Ferric chelate reductase activity under iron deficiency stress in Azalea

Evergreen azaleas grow optimally in acidic soil (pH 4.5 - 6.0) with adequate iron (Fe) levels. To combat Fe deficiency chlorosis when cultivated in alkaline soil under Fe shortage, Fe-efficient Strategy I azalea plants exploit the response mechanism of Ferric Chelate Reductase (FCR) activity. In this study, the ferric (Fe3+) reduction capacity of two azaleas (Rhododendron x pulchrum 'Sen-e-oomurasaki' and Rhododendron obtusum 'Kirin') was evaluated during 10 days of cultivation in control (pH 6) and Fe-deficient (pH 9) nutrient solutions. At day 6, Fe deficiency tolerant and sensitive genotypes were distinguishable based on FCR activity. The survey of FCR response is suggested for rapid screening before visual symptoms occur in Fe deficiency tolerant azaleas.