Cucurbit Genetics Cooperative Report 23:64-67 (article 21) 2000
Haim Nerson and Harry S. Paris
Department of Vegetable Crops, Agricultural Research Organization, Newe Ya’ar Research center, P.O. Box 1021, Ramat Yishay, 30-095, Israel
The seed yield of any fruit is a function of seed number and seed size. Seed number is determined early in fruit development by ovule fertilization. Seed size is determined later, and actually during the while period of fruit development, depending on a complex of environmental factors. Different types of relationships between fruit size and seed yield components have been reported. In Capsicum (3) and summer squash (6), a linear relationship between fruit weight and seed number was found. Less information is available concerning the relationship between fruit weight and individual seed weight. It is widely accepted that larger seeds of any crop have higher germinability and faster seedling development (1,4,5). This gives a potential advantage to the crop which is not realized in many cases (2). Herein are described the results of a cooperative study on the size of the fruit and the mean weight of its seeds, in four species of cucurbit crops.
Materials and Methods. Cucumber (Cucumis sativus): in one experiment, a plot of the U.S.A. slic9ing cultivar Poinsett 76 was grown under simulated commercial conditions in the field at Newe Ya’ar (northern Israel) in the summer of 1998. Each plant was allowed to set five fruits, at 2-3 day intervals between each fruit. Each fruit had been tagged on the day of anthesis and was harvested 42 days later. Each fruit was weighed at harvest and its seeds extracted and dried. Four samples of 25 seeds each were then weighed. There were four replicates of 10 plants each. Another experiment was conducted the subsequent winter in a greenhouse at Shefeye (northern Israel). Three cultivars differing in fruit size were grown” ‘Jinchun No. 4’, a hybrid from china having fruits 40-50 cm long; ‘Poinset 76’ a slicing-type from the U.S.A. having fruits ~25 cm long; and ‘Triple Mech’, a pickling-type from the U.S.A. having fruits ~15 cm long. Mature fruits were harvested 40-50 days past anthesis and weighed. Dry seeds were also weighed. There were four replicates of ten plants each.
Melon (Cucumis melo): One experiment, conducted in the field at Newe Ya’ar under commercial conditions in the summer of 1997, had two muskmelon cultivars, ‘Noy Yizre’el’ from Israel and ‘Top Mark’ from the U.S.A., grown in four replicates of 20 plants each. At maturation, the fruits and seeds were weighed. The second experiment on muskmelon was conducted the following year and next to the cucumber plot; it was conducted in the same fashion as the first experiment with cucumber, using ‘Noy Yizre’el’.
Watermelon (Citrullus lanatus ): ‘Malai’, an Israeli cultivar, and two breeding lines, nos. 203 and 239-4, were grown in a commercial dryland field for production of edible seeds near Daverat (northern Israel) in the summer of 1998. At harvest, the fruits were divided into five size group (<500 g, 500-1000 g, 1000-1500 g, 1500-2000 g and >2000 g) and the seed yield and yield components were observed for each group separately. There were four replicates for each accession, and the area of each replicate was 20 m2.
Pumpkin/Gourd (Cucurbita pepo): At the Newe Ya’ar research Center in summer 1998, 15-20 plants of each two cultivars were grown: ‘Tondo Schro di Piacenza’, a pumpkin from Italy, and ‘Flat Striped’, an ornamental gourd from Canada. These two differ markedly (Approximately 7-fold) in fruit size. Ten mature fruits were harvested from each and weighted, and their dried seeds were weighted.
Results and discussion. Fruit order had a significant effect on fruit weight in ‘Noy Yizre’el melon and ‘Poinsett 76’ cucumber (Table 1). However, the two species differed in the relationship between fruit and mean seed weight. In ‘Noy Yizre’el’ melon, there was a linear relation between these two variables while in ‘Poinsett 76 cucumber these two were not correlated. A comparison among cultivars of these species enhanced this conclusion. The seed size of the two melon cultivars differed significantly, as did their fruit size. However, the seed size was the same in cucumbers, even though the three cultivars differed markedly in fruit size (Table 2).
