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Factors Associated with Differential Response of Oat Cultivars to Iron Stress¹

Oat (Arena byzantina C. 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.

Key Words: Fe deficiency • Fe-stress response • Differential absorption of Ca • Reduced Fe • Alkaline soils • Avena byzantina

² Research soil scientist, USDA, SEA, FR, Plant Stress Laboratory, Beltsville, MD 20705 and associate professor, Dep. of Soil and Crop Sciences, Texas A & M Univ., College Station, TX 77843.