Sequential development of acid soil tolerant sorghum genotypes under field stress conditions

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Abstract
A plant breeding program to develop acid soil stress tolerant (AST) sorghum [Sorghum bicolor (L.) Moench] genotypes under subtropical field environmental conditions in the southeastern U.S.A. has evolved into a dual‐phase process. Since sorghum is highly sensitive to acid soil infertility, initial screening of F1 hybrids and advanced generation material is conducted concurrently on 6 soil types (Congaree sl ‐ Typic Udifluvents, Dyke cl ‐ Typic Rhodudults, Cedarbluff sil ‐ Fragiaquic Paleudults, Cecil si and cl ‐ Typic Hapludults, Pacolet scl ‐Typic Hapludults, and Appling csl ‐ Typic Hapludults) at 3 locations and at soil pH levels varying from 4.4 to 4.8 = water extraction [KCl = 3.9–4.2] (range of 5 to 15% Al saturation but Mn toxic). Both conventional (pedigree/backcross) and recurrent selection breeding techniques are being used in the program. Advanced generation material that survives the initial screening process at all locations are reciprocally backcrossed and/or backcrossed to known tolerant genotypes before evaluation at soil pH levels of 3.9 to 4.3 = water extraction [KCl = 3.7–3.9] (range of 40 to 60% Al saturation, and <5% Mn saturation). A satellite Colorado State University tissue culture screening procedure [Al toxicity, salt stress, drought (ethylene glycol) stress] is being initiated in conjunction with the field breeding program. Germplasm with regionally adapted agronomic characteristics, disease resistance, and multiple acid soil stress tolerance is emerging from the sequential developmental program involving environmentally controlled and field stress evaluations.