Irradiation of seeds of an autodiploid strain of L. pimpinelifolium.<p>

Palenzona, D. L.<p>
                                  
In order to compare the induced mutability from X-ray irradiation with
spontaneous mutability rate, dormant seeds of an autodiploid strain of L.
pimpinellifolium received from Prof.  A.  B.  Burdick, Lafayette, Indiana,
were irradiated with 4000r.  According to Lindstrom (Genetics 26: 387-397,
1941) it is assumed that in such a strain no genetic variability is present.
The experimental plan is shown in the following table.<p>

<pre>
X\1 Gen.                             X\2 Gen.
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Control   1st group = plants from seeds of the 1st inflorescence
Control   2nd group = plants from seeds of the 4th inflorescence
4000r     3rd group = plants from seeds of the 1st inflorescence
4000r     4th group = plants from seeds of the 4th inflorescence
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</pre>
The experiment was thus planned in order to obtain estimates of the effects of
various types of selection (intrasomatic, gametic, zygotic) with suitable
comparisons between groups.<p>

Results: Differences in number of seeds per fruit between the two treatments
in X\1 gives an estimate of gametic selection: in our experiment gametic
selection acts more intensively on plants from irradiated seeds.  Intrasomatic
selection can be estimated by the differences between the 1st and 2nd groups,
for plants from non-treated seeds and the 3rd and 4th groups, for plants from
treated seeds.  Our results show consistent differences both in germinability
and in average day of germination.<p>

Zygotic selection can be eatimted by differences in germinability between
plants from irradiated and non-irradiated seeds.  This comparison shown a more
striking mortality in seeds from plants grown from irradiated seeds.<p>

We found a great amount of variability in plants from non-irradiated seeds.
This result suggests that the assumption of complete homozygosity of
autodiploid strains must be reconsidered.  In our experiment, however, such
results may be a consequence of aging of the seeds which were obtained in 1951
and grown in 1959.  Analysis of variance of weight of fruits shows that the
variability does not differ in plants of different treatments; gametic and
zygotic selections can be involved in explaining such discrepancy from
expectation.<p>

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