A cytogenetic approach to the improvement of aluminium tolerance in wheat.
High levels of soil aluminium place serious constraints on wheat production on acidic soils, especially in the tropical areas of Africa and South America. Conventional plant breeding has improved the tolerance of the wheat crop, but available genetic variation is limited. The wild relatives of wheat provide a valuable gene pool for the introduction of further genetic variation. One wild species, Aegilops uniaristata (2n = 2x = 14, NN), is being utilized as a new source of tolerance. Of the addition lines of individual N genome chromosomes of A. uniaristata to wheat (Triticum aestivum) which have been established and characterized, chromosome 3N was shown to confer tolerance to wheat. The three substitution lines in which 3N replaces the homoeologous wheat chromosomes, 3A, 3B or 3D, have also been produced. Growing plants to maturity in a low pH/high Al hydroponics system confirmed that chromosome 3N conferred tolerance to the substitution lines as well as to the addition line. By manipulating the genetic control of homoeologous chromosome pairing, chromosome 3N was recombined with its wheat homoeologue in order to introduce a smaller alien segment which carries the gene(s) for tolerance but not the agronomically unacceptable brittle rachis gene also carried on chromosome 3N.