Location: Crop Genetics Research2009 Annual Report
1a. Objectives (from AD-416)
Broaden soybean germplasm for genetic resistance to new and emerging nematode populations; identify shifts in genetic profiles and virulence of soybean cyst nematode; and measure effects of cultural practices and diseases on soybean cyst nematode reproduction.
1b. Approach (from AD-416)
Evaluate accessions of Glycine max and Glycine soja for resistance to multiple populations of soybean cyst nematode (SCN), particularly those capable of reproducing on cultivars utilizing PI 88788 as resistance source. Characterize new sources for unique resistance genes and develop molecular markers associated with resistance. Pyramid resistance genes into elite backgrounds of maturity groups III, IV, and V in combination with resistance to predominant fungal pathogens to develop improved germplasm/ cultivars. Characterize SCN field populations to determine effectiveness of current sources of resistance. Predict stability and changes in SCN populations by accelerated selection pressure in greenhouse tests. Determine rhizosphere factors that influence SCN reproduction under different tillage and cropping schemes. Evaluate effects of concomitant infection of charcoal rot and other diseases on SCN reproduction.
3. Progress Report
Populations of unique soybean plant introductions with broad-based resistance to soybean cyst nematode (SCN) that were crossed to elite cultivars are being progeny tested for release. Twenty advanced lines in maturity groups, IV, South (Early and Late), North and V, resistance derived from Hartwig source and PIs 438489B, 507354 and 89772 are being yield tested. Two advanced lines with resistance derived from a new source, PI567516C in maturity V group are also being evaluated in USDA uniform tests. Twenty-seven lines in maturity group IV and twenty-two lines in maturity group V were advanced for yield test in both locations at Jackson, TN, and Ames Plantation. The resistance was derived from Peking, PI88788, Hartwig and plant introductions 07471, 567328 and 567516C. Subline selection was continued in these lines for agronomic traits. JTN-5203, which ranked high in USDA Uniform Tests, was reconfirmed for its resistance, especially for SCN Race 14. It is also resistant to fungal pathogens stem canker and sudden death syndrome (SDS) and is proposed for release. Characterization of soil samples from Tennessee soybean production fields has been completed for all soil samples collected over the past three years with high egg population density. No soybean cyst nematode populations characterized fit the profile of the wild type but rather were able to reproduce on the most common source of plant resistance (PI88788) as well as some other sources of soybean resistance. Application of poultry litter to create an environment unfavorable for plant parasites produced increased above-ground plant biomass but there was no evidence of increased root biomass as measured by increased soybean cyst nematode reproduction. Preliminary research did not detect differences in interactions between tillage regimes and effects of poultry litter. Bacterial pathogens of soybean cyst nematode have been recovered from field plots and some soybean production fields selected at random throughout the state. Studies are continuing with one promising isolate for use as a biological control agent.
1. Identification of Additional Sources of Resistance to Soybean Cyst Nematode in USDA Soybean Germplasm Collection. Soybean cyst nematode is consistently the leading limiting root parasite affecting soybean yield. Resistant cultivars have reduced yield losses in soybean; however, continuous use of soybean cultivars with resistance nearly derived from a single source of resistance has caused shifts in nematode populations over a period of time, rendering the resistant cultivars susceptible. Additional sources of resistance to soybean cyst nematode in soybean are needed for the development of new germplasms with broad resistance to be used by public and private sector scientists in the U.S. and abroad. The greenhouse screenings of new soybean germplasm lines that were recently introduced from China whose reaction to nematode populations is unknown have identified nine new soybean germplasm lines (PIs 33243-2, 468904, 468905, 468919, 567488-A, 567488B, 567676-A, 567679-B, and 567700) with various levels of SCN resistance. The potential impact of this research could be that the newly identified soybean lines will be used to develop soybean germplasm with broad and improved resistance to SCN with DNA markers tagged to resistance genes to assist in selection of resistant lines.
2. Detection of Pasteuria nishizawae. Soybean cyst nematode, like all plant parasitic nematodes, has parasites which can be exploited to help reduce the population density. A bacterial parasite of soybean cyst nematode was recovered from field plots with a 30+ year history of soybean cultivation. Fifty-one soil samples from Tennessee soybean production fields in 11 counties indicated that the parasite was present in 35% of the samples at an average level of 30% parasitism of the cysts in each sample. The potential impact is that in fields where the parasite is already present one may be able to boost the level of the bacterial parasite, providing an additional tool to reduce the impact of soybean cyst nematode on soybean production.Niblack, T.L., Tylka, G.L., Arelli, P.R., Bond, J.P., Diers, B., Donald, P.A., Faghihi, J., Ferris, V.R., Gallo, K., Heinz, R.D., Lopez, N.H., Von Qualen, R., Welacky, T., Wilcox, J.A. 2009. A Standard Greenhouse Method for Assessing Soybean Cyst Nematode Resistance in Soybean: SCE08 (Standardized Cyst Evaluation 2008). Plant Health Progress. doi:10-194/PHP-2009-0513-01-RV