| Summary: | This study was undertaken to evaluate 11 wheat genotypes for aluminium tolerance
using three laboratory based evaluation methods. Four parameters namely the root
length before aluminium treatment, the root re-growth after aluminium treatment, the
portion of the root affected by aluminium treatment, stained with hematoxylin and root
tolerance index were measured on the two longest (primary and secondary) roots of
each seedling to determine the effect of aluminium toxicity on the physiological
development of the seedling roots.
With the root re-growth method it was possible to distinguish between three categories of
tolerance (moderate, intermediate and tolerant) that will be very helpful in future
resistance breeding for aluminium tolerance. With this method it is possible to
discriminate between individuals in a population for aluminium tolerance.
Similar data was obtained for the primary and secondary roots, which indicated that the
age of the roots are not a limiting factor for aluminium tolerance screening with the
nutrient bioassay. Although the root re-growth method discriminated between the
different aluminium tolerance categories, a better indication of aluminium tolerance
categories was achieved with the root tolerance index method. With the above
methodology in place it was possible to observe an increase in aluminium tolerance in
some progeny after gene recombination and it was possible to discriminate between
good aluminium tolerant progeny and progeny showing no genetic gain from the
hybridisation. It was also shown that there were no reciprocal effects for aluminium
tolerance in wheat.
There were genetic differences for aluminium tolerance between the genotypes used in
this study and this methodology can be successfully implemented in an aluminium
tolerance-breeding programme for wheat. This study indicated that there is useful
methodology to effectively follow the genetic gains during gene-recombination for
aluminium tolerance and, secondly that there are different genetic resources available in
wheat that can be utilised to increase aluminium tolerance.
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