Factors Associated with Differential Response of Oat Cultivars to Iron Stress1

Oat (Arena byzantinaC. Koch) cultivars developed differential Fe chlorosis symptoms when grown in field trials on alkaline soils in south Texas. To determine why they differed, ‘TAM 0‐312’ (Fe‐inefficient), ‘Coker 227’ (Fe‐efficlent), and ‘TAM 0‐301’ and ‘73C1952’ (intermediate in Fe response) oats were tested in alkaline soils and in nutrient solutions. Physiologically, Coker 227 responded more favorably to Fe stress (reduced Fe3+to Fe2+at the root) than TAM 0‐312. More significantly, the Ca concentration was consistently about 2,500 µg/g dry matter greater in TAM 0‐312 than in Coker 227. Although not consistent, the P concentration was often greater in TAM 0‐312 than in Coker 227 which would also accentuate Fe chlorosis. We suggest that Ca effectively competes with or inactivates Fe in TAM 0‐312, thus causing Fe chlorosis to develop in this cultivar but not in Coker 227.