17. Allelism test for the genes responsible for sheathed panicle Masahiko Maekawa

Experimental Farm, Faculty of Agriculture, Hokkaido University, Sapporo, 060 Japan


The inheritance of sheathed ear (Sathi type) was reported by Sethi et al. (1957) first, to be controlled by three dominant genes, P, T and E. Jones (1952) reported that the sheathed panicle character was controlled by a recessive gene, but the heterozygotes showed an intermediate phenotype in panicle exertion. Recently, Heu and Shretha (1983) reported that the "gamadiness" (incomplete panicle exertion) was controlled by two dominant genes. In this report, the genes for sheathed panicle of two strains, H-340 and No. 201, are dealt with, although it was not possible to compare them with those reported by the previous workers mentioned above.

H-340 was derived from the cross, L-26 Sheathed (Jodon's marker line, Crowley, USA) x A-5 (Akamuro). No. 201 was selected from the M\2\ generation of gamma- rayed A-5, made available through Dr. N. Shinbashi, Kamikawa Agr. Exp. Station, Hokkaido. Both lines showed a reduction in length of the first and second internodes, and their panicles were enclosed by the flag leaf and second leaf sheaths. The F\1\ plants of H-340 (sheathed) x H-138 (normal) had sheathed panicles and the F\2\ segregated into 1 normal:3 sheathed types (Table 1-F\2\ segregations for sheathed panicle), suggesting that the sheathed panicle character of H-340 was controlled by a dominant gene. It is symboled Shp-1. Linkage analysis demonstrated Shp-1 was linked with Rd and A in the third linkage group, with recombination values of 2.4+ 1.4% and 3.1+1.6%, respectively. Between Rd and A, a recombination value of 0.3% was found by Nagao and Takahashi (1963), but the value in the present experiment was 4.6+4.8%. Therefore, the locations of Shp-1, Rd, and A in the third linkage group are assumed as follows:




On the other hand, the F\1\ plants of No. 201 (sheathed) x A-5 (normal) and H- 138 (normal) x No. 201 (sheathed) were normal, and the F\2\ segregated into 3 normal:1 sheathed types. This indicates that the sheathed panicle character of No. 201 is controlled by a recessive gene. It is symboled shp-2(t). When H-340 and No. 201 were crossed, the F\1\ plants had sheathed panicles and the F\2\ segregated into 3 normal:13 sheathed types. The 3:13 ratio is expected when Shp-1 and shp-2(t) are independent. It was not possible to distinguish between the sheathed panicle types from H-340 and from No. 201 in the F\2\ population. Gene shp-2(t) showed no linkage relation with wx (I), Rd (III), Rc, g and d-6 (IV). Its linkage relation is left for investigation in the future.

As the sheathed panicle types due to both Shp-1 and shp-2(t) showed a reduction in length of the first and second internodes, it may be presumed that the two genes differ from the genes for "Sathi" type or from that reported by Jones (1952).


Table 1. F\2\ segregations for sheathed panicle

=============================================================================
Cross comb.   Phenotype of      F\2\ segregation       total   Ratio  Chi-
                F\1\        =======================                   square
                            Normal    Sheathed pan.
=============================================================================
                              +         Shp-1
H-340xH-138    sheathed       70         243            313    1:3     1.16
(Shp-1) (+)    (Shp-1  +)
=============================================================================
                              +         shp-2
No.201xA-5     normal        227          70            297    1:3     0.32
(shp-2) (+)    (+ shp-2)
H-138xNo.201   normal        135          35            170    1:3     1.76
(+)   (shp-2)  (+ shp-2)
=============================================================================
                            +   +     Shp-1 +, + shp-2,
                                      Shp-1 shp-2
No.201xH-340   sheathed1)     58         278            336    3:13    0.49
(+ shp-2) (Shp-1 +)
=============================================================================
1); Genotype of F\1\ was Shp-1+ +shp-2




References

Heu, M.H. and G.L. Shretha, 1983. Inheritance of gamadiness (incomplete panicle exertion) and internode contraction due to GA\3\ application in rice. Korean J. Breed. 15: 12-16.

Jones, J.W., 1952. Inheritance of natural and induced mutations in Caloro rice. J. Hered. 43: 81-85.

Nagao, S. and M. Takahashi, 1963. Trial construction of twelve linkage groups in Japanese rice. Genetical studies on rice plant, XXVII. J. Fac. Agr. Hokkaido Univ. 53: 72-130.

Sethi, R.L., B.L. Sethi and T.R. Mehta, 1937. Inheritance of sheathed ear in rice. Ind. J. Agr. Sci. 7: 134-148.