2011 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.
Populations developed from genetically diverse plant introductions with broad-based resistance to soybean cyst nematode (SCN), that were crossed to elite soybean cultivars, continued to be progeny tested, screened in the greenhouse for SCN resistance, resistance confirmed using DNA markers tagged to resistance genes, and evaluated for yield and other desirable traits. Two advanced lines JTN-5109 and JTN-5209 with SCN resistance derived from a new source, soybean PI567516C developed using a combination of traditional and marker-assisted breeding methods continue to be evaluated in USDA Uniform Tests for Southern States for release. Seeds for both were provided to commercial companies in U.S. and Argentina through official MTAs. These lines will be used for source materials for developing elite cultivars with broad resistance to nematode populations. A manuscript on mapping for resistance was published in a refereed journal. Soybean JTN-5203, a selection with resistance to race 2 nematode population in maturity group V, with superior yield potential is in approval process for official release. This line was ranked number 1 for yield in Tennessee State Variety Tests. Multi-location evaluation tests were conducted for nine selected progenies with broad nematode resistance for yield and desirable agronomic traits including resistance to predominant fungal pathogens.
Collection and characterization of Heterodera glycines (HG) present in soybean production fields continues in west Tennessee and has expanded into middle Tennessee. Heterodera glycines populations in western Tennessee where resistance has been deployed for decades have HG types indicating that the populations can reproduce on PI 88788. HG types from middle Tennessee have some ability to reproduce on PI88788 but also contain populations which are easily managed with existing sources of resistance present in commercial varieties. Studies on management and interactions of soil rhizosphere organisms on H. glycines reproduction are ongoing. Data indicate that even when soybean production has been no-tillage for more than 30 years, the predominant soil microbes are bacteria. This suggests that tillage or lack of tillage is not the driving force to a fungal system but rather the amount and rate of decomposition of organic material from the crop. All soybean lines identified by Stoneville as resistant to soybean rust have been tested against H. glycines, and all lines were susceptible. Multiple populations including HG type 7 which is rarely found where H. glycines resistance has been used consistently and HG types which are characterized as possessing the ability to reproduce on PI 88788 were used in the testing.
Develop genetic markers associated with resistance to cyst nematode in a new soybean line. In the United States, nearly a billion dollars are lost in annual soybean production due to a tiny root parasite, soybean cyst nematode. Cultivars with genetically controlled resistance will reduce these losses. ARS researchers at Jackson, TN, (worksite) have used a new source of resistance in soybean and identified three new genetic markers tagged to nematode resistance. These markers will select resistant lines in soybean development with more accuracy. Marker based selection offers significant benefits worldwide; for growers to choose varieties with more durable resistance, and for soybean industry a quicker turn-around for production of newer high yielding cultivars with broad resistance.
Arelli, P.R., Concibido, V.C., Young, L.D. 2010. QTLs associated with resistance in soybean PI567516C to synthetic nematode population infecting cv. Hartwig. Journal of Crop Science and Biotechnology. 13:163-167.