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Julia Weiss, Avinoam Nerd, and Yosef Mizrahi

The reproductive biology of the climbing cacti Hylocereus polyrhizus (Weber) Britt. & Rose, H. undatus (Haworth) Britt. & Rose, H. costaricensis (Weber) Britt. & Rose, and Selenicereus megalanthus (Schum. ex Vaupel) Moran (syn. Mediocactus megalanthus) was studied with the aim of cultivating the cacti in Israel as fruit crops. Flowering in Hylocereus spp. occurred in two to three waves during the summer, whereas in S. megalanthus, flowering was concentrated at the end of autumn. Flowers of all species opened 1 to 1.5 hours before sunset and closed ≈6 hours after sunrise. In the Hylocereus spp., H. polyrhizus and H. costaricensis were self-unfruitful, and cross-pollination with other species led to high fruit set (100%). Hylocereus undatus was self-fruitful, setting fruit with self-pollen. Cross-pollination between the clones of S. megalanthus led to a high fruit set and each clone was self-fruitful. In contrast to H. undatus, S. megalanthus clones could set fruit without pollen vector involvement, although the set was slightly lower than with hand pollination. Pollen source influenced fruit weight. In the self-fruitful species of Hylocereus, fruit obtained by hand cross-pollination with other Hylocereus spp. were significantly heavier than fruit obtained by hand self-pollination. The largest fruit in each of the Hylocereus spp. were obtained by specific cross-combinations within the group. Fruit of S. megalanthus had a lower weight than fruit of the Hylocereus spp. Flowers of all species were visited by day-active honeybees only. Fruit set and fruit weight with open pollination was lower than with hand pollination in Hylocereus spp. Since stigma receptivity and pollen germinability stayed high during anthesis, the low pollination effectivity has to be related to other factors, such as the short bee visits and the absence of specific adaptation by the bees to the flower. In S. megalanthus, fruit set and fruit weight with open pollination were similar to values obtained with hand pollination. This similarity is probably related to the fact that pollen transfer in open pollination is achieved by bee visits and direct transfer of pollen to the stigma, which occurs via physical contact between anthers and stigma during flower closing.

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Solveig J. Hanson and Irwin L. Goldman

planted with a continuous drill seeder (Planet Junior; Cole Planter Co., Albany, GA) modified with a cone attachment at two sites in each of 2 years (2016–17) in a split-split plot design. The genotypes comprised open pollinated cultivars Bull’s Blood and

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Perry E. Nugent and Jeffrey Adelberg

Thirteen triploid lines of melon (Cucumis melo L.) were derived from crosses involving five tetraploid and seven diploid lines. Fruit characters were assessed. When allowed to open pollinate in field plots with adjacent diploid pollinators, eight triploid genotypes were sterile or nearly sterile (<1% viable seed). Five triploid genotypes were partially fertile, indicating viable pollen grains were present. Cytological analysis performed on progeny of a partially fertile triploid plant fertilized by open pollination indicated euploid female gametes were common. Triploid hybrids between tetraploid `Miniloup' and several other diploid parents had vegetative and fruit characteristics intermediate to the parents. Most triploid genotypes yielded round fruit in contrast to their diploid parent whose fruit were oval to oblong and the tetraploid parent that had oblate fruit. Sugar levels of some triploid hybrids were as high as diploid parents.

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S. Alan Walters

Cucurbit vegetable crops, such as watermelon (Citrullus lanatus), require insect pollination for fruit set, which is usually achieved by placing honey bee (Apismellifera) colonies in a field or relying upon natural bee populations. Pistillate (or female) watermelon flowers require multiple honey bee (or other bee) visitations after visiting staminate (or male) flowers for fruit set, and pollination is even more of a concern in triploid watermelon production since staminate flowers contain mostly nonviable pollen. Six honey bee visitation treatments, 1) no visitation control, 2) two visits, 3) four visits, 4) eight visits, 5) 16 visits, and 6) open-pollinated control, were evaluated to determine the effect of honey bee pollination on `Millionaire' triploid watermelon fruit set, yield, and quality utilizing `Crimson Sweet' at a 33% pollinizer frequency. No differences (P> 0.05) between honey bee pollination treatments were observed for `Millionaire' quality characters (hollow heart disorder or percent soluble solids). The lowest pistillate flower abortion rate (20%) and subsequently the greatest triploid watermelon yields (fruit numbers and weights per hectare) occurred with the openpollinated control compared to all other honey bee visitation treatments. Fruit abortion rates decreased linearly, while fruit numbers and weights per hectare increased linearly as number of honey bee visits to pistillate flowers increased from 0 (no visit control) to the open-pollinated control (≈24 visits). This study indicated that >16 honey bee visits are required to achieve maximum triploid watermelon fruit set and yields, which is twice the number of honey bee visits required by diploid watermelons to achieve similar results.

