47. RFLP mapping of major genes and minor genes for heading date in rice

    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.