Download PLEIOTROPIC EFFECT OF Rht3 DWARFING GENE ON SOME

Poljoprivreda, 2001,7(1):10-14.
PLEIOTROPIC EFFECT OF Rht3 DWARFING GENE ON
SOME TRAITS OF WHEAT (Tr. aestivum L. em Thell)
M. Jošt, Vesna Samobor and S. Srečec
Summary
True-isogenic lines, differing only in the semi-dominant Rht3 dwarfing gene were
developed from cross 'Tom Thumb x Bankuty 1201' during 17 years of continuous
selection on heterozygous semi-dwarf plant. The effect of double (Rht3 Rht3 = full-dwarf),
single (Rht3 rht3 =semi-dwarf), or no dwarfing gene (rht3 rht3 = 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 Križevci, Croatia. Significant main
effect of Rht3 gene was in shortening of plant height for 54% and 28% in double and
single gene dosage respectively. Full-dwarf genotype (Rht3 Rht3) had by 12% more
heads/plant, but the other yield components as number of grains/head, and grain
weight/head were lower for 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 Rht3 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 (Rht3
Rht3) has no agronomic value, but single gene dosage could be of commercial interest in
hybrid wheat breeding.
KEY WORDS: Wheat - Triticum aestivum, dwarfism, Rht3 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 in grain yield
(PUGSLEY 1983, PINTHUS and LEVY 1984, GALE and YOUSSEFIAN 1984, W ORLAND et al. 1990.
Gent and Kiyomoto, 1998.) In spite of the fact that over twenty different dwarfing genes were
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Poljoprivreda, 2001,7(1):10-14.
identified till today (Gene catalog-gopher, 1998), only five of them are extensively used in
World wide cultivated wheat varieties. Those are: Rht1, Rht2, (known as 'Norin 10'),
Rht1(B.dw) (known as Bezostaya 1 dwarf), rht8 (known as 'Akakomugi') and Rht1S gene
(known as Saitama 27). All of them, except Rht1(B.dw.) originated from Japanese germplasm.
While Rht1 and Rht2 are common in American, Australian and West European cultivars, rht8
and Rht1S are prevalentin Southern European cultivars (W ORLAND and LAW 1986). There
were trials of using some other Rht dwarfing genes, but without significant success (W ORLAND
et al. 1980). For now, only strong dwarfing allel Rht3 (known as 'Tom Thumb' or 'Minister
dwarf' gene) shows some breeding value, at least for hybrid wheat (Gale et al. 1989).
The major genes Rht1 and Rht2 have been located on chromosomes 4BS (GALE and MARSHAL
1976) and 4DS (GALE et al. 1975) respectively. The dwarfing gene Rht3 has been located on
4BS chromosome also. It is multiple allele with Rht1, Rht1S and Rht1(B.dw.) since all of them
share a common locus of the same chromosome (M ORRIS et al. 1972; GALE et al. 1975;
Worland, Petrović, 1988). The Rht1 and Rht2 are dominant genes, and the third Rht3 is semidominant gene with strong dwarfing effect. All of the tree have a pleiotropic effect on plant's
insensitivity to exogenous gibberellic acid. The dwarfing gene rht8, common in SouthEuropean 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
(W ORLAND and LAW 1985) and do not confer insensitivity to exogenous gibberellic acid
(W ORLAND and LAW 1986). The Rht1S is a weak source of giberelic acid insensitivity derived
from cv. Saitama 27.
The interest for using Rht3 gene in breeding work was renewed after discovery of its ability to
inhibit the release of the enzyme α-amylase in germinated grain, the trait important for regions
threatened by preharvest sprouting and consequently deleterious effect on bread quality (GALE
and MARSHAL 1973).
A number of studies of possible pleiotropic effect of dwarfing genes were reported, and often
non compatible and conflicting conclusions were brought (B ORNER and W ORLAND, 1994).
