Acid Soil Stress Tolerance in Tissue Culture-Derived Sorghum Lines

Acid soil stress limits crop productivity on nearly one-half of the nonirrigated arable land in the world. Improvement of acid soil tolerance in sorghum [Sorghum bicolor (L.) Moench] has been approached through conventional breeding programs and more recently through biotechnology. This study was initiated to determine if improved acid soil tolerant tissue culture regenerates could be developed from sensitive parental lines and whether tolerant regenerants with desirable agronomic traits could be selected under field stress conditions. Tissue culture regenerated lines of sorghum and their non regenerated checks were field tested for acid soil [Typic Kanhapludult] tolerance (50% Ai saturation at pH 4.2-4.6) near Griffin, GA, from 1986 to 1990. Two R₅ lines derived from ‘Hegari’ and two R₅ lines from RTx430 demonstrated improved acid soil tolerance in 1989. Field test results indicated that these four lines had significantly higher ratings for vigor (2.6-3.4 vs. 4.8-4.9), plant survival (12–30 vs. panicles harvested (2–9 vs. 0), and seed yield (20-85 g plot⁻¹ vs. 0) than their nonregenerated checks. During 1990, selected R₇ lines were advance tested on acid soils near Griffin with similar results. Three of these improved selections were then evaluated for early seedling development in a greenhouse soil study using the same acid soils from the field. These results showed that one Tx430 regenerated line had improved root development at low pH during the seedling stage. This research indicated that variation for acid soil stress tolerance was produced through tissue culture and that agronomically desirable genotypes were selected using appropriate field testing procedures and stress levels. Partial funding provided by the U.S. Agency for International Development under Cooperative Agreement no. DAN-4137-A-00-4053-00 and Health funds allocated to the Univ. of Georgia Agric. Exp. Stn.