Study on the sensitive period and screening index for iron deficiency chlorosis in peanut.

A pot experiment was done for sixteen peanut cultivars grown on a calcareous soil.Genetic differences in chlorosis score,active Fe concentration and SPAD value in newly expanded leaves and their dynamic changes within the growth season were also analyzed.Results showed that under iron deficiency stress,significant differences in chlorosis degree were existed between iron-resistant and iron-susceptible peanut cultivars.The highest chlorosis scores for susceptible cultivars appeared at 50-65 days after emergence.During the growth season,SPAD value and active Fe contents in the newly expanded leaves varied in the range of 4.5-3.6 and 8.0-36.3 mg/kg, FW,respectively.Tendency of these two parameters changed from high to low to high with time.At early growth stage,SPAD value and active Fe content in young leaves of iron-resistant cultivars were significantly higher than those of iron-susceptible ones.Flowering stage was the most sensitive period to iron deficiency when the most severe chlorosis was observed, and the lowest SPAD value and active Fe content in young leaves were tested.Highly significant correlations were found between SPAD value and chlorosis score, active Fe content and pod yield at early growth stage.SPAD value in young leaves can be a feasible screening indicator to select iron-resistant peanut cultivars.