International effort toward a SSR-based linkage map for C. clementina : [P128]

Following the difficulties encountered for assembling a 1.2 x sequencing of the highly heterozygous sweet orange genome, the International Citrus Genomic Consortium (ICOC) decided to estab1ish the first reference sequence of a whole nuclear citrus genome from a haploid Clementine. A saturated genetic linkage map of Clementine based on sequence-characterized markers was considered by the ICGC as an important too1 for genome sequence assemb1y. In this framework, CIRAD proposed to use an interspecific population C. maxima x C. clementina to implement the reference Clementine genetic map. A population of 250 hybrids of Chandler pummelo x Clementine was established in Corsica and 190 hybrids were used in this first phase of mapping. Collaboration was established between two French organizations (CIRAD and INRA), two groups from United States (UF-CREC and UCR), one Spanish institute (IVIA), INRA Morocco and Cukurova University from Turkey. Forty markers were found heterozygous in Clementine among a previous set of 90 SSR markers developed by CIRAD from microsatellite-enriched genomic libraries. With the objective to integrate the physical and genetic maps of Clementine, CIRAD and IVIA have developed new SSR markers from microsatellite sequences identified in BAC End Sequences (BES) of diploid Clementine. On hundred and 10 of these new markers were found heterozygous for Clementine or Chandler pummelo and were used for genotyping. INRA France deve1oped 500 SSR markers from ESTs databases and found 170 markers heterozygous for Clementine. INRA Morocco contributed to the genotyping of 112 SSR markers developed from EST databases and genomic libraries, while 50 ESTs SSR were analysed by Cukurova University. SSR markers mainly developed from EST databases and already mapped for sweet orange were genotyped by UF-CREC (70 markers) and UCR (60 markers) to allow comparisons among the C. sinensis. C. maxima and C. c1ementina maps. lndeed, taking advantage of the important allelic differentiation between Clementine and Chandler, two parallel linkage maps can be developed from this population. As perspective, in the framework of the global haploid Clementine sequencing project, a collaboration between the French and Spanish groups plans: (i) to extend the population size to 380 hybrids between Clementine and pummelo. and (ii) to develop an array from SNPs identified in Clementine BES for High- Throughput Genotyping. All genotyping data will be stored in the online TropGene database (http://tropgenedb.cirad.fr/). Additional international groups are very welcome to join the project, using these progenies for genotyping their own markers. This should contribute to a very high density map of Clementine and to comparative mapping studies between citrus species. (Texte intégral

Comparison of photosynthesis and antioxidant performance of several Citrus and Fortunella species under natural chilling stress : S08P24

Citrus plants originate from southeastern Asia, in a large area with various climates characterized by a broad range of temperatures. Temperature is assumed to be a key factor in Citrus species adaptation and diversification. In a field experiment, the tolerance of the three fundamental Citrus species (C. medica -citron-, C. reticulata -mandarin- and C. maxima -pummelo-) and Fortunella japonica -kumquat- to photooxidative stress caused by seasonal climatic changes was evaluated on adult trees by measuring net photosynthesis (Pnet), stomatal conductance (Gs), maximum photosynthesis (Pmax) and chlorophyll fluorescence (Fv/Fm). In addition, seasonal changes in oxidative status, antioxidant enzymes and antioxidant metabolites were monitored. Mandarin and pummelo appeared to be the most tolerant, showing the lowest down-regulation of photosynthetic parameters, and the lowest accumulation of oxidized compounds associated with efficiency of their antioxidant system. Kumquat showed intermediate behaviour, with a large diminution of photosynthetic parameters and marked accumulation of hydrogen peroxide, whereas the malondialdehyde content remained low, with a strong induction of glutathione synthesis. Finally, citron appeared to be the most sensitive genotype with a marked decrease in photosynthetic performance, the largest accumulation of oxidative parameters, insufficient induction of antioxidant enzymes and down-regulation of ascorbate and glutathione synthesis. (Texte integral

Pemupukan Npk dan Kelayakan USAhatani Jeruk Pamelo di Kabupaten Pangkep Sulawesi Selatan