Beside the positive effects on grain yield (A LLAN 1989, GALE et al. 1989 and many others), a
neutral or even negative effects of the Rht genes due to a large decrease in grain size were
reported (ALLAN 1986, KERTESZ et al. 1991). There could be several reasons for this
disagreements in results obtained:
i)
some investigators prefer to perform 'inter-cultivar' rather than 'inter-gene'
comparisons, while
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Poljoprivreda, 2001,7(1):10-14.
ii)
the others in wish to get the results as soon as possible, used near-isogenic lines in
gene action comparisons.
iii)
Influence of environmental conditions seems to be important also.
From that reason, in the present investigation, by using true-isogenic lines, the effects of Rht3
semi-dominant gene in double, single and no-dosage on some plant, seed, and flour
characters, was examined.
Materials and Methods
Development of isogenic lines
In 1977, the F1 seed of cross 'Tom Thumb x Bankuty1201' was received from late Dr. Zoltan
Barabas, Cereal Research Institute, Szeged, Hungary. As Rht3 is semi-dominant gene, in the
following generations segregates on true dwarf (Rht3 Rht3), semi-dwarf (Rht3 rht3) and tall
(rht3 rht3) plant types were obtained. According to method described by A TKINS and
MANGELSDORF (1942), a constant selection on heterozygous (Rht3 rht3) semi-dwarf types were
performed in each successive generation. After 14 and 17 generations the seeds of true
isogenic lines were used in the experiment. The method described allowed us to test dosage
effect for Rht3 gene in the three true-isogenic lines, having constitution: Rht3 Rht3 (dwarf), Rht3
rht3 (semi-dwarf) and rht3 rht3 (tall).
Experimental design
Es 1:2:1 segregation ratio was expected between progeny of heterozygous (semi-dwarf)
plants, it was impossible to forecast the genotype of the certain plant. For this reason the
honeycomb design (Fasoulas 1979) was adopted in experiment planting. In this way
comparisons between the neighbor plants of the three expected different plant type (different
isolines) was possible. To ensure adequate number of homozigous plants each second row
was planted with homozigous seeds. (Fig.1) In fact, to ensure normal stand, all seeds were
planted in paper pots in October, and than normally developed and vernalized three leaf
seedlings were replanted in field in March next year. The between plant spacing in honeycomb
was 27 cm, it means the space precise planting was performed. All together 133 plants of each
homozygous genotype and 247 progeny seedlings of heterozygous parent plants were
replanted each year.
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Analytical methods
In spite of the honeycomb design applied, only a 40 couples of each of the three possible
genotype comparisons (Rht3Rht3 /Rht3rht3, Rht3Rht3 /rht3rht3, Rht3rht3 /rht3rht3) were
analyzed each year. In the field, the plant couples, sharing the same neighborhood, were
provided with adequate tags, and some characters (plant height, number of nodes/main shoot,
length of the top internode per main shoot, number of tillers/plant, number of heads/plant and
flag leaf area) were determined before harvest. The flag leaf area was determined by the
multiplying the flag leaf width, length and coefficient 'b':
Leaf area (sq cm) = width (cm) x length (cm) x b
The coefficient b=0.739 was previously determined on representative samples of 25 leaves of
each height class by gravimetric method (KVET and MARSHALL, 1971). After harvest the other
plant characteristics (ear length, number of spikelets/ear, number of kernels/ear, grain
weight/ear, grain weight/plant) were determined. The differences between the two means were
calculated and their significancy tested by t-test.
The kernel and quality characteristics (moisture, test weight, thousand kernel weight, grain
protein, milling, flour ash, and flour amylogram) were determined on average
samples, without possibility of statistical measures the differences between the means.
Results and Discussion
A problem in explanation of this type of investigations is frequent disability to distinguish the
primary effect of dwarfing genes and the secondary effect of reduced other values - source
capacity, for instance. Beside this, till now reported results often disagree in findings. One
reason could be frequent use of near-isogenic lines, and 'inter-cultivar' rather than 'inter-gene'
comparisons. In this experiment we tried to avoid this misleading procedure by using trueisogenic lines and 'inter-gene' comparison.
