Cucurbit Genetics Cooperative Report 9:68-69 (article 21) 1986
G. Risser
INRA, Station d’Amelioration des Plantes Maraicheres, 84140 Montfavet, France
Seed size varies considerably in melon (Cucumis melo L.). Weight of 100 seeds varies from less than 0.5 g to more than 7 g. This seed size variation influences seedling size and is very troublesome in growth studies on young plants.
We reported here observations made on 2 lines, ‘Persian Small Type’ (P) and ‘Freeman’s Cucumber’ (FC), and their reciprocal F1 hybrids.
Methods. 11 January : sowing in 6×6 cm pots in heated greenhouse
11 February : measure of one cotyledon on 10 plants
27 February : measure of young seedlings on 7 plants repotting in 12×12 cm pots
12 April : measurements on 7 plants
Plants were not pinched.
Statistical comparison of means is made by Student’s t test.
Results. The dates of unfolding of successive leaves are reported in Figure 1.
Other observations are reported in Table 1.
Figure 1. Date of unfolding of successive leaves.
Table 1. Measure of different characters on ‘Persian Small Type; (P), ‘Freeman’s Cucumber’ (F) and their reciprocal F1 hybrids.
Date of measures |
Observation |
FC |
FC x P |
P x FC |
P |
PF |
P x FCPC x P |
Weight of 100 seedsy |
2.0 | 2.0 | 5.3 | 5.0 | 2.5 | ||
| 11 February | cotyledon length = L (mm) | 22 az | 24 b | 38 d | 36 c | 1.6 | 1.6 |
| cotyledon width = 1 (mm) | 14 a | 14 a | 23 c | 21 b | 1.5 | 1.6 | |
| cotyledony Lx1 (mm2) | 306 | 341 | 851 | 761 | 2.5 | 2.5 | |
| 27 February | hypocotyl length (mm) | 38 a | 54 b | 70 c | 84 d | 2.2 | 1.3 |
| number of leavesy | 3.0 | 3.0 | 3.6 | 3.9 | 1.3 | 1.2 | |
| length of the first leaf (mm) | 59 a | 67 b | 81 d | 76 c | 1.3 | 1.2 | |
| total length of leaves | 115 a | 130 b | 192 d | 186 c | 1.6 | 1.5 | |
| 12 April | fresh weight (g) | 107 a | 119 a | 139 b | 128 b | 1.2 | 1.2 |
| number of leaves on main stem | 17.6 | 17.4 | 18.2 | 16.8 | 1.0 | 1.0 | |
| main stem length (cm) | 86 | 117 | 119 | 109 | 1.3 | 1.0 | |
| ramification number | 2.3 a | 2.9 | 2.8 | 3.7 c | 1.6 | 1.0 | |
| total length of ramification (cm) | 122 | 123 | 160 | 131 | 1.1 | 1.3 | |
| number of plants with female flowersy | 3 | 2 | 6 | 0 | |||
| date of first ramificationy | 14/03 | 12/03 | 10/3 | 11/03 | |||
| date of tendril apparitiony | 9/03 | 10/03 | 4/03 | 12/03 | |||
| date of male flower apparitiony | 3/04 | 3/04 | 1/04 | 3/04 | |||
z = mean separation in rows by student’s t test, 5% level.
y = no statistical analysis
Discussion. As expected, cotyledon size is very dependent on maternal seed size and a significant maternal effect is measured on one month old seedlings. At the end of the trial, when the plants were more than 2 months old, maternal effect was still significant for fresh weight but not significant for the other measured characters.
The F1 hybrid PxFC is earlier than the reciprocal FCxP for apparition of ramifications, tendrils, male and female flowers. We cannot exclude that other factors than seed size may contribute to the maternal effect but surely seed size is a major factor because it is found in every observed cross.
Conclusion. The influence of seed size cannot be neglected when breeders wish to screen young plants for vigor or in adaptation studies.