SOYBEAN GENOTYPE EVALUATION FOR IRON-DEFICIENCY CHLOROSIS USING SODIUM-BICARBONATE AND TISSUE-CULTURE

The evaluation of soybean genotypes for resistance to iron deficiency through field experiments is complicated by variation in symptom expression. The objective of this study was to develop a tissue culture technique that could distinguish between Fe-efficient and Fe-inefficient genotypes. Ten soybean genotypes varying in sensitivity to iron deficiency were planted at 5 locations and rated based on chlorosis expression. For the lab evaluation, friable callus of the ten genotypes was placed on a 4MSII medium amended with 10 mM NaHCO3. Callus growth reduction relative to a control medium without NaHCO3 Was recorded. Callus weight of all cultivars was affected by the addition of NaHCO3 however, significant differences in growth reduction among genotypes was observed. The high correlation between callus growth reduction and field chlorosis ratings observed (r2=0.92) and the fact that the explant source plant can be grown to produce seed indicates that this technique would be useful in a soybean breeding program.