The main effect of Rht3 gene is significant shortening of plant stature for about 54% and 28%
in double and single gene dosage respectively, as well as significant decrease of α-amylase
activity (determined by amylograph) in double gene dosage only (Tab.1, Fig 2.). In double gene
dosage decreased spike fertility (number of kernels per spike for -25.04%, TKW for -16.06%
and test weight for -4.08%) could not be compensated by slightly increase in number of tillers
per plant (9,69%) and spikes
per plant (12,18%). As results, in environmental conditions of Croatia, grain yield per plant, in
space planting, was strongly lowered for -26.56 in double and -7.02% in single gene dosage
respectively. To some extent this negative effect could be compensated in dense planting due
to better lodging resistance of dwarf and semi-dwarf plants. However, even in this case, too
dense distribution of leaves in double gene full dwarf, and bad light interception into canopy,
seems to be unfavorable for photosynthesis.
However, our findings disagree with the results obtained recently by BORNER and A.J.
W ORLAND (1994). According to them, a higher number of grains per ear was
accompanied by a lower grain weight, but depending on the climatic conditions in a particular
year, the increase in grain number was sufficient to compensate for the reduction in grain size
and resulted in higher yields. Obviously, the environmental conditions of Croatia is to worm in
period of heading and flowering, resulting in empty, non-fertilized flowers, and consequently
lower grain number per head.
On the contrary, single gene dosage (heterozygous genotype - Rht3 rht3) seems more
acceptable when plant stature is in question (semi-dwarf of 83 cm). Lower grain yield per plant
in experiment (space planing) for about 7% could be compensated in dense population in
commercial planting. However, this type could be exploited only as F 1 hybrid due to its
heterozygous stage. In this way, the F 1 seed production could be more efficient due to the
difference in plant height (dwarf mother plant and tall pollinator plant) and hybrid vigor could be
expressed beneficially on grain yield of semi-dwarf F1 plants.
References
1. ALLAN, R. E. 1986. Agronomic comparisons among wheat lines nearly isogenic for three reducedheight genes, Crop Sci. 26:257-286.
2. ALLAN, R.E. 1989. Agronomic comparisons between Rht1 and Rht2 semidwarf genes in winter
wheat. Crop Sci. 29:1103-1108.
3. ATKINS, I. M., and P. C. MANGELSDORF. 1942. The isolation of isogenic lines as a means of
measuring the effects of awns and other characters in small grains. Jour. Amer. Soc. Agron.,
34:667-668.
4. BORNER, A., and A.J. W ORLAND. 1994. Breeding for lodging resistance in wheat and the utilization of
dwarfing genes. Abstracts of EUCARPIA Symp.on Prospectives of Cereal Breeding in Europe,
Landquart, Switzerland, p. 169-170.
5. FASOULAS, A. 1988. The honeycomb method of plant breeding. Aristotelian University of Thesaloniki,
Greece, p. 167.
6. GALE, M. D. and G. A. MARSHALL. 1973. Insensitivity to gibberellin in dwarf wheats. Ann Bot. 37:729735.
7. GALE, M. D., C. N. LAW and A. J. W ORLAND. 1975. The chromosomal location and a major dwarfing
gene from Norin 10 in new British semi-dwarf wheats. Heredity, 35(3):417-421.
8. GALE, M.D. and G.A. MARSHALL. 1976. The chromosomal location of Gai 1 and Rht 1, genes for
gibberellin insensitivity and semidwarfism, in a derivative of Norin 10 wheat. Heredity. 37(2):283-289.
9. GALE, M. D. 1979. The effects of Norin 10 dwarfing genes on yield. Proc. 5th Int. Wheat Genet.
Simp., New Delhi, p. 978-987.
