PNL Volume 20                       1988 RESEARCH REPORTS 9
NEW CHLOROT1CA GENE (chi 32) IN CHROMOSOME 3
Czerwinska, St.
Plant Breeding Station, Wiatrowo, Poland
Physical mutagens were compared in investigations on the influence of genotype x mutagen combinations on the mutation spectrum in pea. Seeds of line Wt 3519 (cv. 'Porta') were treated with three doses of fast neutrons from a cyclotron (200r, 350r. 500r) and from a reactor (170r, 290r, 400r) and with gamma rays from a 60Co source (4000r, 7000r, lOOOOr) . In the M2 generation containing about 21,000 plants, 720 mutation cases were selected. Among them about 30 percent were chlorophyll mutations. Most numerous was the chlorotica type (72 mutation cases) . Some of them were phenotypically similar to those described by Blixt (1) , but mutant Wt 15325, induced by 350r Nf, was distinguishable. Plants were charac­terized by a yellow-green color affecting the whole plant (leaves, stem, tendrils, and sepals) being more visible in later stages of plant deve­lopment .
The segregation in M2 family as well as the results of the original tost cross showed Mendelian, recessive inheritance: [Wt 15325 (mutant) x Wt 3519 (initial line)]=91:34 observed (Chi-square=0.32); [Wt 3519 x Wt 15325]=130:40 observed (Chi-square=0.20) .
There are 30 recessive genes of the chlorotica type described ear­lier. So to prove novelty of a new isolate a locus identity test cross should be performed. To shorten the process, we conducted linkage tests with the hope that the results would show the presence of a new gene. The mutant Wt 15325 was crossed with tester lines for the seven chromosomes. In F2, undisturbed monohybrid inheritance for most of gene markers was found; the populations also confirmed the recessive nature of the chloro­tica mutant (Table 1A) .
Table 1. Phenotypic distribution in an F2 population segregating f o r chlorotica f r o m WL 1288 (testerline) x Wt 15325 mutant.
A. Monohybrid F. segregation
Locus
Chi B St M A
X
296 185 302 230 301
X
104 67 94 50 88
Total
400 252 396 280 389
Chi-square (3:1)
0.21
0.34
0.34
7.62*
1.17
l. Joint segregation of chlorotica with b st M
Gene
pair          X Y
Chi-B     153
Chi-St   219
Chi-M     217
B-St       163
Xy 54 76 9 22
xY
32 83 11 30
xy
13
18
41.
37
10
Total
252 396 278 252 232
Joint Chi-square
0.14ns
2.64ns
168.10**
49.57**
0.00ns
Recomb. fract.
S.E.
8.5 23.1
1.8 3.1
B-M
141
26 55
10                           PNL Volume 20                      1988 RESEARCH REPORTS
There was no evidence of linkage with markers on chromosomes 1,2,4,5,6,7. But deviations from independent dihybrid segregation of the gene pair Chi-M were found with a CrO value of 8.5 (Table IB) . According to the present Pisum map there are no known chlorotica genes in the M-segment of chromosome 3, although chi-6 and chi-16 are known to reside elsewhere on the same chromosome. On these grounds I propose the symbol chi-32 for the new gene of chlorotica type. For final mapping we plan to confirm the above results in comparison to two loci using uni or pre­ferably isozymic loci Lap-2, Acp-3.
1. Blixt, S. 1972. Agri Hort. Genet. 30.
My cordial thanks are due to Dr. W. K. Swiecicki and to K. Leraczyk for their help, encouragement, and use of Station facilities.
*****