Marigold cultivars vary in susceptibility to iron toxicity

The susceptibility of seven African marigold (Tagetes erecta L.) cultivars to iron toxicity was assessed. Plants were grown in a greenhouse in a soill ess medium and Fe-DTPA was incorporated into the nutrient solution at eithe r 0.018 mmol.L-1 (low) or 0.36 mmol.L-1 (high). Symptoms of Fe toxicity (br onze speckle disorder in marigold characterized by chlorotic and necrotic s peckling and downward leaf cupping and curling) developed only in the high- Fe treatment. The concentration of Fe in leaves in the high-Fe treatment wa s 5.6 and 1.7 times as great as in the low-Fe treatment for 'Orange Jubilee ' and 'Discovery Orange', respectively. Based upon the percentage of plants affected and leaf symptom severity, relative cultivar susceptibility to Fe toxicity was Orange Jubilee > First Lady > Orange Lady > Yellow Galore > G old Lady > Marvel Gold > Discovery Orange. Chemical names used: ferric diet hylenetriaminepentaacetic acid, disodium salt dihydrate (Fe-DTPA).