Citrus Rootstock Breeding and Selection

Rootstocks are crucial for the sustainability of the citrus industry worldwide. Diploid intergeneric Citrus × Poncirus hybrids have contributed considerably to citrus rootstock improvement and their tetraploid (doubled-diploid) forms are important resources for the creation of a new generation of tetraploid rootstocks. To optimize the efficiency of tetraploid rootstock breeding strategies, more knowledge is required on inheritance in the allotetraploid genitors. A set of 159 new SNP markers that fully distinguish Poncirus trifoliata (L.) Raf. from Citrus species was developed from polymorphisms mined in GBS data and used to establish a genetic map of tetraploid citrumelo (C. × paradisi Macfad. × P. trifoliata) and to analyze the meiotic behavior of tetraploid citrumelo and citrandarin (C. reticulata Blanco × P. trifoliata). The tetraploid citrumelo genetic map was highly syntenic and collinear with the clementine reference genome. The apparent intergeneric recombination rate was strongly limited by high preferential chromosome pairing, resulting in intermediate inheritance with disomic tendency. Such inheritance, also observed in tetraploid citrandarin, results in the transmission by the diploid gametes of a high rate of intergeneric heterozygosity. It is therefore expected that a large part of the genetic value selected in the original diploid intergeneric rootstock is transmitted to the tetraploid sexual progenies.

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In vitro propagation of Troyer Citrange : A horticulturally important citrus rootstock

Green Farming ◽

10.37322/greenfarming/11.2-3.2020.130-134 ◽

2020 ◽

Vol 11 (2-3) ◽

pp. 130

Author(s):

VIJAYAKUMARI N. ◽

P. GHOSH ◽

Y.B. LAHANE ◽

K.P. FISKE

Keyword(s):

In Vitro Propagation ◽

Citrus Rootstock ◽

Troyer Citrange

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NITROGEN NUTRITION OF CITRUS NURSERY STOCK IN PINE BARK SUBSTRATES.

HortScience ◽

10.21273/hortsci.25.9.1161f ◽

1990 ◽

Vol 25 (9) ◽

pp. 1161f-1161

Author(s):

John D. Lea-Cox ◽

Irwin E. Smith

Keyword(s):

Nutrient Solution ◽

Nitrogen Nutrition ◽

Dry Mass ◽

Pine Bark ◽

Growing Period ◽

Rough Lemon ◽

Nursery Stock ◽

Citrus Rootstock ◽

Cleopatra Mandarin ◽

Nutrient Solutions

Pine bark is utilized as a substrate in citrus nurseries in South Africa. The Nitrogen (N) content of pine bark is inherently low, and due to the volubility of N, must be supplied on a continual basis to ensure optimum growth rates of young citrus nursery stock. Three citrus rootstock (rough lemon, carrizo citrange and cleopatra mandarin) showed no difference in stem diameter or total dry mass (TDM) when supplied N at concentrations between 25 and 200 mg ·l-1 N in the nutrient solution over a 12 month growing period. Free leaf arginine increased when N was supplied at 400 mg·l-1 N. The form of N affected the growth of rough lemon. High NH4-N:NO3-N (75:25) ratios decreased TDM when Sulfur (S) was absent from the nutrient solution, but not if S was present. Free arginine increased in leaves at high NH4-N (No S) ratios, but not at high NH4-N (S supplied) ratios. Free leaf arginine was correlated with free leaf ammonia. These results have important implications for reducing the concentration of N in nutrient solutions used in citrus nurseries and may indicate that higher NH4-N ratios can be used when adequate S is also supplied.

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Genome of a citrus rootstock and global DNA demethylation caused by heterografting

Horticulture Research ◽

10.1038/s41438-021-00505-2 ◽

2021 ◽

Vol 8 (1) ◽

Author(s):

Yue Huang ◽

Yuantao Xu ◽

Xiaolin Jiang ◽

Huiwen Yu ◽

Huihui Jia ◽

...

Keyword(s):

Sweet Orange ◽

Epigenetic Modification ◽

Epigenetic Modifications ◽

Genetic Effects ◽

Dna Demethylation ◽

Poncirus Trifoliata ◽

Protein Coding ◽

Horticultural Crops ◽

Citrus Rootstock ◽

Methylome Analysis

AbstractGrafting is an ancient technique used for plant propagation and improvement in horticultural crops for at least 1,500 years. Citrus plants, with a seed-to-seed cycle of 5–15 years, are among the fruit crops that were probably domesticated by grafting. Poncirus trifoliata, a widely used citrus rootstock, can promote early flowering, strengthen stress tolerance, and improve fruit quality via scion–rootstock interactions. Here, we report its genome assembly using PacBio sequencing. We obtained a final genome of 303 Mb with a contig N50 size of 1.17 Mb and annotated 25,680 protein-coding genes. DNA methylome and transcriptome analyses indicated that the strong adaptability of P. trifoliata is likely attributable to its special epigenetic modification and expression pattern of resistance-related genes. Heterografting by using sweet orange as scion and P. trifoliata as rootstock and autografting using sweet orange as both scion and rootstock were performed to investigate the genetic effects of the rootstock. Single-base methylome analysis indicated that P. trifoliata as a rootstock caused DNA demethylation and a reduction in 24-nt small RNAs (sRNAs) in scions compared to the level observed with autografting, implying the involvement of sRNA-mediated graft-transmissible epigenetic modifications in citrus grafting. Taken together, the assembled genome for the citrus rootstock and the analysis of graft-induced epigenetic modifications provide global insights into the genetic effects of rootstock–scion interactions and grafting biology.

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