Location: Crop Genetics Research
2018 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
ARS scientists at the Jackson, Tennessee, worksite evaluated progenies from 12 different specific crosses planted in progeny-rows for developing improved soybean germplasms for broad resistance to nematode populations. Approximately 600 single plants and/or progeny rows were individually selected and harvested separately for further evaluations. These selections were made based on visual appearance, primarily for their agronomically desirable traits and uniformity. From these selections, approximately ten thousand single plants at seedling stage were evaluated in the greenhouse for infection by predominant soybean cyst nematode populations. These nematodes are curated in the greenhouse and methods used for evaluations are further improved and standardized at the worksite. These greenhouse tests will identify and/or confirm reaction of seedlings for nematode infection, i.e., resistant, moderately resistant, moderately susceptible and susceptible. Concurrently, the DNA (genetic material) from leaves of these greenhouse-grown seedlings was collected and tests were conducted in the laboratory using known molecular markers associated with nematode resistance. This methodology is called as “marker assisted selection” and is intended for further confirmation.
In 2017, scientists also evaluated a total of 76 Roundup Ready soybean cultivars and 69 conventional breeding lines for resistance to charcoal rot, an important disease caused by a fungus. Compared to the reactions of susceptible and resistant checks, 30 lines showed moderate resistance. In addition, 47 soybean breeding lines with drought tolerance were tested, and 4 lines in maturity group IV and 4 in maturity group V were identified with resistance to both drought and charcoal rot. Conventional varieties and breeding lines were also evaluated for another important fungal disease, frogeye leaf spot. Alternative sources of resistance other than resistance from the cultivar Davis, the current source of resistance for frogeye leaf spot, were identified and continue to be evaluated to ensure that these lines are resistant to many of the field isolates.
Research on management of fungal diseases of soybean using cultural practices was also conducted. The impact of planting date and variety type on charcoal rot was monitored in 2017, and disease progress was recorded across growth stages. Based on the first year’s data, the soil moisture readings (% Volumetric Water Content and kPa) correlate well with irrigated and non-irrigated plots. Data on the effects of fungicides and tillage on frogeye leaf spot severity and yield of soybean were recorded. Significant effects from tillage and fungicide were noted, and scientists will determine if these effects will be repeated in subsequent years.
Accomplishments
Review Publications
Espina, M.J., Ahmed, S.M., Bernardini, A., Adeleke, D., Yadegari, Z., Pantalone, V.R., Arelli, P.R., Taheri, A. 2018. Development and phenotypic screening of an ethyl methane sulfonate mutant population in soybean. Frontiers in Plant Science. 9:394. https://doi.org/10.3389/fpls.2018.00394.
Cianzio, S.R., Arelli, P.R., Swaminathan, S., Lundeen, P., Grebhart, G.D., Rivera-Velez, N., Guilherme, S.R., Diers, B., Westgate, M.E. 2018. Genetically diverse soybean cyst nematode-resistant full-sib soybean germplasm lines AR4SCN, AR5SCN, AR6SCN, AR7SCN, and AR8SCN. Journal of Plant Registrations. 12:124-131. https://doi.org/10.3198/jpr2017.03.0015crg.
Pantalone, V.R., Smallwood, C., Fallen, B., Hatcher, C.N., Arelli, P.R. 2018. Registration of 'TN09-008' soybean cyst nematode-resistant cultivar. Journal of Plant Registrations. https://doi.org/10.3198/JPR2017.11.0084crc.
