摘要：
Citrus canker is a significant bacterial disease caused by Xanthomonas citri subsp. citri (Xcc) that severely impedes the healthy development of the citrus industry. Especially when citrus fruit is infected by Xcc, it will reduce or even lost its commercial value. However, due to the prolonged fruiting cycle and intricate structure, much less research progress had been made in canker disease on fruit than on leaf. In fact, limited understanding has been achieved on canker development and the response to Xcc infection in fruit. Herein, the progression of canker disease on sweet orange fruit was tracked in the field. Results indicated that typical lesions initially appear on the sepal, style residue, nectary disk, epicarp, and peduncle of young fruits after petal fall. The susceptibility of fruits to Xcc infection diminished as the fruit developed, with no new lesions forming at the ripening stage. The establishment of an efficient method for inoculating Xcc on fruit as well as the artificial inoculation throughout the fruit's developmental cycle clarified this infection pattern. Additionally, microscopic observations during the infection process revealed that Xcc invasion caused structural changes on the surface and cross-section of the fruit. An efficient system for inoculation on citrus fruit with Xcc was established, by which it can serve for the evaluation of citrus germplasm for canker disease resistance and systematic research on the interactions between Xcc and citrus fruits.
摘要：
The citrus cultivar 'Local Juhong', which has historically been used as a traditional Chinese medicinal material, originated in Yuanjiang County, Hunan Province.Its parental type and genetic background are indistinct as of yet. Morphological observation shows that 'Local Juhong' has a slight oblateness in fruit shape, a relatively smooth pericarp, a fine and slightly raised oil vacuole, and an inward concave at the blossom end. The tree form and fruit and leaf morphology of 'Local Juhong' are similar to those of 'Huangpi' sour orange. To reveal the genetic background of 'Local Juhong', 21 citrus accessions were evaluated using nuclear and chloroplast SSR markers and whole-genome SNP information. 'Local Juhong' was grouped with mandarins and sub-grouped with 'Miyagawa Wase' and 'Yanxi Wanlu' in a nuclear SSR analysis, which indicated that its pollen parent might be mandarins. It was closely clustered with orange and pummelo in the chloroplast SSR analysis. The genomic sequence similarity rate of 'Local Juhong' with mandarin and pummelo heterozygosity was 70.88%; the main part was the heterozygosity, except for the unknown (19.66%), mandarin (8.73%), and pummelo (3.9%) parts. Thus, 'Local Juhong' may be an F1 hybrid with pummelo as the female parent and mandarin as the male parent, sharing sisterhood with 'Huangpi' sour orange.
摘要：
Citrus bacterial canker disease, caused by Xanthomonas citri subsp. citri (Xcc), poses a significant global threat to the citrus industry. Lateral organ boundaries 1 (Lob1) is confirmed as a citrus susceptibility gene that induces pathogenesis by interaction with the PthA4 effector of Xcc. Citron C-05 (Citrus medica) is a Citrus genotype resistant to Xcc. However, there is little information available on the regulation of Lob1 in resistant genotypes, which is important for the breeding of citrus cultivars resistant to canker disease. This study aimed to identify upstream regulatory factors of Lob1 in Citron C-05 and to investigate its function in disease resistance. 'Bingtang' sweet orange (C. sinensis), a susceptible genotype, was utilized as the control. cDNA yeast libraries of Xcc-induced Citron C-05 and 'Bingtang' sweet orange were constructed. The capacities of 'Bingtang' and Citron C-05 were 1.896 x 10(7) and 2.154 x 10(7) CFU, respectively. The inserted fragments ranged from 500 to 2000 bp with a 100% recombination rate. The promoter of Lob1 was segmented into two pieces and the P1 fragment from both genotypes was used to construct a bait yeast (PAbAi-CsLob1-P1; PAbAi-CmLob1-P1). Through library screening with the bait yeast, upstream regulators interacting with the Lob1-P1 promoter were identified and then validated using Y1H and dual-luciferase tests. The expression analysis of the three transcript factors indicated that RMA3 was upregulated by inoculation with Xcc in the resistant Citron C-05, but not in the susceptible sweet orange. The overexpression of CsRMA3 in 'Bingtang' sweet orange led to reduced canker symptoms, with a significantly lower pathogen density in the leaves following Xcc inoculation. When CmRMA3 was silenced by virus-induced gene silencing (VIGS) in Citron C-05, typical canker symptoms appeared on the CmRMA3-silenced leaves at 15 days post-inoculation with Xcc. Further expression analyses revealed that the CmRMA3 transcription factor suppressed the expression of Lob1. These results suggest that RMA3 participates in the resistant reaction of Citron C-05 to Xcc infection, and such a response might be in relation to its suppression of the expression of the pathogenic gene Lob1.
