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The set of ANK-29 phenotypic traits (low stiff straw, weak tillering,
vertical leaves, short and closely packed spike, and spherical grain)
was inherited jointly by the progeny during both the NIL development
(nine backcrosses) and hybrid segregation in test crosses. It is
likely that this set of phenotypic traits is determined by either a
single gene s1 or a tightly linked group of genes.
ANK-29 differs considerably from Novosibirskaya 67 and ANK-30 in the
lengths of glume, lemma, and palea. Pronounced differences between
ANK-30 and Novosibirskaya 67 in the lengths of the glume and lemma
were recorded in both years of observation, while the grain and palea
were of similar lengths (Table 2).
Therefore, the grain length is unconnected to the lengths of glume
and lemma. On the contrary, the shortened palea of ANK- 29 suggests
that it is the size of palea that determines the grain length.
ANK-29 was inferior to the standard in all productivity constituents
except for the number of spikelets in a spike. The decrease in the
grain number per spike along with the equal number of spikelets
indicates the decreased fertility of the florets of this genotype.
ANK-30 did not differ from the recurrent parent in productivity
(Table 3) during both years of observation,
despite the contrasting weather conditions.
Discussion
The absence of segregation in the F2 generation of the
hybrids of the NILs with the corresponding aneuploids confirms the
known location (McIntosh 1988; Arbuzova et al. 1996) of the marker
genes, s1 (ANK-29) on chromosome 3D and Eg1 (ANK-30) on
7A.
We have earlier recorded a regular decrease in plant biomass and
grain size in reduced height genotypes marked with Rht genes
(Koval and Koval 1997). The reason lay with an insufficient capacity
of the intermediate metabolite depot in vegetative organs. Similarly,
the shortened grain in ANK-29 is unable to utilize the metabolites
transported from the plant, thus resulting in a decreased
productivity. The low harvest index of ANK-29 indicates that
metabolites have been utilized incompletely during grain filling and
their considerable portion remained in vegetative organs.
One thousand kernel weight is known to correlate very well with the
plant productivity and@yield (Millet 1984), thus representing an
important breeding trait. However, the NILs have almost reached the
limits of grain filling with metabolites, since the linear size of
the grain restricts the amount of nutritive substances. Further
increase in the 1,000 kernel weight will be possible only with the
increase in metabolite capacity of the grain, that is, with an
increase in linear size.
Basing on the high ecological stability of the grain linear size
(Afanas'ev 1985) compared with its weight (filling of the grain),
several plant breeders have suggested selection for the maximal
length of the grain aiming to obtain the biggest grain (Korobeinikov
1985). Therefore, the search for the wheat polymorphism in the palea
length is an ongoing problem.
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