Document Type : Research Article
Authors
1 Department of Horticultural Sciences, Faculty of Agriculture, Bu-Ali Sina University, Hamedan, Iran.
2 Department of Horticultural Sciences, Faculty of Agriculture, Bu-Ali Sina University, Hamadan. Iran.
Abstract
Introduction
At present, garlic production is completely dependent on asexual propagation, but a wide diversity of bolting and scape formation is observed in garlic. Based on their ability to produce flowering stem (scape), garlic clones are classified into non-bolting, semi-bolting, and bolting clones. In non-bolting clones, scape is not formed or abort at early stages. In semi-bolting clones, cessation of scape development often results in the formation of very short scape between the leaves and development of the elongated leaf-like bracts in the center of the inflorescence. In bolting clones after exposure to low temperature during autumn and winter (vernalization) and long day during spring, long and thick scape is formed which contains inflorescence with flowers. Transition from vegetative to reproductive phase and formation of scape, inflorescences and flowers in plants includes a series of continuous stages which control by several gene groups. Vernalization reduces the expression of the flowering inhibitors like FLOWERING LOCUC C (FLC), resulting in increased flowering integrators expression like SUPPRESSOR OF OVER EXPRESSON OF CONSTANT 1 (SOC1), APETALA 1 (AP1) and APETALA 1 (AP2). So, a correct understanding of the vernalization control genes expression pattern will improve garlic flowering and breeding programs. The aim of this study is to investigate the relative expression of AsFLC, AsSOC1, AsAP1 and AsAP2 before and after vernalization in Iranian bolting, semi-bolting and non-bolting garlic clones.
Material methods
In this study, three garlic clones including, bolting (Mazand Zabol), semi-bolting (Langrud), and non-bolting (Hamedan) garlic clones were selected from vegetable collection of Bu-Ali Sina university (Hamedan, Iran). At first, RNA extracted from meristems of three clones monthly, from 4 to 20 weeks after planting (for AsFLC, AsSOC1, AsAP1 and AsAP2 expression analysis) and from inflorescence of semi-bolting and bolting clones at 24 weeks after planting (for AsSOC1, AsAP1 and AsAP2 expression analysis) at 2 biological replicates. Then, cDNA synthesized using Oligo d(T) primer and relative expression pattern of the mentioned genes were analyzed using quantitative Real time- PCR.
Results and dissection
The highest expression of the AsFLC in all three clones were observed at 4 weeks after culture (before vernalization). Its expression in non-bolting clone at 4 weeks after planting was 2.03 and 1.13 times more than bolting and semi-bolting garlic, respectively. After vernalization AsFLC expression decreased in the meristem of the all three clones. The decrease in the relative expression of AsFLC in bolting garlic occurred at a faster rate compared to the other two garlic clones. Then the relative expression of the AsSOC1 was increased in the meristem during vegetative to reproductive transition phase (12 weeks after planting). The highest AsSOC1 expression was observed in the meristem of bolting garlic at 12 weeks after planting which was 10.98 and 18.41 times more than the meristem of semi-bolting and non-bolting garlic, respectively. AsAP1 was expressed in the meristem of three clones in the vegetative to reproductive phase, but its highest expression was in bolting clone at 12 weeks after planting and was 1.22 and 3.64 times more than the meristem of semi-bolting and non-bolting clone respectively. AsAP2 was just expressed in the meristem of semi-bolting and bolting clones and after reproductive transition. The highest expression of the AsAP2 was observed at 16 weeks after planting in the meristem of semi-bolting and bolting garlic, which was higher in bolting garlic (2.33 times) in comparison to semi–bolting garlic. Decreases in the expression of the AsFLC during vernalization and increases in the expression of the AsSOC1 and AsAP1 during vegetative to reproductive phase in the meristem may lead to scape formation in bolting garlic. But the higher AsFLC and the lower AsSOC1 and AsAP1 expression in the meristems of non- and semi bolting garlics in comparison to bolting garlic inhibit scape formation. So that in non-bolting garlic scape aborts and in semi-bolting garlic short and thin scape formed in the middle of leaves. According to the results AsSOC1 and AsAP1 were expressed in the inflorescence of semi-bolting and bolting garlic. AsSOC1 and AsAP1 relative expression in the inflorescence of bolting garlic were 4.28 and 11.25 times more than semi-bolting garlic, respectively. AsAP2 was just expressed in the inflorescence of the bolting clone but wasn’t expressed in the inflorescence of semi-bolting garlic. The differences in the expression pattern of AsSOC1, AsAP1 and AsAP2 in the inflorescence of the garlic clones could be the reason of the abnormal inflorescence in semi-bolting garlic.
Conclusion:
Finally, it seems that AsFLC is as a flowering inhibitor and AsSOC1 and AsAP1 are as flowering integrators in bolting garlic. As AsFLC expression decreased after vernalization and AsSOC1 and AsAP2 were expressed highly in the time of vegetative to reproductive transition in the meristem of all clones, and there was difference in the bolting of clones, it is suggested that these genes may influence flower induction but their low relative expression cause incomplete bolting in semi-bolting garlic and forbid bolting in non-bolting garlic.
Keywords
Main Subjects
)
Send comment about this article