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S. Alan Walters

Honey bees (Apis mellifera L.) are important pollinators of triploid watermelon [Citrullus lanatus (Thunb.) Matsum & Nakai]. Pistillate (or female) watermelon flowers require multiple honey bee or other wild bee visitations after visiting staminate (or male) flowers for fruit set, and pollination is even more of a concern in triploid watermelon production since staminate flowers contain mostly nonviable pollen. Six honey bee visitation treatments—1) no visitation control, 2) two visits, 3) four visits, 4) eight visits, 5) 16 visits, and 6) open-pollinated control—were evaluated to determine the effectiveness of honey bee pollination on `Millionaire' triploid watermelon fruit set, yield, and quality utilizing `Crimson Sweet' at a 33% pollenizer frequency. `Millionaire' quality characters (hollow heart disorder or percent soluble solids) did not differ (P > 0.05) between honey bee pollination treatments. The open-pollinated control provided the highest fruit set rate (80%) and the greatest triploid watermelon numbers and weights per plot compared to all other honey bee visitation treatments. Fruit set, and fruit numbers and weights per plot increased linearly as number of honey bee visits to pistillate flowers increased from 0 (no visit control) to the open-pollinated control (about 24 visits). This study indicated that between 16 and 24 honey bee visits are required to achieve maximum triploid watermelon fruit set and yields at a 33% pollenizer frequency, which is twice the number of honey bee visits required by seeded watermelons to achieve similar results. This is probably due to many honey bees visiting staminate triploid watermelon flowers (that are in close proximity) before visiting pistillate flowers thus providing mostly nonviable pollen that is useless for fruit set and development. Therefore, more honey bee visits to pistillate triploid watermelon flowers would be required to achieve maximum fruit set and subsequent development compared to seeded watermelons.

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Gale H. McGranahan, Demetrios G. Voyiatzis, Peter B. Catlin, and Vito S. Polito

The role of pollen in abscission of pistillate flowers of Persian walnut (Juglans regia L.) cv. Serr was investigated over a 4-year period by controlled pollinations and pollen counts. Self-pollen, pollen from other walnut selections or cultivars, or dead pollen was applied at high and low doses to pistillate flowers enclosed in pollination bags. Unbagged, open-pollinated flowers and bagged, nonpollinated flowers served as controls. In all cases, presence of pollen significantly increased the probability of pistillate flower abscission (PFA). Dead pollen resulted in as much PFA as live pollen. Counts of pollen grains confirmed that PFA-type flowers had significantly more pollen than normal flowers. In the fourth year `Serr' pollen was applied to unbagged flowers of `Serr' and ten other Persian walnut cultivars, and the amount of PFA on the artificially pollinated flowers was significantly higher than on the open-pollinated flowers, while the control flowers dusted with talc or pine pollen had almost no PFA. These results clearly indicate that excess pollen is involved in pistillate flower abscission in `Serr' walnut and suggests that other cultivars may also be sensitive to pollen load. This phenomenon may have implications in the biology of selfing and evolution.

