ij-affected tissues show yellow or white color depending on genetic background. While ij plants of Oh5la inbred line always have yellow or yellow-striped tissues, ij plants with Tr, Mo17, Ky21, K55, and Wg (R-g conversion of W23) backgrounds have only white-striped tissues. Oh5la has been known to carry homozygous l (luteus) gene, and the Stock Center supplies this inbred as an l stock. The l locus is located on chromosome 10 and is 2 map units distal to the R locus (Emerson et al., Cornell Univ. Agri. Exp. Stn. Mem., 1935)
Coe et al. (Stadler Symp., 1982) reported that some of the maternal exceptions derived from Wg background are germless and fail to germinate. Also, heritability in backcrosses and the distribution of germless kernels in ear maps indicated the possibility of involvement of a nuclear factor or factors (very possibly Isr, which is tightly linked to the R locus) in the germlessness.
To obtain genetic evidence for l as a genetic factor determining yellow in ij, and to examine whether R or a gene closely linked to the R locus could be involved in germlessness, we selected and planted the colored kernels from the cross ii ii (Oh51a/Wg) x + + (Oh51a). Since the constitution of Oh51a is c r-r, the ratio of colored and colorless kernels is expected to be 1:3 from the progeny of the backcross. Among a total of 645 kernels examined, 198 kernels showed colored aleurone and the rest (447) of the kernels were colorless. Our previous experience indicated that Oh51a contains a dominant pale inhibitor(s) of aleurone pigment. Consequently, we could only score the colored class properly. Among the 198 colored kernels, 121 seedlings were white and 64 seedlings were green. We did not find any yellow seedlings even though a couple of yellows are expected by recombination.
We scored the kernels with no germ and those failing to germinate in both the colored and the colorless classes. Percentages of germless kernels were 6.5 and 5.2 in colored and colorless kernels, respectively. Our data do not suggest that R or a genic factor linked to the R locus is involved in germlessness of maternal exceptions. More detailed genetic work on the relation between germlessness and R is in progress, using the different R stocks kindly supplied by Dr. J.L. Kermicle (University of Wisconsin).
Chang-deok Han and Ed Coe
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