Viability of Pollen of Two Fruit Crop Cacti of the Genus Hylocereus Is Affected by Temperature and Duration of Storage

Abstract

<jats:p><jats:italic>Hylocereus undatus</jats:italic> (Haw.) and <jats:italic>H. polyrhizus</jats:italic> (Weber) are new fruit crops of the Cactaceae. In Israel, flowers of the two species, which are self-incompatible, are hand cross-pollinated. In order to ensure a current supply of compatible pollen and guarantee good yields, we have developed a procedure for long-term storage of pollen. Pollen for storage was collected in the evening or in the morning. Its moisture content ranged between 45% to 50% in the evening and between 18% to 22% in the morning. Pollen was first dehydrated in a vacuum desiccator until the moisture content was reduced to 5% to 10% and then stored at various temperatures (+4, -18, -70, -196 °C) for 3 or 9 months, after which it was used for cross-pollination. Percent fruit set and fruit fresh weight (FW) were affected by the temperature but not the duration of pollen storage; storage at +4 °C reduced fruit set, fruit FW, and seed number more than did storage at subfreezing temperatures. The FW of fruits produced by frozen pollen was similar to that produced by fresh pollen in commercial orchards. The rate of seed germination was high (≈90%) regardless of the temperature during pollen storage.</jats:p>

Heat Stress Leads to Poor Fruiting Mainly Due to Inferior Pollen Viability and Reduces Shoot Photosystem II Efficiency in “Da Hong” Pitaya

“…The results of in-vitro pollen germination and pollination combinations at various temperature treatments confirmed the previous hypothesis that HT reduces pollen viability, resulting in poor fertilization and small fruit size in "Da Hong" red-fleshed pitaya [6]. Metz et al [33] revealed that the in-vitro germination rate of "clone C" red-fleshed pitaya decreased to <11% when pollen was stored for 3 months, but when the pollen intensity (pollen amount) was sufficient, the pollen remained able to promote fruit set by artificial pollination. Therefore, although pollen viability was significantly reduced under MH treatment, the function of the pistil was less affected by HT treatment.…”

In Vitro Germination of Pollen Grains in Pitahaya Species

“…For H. undatus, the highest average obtained was (99.87%), adjusted for 619 mg L −1 boric acid, which represents an increase of more than 100% in relation to the absence of this substance (Figure 5b). Metz et al (2000) worked with these two pitahaya species and found similar results for H. polyrhizus with an average germination of 82.8%, however, their results were divergent to the present study for the H. undatus species, which reached an average of 79.2%. Boric acid had the same effect for pollen grains germination of pear (Nogueira et al, 2016).…”

Pollen available during anthesis of Hylocereus undatus flowers

“…• Phase III shows the pollen with a mealy characteristic, very manageable, easily detached from the anthers and it is precisely when the pollen samples observed the highest percentage of viable pollen. Metz et al [22] pointed out that for H. undatus and H. Polyrhizus pollen is more humid during the night, reducing in the morning. These data coincide with phases I and II, of the first part of the night, as well as with phase III, which occurs at dawn, which shed floury pollen due to the fact that it is more dehydrated.…”