|Abstract or Summary
- A technique previously designed to screen wheat cultivars and
segregating populations for tolerance to Aluminum utilizing nutrient
solutions in growth chambers was found to be efficient in differentiating
among cultivars of wheat, rye, and triticale for tolerance to Al
under greenhouse conditions. A 5°C increase in temperature, from
25°C to 30°C of the nutrient solutions increased the toxicity of a
given Al concentration.
Screening of 263 entries including diploid, tetraploid and
hexaploid wheat species and diploid rye provided evidence that
adequate tolerance levels to Al in triticale can only be derived
from some hexaploid wheats and some diploid ryes.
The level of tolerance present in both wheat and rye was
expressed in the F₁ hybrids but did not interact to produce hybrids
that were more tolerant than the more tolerant parent. When the
rye was more tolerant than the wheat and the Al concentration
exceeded the level of tolerance provided by the wheat, the
heterogencity of rye for Al tolerance was expressed in the resulting
F₁ hybrids. When a tolerant wheat was crossed to a sensitive
rye and the Al concentration exceeded the tolerance level of the
rye, the F₁'s were uniformly tolerant indicating the parent wheat
was homozygous for tolerance of Al. Chromosome doubling of F₁
hybrids did not cause any dosage effects in the reaction of
amphiploids to Al.
The F₁ progeny from the Penjamo 62 x Rye 1003 cross was
tolerant to 1 ppm while sensitive plants to this Al concentration
were observed in the amphidiploids derived from this F₁ possibly
resulting from chromosome(s) loss or aneuploidy.
The level of tolerance in tolerant wheats was somewhat reduced
in the F₁
hybrids when crossed to sensitive ryes, but was fully
recovered in the amphidiploids derived from these Fi's. The
opposite was true when a tolerant rye was crossed to a sensitive
wheat. The F₁
hybrid was almost as tolerant as the rye parent but
this level of tolerance was not recovered in the amphidiploid. If
aneuploidy was present it did not involve rye chromosomes because
rye was the only tolerant parent and the amphidiploid was uniformly
as tolerant as Atlas 66.
Although the amphidiploid derived from the cross involving
tolerant wheat x tolerant rye showed the highest level of tolerance,
this was not as tolerant as the rye parent. It was believed
that modifier genes from the wheat genotype influenced the expression
of the full level of tolerance contributed by the rye parent
in the amphidiploids. Nevertheless, it provided the resulting
amphidiploids with a level of tolerance approximately twice that of Atlas 66. When tolerant rye was crossed to a sensitive wheat,
the amphidiploid obtained had a level of tolerance similar to
the tolerant wheat cultivar, Atlas 66.
Aluminum affected mitotic activity of wheat, rye and triticale
within the first three hours of Al treatment. Cell division decreased
as exposure to Al increased; however, the mitotic activity of tolerant
plants never reached zero. It appeared that a protective
mechanism was induced and allowed mitotic activity to continue progressively
causing roots to continue to elongate in the Al solution.
It appears that Al affects some processes at interphase. Binucleated
cells were observed in both Al treatments and controls.
Therefore, Al alone cannot be responsible for inducing this type