The Fertilizing of NPK and the Feasibility of Pummelo's Farming in Pangkep Regency, South Sulawesi. Pummelo Pangkep has more advantages over other citrus, such as, specific taste, sweet juicy, pink flesh, fair texture flesh, flavorful soft and almost no seeds. The purpose of this study was to (i) know the influence of fertilizers N, P and K in the production of pummelo; (ii) produce pummelo fertilizer recommendations based on the analysis of leaf tissue and define the nutrient adequacy levels and optimal dosage of pummelo; and (iii) analyze the feasibility of pummelo. Research was arranged in a randomized block design (RBD) with five treatments consisting of six replicates for each treatment. Each fertilizer (N, P and K) by 90 productive lifespan of pummelo trees less than 7 years old are selected with a relative uniform and healthy level. The treatment for N fertilizer dosage consists of: N= 0, 100, 200, 300, 400; P= 0, 100, 200, 300, 400 P2O5; K= 0, 150, 300, 450, 600 K2O/tree/year. Each of fertilizer application was conducted in a single study, respectively. The results showed that pummelo recommended fertilizing of N, P and K in low nutrient status, namely: 475.30 g N, 582.24 g P2O5 and 495.75 g K2O/tree/year or equal to 1.03 kg urea, 1.62 kg SP-36 and 0.83 KCl kg/tree/year. Based on the calculation of cost, revenue, and profit with 20% of discount factor, it was obtained B/C value of 3.9, NVP with positive value and IRR value that exceeds the standard of DF. It means that pummelo farming system is profitable and feasible for investment

Sequencing of diverse mandarin, pummelo and orange genomes reveals complex history of admixture during citrus domestication

Cultivated citrus are selections from, or hybrids of, wild progenitor species whose identities and contributions to citrus domestication remain controversial. Here we sequence and compare citrus genomes-a high-quality reference haploid clementine genome and mandarin, pummelo, sweet-orange and sour-orange genomes-and show that cultivated types derive from two progenitor species. Although cultivated pummelos represent selections from one progenitor species, Citrus maxima, cultivated mandarins are introgressions of C. maxima into the ancestral mandarin species Citrus reticulata. The most widely cultivated citrus, sweet orange, is the offspring of previously admixed individuals, but sour orange is an F1 hybrid of pure C. maxima and C. reticulata parents, thus implying that wild mandarins were part of the early breeding germplasm. A Chinese wild 'mandarin' diverges substantially from C. reticulata, thus suggesting the possibility of other unrecognized wild citrus species. Understanding citrus phylogeny through genome analysis clarifies taxonomic relationships and facilitates sequence-directed genetic improvement. (Résumé d'auteur

Plant Regeneration of Pummelo CV. Cikoneng From Cotyledon and Epicotyl

In vitro conservation needs highly efficient micropropagation protocol. The objective of the research was to obtain an efficient and reproducible protocol for pummelo (Citrus maxima(Burm.) Merr.) micropropagation through direct shoot formation. The experiment was arranged in a completely randomized design with two factors and 20 replications. The 1stfactor was type of explant, i.e. cotyledon and epicotyl segments of Pummelo cv. Cikoneng, while the 2ndfactor was the media composition as follow (1) MS + 1.0 mg BAP L-1 + 0.5 mg Kinetin L-1 + 0.5 mg NAA L-1; (2) MS + 2.0 mg BAP L-1 + 0.5 mg Kinetin L-1 + 0.5 mg NAA L-1; (3) MS + 1.0 mg BAP L-1 + 1.0 mg Kinetin L-1 + 0.5 mg NAA L-1; (4) MS + 2.0 mg BAP L-1 + 0.5 mg Kinetin L-1+ 1.0 mg NAA L-1; (5) MS + 2.0 mg BAP L-1+ 1.0 mg Kinetin L-1 + 1.0 mg NAA L-1. Observation was conducted on days to shoot induction, number of explant forming shoots, shoot height, number of shoots, leaves, and roots. The results showed that adventitious shoots emerged from callus in epicotyl (6-8 WAP), but adventitious shoots could emerge directly without an intervening callus phase from cotyledon (4-5 WAP). Shoots emerged from epicotyl were weak and vitrous due to hyperhydricity, thus they can not be used for micropropagation. Cotyledons cultured in media MS + 1.0 mg BAP L-1 + 0.5 mg Kinetin L-1 + 0.5 mg NAA L-1or media MS + 1.0 mg BAP L-1 + 1.0 mg Kinetin L-1 + 0.5 mg NAA L-1gave the highest percentage of explant forming adventitious shoot (38.8 and 26.3%), highest efficiency of shoot formation (62.5 dan 72.5%), and highest numbers of leaves (value of 1.9 leaves shoot-1) and roots (1.1 roots shoot-1) compared to other media. Since shoot height and number of leaves and root were not significantly different in both media, thus cotyledon and media MS + 1.0 mg BAP L-1 + 0.5 mg Kinetin L-1+ 0.5 mg NAA L-1which was less in Kinetin is suggested to be used for pummelo micropropagation

