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10 Agriculture 7(2001)
ISSN 1330-7142
UDK = 631.523.11:633.11
PLEIOTROPIC EFFECT OF Rht3 DWARFING GENE ON SOME TRAITS OF
WHEAT (Tr. aestivum L. em Thell)
M. Jo{t, Vesna Samobor, S. Sre~ec
SUMMARY
Izvorni znanstveni ~lanak
Original scientific paper
True-isogenic lines, differing only in the semi-dominant Rht 3 dwarfing gene, were developed
from the cross ’Tom Thumb x Bankuty 1201’ during 17 years of continuous selection on heterozygous
semi-dwarf plant. The effect of double (Rht 3 Rht 3 = full-dwarf), single (Rht 3 rht 3
=semi-dwarf), or no dwarfing gene (rht 3 rht 3 = tall) dosage on some plant, seed, and flour
quality traits were observed in the isogenic lines during two years field experiment, planted by
’honey-comb design’ at Kri`evci, Croatia. Significant main effect of Rht 3 gene was in shortening
of plant height by 54% and 28% in double and single gene dosage respectively.
Full-dwarf genotype (Rht 3 Rht 3 ) had by 12% more heads/plant, but the other yield components
as number of grains/head, and grain weight/head were lower by 25 and 28% respectively, resulting
in significantly lower grain yield/plant (-27%). However, this also could be a secondary
side effect of prolonged vegetation influenced by doubled Rht 3 gene. There was no
significant effect on flour protein content. Double gene effect was strong and significant for
maximum dough viscosity measured by amylograph in BU (101%). In our environment full
dwarf (Rht 3 Rht 3 ) has no agronomic value, but single gene dosage could be of commercial interest
in hybrid wheat breeding.
Key-words: wheat - Triticum aestivum, dwarfism, Rht 3 gene, pleiotropic effect, yield components,
grain yield, protein content, amylogram
INTRODUCTION
There is a general opinion that, discovery of dwarfing
genes and replacement of conventional tall wheat cultivars
by semi-dwarf ones, contributed to increase grain yield
(Pugsley, 1983, Pinthus and Levy, 1984, Gale and Youssefian,
1984, Worland et al., 1990, Gent and Kiyomoto,
1998). In spite of the fact that over twenty different dwarfing
genes have been identified so far (McIntosh, 1988),
only five of them are extensively used in World-wide cultivated
wheat varieties. These are: Rht 1 and Rht 2 , (known as
’Norin 10’), Rht 1 (B.dw) (known as Bezostaya 1 dwarf),
Rht 8 (known as ’Akakomugi’) and Rht 1 S gene (known as
Saitama 27). All of them, except Rht 1 (B.dw.) originated
from Japanese germplasm. While Rht 1 and Rht 2 are common
in American, Australian and West-European cultivars,
Rht 8 and Rht 1 S are prevalent in South-European
cultivars (Worland and Law, 1986). There were trials where
some other Rht dwarfing genes were used, but without
significant success (Worland et al., 1980). For now, only
strong dwarfing allel Rht 3 (known as ’Tom Thumb’ or ’Minister
dwarf’ gene) has shown some breeding value, at least
for hybrid wheat (Gale et al., 1989). The major genes
Rht 1 and Rht 2 were located on chromosomes 4AS (McVittie
et al., 1978, McIntosh, 1988) and 4DS (Gale et al.,
1975, McIntosh, 1988) respectively. The dwarfing gene
Rht 3 was also located on 4AS chromosome. It was multiple
allele with Rht 1 , Rht 1 S and Rht 1 (B.dw.) since all of them
share a common locus of the same chromosome (Morris
et al., 1972, Gale et al., 1975, Worland and Petrovi},
1988). The Rht 1 and Rht 2 are dominant genes, and the
third Rht 3 is semi-dominant gene with strong dwarfing effect.
All of the three have a pleiotropic effect on plant’s insensitivity
to exogenous gibberellic acid. The dwarfing
gene Rht 8 , common in South-European germplasm, has
been located on chromosome 2DL, and unlikely to previously
mentioned ’Norin 10’ and ’Tom Thumb’ dwarfing genes,
it is recesive height promoting gene (Worland and
Law, 1985) and do not confer insensitivity to exogenous
gibberellic acid (Worland and Law, 1986). The Rht 1 S is a
weak source of giberelic acid insensitivity derived from cv.
Saitama 27.
The interest for using Rht 3 gene in breeding work was
renewed after discovery of its ability to inhibit the release
of the enzyme a-amylase in germinated grain, the trait im-
Prof.dr.sc. Marijan Jo{t, mr.sc. Vesna Samobor and mr.sc. Sini{a Sre~ec -
Agricultural College Kri`evci, M.Demerca 1, 48260 Kri`evci