作者机构：
[李益; 金燕; 王萍; 盛玲; 麻明英; 邓子牛; 马先锋; 张凯] Engineering Research Center for Horticultural Crop Germplasm Creation and New Variety Breeding, Ministry of Education, National Center for Citrus Improvement Changsha, College of Horticulture, Hunan Agricultural University, Changsha, 410128, China
通讯机构：
[Ma, X.] E;Engineering Research Center for Horticultural Crop Germplasm Creation and New Variety Breeding, China
摘要：
The cultivated landrace 'Huarongdao Zhoupigan' originated in China, and it has a history of more than a hundred years. It is widely cultivated for its distinctive pericarp, soft juicy pulp, slight bitter taste, and rich flavonoids and vitamin C (17.2 +/- 0.08 mg.mL(-1) ). Morphological observation shows that 'Fluarongdao Zhoupigan' is mandarin-like in leaf shape, fruit flesh, easy peeling and crumpled pericarp, implying this variety may be a hybrid of orange and mandarin. To reveal the genetic background of 'Fluarongdao Zhoupigan', 21 citrus accessions were evaluated using nuclear and chloroplast SSR markers and whole-genome SNP information. 'Fluarongdao Zhoupigan' was grouped with mandarins and closely clustered with 'Yuanjiang Nanju' in the nuclear SSR analysis and sub-grouped with 'Goutou' sour orange, 'Dahong' sweet orange and 'Newhall' navel orange in the chloroplast SSR analysis. The genomic sequence similarity rate of 'Fluarongdao Zhoupigan' with mandarin was 36.09%, with mandarin hetemzygosity of 46.50%; the rough ratio of the two main parts was nearly 1:1, except for the unknown (19.11%) and pummelo (1.46%) parts. Thus, 'Fluarongdao Zhoupigan' may be a natural hybrid with sour orange (a sexual hybrid of pummelo and mandarin) as the seed parent and mandarin as the pollen parent.
摘要：
<jats:p>Among Citrus species, lemon is one of the most susceptible to mal secco disease, a tracheomycosis caused by the mitosporic fungus Plenodomus tracheiphilus, which induces chlorosis followed by leaf drop and progressive desiccation of twigs and branches. Severe infection can cause the death of the plant. Since no effective control strategies are available to efficiently control the pathogen spread, host tolerance is the most desirable goal in the struggle against mal secco disease. To date, both traditional breeding programs and biotechnological techniques were not efficient in developing novel varieties coupling tolerance to mal secco with optimal fruit quality. Furthermore, the genetic basis of host resistance has not been fully deciphered yet, hampering the set-up of marker-assisted selection (MAS) schemes. This paper provides an overview of the biotechnological approaches adopted so far for the selection of mal secco tolerant lemon varieties and emphasizes the promising contribution of marker-trait association analysis techniques for both unraveling the genetic determinism of the resistance to mal secco and detecting molecular markers that can be readily used for MAS. Such an approach has already proved its efficiency in several crops and could represent a valuable tool to select novel lemon varieties coupling superior fruit quality traits and resistance to mal secco.</jats:p>
作者：
Mario, Di Guardo;Marco, Moretto;Mirko, Moser;Chiara, Catalano;Michela, Troggio;...
