Marker Assisted Soybean Breeding for Improved Resistance to Cyst Nematode Populations.

Worldwide, cyst nematode (SCN) Heterodera glycines Ichinohe is the most destructive pathogen on cultivated soybean [Glycine max (L.) Merr.].  In the USA, recent annual losses were estimated to be nearly 60 million dollars. Resistant cultivars reduce yield losses.  Nematode populations are variable and over time have adapted to reproduce on resistant cultivars.  Cultivar Hartwig was released with comprehensive resistance to most nematode populations and continues to be used in breeding programs in the Southern USA. We recently developed four soybean populations, JTN-4307, JTN-4408, JTN-5110 and JTN-5208, for nematode resistance.  All have resistance genes deployed from Hartwig.  Breeding methodology included a combination of pedigree and mass selection.  Resistant progenies were identified in F_6:7 lines in established greenhouse bioassays using near homogeneous nematode populations.  Resistant lines were confirmed using SSR markers associated with nematode resistance.  Five markers, Satt 632 (A2), Satt 082 and Satt 574, both on LG D2, and Sat_168 and Satt 309 on G were polymorphic in PCR reaction.  These selections were advanced and entered into USDA Uniform Tests for Southern Region, during 2008-2010 and, their yields ranged from 45 Bushels/Acre to 50 Bushels/Acre.  We plan to release them.