Glossary Plant Breeding

Allosomes. Accessory chromosomes that differ from the rest chromosomes (autosomes)
in shape, size, and other attributes.
Allosyndesis. Pairing between chromosomes belonging to different genomes.
Allozymes. Allelic forms of enzyme loci that can be distinguished by electrophoresis.
Alternate Hypothesis. The conclusion drawn after rejection of the null hypothesis (Ho).
It is denoted by H 1 . If sample result fails to substantiate the null hypothesis, it is
concluded that something else is true; this conclusion is referred to as alternate
hypothesis. (Also see null hypothesis).
Alternate Segregation. The passage of both normal chromosomes to one pole and both
translocated chromosomes to the other pole in a translocation heterozygote
(reciprocal). As there is no net loss or gain of hereditary materials, gametes are 100%
functional.
Alternation of Generations. The alternation of gametophytic and sporophytic stages in
the life cycle of a plant.
Aluminium Toxicity. A form of abiotic stress limiting crop production in acid soils. The
problem is particularly serious in strongly acid subsurface soil horizons (pH<5.5) that
are difficult to lime. Aluminum (Al) toxicity negatively affects growth of both root
and shoot. The root growth reduction may stem from restricted absorption of water
and nutrients, and ultimately causes yield reduction in such a problem soil. Under
such a situation, use of tolerant cultivars may be a satisfactory solution to this
problem. Use of tolerant genotypes and breeding of crops for Al tolerance is a reliable
approach to enhance production on acidic soils. This requires a rapid and effective
technique to discriminate between tolerant and sensitive genotypes. There are several
screening methods for Al tolerance such as solution, sand and soil cultures, root regrowth
and hematoxylin staining techniques, and field screening. Selection of
seedlings in hydroponic assay has been used as a rapid screening method to screen for
aluminum tolerance in several crops. Hematoxylin staining and root re-growth
techniques are also frequently used techniques because they have produce consistent
results. In addition, the results obtained with solution culture screening method
correlate positively with those obtained using field screening, showing that this
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