LIBRO-CONGRESO-CITRUS

citrus, somatic embryogenesis is an efficient method of plant regeneration and embryogenic callus is valuable
for propagation as well as for genetic improvement. Anther culture, among the in vitro regeneration systems,
is a widespread method to produce haploids (Hs) and doubled-haploids (DHs), drastically reducing the time
needed to produce homozygous lines compared to conventional breeding methods, that include several
generations of self-pollination. In addition, in vitro anther culture is also utilized to obtain somatic embryos
and clonal plant propagation in many woody plants. Actually, in vitro anther culture is, in citrus, an efficient
approach to obtain both gametic and somatic embryogenesis. In this study, anther culture has been applied
to several citrus genotypes: four cultivars of C. sinensis and two of C. clementina, testing two temperature
shocks. The strong influence of the genotype on the response of anthers in vitro cultured has been confirmed.
Actually, the same treatments applied to the explants in culture resulted in the production of gametic
embryos in clementines and of somatic embryos in sweet oranges. Clementine confirmed its tendency to
regenerate homozygous and tri-haploids embryos and plantlets. Further studies should be performed, in
other citrus genotypes aimed to obtain in vitro regeneration procedures, suitable for different applications,
as new opportunities for genetic improvement and for the innovation in propagation methods.
S05O11
Bioethanol production from mandarin (Citrus unshiu) peel waste
Choi I.S. 1 , Wi S.G. 1 , and Bae H.J. 2
1 Bioenergy research center (BRC), Department of Wood Science and Landscape Architecture, Chonnam National University, South
Korea; and 2 Bioenergy resecenter (BRC), Department of Bioenergy Science and Technology, Chonnam National University, South
Korea. is.troy@hotmail.com
Mandarin peel waste (MP), waste biomass recovered after juice extraction, is the main mandarin juice process
waste. In this study, MP was studied for the potential to produce bioethanol. We designed a new popping
pretreatment method to produce ethanol from MP. Popping pretreatment was performed at 150°C for 10 min
without chemical treatment. Popping pretreatment reduced the size of MP particles to less than 1 mm and
decreased the concentration of D-limonene, a yeast fermentation inhibitor, from 0.21% to 0.01%. Enzymatic
hydrolysis of pretreated MP was performed in sodium acetate buffer (50 mM and pH 4.8) at 45°C for 6 h,
and the total saccharification rate was approximately 95.6%. The vacuum evaporation process increased the
fermentable sugar concentration to 10%. Subsequent fermentation at 30°C at pH 5.0 for 12 h in a laboratory
bioreactor increased the ethanol yield to 90.6%, compared to 78% at 36 h from raw MP.
S05P01
Screening and analyzing the root-specific genes of Poncirus trifoliata
Yao L.X., Chen S.C., He Y.R., Lei T.G., Xu L.Z., Liu X.F., and Peng A.H.
Citrus Research Institute, Chinese Acadamy of Agricultural Science (CRIC), China. syaolixiao@126.com
Poncirus trifoliata is a close relative of citrus species and has been widely used as a rootstock for citrus
production in China. To isolate root-specific genes from this good genetic source, a root cDNA library of P.
trifoliata was constructed by polymerase chain reaction (PCR)-based suppressive subtractive hybridization
(SSH). The cDNA of seedling roots was used as a tester and cDNA of leaves was used as a driver. A total of 1362
randomly picked clones were sequenced, and 1177 sequences with over 100 base pairs were obtained. The
majority of these expressed sequence tags (ESTs) showed sequence homology to previously identified genes
in GenBank, which came from Citrus sinensis (34.5%), Populus trichocarpa (19.1%), Ricinus communis (16.2%)
and Vitis vinifera (12.2%). The ESTs with gene ontology took part in biology processes such as metabolic process
(29.8%), cellular process (19.8%), biological regulation (9.8%), developmental process (8.6%), and response
to stimulus (8.4%), with the biological function of binding (42.1%), catalytic activity (36.6%), transcription
(8.6%), transporter activity (5.1%) and so on. Through clusting the ESTs with DNAstar software, 455 unigenes
were accepted, including 121 contigs and 334 singlets. 53 unigenes were selected and analyzed by real time
RT-PCR. Singlet 52, contig 56, singlet 297, contig 22, singlet 86, contig 28, and singlet 283 showed significantly
higher expression in roots than in leaves. As well, the full-length cDNA sequences and DNA sequences of
these genes were obtained by RT-PCR and PCR. Singlet 52 and contig 56 belong to cytochrome P450 family,
and were named as CYP88A36 and CYP88A37, respectively by Cytochrome P450 Nomenclature Committee.
Singleton 297, contig 22, and singleton 86 belong to bet_v_I protein family.
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