(go
to KOMUGI Home) (go
to WIS List) (go
to NO.82 Contents)
Materials and methods
The male genotype HS 131 was selected from a Cobalt irradiated
Triticum aestivum population derived from the cross {[(Jinfeng 1
/ Xiaoyan 6) / (T 808 / Datuowang)] / (Xiaofeshou / Aifeng 1)}.
Its pedigree no. is Hengshui 86-171-131. The female parent used in
this experiment, were HS 86-86 [(Yanda 1817 / Taishanl) / Weimai
5], HS 90-4-11(Jimai 7 / Changshui 16) and HS 89-62 [(Punong
3665 / Jimai 3) /
Hengshui 6404].
Three crosses were made (HS 86-86 / HS 131, HS 90-4-11 / HS 131 and
HS 89-62 / HS 131) among 4 genotypes. All the crosses were made by
hand emasculation and pollination under controlled condition.
F1, F2 and F3 generations were grown
in the field using all seed obtained in the experiment. Before
harvesting, characters such as plant height (PH), ear length (EL),
number of florets per head (FL/H) and seed per head (S/H) were
recorded on 100 F3 plants from a single uniform li ne, and
another 100 plants were used from the check. T-test method was used
to compare the characters under study. Also, F2
segregating ratio was calculated using X2
test.
Results and
discussion
Above 100-120 florets from five heads were emasculated and bagged
in all male and female parents. No seed sets was observed in any of
them, suggesting that pollination was necessary for reproduction
particularly for genotype HS 131. If it behaves like a facultative
apomictic it belongs to pseudogamous apomixis. All the three
combinations demonstrated good heterosis in the F1 generation. But HS
90-4-11/HS 131 performed more vigorous than the other two, so more
attention was paid to it. Among the F2 segregating
nurseries, the progenies of the three combinations (HS 86-86/HS
131, HS
90-4-11/HS 131
and HS 89-62/HS
131) showed
a subsegregation. Only a few kind of types emerged comparing with
others from the agronomic characters' point of view. This unexpected
performance could not be explained based on Mendelian law, as the
parents' pedigree or the agronomic characters were all much
different. So single plants were selected from three of them and
planted for F3 observation. The F3 progenies of
all three combinations showed both uniform and segregating lines.
Results presented in Table
1 show the
apomictic gene(s) probably from the male parent, genotype HS 131.
One hundred plants were randomly selected from each of twenty
two uniform or unsegregating single line for recording characters PH,
EL, FL/H and S/H in the field and compared with the check by means of
t-test for the combination of HS 90-4-11/HS 131, as it had more'
populations than the other two. Results shown in Table
2 suggest no
difference within every single line for all tested characters,
indicating that all the uniform lines behaved like truebreeding
hybrids.
In order to identify F2 segregating ratios, 120 seeds were
collected and planted to produce F3 line.
X2
method was used to
calculate the segregating ratio. Results in Table
3 show that at
least 2 phenomena could not be explained by Mendelian law: First,
several characters such as PH, EL, FL/H and S/H controlled by a
number of genes can not attain homozygosity in one year of
self-pollination. Second, by no means the proportion of 26.9% of
uniform lines emerge in F3 generation. This means some
unexpected segregating proportion might have happened. This can be
explained by the way other than sexual reproduction, i. e. both
sexual and apomictic reproduction involved in the progeny and thus
fixing the heterosis in the F2 generation. Only in this
genetic system the uniform F3 lines can be emerged and
this phenomenon could be explained.
<--Back | -->Next
(go
to KOMUGI Home) (go
to WIS List) (go
to NO.82 Contents)