Rick, C. M.
Harrison's Me proves to be an exceptionally good seedling marker. It is a pity therefore that it lies on the already overcrowded chromosome 1 instead of accomodating us by having a locus on one of the more poorly marked chromosomes. Not only is it a good dominant seedling mutant, but also it is one of the very few (Wo^m and H) that are viable homozygous and whose three genotypes can be distinguished in seedlinghood as well as at maturity. The deformity of true leaves is more extreme and total plant growth is reduced in Me/Me. In one family of good germination and classified at maturity in the field, the segregation was 96 Me/Me:175 Me/+:89+/+, providing a remarkably good fit to 1:2:1.
In all of the following data Me/Me and Me/+ classes are lumped except for linkage calculations, since the separation between the two was not made in all families. Considering first the segregation of Me alone, the F2 data of 11 different crosses show a highly significant deficiency of Me and a highly significant heterogeneity between families. But when one family with a very great delficiency of Me is subtracted, the remaining 10 families do not deviate significantly from 3:1 (206OMe:746+) or from homogeneity (X^2=16.54, p=0.1-0.05).
For the linkage screening tests no difficulties were encountered in classification except with c and e in the seedling stage. The interactions for shape of seedling true leaves are so complex that we find it more dependable to classify mature plants. This difficulty no doubt explains the spurious dissociation between Me and c in the following data. The three estimates for the d-Me interval give a mean figure of 31 units, which likely places MB close to Wo.
Contingency
Tester + + + t Me + Me t chi square co.
a 68 26 194 78 0.003
a 47 21 120 42 0.37
a 29 14 90 30 1.48
ah 50 14 168 44 0.01
ah 24 9 96 23 1.00
c 25 18 98 22 13.94
c 56 12 138 24 0.10
c 34 10 83 31 0.18
d 36 32 134 28 20.56 31.0 +- 2.6
d 67 66 253 76 30.04 34.0 +- 1.9
d 18 25 97 23 23.1 27.5 +- 2.8
dl 51 13 158 54 0.46
dl 27 6 88 31 1.61
e 118 37 250 113 2.45
H 121 30 226 43 1.01
l\1 42 26 129 33 7.12
l\1 28 15 90 30 2.83
La 23 35 75 165 0.02
mc 42 12 102 27 4.09
Wf 37 17 89 33 0.06
Xa 70 81 128 141 0.06
yv 29 4 92 27 1.75
yv 54 10 167 45 0.06