Citation: Thies, J.A., Fery, R.L. 2006. Reactions of regional cooperative southernpea (cowpea) breeding lines and checks to southern root-knot nematode race 3, 2004. Biological and Cultural Tests for Control of Plant Diseases. 21:V017. Technical Abstract: Southernpea breeding lines from the Regional Southernpea Cooperative Trial were evaluated for resistance to southern root-knot nematode, Meloidogyne incognita race 3, in a greenhouse test. The experimental design was a randomized complete block with four replicates. Each plot consisted of five seeds of an entry planted 10 cm apart and 2 cm deep in a greenhouse bench containing steam-pasteurized soil (2 parts sand : 1 part loamy sand). Nematode inoculum was cultured on Rutgers tomato (Lycopersicon esculentum) in the greenhouse. Eggs were extracted from tomato roots using 0.5% NaOCl. Seeds were planted on 7 Sept 2004 and the soil surrounding each seed was infested with ca. 2,500 M. incognita eggs suspended in 5 ml H2O. The greenhouse conditions were maintained for favorable growth of southernpea (25-32 °C) and nematode development. On 25 Oct 2004, the roots of the plants were lifted, washed, and evaluated for resistance to root-knot nematode using a 1 to 5 rating system, where 1 = 0 to 3% of root system galled or covered with egg masses, 2 = 4 to 25%, 3 = 26 to 50%, 4 = 51 to 79%, and 5 = >80% of root system galled or covered with egg masses. The standard resistant and susceptible check cultivars performed as expected. Three observational lines (AR01-1165, AR00-855, and LA 96-10) and five advanced lines (US-1076, TX 152 PEgc, TX 158 BEgc, TX 160 BEgc/gt, and LA 95-17) were resistant (R), similar in reaction to the resistant check Mississippi Silver. Nine observational lines (US-1086, US-1090, US-1094, US-1096, AR01-874, AR01-1237, LA 96-30, LA 96-37, and LA 96-74) and seven advanced lines (US-1071, US-1080, AR01-1293, AR96-854, AR00-178, LA 96-4, and LA 96-18) were susceptible (S), similar in reactions to the susceptible checks Arkansas Blackeye #1, Pinkeye Purple Hull - BVR, and New Era.