| Among tetraploid species a greater diversity was noticed between and within
species T. turanicum being the only cultivar sensitive to aluminum.
This species had a mean relative root length of 37 percent in comparison
to relatively tolerant species T. dicoccum (70%) (Table
2). SLOOTMAKER (1974) reported that T. dicoccum was sensitive
to aluminum in wheat medium but intermediate in barley medium. T. durum
showed less tolerance than T. dicoccum. Durum cultivars showed varying
responses to aluminum, some were highly tolerant while others highly sensitive.
Similar observations have been made in durum wheats by Foy (personal communication).
Other tetraploid species such as T. dicoccoides and T. timopheevi
were intermediate in reaction (Table 2). Among hexaploid species, Agropyron elongatum (AABBEE) was highly sensitive to aluminum due to presence of E genome. Similar response to aluminum was noticed at the other ploidy level of A. elongatum (AABBDDEE) (Fig. 2). In this octaploid elongatum, the degree of tolerance was probably contributed by the presence of D genome. SLOOTMAKER (1978) showed that gene or genes carrying aluminum tolerance are located on D genome in hexaploid wheats. In this study, we did not try to discuss the variation that exists for this trait in triticale as authors have already reported these trends (SAPRA et al., 1978). In general, octaploid triticales were more tolerant than hexaploid triticales. Rye showed highest degree of tolerance in comparison to wheat species but rye species responded differently to aluminum (Fig. 1) The present study reveals that genomes A and E of triticinae contribute to the aluminum sensitivity in wheat and related species. In recent years plant breeders have been utilizing the E genome as a bridge species in developing new hexaploid wheats and transferring disease resistance, winter hardiness and forage characters. The effect of E genome (Agropyron elongatum) carrying aluminum toxicity should be studied further especially in those areas with high acid sub-soils. Plant breeders and soil scientists should be aware of the role of A, B and D genomes as pointed out by SLOOTMAKER (1974) and of E genome reported in our findings. Additional work on the role of these genomes to other mineral stress levels (salinity etc.) should be studied further. Such efforts are being made in our laboratory. |
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