期刊：
TREE GENETICS & GENOMES,2021年17(6):1-12 ISSN：1614-2942
通讯作者：
Gaetano Distefano<&wdkj&>Luca Bianco
作者机构：
[Mario, Di Guardo; Chiara, Catalano; Gaetano, Distefano; Stefano, La Malfa] Department of Agriculture, Food and Environment (Di3A), University of Catania, Catania, Italy;[Marco, Moretto; Mirko, Moser; Michela, Troggio; Alessandro, Cestaro; Luca, Bianco] Research and Innovation Centre, San Michele All’ Adige, Trento, Italy;[Ziniu Deng] College of Horticulture and Landscape, Hunan Agricultural University, Changsha, China;[Marco, Caruso] Research Centre for Olive, Fruit and Citrus Crops, CREA, Acireale, Italy;[Aalessandra, Gentile] Department of Agriculture, Food and Environment (Di3A), University of Catania, Catania, Italy<&wdkj&>College of Horticulture and Landscape, Hunan Agricultural University, Changsha, China
通讯机构：
[Gaetano Distefano] D;[Luca Bianco] R;Department of Agriculture, Food and Environment (Di3A), University of Catania, Catania, Italy<&wdkj&>Research and Innovation Centre, San Michele All’ Adige, Trento, Italy
摘要：
Lemon (Citrus limon (L.) Burm. f.) is an evergreen tree belonging to the genus Citrus. The fruits are particularly prized for the organoleptic and nutraceutical properties of the juice and for the quality of the essential oils in the peel. Herein, we report, for the first time, the release of a high-quality reference genome of the two haplotypes of lemon. The sequencing has been carried out coupling Illumina short reads and Oxford Nanopore data leading to the definition of a primary and an alternative assembly characterized by a genome size of 312.8 Mb and 324.74 Mb respectively, which agree well with an estimated genome size of 312 Mb. The analysis of the transposable element (TE) allowed the identification of 2878 regions on the primary and 2897 on the alternative assembly distributed across the nine chromosomes. Furthermore, an in silico analysis of the microRNA genes was carried out using 246 mature miRNA and the respective pre-miRNA hairpin sequences of Citrus sinensis. Such analysis highlighted a high conservation between the two species with 233 mature miRNAs and 51 pre-miRNA stem-loops aligning with perfect match on the lemon genome. In parallel, total RNA was extracted from fruit, flower, leaf, and root enabling the detection of 35,020 and 34,577 predicted transcripts on primary and alternative assemblies respectively. To further characterize the annotated transcripts based on their function, a gene ontology and a gene orthology analysis with other Citrus and Citrus-related species were carried out. The availability of a reference genome is an important prerequisite both for the setup of high-throughput genotyping analysis and for functional genomic approaches toward the characterization of the genetic determinism of traits of agronomic interest.
作者：
Di Guardo, Mario;Moretto, Marco;Moser, Mirko;Catalano, Chiara;Troggio, Michela;...
期刊：
TREE GENETICS & GENOMES,2021年17(6):1-1 ISSN：1614-2942
通讯作者：
Distefano, Gaetano;Bianco, Luca
作者机构：
[Catalano, Chiara; Distefano, Gaetano; Gentile, Alessandra; Di Guardo, Mario; La Malfa, Stefano] Univ Catania, Dept Agr Food & Environm Di3A, Via Valdisavoia 5, I-95123 Catania, Italy.;[Bianco, Luca; Troggio, Michela; Moretto, Marco; Cestaro, Alessandro; Moser, Mirko] Fdn Edmund Mach, Res & Innovat Ctr, San Michele All Adige, Trento, Italy.;[Deng, Ziniu; Gentile, Alessandra] Hunan Agr Univ, Coll Hort & Landscape, Changsha 410128, Peoples R China.;[Caruso, Marco] CREA, Res Ctr Olive Fruit & Citrus Crops, Corso Savoia 190, I-95024 Acireale, Italy.
通讯机构：
[Distefano, Gaetano] U;[Bianco, Luca] F;Univ Catania, Dept Agr Food & Environm Di3A, Via Valdisavoia 5, I-95123 Catania, Italy.;Fdn Edmund Mach, Res & Innovat Ctr, San Michele All Adige, Trento, Italy.
摘要：
The efficacy of 3-min-dip treatments with 3% sodium carbonate solutions at 20 or 50 degrees C was tested on lemons individually, not hermetically, sealed within low density polyethylene (LDPE) bags. Before sealing, treated lemons were rinsed (SCR) or not rinsed (SC) with fresh water. SC treatment almost completely inhibited green mold (Penicillium digitatum) development in wound-artificially inoculated lemons both wrapped and not wrapped after 15 d at 5 degrees C followed by 7 d at 20 degrees C or in those stored for 10 d at 20 degrees C. In SCR lemons, decay control was inferior, especially in wrapped lemons treated at 20 degrees C. Similar results were achieved with sound fruit inoculated 24 h before the treatments and stored for 30 d at 20 degrees C. SC and, at a less extent, SCR treatments increased dramatically mass loss of un-wrapped fruit compared to control fruit, whereas in wrapped fruit overall mass loss was almost completely inhibited. Wrapping the fruit in LDPE bags allowed to maintained fruit freshness and firmness and chemical quality along the whole storage time, regardless the treatments.