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Alireza Talaie*, Ahmad Ershadi, and Ali Vezvaei

In order to study pollination and fruit set and determine the best pollinizers for two Iranian apple cultivars, Golab Kohanz and Shafiabadi, experiments were conducted during two years. Different pollen sources including pollen of cultivars Golab Isfahan, Golab Kohanz, Mashhad Nouri, Shafiabadi and also open pollination were used. Pollen sources had significant effects on fruit set, fruit weight, diameter, shape, dry weight, total soluble solids (TSS), sugar and seed contents in cv. Golab Kohanz. Trees pollinated by pollen of Shafiabadi had highest fruit set, fruit weight, diameter, shape, dry weight, TSS., sugar, and seed content. Pollen sources significantly affected fruit set, fruit weight, diameter, shape, and seed content in cv. Shafiabadi. The highest fruit set, fruit weight, diameter, and seed content was resulted from flowers pollinated by Golab Kohanz. Golab Kohanz and Shafiabadi had 3.3% and 0.5% fruit set from self pollination, respectively, and seemed to be completely incompatible. Fruit resulted from self pollination were generally small and of low quality. Regardless to fruits obtained from pollination, different pollen sources had small effects on fruit quality. The results indicated that cvs. Shafiabadi and Mashad Nouri are the best pollinizers for Golab Kohanz and Golab Kohanz was superior pollinizers for Shafiabadi.

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G. Costa, R. Testolin, and G. Vizzotto

The aim of the experiment was to define the wind and the bees effect on kiwifrut pollination. Experiment was carried out for two years in an adult kiwifruit orchard, with a ratio between staminate (cv Matua) and pistillate (cv Hayward) vines of 1:7. Four different pollination treatments were tested on kiwifruit. Bees effectiveness was evaluated on both open pollination (OP-Bees) or net-isolated vines conditions (IV-Bees). The results obtained were compared with those achieved on net-isolated vines without bees in (IV-Wind) and on hand-pollinated vines (HP). Four rows (80 vines) were net-isolated and 14 uniform vines per treatment were choosen to collect productive data. In the IV-Wind treatment traps were used to capture insects present inside the nets. Wind speed was detected inside and outside the nets. Data showed that the net isolation system did not consistently modify wind speed and no insects were founds in the traps. As far as productive data best results were obtained on HP vines. Bee-pollinated vines always reached higher yield and average fruit weight than wind-pollinated vines. However no statistical differences were detected between fruit weight of OP-Bees and IV-Wind vines treatments. The results showed that in general bees represent a more efficient pollination agent than wind, even if the health of the bees and the position of the hives in the orchard have to be carefully considered to achieve best results.

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Zhongbo Ren, Jiang Lu, and Xia Xu

`Pam' is a popular muscadine grape (Vitis rotundiforia) used for the fresh fruit market. It is characterized with large berry, nice appearance, good texture and flavor, and high disease resistance. This cultivar, however, requires pollinators because it is pistillate. To select a better pollinator for this pistillate cultivar, a 2-year study was conducted at Florida A&M University in 2003 and 2005. Fresh pollen of muscadine grape `Alachua', `Nesbitt', and `Noble' was used for pollination. `Nesbitt' pollen resulted in 100% of the pollinated clusters setting fruits in both years, while pollination with `Alachua' yielded 70% (2003) to 87% (2005) of fruiting clusters, and `Noble' pollen yielded 72% (2003) and 97% (2005) fruiting clusters, respectively. Fruit numbers per fruiting cluster also varied among pollen sources. `Alachua' pollen resulted in 7.2 (2003) and 8.1 (2005) fruits per cluster, while `Nesbitt' produced 10.1 (2003) to 10.5 (2005) fruits per cluster, and `Noble' produced 8.3 (2003) and 9.0 (2005) berries per cluster. Open pollinated `Pam' had 100% clusters set fruits, averaging about 11 fruits per cluster in both seasons. No difference of berry size was observed among fruits produced from different pollen sources. Both sugar contents and acids levels were a little bit higher in 2005 than that in 2003. However, no differences of sugar content and acid level were found among the fruits derived from different controlled pollen sources. These data suggested that `Nesbitt' is a better pollinator than `Alachua' and `Noble' for `Pam' muscadine grape.

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Manfred Jusaitis

Flowers of Swainsona formosa (G. Don) J. Thompson (syn. Clianthus formosus) developed through seven floral stages from buds to open flowers in 17 days. Floral stages were correlated with the sigmoidal growth pattern of the peduncle. Self-pollination was prevented in the species by the presence of a stigmatic cuticle that precluded pollen germination until ruptured, exposing the receptive surface below. Cuticular rupture occurred in nature during bird-pollination and was emulated manually by lightly rubbing a pollen-covered finger across the stigma. The species was self-compatible, and to ensure cross-fertilization when breeding, emasculation before anther dehiscence was essential.