Variation in the Inheritance of Resistance to Iron Deficiency Chlorosis in Soybeans 1

Abstract

Past research has indicated that iron utilization of soybeans [Glycine max (L.) Merr.] on calcareous soil controlled by a major gene with complete dominance for iron efficiency. We conducted a backcrossing program to transfer the resistance to iron deficiency chlorosis of line ‘A2’ to a highly susceptible cultivar ‘Pride B216’. The segregation that we observed was different from previous reports on inheritance of the character. The F1 generation of the cross Pride B216 ✕ A2 was evaluated in replicated tests on calcareous soils in Iowa during 1979 and 1980. The F1 showed no dominance for chlorosis expression, with a mean chlorosis score of 3.3 compared with a midparent value of 3.2 (4.4 for Pride B216 and 1.9 for A2). The range among F2-derived lines in 1979 was 1.2 to 4.8, with a mean of 2.8. Seven of 200 random F2-derived lines from the cross had chlorosis scores equal to or better than A2 in 1979, and each line was backcrossed to Pride B216. An extensive evaluation of the seven F2-derived lines on calcareous soil in I980 showed that none were as resistant as A2, and none of the 280 BC1F2-derived lines from the first backcross were as resistant as A2 in 1980. Inheritance of iron deficiency chlorosis in the cross of Pride B216 ✕ A2 was typical of a quantitative character controlled by additive gehe action. Comparison of our results with those of previous research indicated that the inheritance of resistance to iron chlorosis in soybeans can vary, depending on the parents used in developing the populations and the test conditions used to evaluate the character.