The Ta DREB 3 transgene transferred by conventional crossings to different genetic backgrounds of bread wheat improves drought tolerance

Summary Drought tolerance of the wheat cultivar Bobwhite was previously enhanced by transformation with a construct containing the wheat DREB 3 gene driven by the stress‐inducible maize Rab17 promoter. Progeny of a single T 2 transgenic line were used as pollinators in crosses with four elite bread wheat cultivars from Western Australia: Bonnie Rock, IGW ‐2971, Magenta and Wyalkatchem, with the aim of evaluating transgene performance in different genetic backgrounds. The selected pollinator line, BW 8‐9‐10‐3, contained multiple transgene copies, had significantly improved drought tolerance compared with wild‐type plants and showed no growth and development penalties or abnormalities. A single hybrid plant was selected from each cross‐combination for three rounds of backcrossing with the corresponding maternal wheat cultivar. The transgene was detected in all four F 1 BC 3 combinations, but stress‐inducible transgene expression was found in only three of the four combinations. Under well‐watered conditions, the phenotypes and grain yield components of the F 2 BC 3 transgene‐expressing lines were similar to those of corresponding recurrent parents and null‐segregants. Under severe drought conditions, the backcross lines demonstrated 12–18% higher survival rates than the corresponding control plants. Two from four F 3 BC 3 transgenic lines showed significantly higher yield (18.9% and 21.5%) than control plants under limited water conditions. There was no induction of transgene expression under cold stress, and therefore, no improvement of frost tolerance observed in the progenies of drought‐tolerant F 3 BC 3 lines.