Tolerance of sorghum genotypes to an acid, aluminum toxic Tatum subsoil

Abstract

Aluminum (Al) tolerant sorghum (Sorghum bicolor L. Moench) genotypes are needed for use on strongly acidic, infertile soils of the tropics and subtropics, where the crop is often grown in a low input, subsistence type of agriculture. Eleven genotypes were first screened for Al tolerance in greenhouse pots of acid, Al‐toxic Tatum subsoil (clayey, mixed, thermic, Typic Hapludult) at pH 4.3 and 5.3. In two subseguent experiments, four genotypes showing wide differences in acid soil tolerance in the first test were grown over pH ranges of 4.3 to 6.4 and 4.7 to 7.0. Acid soil tolerance was determined by absolute dry shoot and root weights at low pH and relative (low pH/high pH %) shoot and root weights. Genotypes differed by as much as 10 fold in relative shoot weight and 8 fold in relative root weight. Genotypic tolerances to acid, Al toxic Tatum subsoil were in good agreement with those obtained on acid field sites in Georgia and Brazil. Hence, results indicated that Al toxicity is a major selection pressure factor in sorghum breeding programs of both regions. SC283 and SC574, originating in Tanzania and Pakistan, respectively, were most tolerant to the acid Tatum subsoil. RTx430 and RTAM42S, both from Texas, were among the least tolerant. Other sensitive genotypes included RTx2536, SC214, SC170, SC369, and SC599. A tissue culture derivative of the acid soil sensitive RTx430 genotype [RTx430 (TC)], showing tolerance to drought/salinity in Arizona and acid soil in Georgia, ‘ was significantly more tolerant to the acid soil than the RTx430 parent. The acid soil tolerance of this genotype also exceeded that of SC574 and approached that of the most tolerant genotype SC283.