Cucurbit Genetics Cooperative Report 14:111-112 (article 39) 1991
R. Bruce Carle and J. Brent Loy
Department of Plant Biology, University of New Hampshire, Durham, NH 03824
Few morphological markers are known for Cucurbita pepo that can be used to detect outcrossing during commercial seed production.(1). A new mutant leaf form, fused vein, shows potential as a roguing marker. The fused vein trait was first observed in 1987 in breeding material for high yielding hull-less seeded pumpkins, descending from a cross between ‘Trickijack’ and Minijack’.
The trait is characterized by a partial fusion of thelateral leaf veins to the main central vein. The fusion begins at the distal point of the petiole and extends 10 to 15 centimeters into the leaf blade. Branching of the veins is delayed and there is a reduction of the intraveinal leaf blade. Consequently, the dorsal leaf surface appears puckered or wrinkled. The trait is expressed beginning that the fourth to sixth leaf stage and then throughout vegetative growth. The extent of fusion along the central vein is less on early leaves and becomes pronounced by the tenth leaf stage. There is no apparent fusion of other plant parts associated with this trait. Comparison of fused vein and normal sister lines shows no appreciable differences in fruit yield per plant or seed yield in open pollinated fruit. There is, however, greater variation in seed yield per fruit from fused vein self pollinations than from normal self pollinations.
The fused vein trait is stably inherited once fixed. The trait is recessive; reciprocal F1s between fused vein and normal plants appear normal. In reciprocal F2 and backcross generations the percent recovery of the fused vein phenotype varies with each pollination event. F2 fused vein recovery ranges from 0 to 19%, well below the expected 25% for a single recessive gene (Table 1). In backcross generations, recovery ranges from 3 to 63% (Table 2). Total fused vein recovery for all backcross generations is 39% which is between the expected 50% for one recessive gene and 25% for two recessive genes. One interpretation of the data is that the trait is governed by a single gene (or genetic event) with associated subvitality in both male and female gametes.
Gametic subvitality, observations of rare partially fused leaves in F1 plants, and occasional fused vein sectoring within otherwise F2 and backcross segregants, suggest that the fused vein trait may be caused by a chromosomal aberration.
Table 1. F2 fused vein inheritance data.
Table 1.1. Fused x Normal F2
crosses
|
fused
|
normal
|
% fused
|
X2 one gene
|
P
|
| 1 |
0 |
200 |
0.0 |
66.66 |
<.001 |
| 2 |
0 |
373 |
0.0 |
124.33 |
<.001 |
| 3 |
0 |
225 |
0.0 |
75.0 |
<.001 |
| 4 |
0 |
48 |
0.0 |
16.0 |
<.001 |
| 5 |
2 |
46 |
4.2 |
11.11 |
<.001 |
| 6 |
3 |
45 |
6.3 |
9.0 |
.001 – .01 |
| 7 |
9 |
74 |
10.8 |
8.47 |
.001 – .01 |
| 8 |
7 |
41 |
14.6 |
2.78 |
.05 – .10 |
| 9 |
18 |
76 |
19.1 |
1.72 |
.10 – .20 |
Table 1.2 Normal x Fused F2
crosses
|
fused
|
normal
|
% fused
|
X² one gene
|
P
|
| 1 |
0 |
48 |
0.0 |
16.0 |
<.001 |
| 2 |
0 |
48 |
0.0 |
16.0 |
<.001 |
| 3 |
0 |
48 |
0.0 |
16.0 |
<.001 |
| total |
39 |
1128 |
3.3 |
|
|
Table 2. Backcross fused vein inheritance data.
Table 2.1. Fused (Fused x Normal)
crosses
|
fused
|
normal
|
% fused
|
X2 one gene
|
P
|
| 1 |
4 |
26 |
13.3 |
16.13 |
<.001 |
| 2 |
4 |
26 |
13.3 |
16.13 |
<.001 |
| 3 |
7 |
23 |
23.3 |
8.53 |
.001 – .01 |
| 4 |
21 |
37 |
36.2 |
4.41 |
.01 – .05 |
| 5 |
34 |
39 |
46.6 |
0.34 |
.50 – .70 |
| 6 |
14 |
16 |
46.7 |
0.13 |
.70 – .80 |
| 7 |
14 |
16 |
46.7 |
0.13 |
.70 – .80 |
| 8 |
22 |
17 |
56.4 |
0.64 |
.30 – .50 |
| 9 |
62 |
38 |
62.0 |
5.76 |
.01 – .05 |
Table 2.2. (Fused x Normal) Fused
crosses
|
fused
|
normal
|
% fused
|
X2 one gene
|
P
|
| 1 |
1 |
29 |
3.3 |
26.13 |
<.001 |
| 2 |
2 |
26 |
7.1 |
20.57 |
<.001 |
| 3 |
9 |
29 |
23.7 |
10.52 |
.001 – .01 |
| 4 |
33 |
76 |
30.3 |
16.96 |
<.001 |
| 5 |
10 |
17 |
37.0 |
1.81 |
.10 – .20 |
| 6 |
21 |
21 |
50.0 |
0.00 |
1.0 |
| 7 |
19 |
11 |
63.3 |
2.13 |
.10 – .20 |
Table 2.3. Fused (Normal x Fused)
crosses
|
fused
|
normal
|
% fused
|
X2 one gene
|
P
|
| 1 |
9 |
19 |
32.1 |
3.57 |
.05 – .10 |
| 2 |
10 |
20 |
33.3 |
3.33 |
.05 – .10 |
| 3 |
11 |
19 |
36.6 |
2.13 |
.10 – .20 |
| 4 |
15 |
15 |
50.0 |
0.00 |
1.0 |
Table 2.4. (Normal x Fused) Fused
crosses
|
fused
|
normal
|
% fused
|
X2 one gene
|
P
|
| 1 |
13 |
17 |
43.3 |
0.53 |
.30 – .50 |
| 2 |
13 |
17 |
43.3 |
0.53 |
.30 – .50 |
| total |
348 |
544 |
39.0 |
– |
– |
Literature Cited
- Cucurbit Genetics Cooperative Report no. 11. July 1988. University of Maryland, College Park, MD pp 96-103.