In MNL 57:20, 1983, I reported that golden-2 (g2) was located on the short arm of chromosome 3, distal to the breakpoint of TB-3Sb. The present note reports F2 and backcross data involving g2 and the chromosome 3 genes d1, ra2, Rg, and gl6.
The d1 allele used was d-6016, which never gives segregates of intermediate stature. B. O. Phinney and M. Ritzel (MNL 29:44, 1955) reported d-6016 to be allelic to d1, and this was confirmed by us. Good greenhouse classification of g2 seedlings was possible by their pale green leaves and whitish stems when the plants were grown under conditions of good sunlight. Confirmation of g2 classification among the dwarf segregates was made by elongating the culms with a single spray application of aqueous gibberellic acid (137.5 mg/l).
The g2-Rg data were obtained from Rg/g2 ra2 x g2 ra2 testcrosses. The g2-m2 coupling data from these crosses are not reported here because of difficulty in scoring ra2 on g2 plants which, because of shading, often attain a height of only one or two feet. This problem was not encountered with the g2-ra2 repulsion progenies.
These data place g2 about 32 map units distal to d1, with g2 a little closer to d1 than to ra2. As the current map (MNL 59:172, 1985) shows Rg and gl6 to be 25 and 27 units to the right of d1 respectively, if g2 were proximal rather than distal to d1 it would have shown linkage with Rg and gl6; that was not the case. The current map indicates that cr1 is 18 units distal to d1, so g2 must be distal to cr1. The following map is suggested for distal 3S:
g2 cr1
d1 ra2
0 14
32 34
This extends the known genetic length of chromosome 3 by 14 map units.
R. H. Whalen
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