Abstract
To obtain insight into potential mechanisms underlying the influence of rootstock on scion growth, we performed a comparative analysis of ‘Shatangju’ mandarin grafted onto 5 rootstocks: Fragrant orange (Citrus junons Sieb. ex. Tanaka), Red tangerine (Citrus reticulata Blanco), ‘Shatangju’ mandarin (Citrus reticulata Blanco), Rough lemon (Citrus jambhiri Lush) and Canton lemon (Citrus limonia Osbeck). The tree size of ‘Shatangju’ mandarin grafted onto Canton lemon and Rough lemon were the largest, followed by self-rooted rootstock trees, and the lowest tree sizes correspond to ones grafted on Red tangerine and Fragrant orange rootstocks. The levels of indoleacetic acid (IAA) and gibberellin (GA) were significantly and positively related to growth vigor. The differences of gene expression in leaves of trees grafted onto Red tangerine, Canton lemon and ‘Shatangju’ mandarin were analyzed by RNA-Seq. Results showed that more differentially expressed genes involved in oxidoreductase function, hormonal signal transduction and the glycolytic pathway were enriched in ‘Red tangerine vs Canton lemon’. qRT-PCR analysis showed that expression levels of ARF1, ARF8, GH3 and IAA4 were negatively correlated with the growth vigor and IAA content. The metabolism of GA was influenced by the differential expression of KO1 and GA2OX1 in grafted trees. In addition, most of antioxidant enzyme genes were up-regulated in leaves of trees grafted onto Red tangerine, resulting in a higher peroxidase activity. We concluded that different rootstocks significantly affected the expression of genes involved in auxin signal transduction pathway and GA biosynthesis pathway in the grafted plants, and then regulated the hormone levels and their signal pathways.
Highlights
Citrus is grown in more than 140 countries in tropical, subtropical and Mediterranean region, and the total output of citrus in the world was at over 135 million tons in 2013 [1]
Total RNA was extracted from the leaf, scion bark, rootstock bark, and root samples of ‘Shatangju’ mandarin grafted onto the different rootstocks (Fragrant orange, Red tangerine, ‘Shatangju’ mandarin, Canton lemon, and Rough lemon) using a Trizol kit (TaKaRa, Japan)
The most vigorous growth and the longest shoot lengths were obtained for the ‘Shatangju’ mandarin grafted onto Rough lemon and Canton lemon rootstocks
Summary
Citrus is grown in more than 140 countries in tropical, subtropical and Mediterranean region, and the total output of citrus in the world was at over 135 million tons in 2013 (the FAO) [1]. Transcriptome Profiling to Understand the Effect of Citrus Rootstocks on the Tree Growth horticultural and pathological traits of citrus cultivars. The effect of rootstocks is significant on tree nutrition [2], growth vigor [3], stress resistance [4], and fruit quality [5] of the scion. The rootstock use holds an important position in fruit cultivation. The study of rootstocks has been a major topic in citrus research for nearly half a century and has rapidly been developed worldwide [6]. The rational use of rootstocks can enhance the stress resistance, regulate the production period, and improve the fruit quality of citrus. Systematic and thorough studies on citrus rootstocks are important to the citrus industry development
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