Zhengzhou, China
Henan Agricultural University
Mapping the major restorer genes for C-type cytoplasmic male sterility using SSR markers --Tang, JH, Liu, ZH, Chen, WC, Hu, YM, Ji, HQ, Ji, LY For a long time, the fertility restoration of cms-C has been found to be a very complex system of inheritance in some analyses, and only the restorer gene Rf4 on chromosome 8S has been mapped. In this study, restoring line Fengke1 and male sterile lines cms-CMo17 and cms-C237 were used to study the inheritance of restoration of cms-C. The F2 and BC1 progeny were planted in Zhengzhou, China, and scoring was done in the spring and summer 1999-2000. The data indicated that fertility segregation in F2 and BC1 progeny of two crosses suited the theoretical ratio 15:1 and 3:1 (Table 1), and that Fengke1 had two dominant duplicating restorer genes Rf4 and Rf5. This result was the same as Chen WC et al. (1979).

Table 1. The results of restoration of segregating populations of a restoring line and two sterile lines.
Year Combination Total numbers Restorer numbers Sterile numbers Theoretical ratio Chi-square test
1999, Spring (cms-CMo17 x Fengke1) F2 315 292 17 15:1 0.294
  (cms-CMo17 x Fengke1) BC1 87 70 17 3:1 1.673
  (cms-C237 X Fengke1) F2 195 180 15 15:1 0.692
  (cms-C237 x Fengke1) BC1 118 92 26 3:1 0.544
1999, Summer (cms-CMo17 x Fengke1) F2 324 292 21 15:1 0.113
  (cms-CMo17 x Fengke1) BC1 148 116 32 3:1 1.01
  (cms-C237 x Fengke1) F2 114 103 7 15:1 0.002
  (cms-C237 x Fengke1) BC1 122 80 41 3:1 4.091*
2000, Spring (cms-CMo17 x Fengke1) F2 391 365 26 15:1 0.107
  (cms-CMo17 x Fengke1) BC1 83 61 22 3:1 0.100

Note: *, Chi-square test did not suit to theoretical ratio

Equal amounts of DNA from 20 restorer plants and 20 sterile plants, from the F2 progeny of the crosses (cms-CMo17 x Fengke1), were mixed randomly to get the bulked pools. One hundred and sixteen pairs of microsatellite primers were used to screen parents and pools. Primers bnlg1711, umc1225, bnlg1346, umc1072, phi058 on chromosome 5L and the primer bnlg2307 on chromosome 8S produced polymorphic fragments which amplified in one parent or pool and not the other.

The primers, bnlg1711, bnlg1346, phi058, linked tightly with Rf5, and bnlg2307 linked with Rf4, amplified successfully for both parents and 141 individuals selected from F2 progeny (Table 2). Microsatellite DNA products amplified by bnlg1711 and bnlg1346 are shown in Figure 1 and Figure 2.

Table 2. The statistical results of molecular markers and phenotypes of F2 segregating populations of (cms-CMo17 x Fengke1).
  A   H   B   U  
SSR primers Sterility Restorer Sterility Restorer Sterility Restorer Sterility Restorer
bnlg1711 0 32 3 75 2 29 0 0
phi058 3 28 2 77 0 31 0 0
bnlg1346 0 20 5 78 0 36 0 2
bnlg2307 0 24 1 89 4 23 0 0

Note: A: Labeled band of Fengke1; B: Labeled band of cms-CMo17; H: Hybrid band; U: Unknown band

Figure 1. Microsatellite DNA products amplified by bnlg1711 in parents and some individuals of F2 progeny.

Figure 2. Microsatellite DNA products amplified by bnlg1346 in parents and some individuals of F2 progeny.

The linkage analysis between Rf5 and microsatellite markers was performed by JOINMAP version 1.4. The linkage distances between bnlg1346-Rf5-bnlg1711 were 1.68 cM and 7.51 cM respectively, and for phi058-Rf5 the distance was 9.87 cM. As the three microsatellite primers tightly linked with Rf5 are in bin 5.07 of chromosome 5, the restorer gene Rf5 is also at bin 5.07 of chromosome 5. The locations of the markers, phi058, bnlg1346, bnlg1711, and Rf5 are displayed in Figure 3.

Figure 3. Map location of Rf5/rf5 and the microsatellite markers.

Please Note: Notes submitted to the Maize Genetics Cooperation Newsletter may be cited only with consent of the authors.

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