H-X Lin1 , H-R Qian1 , J-Y
Zhuang1 , J Lu1 , Z-M Xiong1 , S-K Min1
, N Huang2 , K-L Zheng1
1China National
Rice Research Institute, Hangzhou 310006, P. R. China
2. International
Rice Research Institute, P. 0. Box 933. 1099 Manila, Pilippines
Heading date is a qualitative-quantitative trait controlled simultaneously by major and minor genes (Mo et at. 1993). In this study, based on two RFLP maps that were consturcted, major and minor genes controlling heading date have been identified by ANOVA (PROC GLM procedure in the Statistical Analysis System, SAS Institute Inc., 1988) and MAPMAKER/QTL (Lander and Botstein 1989).
In Tesanai 2/CB (Tesanai 2 is a indica variety
from Guangdong, China. CB, a variety inclining to indica type is
from California, USA) F2 population (171 individuals),
5 marker loci were detected linked to QTLs for heading date by one way
ANOVA (Table 1). Two of the loci (RG348, RZ562) had a more significant
effect than other loci. Four QTLs for heading date were indentified by
interval mapping (Table 2) and approximated to a significant marker loci
on some chromosome detected by one way ANOVA respecitvely. Two genes for
heading date, hd3 and hd8 of the QTLs had major effect with
LOD values of 10.19 and 7.20, and explained 26.1% and 23.1% of the observed
phenotypic variation respectively, hd3 and hd8 had additive
effects of-7 and 6 days, respectively. Both of these genes had a small
dominant effect of 3-4 days. hd3 is on chromosome 3 between RG104
and RG348, approximately 2 cM from the marker RG348, and hd8 is
on chromosome 8 between RZ562 and RG978 approximately 6 cM from RZ562.
The other 2 QTLs have minor effects, hdl was on chromosome 1 and
hdl2 on chromosome 12. hdl and hdl2 only explained
8.3% and 9.6% of the observed phenotypic variance respectively and both
had a small additive effect.
In Waiyin 2/CB (Waiyin 2 is a indica veriety
from International Rice Research Institute) Pi population (171 individuals),
4 marker loci were detected linked to QTLs for heading date by one way
ANOVA (Table 1), including 2 marker loci (RG64, waxy, waxy is rice glutinous
gene) with a higher significant level. Based on interval mapping, 3 QTLs
near to the 3 marker loci were detected (Table 2). Two major genes (hd6a,
hd6b) were also detected on chromosome 6. hd6a is located between
waxy and RG213, 12 cM from waxy, and hd6b is located between RG138
and RG64, 10 cM from RG64. The 2 major genes with large additive effect,
explained 35.5% and 27.4% of the observed phenotypic variations, respectively.
In addition, a minor gene hd8 was also detected, which is located
Table 1. Marker loci associated to heading date determined by analysis
of variance
in two F2 populations
Cross | Marker | Chrorn. 1 | F-value | P-value | Additive 2 | Dominance | ||
F-value | P-value | F-value | P-value | |||||
Tesanai2/CB | RG374 | 1 | 5.11 | 0.0070 | 4.57 | 0.0339 | 5.31 | 0.0225 |
RG348 | 3 | 23.72 | 0.0000 | 36.83 | 0.0001 | 10.22 | 0.0017 | |
RZ562 | 8 | 15.96 | 0.0000 | 29.17 | 0.0001 | 1.79 | 0.1831 | |
RG235 | 12 | 7.78 | 0.0006 | 11.42 | 0.0009 | 3.93 | 0.0492 | |
RG409B | n | 6.13 | 0.0027 | 1.00 | 0.3182 | 10.41 | 0.0015 | |
Waiyin2/BC | RG64 | 6 | 9.98 | 0.0001 | 19.89 | 0.0001 | 0.06 | 0.8117 |
waxy | 6 | 16.63 | 0.0001 | uc | uc | uc | uc | |
RG108 | 8 | 10.91 | 0.0012 | uc | uc | uc | uc | |
RZ66 | n | 4.89 | 0.0087 | 3.61 | 0.0592 | 7.30 | 0.0076 |
1` n=Unmapped yet.
2uc=Additive and dominance can not be distinguished because
the marker has two genotypes
Table 2. QTLs detected for heading date (hd) based on interval
analysis in two F2
populations
Cross | QTL1 | Interval | LOD2 | %variation3 explained | a4 | d5 | d/(a]6 |
Tesanai2/CB | hdl | RZ649-RG374 | 2.44 | 8.3 | 2.80 | -4.25 | -1.52 |
hd3 | RG103-RG348 | 10.19 | 26.1 | -7.00 | -4.40 | -0.63 | |
hd8 | RZ562-RG978 | 7.20 | 23.1 | 6.25 | 3.05 | 0.49 | |
hdl2 | RG341-RG235 | 3.57 | 9.6 | -3.69 | -2.89 | -0.78 | |
Waiyin2/CB | hd6a hd6b | waxy-RG213 RG138-RG64 | 6.38 6.01 | 35.5 27.4 | -14.78 -12.55 | -6.98 -5.24 | -0.47 -0.42 |
hd8 | RG108-RZ562 | 2.92 | 8.9 | 7.14 | 0.89 | 0.12 |
1QTLs are named by trait abbreviations plus chromosomal number,
Letters(a. b) are used to
distinguish QTLs on the same chromosome affecting
the same trait.
2.Log 10-likelihood.
3Percent phenotypic variance explained.
4Additive gene effect.
5. Dominance effect.
6. Degree of dominance.
on chromosome 8 between RG108 and RZ562, nearer RG108. hd8 explained 8.9% of the observed phenotypic variance with a small additive effect and dominant effect.
The data on heading date of F2 plants in two populations, showed that heading date is a quantitative trait. But, this study demonstrated that heading date of rice was a qualitative-quantitative trait controlled by major and minor genes together. In addition, we also dissected the effects of each gene, which could not be achieved by traditional genetics methods.
References
Lander, E.S. and D. Botstein, 1989. Mapping Medelian factors underlying
quantitative traits using RFLP
linkage maps. Genetics 121:185-199.
Mo, H.D., 1993. Genetic analysis for qualitative-quantitative traits
1. The genetic constitution of generation populations and the
identification of major
gene genotypes. Acta Agronomica Sinica 19(1): 1-6. (in Chinese with
English summary)
SAS Institute, Inc. 1988. SAS users Guide: Statistics. SAS Institute,
Gary, N. C.