PNL Volume 19 1987 RESEARCH REPORTS 31
DETERMINATE GROWTH HABIT (det) IN PEAS: ISOLATION, SYMBOLIZATION,
AND LINKAGE
Makasheva, R. Kh. N. I. Vavilov Institute of Plant Industry
and A.. M. Drozd Leningrad, USSR
More than 26 genes are known to control stem characters in
peas, a considerable number of which have implications for
breeding. A mutant conferring a true determinate growth habit was
isolated after chemical mutagenesis and described in 1975 by
Popova (2). Popova's mutant regularly developed two reproductive
nodes, each with a maximum of two flowers and pods, at the top of
the stem.
Segregating populations indicated that the determinate habit
has recessive monogenic inheritance (Table 1), and the gene con-
trolling this character was previously designated as det (3).
An analysis to determine the localization of the new gene was
performed on data from four crosses. Evidence of linkage between
Tl and Det is shown in Table 2.
Estimates of linkage (Rf) intensity were calculated using the
formula:
where rq...^ are the observed frequencies of the XY, Xy, xY,
and xy classes. Linkage in repulsion is shown by 9=rf2 and in
coupling by 9=(l-rf)2. Error estimate was calculated by the
formula:
Estimates of linkage intensity in four crosses (Table 2)
were: 0.12, 0.07, 0.14, and 0.18, with an average of 11.1 + 1.1%.
Our results reveal that gene Det-det is located in linkage
group 7 at a distance of 11.1% from Tl tl.
Offspring from separate crosses segregating for smooth (R)
and wrinkled (r_) seeds confirmed the existence of strong linkage
between _r and det alleles reported by Marx (1); we found no plants
with determinate growth habit among the R offspring.
1. Marx, G. A. 1986. PNL 18:45-48.
2. Popova, I. A. 1975. Trudy po seleccii i semenowodstwu
owoshchnykh cultur VNIISSOC 3:66-72.
3. Volchkov, Yu. A. 1986. Sbornic nauchnykh trudov po
pricladnoj botanike, genetike i selectii 101:46-48.
32 PNL Volume 19 1987 RESEARCH REPORTS
Table 1. Segregation for determinate stem growth (det) in
populations derived from two crosses in peas (5).
Cross
number
Generation
Det
Observed
:det
Expected
Expected
ratio
x2
544
F2
332 :119
338:113
3:1
0.42
544
F3
310 :215
328:197
5:3
2.63
542
F2
363: 99
347 :115
3:1
2.96
Table 2. Joint segregation between Tl_ and Det in progenies
_from four crosses (3)._
Cross no./
phenotypes
Mathematical
model 1/
Segregation ratio
Observed Expected
x2
584
Tl - Det
0.64 84
976
1033.5
3.13
Tl - det det
0.1177
245
187.6
17.56
tl tl - Det
0.1979
373
315.5
10.47
tl tl - det det
0.0359
0
57.2
56.90
601
Tl - Det
0.5808
355
390.9
3.30
Tl - det det
0.1694
150
114.0
11.37
tl tl - Det
0.1932
166
130.0
9.97
tl tl - det det
0.0564
2
37.9
34.01
586
Tl - Det
0.7395
556
581.0
1.16
Tl - det det
0.1105
116
86.0
10.50
tl tl - Det
0.1305
114
102.0
1.40
tl tl - det det
0.0195
0
16.0
16.00
602
Tl - Det
0.7080
375
385.2
0.27
Tl - det det
0.0638
45
34.7
3.06
tl tl - Det
0.2090
124
113.7
0.93
tl tl - det det
0.0188
0
10.2
10.20
1/ Mathematical model is determined taking into account low
survival of recessive homozygotes in both genes.
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