14C labelling as a reliable technique to screen soybean genotypes (Glycine max (L.) Merr.) for iron deficiency tolerance

Fifty diverse soybean genotypes were screened for their ability to tolerate iron deficiency stress in a hydroponics experiment with low iron (−Fe) and sufficient iron (+Fe). We hypothesised that the genotypes with higher root exudation potential would exhibit higher chlorophyll content, dry matter production and Fe acquisition. The relative root exudation capacity of the genotypes was estimated with the help of 14C. As compared to iron inefficient and non responsive (FeINR) category under sufficient availability of iron (+Fe), the average 14C content in the total root exudates (14CTRE) was 39.4% higher in iron efficient and responsive (FeER) category. Further, higher exudation was observed under iron limiting (−Fe) stress condition and reported maximum in FeER (110.0% increase over FeINR under +Fe condition). The strength of positive correlation between 14C released with other parameters related to iron deficiency chlorosis suggested that 14C could be effectively used as a tracer for providing reliable estimate for better screening of iron efficient and responsive categories of soybean genotypes.