The relationship between fruit size and seed size in ‘Malali’ watermelon and two related breeding lines resembled those of cucumber. There were no significant size differences in seeds extracted from large fruits or small fruits down to 500 g (Table 3). Only extremely small fruits (<500 g) produced smaller seeds. the three watermelon secessions differed significantly in mean fruit weight (Table 4) but nevertheless had the same mean seed weight.
The relationship between fruit size and seed size in Cucurbita pepo was nearly linear (Table 5). Thus, the relationship was more similar to that of melon than it was to cucumber or watermelon.
The results presented here are but a small part of a large unpublished investigation of the possible relationships between fruit and seed yield of cucurbits. These selected data show that, in cucurbits, two different relationships between fruit and seed size have developed over the course of evolution. Seemingly, cucumber and watermelon went in one path whilst melon and pumpkin/squash went in another.
Table 1. Effects of fruit order on fruit weight and individual seed weight in cucumber ‘Poinsett ’76’ and melon ‘Noy Yizre’el.
| Fruit order | Cucumber | Melon | ||
| Fruit weight (g) | Seed weight (mg) | Fruit weight (g) | Seed weight (mg) | |
| 1 | 774 a | 23.4 a | 1647 a | 37.4 a |
| 2 | 719 a | 23.8 a | 1553 a | 31.4 b |
| 3 | 636b | 21.4 ab | 1216 b | 25.4 c |
| 4 | 636 b | 20.5 b | 981 c | 2.9 c |
| 5 | 558 c | 22.1 ab | 730 d | 19.5 d |
Table 2. Fruit weight and individual seed weight in different cultivars of cucumber (greenhouse) and melon (field).
| Cucumber | Melon | ||||
| Cultivar | Fruit wt. (g) | Seed weight (mg) | Cultivar | Fruit wt. (g) | Seed weight (mg) |
| Jinchun No. 4 | 1121 a | 28.2 a | Noy Yizre’el | 1065 a | 32.6 a |
| Poinsett 76 | 580 b | 27.8 a | Top Mark | 839 b | 22.7 b |
| Triple Mech | 420 c | 28.3 a | |||
Table 3. Effect of fruit weight (g) on mean seed weight (mg) in ‘Malali; and two breeding lines, 203 and 239-4, of watermelon.
| Fruit weight | Malali | 203 | 239-4 |
| <500 | – | 149 b | 145 b |
| 500-1000 | 161 a | 166 ab | 161 a |
| 1000-1500 | 164 a | 170 ab | 165 a |
| 1500-2000 | 170 a | 161 b | 160 a |
| >2000 | 165 a | 177 a | — |
Table 4. Mean fruit weight and mean seed weight of ‘Malali’ and two breeding lines, 203 nd 239-4, of watermelon.
| Cultivar/breeding line | Fruit weight (kg) | Seed weight (mg) |
| Malali | 2.49 a | 166 a |
| 203 | 0.98 b | 169 a |
| 239-4 | 0.98 b | 163 a |
Table 5. Effect of fruit weight (g) on mean seed weight (mg) in an ornamental gourd and a pumpkin (both Cucurbita pepo)
| Gourd | Pumpkin | ||
| Fruit weight | Seed weight | Fruit weight | Seed weight |
| 244 | 72 | 1720 | —* |
| 225 | 61 | 1670 | 145 |
| 1963 | 45 | 1560 | 155 |
| 191 | 47 | 1520 | 148 |
| 188 | 41 | 1465 | 128 |
| 175 | 42 | 1465 | 120 |
| 160 | 41 | 1430 | 110 |
| 160 | 36 | 1080 | 95 |
| 160 | 32 | 1035 | 118 |
| 153 | 30 | 1000 | 93 |
*no data
Acknowledgement: contribution No. 121/00 from the Institute of Field & Garden Crops, Agricultural REsearch Organization, Bet Dagan, Israel.
Literature Cited
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