2013 Annual Report
1a.Objectives (from AD-416):
Objective 1: Develop new soybean germplasm with resistance to soybean cyst nematode populations, Macrophomina (M.) phaseolina, and other fungal diseases of soybean using traditional and marker-assisted breeding methods.
Sub-objective 1.A. Identify new sources of soybean cyst nematode (SCN) resistance in Glycine max.
Sub-objective 1.B. Characterize new sources for unique resistance genes and develop molecular markers associated with resistance.
Sub-objective 1.C. Pyramid nematode resistance genes into elite backgrounds of maturity groups III, IV, and V in combination with resistance to charcoal rot and other fungal diseases to develop new germplasm/cultivars.
Objective 2: Characterize the variability of Macrophomina phaseolina in soybean and develop improved methods to identify resistance.
Sub-objective 2.A. Phenotype the isolates of M. phaseolina based on pathogenicity.
Sub-objective 2.B. Determine spatial distribution of M. phaseolina populations in a field.
Sub-objective 2.C. Evaluate soybean germplasm, breeding lines and cultivars for host plant resistance against field isolates of (a) M. phaseolina (b) Phomopsis longicolla (Phomopsis Seed Decay) and (c) Cercospora sojina (Frogeye Leaf Spot).
Objective 3: Develop improved management practices to reduce soybean cyst nematode reproduction.
Sub-objective 3.A. Characterize the interaction between Pasteuria nishizawae and H. glycines to reduce the impact of soybean cyst nematode on soybean production.
Sub-objective 3.B. Identify the interaction of soybean cyst nematode with other plant-parasitic nematodes of importance in Mid South soybean production fields.
1b.Approach (from AD-416):
Identify the interaction of soybean cyst nematode with other plant-parasitic nematodes of importance in Mid South soybean production fields. Pyramid nematode resistance genes into elite backgrounds of maturity groups III, IV, and Vin combination with resistance to charcoal rot and other fungal diseases to develop new germplasm/cultivars. Identify new sources of soybean cyst nematode (SCN) resistance in Glycine max. Characterize new sources for unique resistance genes and develop molecular markers associated with resistance. Phenotype the isolates ofM. phaseolina based on pathogenicity. Determine spatial distribution of M. phaseolina populations in a field. Evaluate soybean germplasm, breeding lines and cultivars for host plant resistance against field isolates of (a) M. phaseolina (b) Phomopsis longicolla (Phomopsis Seed Decay) and (c) Cercospora sojina (Frogeye Leaf Spot). Characterize the interaction between Pasteuria nishizawae and Heterodera (H.) glycines to reduce the impact of soybean cyst nematode on soybean production.
Several improved germplasms with durable resistance to nematodes and other fungal diseases were entered into USDA Southern Uniform Tests for multi-location evaluations. A conventional soybean germplasm, JTN-4307, with resistance to multiple soybean cyst nematode (SCN) populations and fungal pathogens and especially to Frogeye Leaf Spot (FLS) is being released. SCN resistance in PI88788 was broadened by crossing it to a diverse line, Columbia, and JTN-3109-3 was selected for more durable resistance. A mapping population was developed to identify new marker(s) tagged to the broadened resistance. USDA Soybean Germplasm Collection was screened in the greenhouse and eleven additional sources of nematode resistance were identified. These included soybean PI lines 512322D, 522186, 522190, 538408, 567488A, 567488B, 567650C, 567679B, 567676A, 567690, and 567726.
Using screening protocols developed for evaluation and identification of resistance, breeding lines and commercial cultivars are being assessed for charcoal rot, Phomopsis Seed Decay and Frogeye Leaf Spot. Thirteen lines that exhibited high level of resistance to charcoal have been identified among 113 germplasm lines having resistance to SCN. These 13 lines will be released as sources of resistance to the disease. In addition, several lines with resistance to Frogeye Leaf Spot and moderate resistance to Phomopsis have been planted for validation of resistance. Among the lines evaluated for Frogeye, 246 are recombinant inbred lines that were developed for charcoal rot resistance, and 100 lines are the same ones being tested for Phomopsis resistance. This approach is valuable to identify multiple disease resistant lines. The effects of planting date and yield effects of charcoal rot on soybeans are also being assessed.
