IDENTIFICATION AND INHERITANCE OF INEFFICIENT ZINC-ABSORPTION IN SOYBEAN

Two experimental soybean [Glycine max (L.) Merr.] lines that had produced nearly similar seed yields when grown at Stoneville, MS, differed widely when grown at Newton, MS. This study was conducted to identify the cause for the low seed yield of one line at Newton. Previous studies at this location on soils limed to a pH of 7.0 had shown that 'Forrest' soybean increased in yield when fertilized with zinc. Data are not available to show that soybean genotypes differ in efficiency of Zn absorption, so studies were initiated to determine whether Zn concentration in the foliage was different between the two experimental soybean lines. Fully developed trifoliolate leaves were taken from the upper part of the plant at the R1 growth stage and analyzed for concentration of Zn. The low-yielding line D82-3298 contained 18 to 25-mu-g g-1 of Zn, while D77-6056, the high yielding line, had 48 to 56-mu-g g-1 of Zn. These results indicated that the two did differ in efficiency of Zn absorption. Three hundred thirty F3 lines from the cross D77-6056 X D82-3298 were grown along with parents in the same area the following year. The mean Zn concentration for the parental lines was 18.8 +/- 1-mu-g g-1 for D82-3298 and 36.9 +/- 2.6-mu-g g-1 for D77-6056. The distribution of F3 lines for Zn concentration suggests that only a few genes control Zn absorption efficiency or inefficiency. In additional plantings, D82-3298, D77-6056, and Forrest were grown with and without Zn fertilization. D82-3298 gave a significant (P < 0.05) increase in foliar Zn concentration and seed yield when fertilized with ZnSO4 at Newton, but not at Stoneville. D77-6056 and Forrest gave no response at either location.