10. GALE, M. D. and S. YOUSSEFIAN. 1984. Pleiotropic effects of the Norin 10 dwarfing genes, Rht1 and
Rht2, and interactions in response to chlormequat. Proc. 6th Int. Wheat Genet. Symp. Kyoto, p. 271277.
11. GALE, M.D., SALTER, A.M. and ANGUS, W.J. 1989. The effect of dwarfing genes on the expression of
heterozis for grain yield in F1 hybrid wheat. In: Maluszynski, M.(Ed.), Current options for cereal
improvement. Doubled haploids, mutants and heterozis. p. 49-61.
12. GENT, P.N.M., and R.K. KIYOMOTO.1998. Physiological and agronomic consequences of Rht genes
in wheat. J.Crop Prod. 1(1):27-46.
13. Gene catalog.
/GeneCatalog
1998.
Internet:
gopher://greengenes.cit.cornell.edu:70/0R89079-92105-
14. KERTESZ, Z., J.E. FLINTHAM and M.D.GALE. 1991. Effects of Rht dwarfing genes on wheat grain yield
and its components under Eastern European Conditions. Cereal Res. Comm. 19:297-304.
15. KVET, J., and J. K. MARSHALL. 1971. Relationships between linear measurements and leaf area. In:
Sestak et al. (Eds.), Plant photosynthetic production - Manual of methods. Dr. W.Junk N.V.
Publishers, The Hague, p. 526-532.
16. MCNEAL, F. H., M. A. BERG, V. R. STEWART and D. E. BALDRIDGE. 1972. Agronomic response of
three height classes of spring wheat, Triticum aestivum L., compared at different yield levels. Agr.
Journ., 64:362-364.
17. MORRIS, R, J. W. SCHMIDT and V. A. JOHNSON. 1972. Chromosomal location of a dwarfing gene in
Tom Thumb wheat derivatives by monosomic analysis. Crop Sci., 12:75-276.
18. PEPE, J. F. and R. E. HEINER. 1975. Influence of two different dwarfing sources on yield and protein
percentage in semidwarf wheat. Crop Sci., 15:637-639.
19. PINTHUS, M. J. and A. A. LEVY. 1984. Genotypic effects of height on grain yield of Triticum aestivum
L. spring wheat. Z. Pflanzenzuchtung, 93:49-55.
20. PUGSLEY, A. T. 1983. Identification and management of major genes monitoring yield and
adaptation. Proc. 6th Int.Wheat Genetics Symp., Kyoto, p. 971-974.
21. W ORLAND, A. J., C. N. LAW and A. SHAKOOR. 1980. The genetical analysis of an induced height
mutant in wheat. Heredity, 45:61-71.
22. W ORLAND, A. J., and C. N. LAW . 1985. Aneuploidy in semi dwarf wheat varieties. Euphyitica, 34:317327.
23. W ORLAND, A. J. and C. N. LAW . 1986. Genetic analysis of chromosome 2D of wheat. I. The location
of genes affecting height, day-length insensitivity, hybrid dwarfizm and yellow rust resistance. Z.
Pflanzenzuchtung, 96:311-345.
24. W ORLAND, A. J., C. N. LAW and S. PETROVIC. 1990. Height reducing genes and their importance to
Yugoslavian winter wheat varieties. Savremena poljoprivreda, 38(3-4):245-258.
PLEIOTROPNI UČINAK Rht3 GENA ZA PATULJASTU STABLJIKU
NA NEKA SVOJSTVA PŠENICE (Tr. aestivum L. em Thell)
M. Jošt, Vesna Samobor and S. Srečec
Visoko gospodarsko učilište u Križevcima, Hrvatska
SAŽETAK
Tijekom 17 godina uzastopnog odabiranja heterozigotnih biljaka iz križanja 'Tom Thumb x
Bankuty 1201', stvorene su čiste izogene linije, koje su se međusobno razlikovale samo u
zastupljenosti poludominantnog gena za patuljastu slamu (Rht3). U Križevcima, tijekom
dvogodišnjih poljskih pokusa sijanih po metodi pčelinjeg saća, u tih je linija promatran učinak
prisustva Rht3 gena (Rht3 Rht3 = patuljak, Rht3 rht3 = polupatuljak i rht3, rht3 = visoka biljka), na
neka svojstva biljke, sjemena i pokazatelje kakvoće brašna.
