 1b). Unique advanced progenies derived from previously-made crosses to combine resistance to soybean cyst nematode, charcoal rot, and frogeye leaf spot were evaluated in the greenhouse for nematode resistance and selected for further charcoal rot and frogeye spot in field. The traditional breeding methods of selection used in the field and the standard greenhouse techniques adopted for testing together with MAS have allowed us to produce unique progenies. Presumably, most of them have combined resistance to these three major diseases. The strategy to combine resistance to all three diseases in a single plant is called gene pyramiding and is difficult to achieve. This is a time-consuming process.
A position for a Research Plant Pathologist with expertise in nematology has been a critical vacancy since the inception of the project. The critical germplasm screening for cyst nematode resistance for the Uniform Soybean Tests for Southern States under Sub-objective 1d has continued under the direction of the project’s lead scientist. Work was on schedule for most of the year, but is currently progressing slower than normal due to onsite work restrictions associated with COVID-19.
Compared to the reactions of susceptible and resistant checks, 20 lines in Roundup Ready and 18 lines in conventional cultivars in MG IV and MG V were identified as having moderate resistance to charcoal rot. In addition, several germplasm lines were advanced based on their resistance based on individual plant selection. After several cycles of selections 10 lines showed a high level of performance for charcoal rot resistance (Sub-objective 2A).
Single-row selections from 400 inbred lines that were derived from various crosses also were selected for resistance, and work will continue through the following year because these populations are still in a very active stage of development. These selections will be advanced for future public release. Their genetic information has been characterized using a marker-trait association analysis (Sub-objective 2A).
Eight lines in Roundup Ready and 21 lines in conventional breeding lines had low levels of frogeye leaf spot severity ratings with less than 10% infection. This screening was intended to identify alternative sources of resistance to those lines derived from the cultivar ‘Davis’. Davis is the source of resistance for all current resistance commercial cultivars (Sub-objective 2A).
Accomplishments
1. First report of soybean lines combining the soybean cyst nematode resistance of ‘Hartwig’ with that of exotic Plant Introduction PI567516C. Three lines developed and released by ARS researchers in Jackson, Tennessee, include JTN-5316, JTN-5416 and JTN-5516 are in maturity group V and provide breeders with parent material containing more durable resistance from both sources, a combination not currently available in soybean cultivars grown in the USA. Yields range from 45 bushels per acre to 48 bushels per acre. These are excellent choices of parent material for breeders, and growers who want to grow conventional soybeans will be the beneficiaries.
2. Contributed to release of Roundup Ready cultivar with improved oil content and disease resistance. Soybean growers are confronted with challenges to control various soybean diseases that cause economic losses to their yield but also have a high demand to improve soybean oil and preference for taller soybean plants with early maturity. In order to fulfill the growers’ needs, ARS researchers in Jackson, Tennessee, worked with a team of researchers led by soybean breeders from the University of Missouri worked together and the University of Missouri ultimately released cultivar S14-15146GT to meet these goals. S14-15146GT was evaluated in multiple environments, including the ARS location in Jackson, Tennessee, that identified disease resistance. This cultivar not only is an early maturity cultivar but is also contains the first-generation of Roundup Ready trait, which is no longer patented and seeds containing it may be saved for subsequent years in certain instances. This cultivar has high oil content, broad disease resistance package and wide adaptation that make it an excellent choice for southern soybean growers. It is also a suitable alternative for farmers who want to grow and save seeds of glyphosate-tolerant soybean cultivar.
3. Grouping of frogeye isolates by their aggressiveness. Frogeye leaf spot is a fungal disease of soybean that causes significant yield loss to growers. Soybean growers are challenged by natural variation in the pathogen population, which can impact their ability to effectively manage the disease. ARS researchers in Jackson, Tennessee, collected eighty-three fungus isolates from the U.S., China and Brazil were infected using 12 soybean lines that could differentiate infections. Based on disease severity measurement, the isolates were classified into five groups and were named ‘Pathogenicity Groups’ (one to five). This grouping represented the aggressiveness and diversity of these isolates. Such grouping has at least three important uses: (1) as a mechanism for assessing and documenting changes among field isolates and making specific management recommendations, (2) for use by plant pathologists and soybean breeders to screen and identify resistant cultivars/germplasms, and (3) as an aid to making management recommendations to growers. The system could widely be adopted by soybean industry, academia and extension workers.
Review Publications
Mengistu, A., Ray, J.D., Kelly, H.M., Lin, B., Yu, H., Smith, J.R., Arelli, P.R., Bellaloui, N. 2019. Pathotype grouping of Cercospora sojina isolates on soybean and their sensitivity to QoI fungicides. Plant Disease. 104:373-380. https://doi.org/10.1094/PDIS-02-19-0368-RE.
Chen, P., Shannon, G., Scaboo, A.M., Crisel, M., Smothers, S.L., Clubb, M.W., Selves, S.W., Vieira, C.C., Ali, L.M., Nguyen, H.T., Li, Z., Bond, J.P., Meinhardt, C.G., Klepadlo, M., Li, S., Mengistu, A., Robbins, R.T. 2020. Registration of ‘S14-15146GT’ soybean as a high-yielding RR1 cultivar with high oil content and broad disease resistance and adaptation. Journal of Plant Registrations. 14(1):35-42. https://doi.org/10.1002/plr2.20018.
Nouri, A., Lee, J., Yin, X., Saxton, A.M., Tyler, D.D., Sykes, V.R., Arelli, P. 2019. Crop species in no-tillage summer crop rotations affect soil quality and yield in an Alfisol. Geoderma. 345 :51-62. https://doi.org/10.1016/j.geoderma.2019.02.026.
Singh, S., Nouri, A., Singh, S., Anapalli, S.S., Lee, S., Arelli, P.R., Jagadamma, S. 2019. Soil organic carbon and aggregation in response to thirty-nine years of tillage management in the southeastern U.S. Soil and Tillage Research. 197:1-9. https://doi.org/10.1016/j.still.2019.104523.
Bellaloui, N., McClure, A.M., Mengistu, A., Abbas, H.K. 2020. Influences of agricultural practices, environment, and cultivar differences on soybean seed protein, oil, sugars, and amino acids. Plants. 9(3),378. https://doi.org/10.3390/plants9030378.
Rambani, A., Pantalone, V., Yang, S., Rice, H., Song, Q., Mazarei, M., Arelli, P.R., Meksem, K., Stewart, N., Hewezi, T. 2020. Identification of introduced and stably inherited DNA methylation variants in soybean associated with soybean cyst nematode parasitism. New Phytologist. 227(1):168-184. https://doi.org/10.1111/nph.16511.
