Abstract
Jujube (Ziziphus jujuba) is a species particularly prone to erratic fruit set. Several causes such as pollen germination and tube growth involve in this behaviour. Thus, the present research aimed to evaluate and compare of pollen grains germination and tube growth of ten Iranian jujube cultivars on in vitro condition. A factorial trial based on completely randomized design with five replications was carried out. The pollen grains were collected from un-opened-flowers of Al-Ghour’, ‘Bardaskan’, ‘Doroh’, ‘Gazik’, ‘Ghom’, ‘Giouk’, ‘Kangan’, ‘Kalkestan’, ‘Magham Sari’ and ‘Noghab’ cultivars at balloon stage. This study showed that there were significant differences among the cultivars in all measured factors. The highest percentage of pollen grains germination was observed for ‘Gazik’, followed by ‘Bardaskan’, while the lowest was in ‘Al-Ghour’. The percentage of pollen grains germination increased with the increasing time of incubation period up to 36 h. Also, flowering times are found to be effective in germination of pollen grains, which 1 flash had highest percentage of germination of pollen grains than in comparison to other flowering times. The results also showed that the mean time germination varied from 24.52-25.92 h, mean hourly germination from 0.67-1.55, hourly germination speed from 0.64-1.48 and coefficient of velocity of germination of pollen grains from 0.058-0.061. The length of pollen tube was found between 44.4 and 624.8 µm. These data demonstrated that cultivar is the main factor determining pollen grains germination and tube growth in jujube, which this important information can be useful for selection of superior desirable jujube genotypes for bringing to commercial cultivation.
Highlights
Ziziphus jujuba M., named jujube, belongs to the Rhamanaceae family
There are various reasons for erratic fruit production in jujube including: a) Strong incompatibility, which results in problems such as reduction or irregularity in fruit production and decrease in yield owing to absence or inadequate compatible pollen grain; b) Cytoplasmic male sterility; unviable pollen grain percentage varied in Chinese jujube cultivars (Mengjun, 2003)
The results showed that the mean time germination (MTG) varied from 24.52 (‘Gazik’) 25.92 (‘Al-Ghour’), mean hourly germination (MHG) from 0.67 (‘Al-Ghour’) -1.55 (‘Gazik’), hourly germination speed (HGS) from 0.64 (‘Gazik’)-1.48 (‘Al-Ghour’) and coefficient of velocity (CVG) of germination of pollen grains from 0.058 (‘Al-Ghour’)-0.061 (‘Gazik’) (Tab. 2)
Summary
Ziziphus jujuba M., named jujube, belongs to the Rhamanaceae family. This genus includes about 40 species of spiny shrubs and small trees, distributed in tropical and sub-tropical regions throughout the world (Soliman et al, 2013), such as Iran.Besides, the high amounts of vitamin A, C and B complexes and minerals in Ziziphus delicious fruits (Pareek, 2004), alkaloids, flavonoids, sterols, tannins, and fatty acids have been isolated from its different species (Croueour et al, 2002; Abdel-Zaher et al, 2005; Bhargava et al, 2005; Kakani et al, 2005). There are various reasons for erratic fruit production in jujube including: a) Strong incompatibility, which results in problems such as reduction or irregularity in fruit production and decrease in yield owing to absence or inadequate compatible pollen grain; b) Cytoplasmic male sterility; unviable pollen grain percentage varied in Chinese jujube cultivars (Mengjun, 2003). It was reported some cultivars had completely unviable pollen grain
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