Karakter Morfologi dan Kimia Kultivar Pamelo (Citrus Maxima (Burm.) Merr.) Berbiji dan tanpa Biji

The objective of this study was to evaluate morphological and chemical characteristics of seeded and seedless pummelofruit. The study was carried out during April 2009 to July 2010. The pummelo fruits were harvested from the productioncenter of Sumedang, Pati, Kudus, Magetan, Bireun (Aceh) and Pangkep (South Sulawesi). Some of seeded cultivars havespherical and ellipsoid form, while the seedless one shown pyriform shape. The edible portion of the fruits (juice vesicles)mainly affected by peel thickness and fruit shape. The edible portion of seedless cultivars (57.22%) were not sigificantlydifferent with seeded (57.07%) and potentially seedless cultivars (59.35%). Generally fruit taste of seedless cultivars weresweet to sweet-bitter, meanwhile seeded and potentially seedless pummelo cultivars have sour-sweet. Pummelo juice tastewas affected by TSS (total soluble solids), TA (titratable acidity), TSS/TA ratio and naringin content. Seedless pummelocultivars have higher pH, TSS, TSS/TA ratio, vitamin C and naringin, but lower in TA content than seeded and potentiallyseedless fruit juice. ‘Jawa 1' and ‘Bali Merah 2' pummelos can be further developed as seedless superior cultivars

Physiological analysis of salt stress behaviour of citrus species and genera: low chloride accumulation as an indicator of salt tolerance : S08O07

Tolerant citrus rootstocks are defined as Cl- excluders. However, little is known about the salt tolerance of cultivars used as scions, particularly the tolerance of monoembryonic citrus genotypes. To enhance the genetic resources for generating improved hybrid rootstocks, the evaluation of large samples of citrus species, including both monoembryonic and polyembryonic genotypes, is necessary. In this study, 12 citrus genotypes representing the major Citrus species and all the three genera of the Rutaceae family were subjected to moderate salt stress (75mM) for 12 weeks to characterise their physiological response to salt stress. Various symptoms and physiological parameters were evaluated to characterise their salt sensitivity. These included plant growth (stem diameter), leaf chlorophyll content, leaf flavonoid content, maximum quantum yield of PSII [(Fm-F0)/Fm)], net photosynthesis, stomatal conductance and leaf Na and Cl- contents. The results clearly demonstrated that the most salt sensitive genotypes accumulated high concentrations of Na and Cl- and maintained a fair growth and photosynthetic rate. By contrast, salt-tolerant genotypes accumulated less Na and Cl- and decreased their growth and gas exchange. 'Poncire commun' citron and 'Marumi' kumquat were the most sensitive species, while mandarins, pummelo and 'Australian' sour orange were the most tolerant species. Among the genotypes, 'Engedi' pummelo presented a specific trait for salt tolerance that has not been previously reported. Taken together, the results suggest that low leaf chloride content can be used as an indicator of salt stress tolerance in citrus genotypes. Exploitation of this indicator will enable the improved evaluation of citrus genetic resources and should lead to the identification of new sources of tolerance for rootstock breeding. (Texte intégral

Maximum parsimony based resolution of inter-species phylogenetic relationships in citrus l. (Rutaceae) using its of rDNA

The present study aims to analyse phylogenetic relationships, using internal transcribed spacer sequence data of ribosomal DNA (rDNA), across 24 Citrus species and close relatives by the evaluation of several parameters such as nucleotide substitution (r), nucleotide diversity (π) and the estimated values of transition/transversion bias (R). The observed results indicated the presence of a wide divergence pattern of rDNA in subfamily Aurantioideae. Maximum parsimony (MP) analysis inferred divergence pattern in the Citrus genus. We observed seven strongly supported clades among the subfamily Aurantioideae. We postulate that the present investigation provides a more robust topology of Citrus and its close relatives, which can significantly prove as an additional support to resolve the phylogenetic relationships in Citrus genera. Therefore, sequences of noncoding regions should exhibit more phylogenetically informative sites than the coding regions do, which is in accordance with the present study