Linkage test between pat-2 and con

When the first crosses were made to test relations between pat-2 and con, pat-2 was thought to be located between bls and sf on chromosome 3 (Vardy et al., 1989) and, according to the last linkage map published by Mutschler et al. (1987), con was also thought to be located in this part of chromosome 3. However, we showed that pat-2 and con are both independent of bls and sf (see 2 preceding notes in this Report).

We used GCR 377, a con stock received from Glasshouse Crops Research Institute, GB. It is an isogenic line of the cv Alisa Craig, in which con was introduced by backcrosses. Two [pat-2] lines were used, Severianin and the parthenocarpic version of Monalbo. The experimental conditions and the way to estimate parthenocarpy were exactly the same as for linkage studies between pat-2, and bls and sf.

The results of the F2 studies are given in table 1. The significant deficit (0.02 < P < 0.05) of [pat-2] plants among [con] plants, from the cross (GCR 377 x Monalbo [pat-2]), could indicate some linkage between pat-2 and con. However this deficit is not symmetrical to an excess of [con+ pat-2] plants. On the other hand, the deficit of [con pat-2] plants is not significant in the cross with Severianin.

The results of the testcross studies are given in table 2. In the light of these results, we have reasons to conclude that pat-2 and con are independent.

Table 1. Studies of F2

______________________________________________________________________
F2 from                No. plants (a+b)   pat-2       X^2  hypothesis
                      ________________              __________________
crosses    Phenotypes Total  +   pat-2   Plants(%)  3:1    Probability
______________________________________________________________________
GCR 377        +      20     19    1        5      3.27    0.05 - 0.10
x Severianin  con     20     17    3       15      0.6     0.30 - 0.50

GCR 377        +      23     20    3       13      1.17    0.20 - 0.30
x Monalbo     con     24     23    1        4      4.51    0.02 - 0.05
______________________________________________________________________

b) "Cold" glasshouse. Sowing on January 21, plantation in soil on March 9, t^o^ minimum: 10 deg.C to 12 deg.C, from the plantation till the end of April"

a & b) Inforescences limited to 8 - 10 flowers.

Table 2. Studies of Testcrosses

________________________________________________________________________
Testcrosses                No. of  plants     pat-2      X^2 hypothesis
                         __________________            _________________
from crosses  Phenotypes Total  [+]  pat-2  Plants(%)  1:1   Probability
________________________________________________________________________
GCR 377         +         25    13     12      48       0         1   
x Severianin   con        25    16      9      36      1.44  0.20 - 0.30

GCR 377         +         25    14     11      44      0.16  0.50 - 0.70
x Monalbo      con        25    14     11      44      0.16  0.50 - 0.70
________________________________________________________________________

Literature cited:

Mutschler, M.A., S.D. Tanksley and C.M. Rick 1987 Linkage maps of the tomato (Lycopersicon esculentum). Tomato Genetics Cooperative Report 37: 5-34.

Vardy, E., D. Lapushner, A. Genizi and J. Hewitt 1989 Genetics of parthenocarpy in tomato under a low temperature regime. Euphytica 41, 9-15.