Increased Fe‐efficiency in soybeans through plant breeding related to increased response to Fe‐deficiency stress. I. Iron stress response

Abstract

A7, a new soybean [Glvcine max (L.) Merr.], developed through plant breeding is considered to be more Fe‐efficient than cultivars currently available. The objective of this investigation was to determine if recognized factors in the Fe‐stress response mechanism may have been altered in A7 soybean to make it more Fe‐efficient than the A2, Hawkeye (HA) and Bragg (Fe‐efficlent) and the Pride B216 (Pride), T203, and Anoka cultivars (Fe‐inef‐ficient). The release of hydrogen ions and ‘reductants’ by the roots were the two parameters of the Fe‐stress response studied in this investigation. The effect of plant number per liter of solution was also considered by using 20 and 28 plants per 14 liters of nutrient solution. Compared to A2, HA, Bragg, Pride, Anoka and T203 soybean cultivars, A7 released more hydrogen ions and ‘reductant’ from its roots in the zero Fe treatment and also maintained higher Fe and chlorophyll concentrations. This could explain why A7 soybean grows better than the other soybeans on calcareous soils where Fe availability limits plant growth. The other cultivars responded to Fe‐stress best when a small amount of Fe was present in the nutrient solution. Greater Fe‐stress response was evident with 28 plants/14 liters than 20 plants/14 liters of nutrient solution. Successful development of the Fe‐efficient soybean should serve as an example for future plant breeding of other Fe‐efficient plant species.

Key words:

• Chlorophyll
• Glycine max (L.) Merr
• Iron Content
• Leaf
• pH
• Reductant
• Root