37. A major gene, Tal and
QTLs affecting tiller and leaf angles in rice
Z. Li1,2. A.H. PATERSON, S.R.M. PINSON3 and G.S. KHUSH2
1) Dept. of Soil and Crop Sciences, Texas A&M University, College
Station 77843, USA
2) International Rice Research Institute, P.O. Box 933, 1099 Manila,
Philippines
3) USDA-ARS, Route 7, Box 999, Imes Rd., Beaumont, Texas 77713, USA
Ideotype is a complicated concept involving
combinations of many morphological and physiological traits into a multi-dimensional
plant structure that maximizes the biomass and its partitioning. Tiller
and leaf angles are important traits associated with the morphology of
ideal plant type. Under the conditions of modern agriculture with increased
application of N fertilizer, larger tiller and leaf angles may cause mutual
shading, increased humidity favoring diseases and insects, and lodging.
On the other hand, a highly compact plant type with completely vertical
tillers and erect leaves tends to be inefficient at utilizing solar energy
at early growth stages, and is vulnerable to those diseases which are favored
by high humidity such as sheath blight. The ideotype that most breeders
favor tends to be intermediate between these extremes with erect leaves
and relatively small tiller angle, allowing a high leaf area index without
causing mutual shading.
A RFLP facilitated analysis was
carried out to characterize genes/QTLs affecting tiller and leaf angles
in high yielding semidwarf rice cultivars. Lemont is a semidwarf japonica
cultivar commercially grown in Southern US. It has a small tiller angle
and intermediate leaf and flag leaf angles (-18 and 25 degrees). Teqing
is a very high yielding indica cultivar from China with a relatively large
tiller angle (30 degrees) and virtually erect leaves and flag leaves (<5
degrees). However, the F4 progeny of the Lemontl Teqing cross showed considerable
transgressive segregation for tiller, leaf and flag leaf angles.
Using 115 well distributed RFLP
markers and 255 F2 (and their derived F4 progeny) the Lemont/Teqing cross
(Li et al. 1995, one major gene and 11 QTLs influencing tiller, leaf anf
flag leaf angles, were mapped to 8 of the 12 rice chromosomes (Table 1
and Fig.
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1).
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The major gene, designated Tal, was mapped in the interval
of 11 cM between RZ228
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and RG667 on chromosome 9 with a LOD score of 32.3, explaining
47.5% of the phenotypic variation. The Teqing allele at the Tal locus causes
increased tiller, leaf and flag leaf angles, but did not cause extreme
spreading habit. Two major QTLs, QF1a2 and QF1aS detected with large LOD
scores had large effects on both leaf and flag leaf angles. An additional
QTL, QTa5, affecting tiller angle was also mapped to chromosome 5, but
was not linked to QFIa5. The relationship between QTa5 or QF1a5 and er(o),
a recessive gene for erect growth habit (Takahashi eta!. 1968), needs to
be investigated. The other QTLs influencing one or two traits had relatively
small effects. Our results suggest that marker assisted selection may generate
different multi-locus genotype(s) at these gene/QTL loci to create well
balanced plant type phenotypes leading to high yield potential in different
environments.
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Table 1.
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Biometric parameters for Teqing alleles at one major gene
and eleven QTLs
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affecting tiller (TA), leaf (LA) and flag leaf (FLA) angles
in the Lemont/Tequing cross
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QTLs
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Trait
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Marker interval
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Chrom.
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A
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d
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R2 (%)
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LOD
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Tal
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TA
l.A
FLA
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RZ228/RGf,67
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9
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0.82
0.36
0.36
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0.3
0.28
0.42
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47.5
20.7
13.2
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32.3
11.1
6.1
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QTa2
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TA
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RG171/RG437
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2
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0.19
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0.60
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5.2
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3.6
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QTa8
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TA
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RG2O/RG1034
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8
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0.28
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0.06
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6.1
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2.3
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QTa5
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TA
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gl-1/RG403
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5
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0.20
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0.00
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3.1
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2.3
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QTaI
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TA
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RG173fRG532
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1
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0.18
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0.12
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2.7
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2.6
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QLa3
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LA
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RG1O4/RG348
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3
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0.15
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0.15
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3.2
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2.6
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QLaJ
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LA
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RG381/CDO388a
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1
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0.20
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0.1
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11.1
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4.4
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QFLa2
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FLA
LA
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R.Z2~Q/RG598b
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2
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0.40
0.21
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0.72
0.16
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8.9
10.7
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9.4
5.8
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QFIa5
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FLA
TA
LA
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RG470/RG346
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5
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0.36
0.25
0.15
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0.12
0.30
0.00
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22.1
4.5
3.5
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7.8
2.3
2.3
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QFIa6
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FLA
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C/RG424
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6
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0.26
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0.06
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5.8
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3.0
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QFfrz7
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FLA
LA
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RG711/RZ687
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7
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0.15
0.11
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0.56
0.28
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4.2
2.8
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3.1
2.0
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QF1a9
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FLA
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RG757/RG463
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9
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0.36
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0.30
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12.3
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6.6
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The underlined markers are those closer to LOD peaks of the
detected QTLs. A and d are additive and dominance effects of the identified
QTLs.
Li, Z.K., S.R.M. Pinson, J.W. Stansel and W.D. Park, 1995.
Identification of quantitative loci QTLs for heading date and plant height
in cultivated rice Oryza sativa L. Theor. Appi. Genet. 91: 374-381.
Takahashi, M., T. Kinoshita and K. Takeda, 1968. Character
expression and causal genes of some mutants in rice plant. Genetical studies
on rice plant, XXXIII. J. Fac. Agr. Hokkaido Univ. 54: 496-512.
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