Abstract
The long history of asexual reproduction of garlic using garlic cloves has resulted in virus accumulation and genetic depression. Propagation of garlic seedlings by tissue culture can both eliminate viruses and improve breeding efficiency. Aerial bulbs are the first-choice materials for breeding virus-free garlic seedlings under external conditions, but they show dormancy just like garlic bulbs. However, low temperatures can quickly break dormancy. In this research, we used a high-throughput sequencing method to sequence aerial bulbs during dormancy and after low-temperature-induced breaking of dormancy to screen out the key differentially expressed genes (DEGs) associated with low temperature and to provide a theoretical basis for exploring the molecular mechanism of low-temperature-induced breaking of aerial bulb dormancy. The high-throughput transcriptome sequencing results showed that 6,675 DEGs were upregulated and 36,596 DEGs were downregulated in the aerial bulbs given low-temperature treatment. Then, 19,507 DEGs were assigned KEGG annotations, among which most DEGs were annotated to the metabolism pathway (11,817 genes, accounting for 60.58%), followed by the genetic information processing pathway (4,521 genes, accounting for 23.18%). The DEGs were mostly concentrated in pathways such as protein processing in the endoplasmic reticulum, plant-pathogen interaction, plant hormone signal transduction, and ribosome biogenesis in eukaryotes, with significant enrichment. The key DEGs related to calcium signaling, hormonal signaling, and transcription factors were screened out, including CaM, CDPK, and CML in accessory pathways of calcium signaling; GA20ox, GAI1, and GA2ox in accessory pathways of hormonal signaling; and transcription factor genes such as MYB, AP2/ERF, bHLH, MADS, and bZIP. qRT-PCR verification results were consistent with the sequencing results, indicating that the transcriptome sequencing data were accurate and reliable. Our results provide a theoretical basis for breaking the dormancy of aerial bulbs with low-temperature treatment to produce virus-free seedlings and increase the output and quality of garlic.
Highlights
Garlic (Allium sativum L.), an annual or biennial herb in the lily family, has a long history of cultivation and originated in Central Asia
The aerial bulbs treated with low temperature quickly germinated after inoculation, while the untreated aerial bulbs remained dormant after inoculation and did not germinate (Figure 1(a))
As the culture period was prolonged, the aerial bulbs treated with low temperature showed a significantly higher plantlet induction rate, while for the untreated aerial bulbs, the induction rate was zero at the early stage and gradually increased but was still much lower than that of the treated aerial bulbs (Figure 1(b))
Summary
Garlic (Allium sativum L.), an annual or biennial herb in the lily family, has a long history of cultivation and originated in Central Asia. Aerial bulbs grow quickly from bulbils inside the receptacles of young garlic shoots and carry very few viruses and are characterized by a small volume, large quantity, high germination percentage, uniform germination, genetic stability, and a high likelihood of forming independent test-tube plantlets. They are the firstchoice materials for the breeding of virus-free seedlings under external conditions and can improve the utilization of International Journal of Genomics young garlic shoots. Aerial bulbs can go dormant right after being picked If they are used to induce virus-free seedlings, their dormancy must first be broken. Research has shown that low temperatures can be used to quickly break the dormancy of aerial bulbs, which can produce remarkable breaking effects
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