David S. Nuland

Screening for resistance to iron deficiency chlorosis in dry bean using iron reduction capacity

Abstract Identifying cultivars resistant to iron (Fe) deficiency chlorosis so prevalent in calcareous soils is a more economical solution than fertilizer application in field crops. The current method of screening for resistance using chlorosis ratings in field trials is time consuming and highly variable. Root Fe reduction successfully separated cultivars or rootstocks, varying widely in resistance, of soybean (Glycine max L.), peach (Prunus persica L.), and grape (Vitis spp.), but was unsuccessful in sub‐clover (Trifolium subterraneum L.). Dry bean (Phaseolus vulgaris L.) exhibits Fe deficiency chlorosis in calcareous soils and initiates Fe reduction by the roots in response to such stress. The resistance of 24 dry bean cultivars to Fe deficiency chlorosis was assessed by measuring and summing daily Fe reduction by the roots. The cultivars were grown both hydroponically in an environmental chamber in low Fe solutions (0.05 mg‐L‐1) and at three field sites in both 1995 and 1996. A significant relationshi...

Use of hydrogen release or a combination of hydrogen release and iron reduction for selecting iron‐efficient dry bean and soybean cultivars

Abstract Iron (Fe) chlorosis continues to be a problem in the world where crops are grown in calcareous soils. Although it is possible to remedy this problem with fertilizer application, selection of cultivars resistant to Fe‐deficiency chlorosis is a more economical and practical solution. In addition to field chlorosis rating studies, several methods have been developed to screen cultivars. One of the most promising is quantifying individual plant response mechanisms induced during Fe‐deficiency stress, such as Fe reduction or hydrogen ion (H+) extrusion by the roots. Eight dry bean (Phaseolus vulgaris L.) and 11 soybean (Glycine max L.) cultivars of varying resistance to Fe‐deficiency chlorosis were grown in solutions of low (0.05 mg L‐1) and no (0 mg L‐1) Fe, respectively. Beginning at day 2 after imposition of low Fe treatments, plant roots were incubated for one hour in a solution to collect H+ ions. This solution was then titrated with NaOH to the pH of the control solutions (no plants grown in sol...