RESISTANCE TO IRON-DEFICIENCY CHLOROSIS IN PI-437654 SOYBEAN

Breeding soybean [Glycine max (L.) Merr.) cultivars for resistance to both the soybean cyst nematode (Heterodera glycines Ichinohe) (SCN) and Fe-deficiency chlorosis (IDC) is an important objective for growing soybean on some calcareous soils. PI 437654 has the highest level of SCN resistance known in soybean; our objective was to investigate its level of IDC resistance. For this purpose, PI 437654 was evaluated along with eight soybean genotypes, including the highly resistant A13 and the highly susceptible T203. The test was conducted on calcareous Harps soils (fine-loamy, mesic Typic Calciaquolls) at Ames, IA, in 1989, and at Ames and Humboldt, IA, during 1990. The IDC symptoms were visually rated on the scale 1 = no yellowing to 5 = severe yellowing and some necrosis. T203 had an average score of 4.9 and A13 had an average score of 1.4. PI 437654 had an average score of 1.7. Thus, PI 437654 is a good source for resistance to Fe-deficiency chlorosis as well as soybean cyst nematode.