ROOT-KNOT NEMATODE RESISTANCE IN SOYBEANS

Twenty-four soybean cultivars/accessions were tested for resistance to the root-knot nematode Meloidogyne incognita wartellei in southwestern Louisiana [USA] where soybean yields were low. Resistance was based on root-knot nematode buildup in the soil, percentage of soybean roots galled, percentage of chlorosis and necrosis on the soybean foliage, and yields. Nematode soil population increased least on Braxton, LA 78-17717, LA 78-17908, Centennial, LA 75-1794 and LA 75-1799. Fewest root galls occurred on LA 75-1794, LA 75-1799, LA 78-17717 and Centennial. Least chlorosis and necrosis occurred on LA 75-1697, LA 75-17941, LA 75-1799, LA 77-10700, Centennial and LA 78-17908. Highest yields were obtained from LA 75-1697, LA 75-1794, Braxton, Forrest and Centennial, which averaged 14.1, 11.2, 11.2, 11.2 and 10.8 bu/A, respectively. Yields among the soybean entries were negatively correlated with percentage of chlorosis and necrosis of the foliage and percentage of galled roots but not with soil populations of juveniles. Soil populations were positively correlated with the root-gall index but not with percentage of chlorosis and necrosis on the foliage. Root-gall index, however, was positively correlated with the amount of chlorosis and necrosis on the foliage.