Research is underway on a long term soybean experiment comparing single-cropped to double-cropped soybeans and winter wheat. The main plots include tillage and no-tillage treatments. Bacterial biological control is one aspect of management of soybean cyst nematode, and two new commercially available seed treatment nematicides contain gram positive bacteria as the active ingredient. One protects soybean roots and the other contains a parasite of soybean cyst nematode. Two bacterial parasites of soybean cyst nematode have been found in two research plots in Tennessee. One hyperparasite has been identified, and the unidentified one was found in the tillage study described above. In greenhouse studies, soil samples collected from pots containing seed treated with a bacterial nematicide and no seed treatment were processed for presence of gram positive bacteria using selective media (crystal violet agar). Results showed that a technique comparing number of bacterial colonies on crystal violet agar to media without the crystal violet could be used to detect the presence of the bacterial nematicide in soil samples.
Identification of soybean accessions resistant to charcoal rot by field screening and laboratory validation. Charcoal rot of soybean has been a problem for soybean farmers in the United States for many years, and recently its incidence and severity has increased in mid-western and north-central states. Although genetic resistance would be the most sustainable control strategy, resistant commercial soybean cultivars are presently unavailable. An ARS scientist at Jackson, TN, and cooperators identified ten soybean accessions with better resistance to charcoal rot than the standard released germplasm DT97-4290. These accessions can serve as additional sources of charcoal rot resistance in breeding programs.
Tillage and fungicide effects on disease progress of Frogeye Leaf Spot of soybean and its impact on yield. Frogeye Leaf Spot of soybean has been a problem in the southern USA for many years but has recently become an increasing problem in the northern USA. Change towards the use of reduced tillage or no-till system has been suggested as one of the contributing factors for an increase in disease severity. Analysis by ARS scientists at Jackson, TN, indicated no significant difference in disease severity between tilled and no-till plots when plots were not treated with Headline fungicide; however, fungicide application reduced disease severity significantly more in tilled than in no-till treatment. Fungicide consistently improved yield in tilled plots in all treatment in all years, but in no-till plots only 50% of the treatments comparisons showed a yield increase from fungicide application. This finding suggests that no-till neither enhanced nor reduced the severity of Frogeye Leaf Spot on soybeans. Current fungicide recommendations need to be reconsidered in order to minimize the risks of loss to the disease.
Effects of soybean maturity on population density of charcoal rot as measured on two sets of maturity isolines. Charcoal rot fungus causes significant yield losses in soybean production in the USA and as well in many other countries around the world. The effect of maturity on the severity of charcoal rot is not well understood mainly because maturity is generally confounded with genotypic background. Therefore, field experiments using the two sets of near-isogenic lines from either cultivar Clark or Harosoy, differing only by genes for maturity, were established on two soil types (sandy loam and clay) and evaluated for two years by ARS scientists in Stoneville, MS. Disease severity, expressed as fungal colony-forming units and evaluated for each soybean line at physiological maturity, showed little evidence of a relationship between soybean maturity and disease severity within the maturity lines tested. Further, disease severity in both types of soils were similar, indicating that disease severity ratings may be equally achieved on either sandy loam or clay soils.
Newly developed soybean JTN-4307 has resistance to multiple pathogens. Soybean cyst nematode (SCN) is a pervasive root parasite in the USA, and the combined yield loss of SCN with Frogeye Leaf Spot in USA is estimated to be more than $1 billion. ARS scientists at Jackson, TN, in cooperation with Missouri and Tennessee Agricultural Experiment Stations, developed conventional soybean JTN-4307 with resistance to multiple pathogens and good yield potential. Seed yields ranged from 43-51 bushels per acre. Traditional breeding methods were supplemented with modern marker-assisted biotechnological selection techniques for rapid gains and development. With resistance to multiple pathogens, JTN-4307 is excellent parent material to develop new cultivars in several maturity groups. Growers in the mid-southern USA may use JTN-4307 directly for planting where diseases are a serious problem.
Donald, P.A., Holguin, C.M., Agudelo, P.A. 2013. First report of Lance Nematode (Hoplolaimus magnistylus) on corn, soybean and cotton in Tennessee. Plant Disease. http://dx.doi.org/10.1094/PDIS-09-12-0881-PDN.
Goheen, S.C., Campbell, J.A., Donald, P.A. 2013. Nutritional requirements for soybean cyst nematode. Intech . 1:1-17.
Mengistu, A., Bond, J., Nelson, R.L., Rupe, J., Shannon, G., Arelli, P.R., Wrather, A. 2013. Identification of soybean accessions resistant to macrophomina phaseolina by field screening and laboratory validation. Online. Plant Health Progress. 10.1094/PHP-2013-0318-01-RS.