Značajan glavni učinak Rht3 gena je smanjenje visine stabljike za 54% u homozigotnih Rht3
Rht3 genotipova, odnosno za 28% u heterozigotnih Rht3 rht3 genotipova. Patuljaste biljke
(Rht3 Rht3) imale su 12% više klasova po biljci, ali su druge komponente uroda – broj zrna/klas
i masa zrna/klas bile slabije za 25 i 28%. Kao zbirni rezultat, patuljaste biljke ispoljile su
značajno umanjen urod zrna po biljci (-27%). Međutim, to bi mogao biti i sekundarni postrani
učinak dulje vegetacije (pet dana kasnije klasanje). Učinak dvostruke doze Rht3 gena na
količinu bjelančevina u zrnu nije bio značajan, ali je maksimalni viskozitet tijesta mjeren
amilografom u BU jedinicama značajno (101%) izmijenjen. U klimatskim uslovima Hrvatske
homozigotni patuljci (Rht3 Rht3) nemaju agronomske vrijednosti, međutim kao heterozigoti,
mogli bi imati stanovitu vrijednost u oplemenjivanju hibridne pšenice.
Ključne riječi: pšenica - Triticum aestivum, patuljasti habitus, Rht3 gen, pleiotropni učinak,
komponente uroda, urod zrna, bjelančevine zrna, amilogram.
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Fig.1. The honeycomb planting design applied ( = tall rht3 rht3 homozygote, o = segregating progeny of
heterozygous Rht3 rht3 semi-dwarf plants, and  = homozygous Rht3 Rht3 full dwarfs).
Fig. 2. Wheat near-isogenic lines differing only in Rht3 dwarfing gene dosage.
Tab.1. Pleiotropic effect of Rht3 dwarfing gene dosage on plant, seed and flour
characteristics.
Average of two years: Križevci, 1991 and 1995
Rht3 Rht3
Semidwarf
wheat
Rht3 rht3
rht3 rht3
double:
Rht3
Rht3
single:
Rht3
Plant height (cm)
53.3
83.1
115.4
46.20**
72.01**
No. tillers per plant
25.35
24.88
23.11
109.69*
107.66NS
Top internode length (cm)
25.04
35.18
50.03
50.05**
70.32**
Character
Full dwarf
wheat
Tall
wheat
Gen dosage effect if
rht3 rht3 = 100%
Flag leaf area (sq cm)
53.84
56.74
58.46
92.10*
97.06NS
No. spikes per plant
23.30
23.08
20.77
112.18*
111.12*
1st spike length (cm)
12.79
11.93
12.57
101,75NS
94.91NS
No. spikelets per 1st spike
21.89
20.56
19.98
109.56*
102.90NS
No. kernels per 1st spike
52.68
60.77
70.28
74.95**
86.47**
Kernels wt. per 1st spike (g)
2.76
3.71
3.84
71.87**
96.61NS
Grain yield per plant (g)
30.22
38.26
41.15
73.44**
92.98*
T K W (g)
43.08
49.63
51.32
83.94**
96.71
Test weight (hl/kg)
77.91
79.63
81.22
95.92**
98.04
Grain moisture (%)
15.12
13.78
13.32
113.51*
103.45
Flour extraction (%)
66.25
73.83
74.10
89.41
99.64
Flour protein (%)
13.12
12.04
13.02
100.77
92.47
Ash content (%)
0.593
0.548
0.550
107.82
99.64
Amylogram max. viscosity BU
2030
960
1010
200.99
95.04
**, *,
NS
= significant at 0,01; 0,05 level or not significant respectively.