Hybrid necrosis as a problem in handling hexaploid × tetraploid wheat crosses

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Abstract
Summary: A tetraploid wheat breeding programme was initiated at the Plant Breeding Institute in 1970. Hexaploid × tetraploid wheat crosses were expected to contribute to the improvement of the tetraploid wheats but severe hybrid necrosis caused the death of the pentaploidFxhybrid plants in most crosses. The genotypes of tetraploid wheat selections derived from crosses involving Rampton Rivet, a non-carrier ofNeuwere determined by test crossing to hexaploid wheat varieties which were known to carry theNeimallele. Similarly, hexaploid wheat selections which did not carryNe2were identified from crosses involving Maris Ranger by test crossing to durum selections which carried theNefallele. By the careful choice of one parent, hexaploid x tetraploid wheat crosses were then made which avoided the hybrid necrosis problem. Segregation of theNe%gene was as expected but selection for agronomic characters appeared to favour the retention of the dominant allele of theNe1gene. Nevertheless, test crossing on a relatively small scale still identified many non-carriers.