da1 is on 10L
--Stinard, P

Little is known about the pale aleurone color mutant da1 (dilute aleurone1), first described by Eyster (J Hered 22:224-225, 1931). Linkage studies reported by Emerson, Beadle, and Fraser (Cornell Univ Agric Exp Stn Mem 180, 1935) place da1 to chromosome 9, but the data are inconsistent. Nothing is known about the interactions of da1 with other aleurone color factors. During the course of propagating the COOP's stocks of da1, it became clear that da1 was not linked to wx1 as was expected (p = .21 according to Emerson et al.). From a two-point coupling backcross linkage test of da1 and wx1, we obtained the following data: 100 Da1 Wx1, 98 da1 wx1, 118 Da1 wx1, and 97 da1 Wx1. This does not differ significantly from a 1:1:1:1 ratio, and indicates that the two mutants are not linked. Similar results were obtained from other crosses.

Since da1 did not map where it was expected on chromosome 9, allelism tests were conducted between da1 and other aleurone color factors. Tests with a1, a2, c1, c2, bz1, and bz2 all yielded kernels with full purple aleurone color. However, crosses with r1 gave a range of pale to colorless kernels, indicating possible allelism, albeit with variable expression.

Subsequent crosses of da1 stocks by TB-10L19 yielded ears segregating for small pale and colorless kernels with purple scutellum (putative hypoploid da1 endosperms with hyperploid embryos) as would be expected if da1 is located on 10L.

Reciprocal crosses of da1 with R1-r A1 A2 C1 C2 gave R1 mottling when the da1 stock was used as a female, and full color kernels when da1 was used as a male. Reciprocal crosses made with an R1-scm2 line gave full color kernels whether da1 was used as a female or as a male.

Allelism of da1 and r1 seemed certain except for one anomalous result. When the heterozygous da1 / r1 kernels from the allelism test ears were planted and the resulting plants crossed again by r1, the ears that were obtained segregated for a consistent, but a low percentage of fully colored kernels (around 10%, see Table 1). This percentage seems extraordinarily high to be accounted for by intragenic recombination. Additional crosses are planned to determine the cause of this phenomenon.

Table 1. Counts of full colored (Cl) and pale or colorless kernels (cl) on ears from the cross [r1 X da1] X r1 and its reciprocal. The differences in percentage of full colored kernels between male and female outcrosses of the heterozygotes are not significant.
 
r1 X da1 parent
r1 X da1 parent as male
r1 X da1 parent as female
No. Cl No. cl % Cl No. Cl No. cl % Cl
96-690-1 41 375 9.9 49 366 11.8
96-690-3 58 491 10.6 40 482 7.7
96-690-6 49 302 14.0 59 421 12.3
96-690-8 23 258 8.2 52 559 8.5
96-690-10 47 412 10.2 36 468 7.1
Totals 218 1838 10.6 236 2296 9.3


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