Isozyme linkage analysis was performed on the BC1 population of a ms-47 (L. esculentum) x L. pennellii hybridization. The segregation of the new male sterile gene (ms-47) indicates linkage to Prx-2 with an RF value of 24.
ms/+ ms/ms Prx-2 +:L. esculentum allele
Prx-2 +/+ 16 65 Prx-2 p:E. pennellii allele
Prx-2 +/p 39 17 X = 34.3
Verification of the linkage was achieved by crossing a Wo^m^ -bip tester line
(LA 1699) with the male sterile and scoring the F2 segregation in the
field.
Phenotype # of Plants Phenotype # of Plants _____________________________________________________________ Wo^m^ bip ms 0 Wo^m^ bip+ 37 Wo^m^ /* ms 0 Wo^m^/* + 20 Wo^m^ + ms 0 Wo^m^ + + 1 /* bip ms 2 /* bip + 24 / / ms 11 / / + 69 / + ms 1 / + + 4 + bip ms 1 + bip + 2 + / ms 16 + / + 8 + + ms 14 + + + 8 _____________________________________________________________ */ = heterozygoteUsing the Maximum Likelihood Equations (Allard, 1956). linkage between Wo^m^ and ms-47 is estimated to be RF=16. These data and the isozyme data give nearly the same result and place ms-47 between positions 62 and 65 on chromosome 2. The linkage calculated between ms-47 and bip (RF=25) does not support this conclusion; however, the scoring of the bip character was complicated by the presence of TMV. The virus can modify +/+ leaves so that they are difficult to distinguish from +/bip or even bip/bip leaves. An excess of the +/bip and bip/bip phenotypes scored supports this explanation (X - 17.4, deviation from 1:2:1). The male sterile mutant ms-15 is located at position 62 and the possibility that these two mutants are allelic is now being investigated. If they prove to be non-allelic, then one more male sterility locus would be added to the group on chromosome 2, bringing the total to six--a disproportionately high number for that chromosome.
Literature cited:
Allard, R.W. 1956. Hilgardia V. 24:10, pp. 235-278.