LIBRO-CONGRESO-CITRUS

S14P28
Setting up and evaluation of new primer sets for the detection of Spiroplasma citri the causal
agent of citrus stubborn disease
Abdel Fattah A., Valentini F., Frasheri D., D’Onghia A.M., and Djelouah K.
CIHEAM-Mediterranean Agronomic Institute of Bari (CIHEAM-MAIB), Integrated Pest Management, Italy. djelouah@iamb.it
Citrus Stubborn disease caused by Spiroplasma citri is a limiting factor for citrus production in countries with
desert or semi arid conditions in the Mediterranean basin. Several polymerase chain reaction (PCR) assays has
been previously developed but most of them lacked specificity or sensitivity for Spiroplasma citri detection.
In order to develop a PCR assay specific and sensitive for detecting Mediterranean S. citri strains, three PCR
primers were designed using the CLC Genomics Workbench 3.0 software, on the basis of repetitive sequences
annotated “Hypothetical proteins”; a BLAST of the selected genes on the GeneBank showed no homology
with genes of other organisms, spiroplasma plasmids, or known spiroplasma virus sequences. The primer
pairs were annotated as ScX7, ScX8, and ScX9, their sensitivity was evaluated by PCR with serial dilutions of
positive S. citri cultures and DNA extracted from S.citri infected plants, while the specificity was determined
by PCR using the DNA extracted from cultures of other Spiroplasma species. Primer pairs were validated by
comparing them with PCR primer pairs previously designed in other laboratories. The ScX7 (sequence derived
from GenBank accession no. AM285309) was selected and used for further detection and surveys, owing to
its high specificity and sensitivity when compared with all other primers.
S14P29
Biological characterization of a new lemon disease in China
Chen H.M., Li Z.A., Zhou Y., Wang X.F., Tang K.Z., and Zhou C.Y.
Citrus Research Institute, Chinese Academy of Agricultural Sciences (CRIC), National citrus Engineering Research Center, China.
chenhongming_21@163.com
In 2009, a new disease was discovered on Eureka lemon (Citrus limon) in an orchard of the Yunnan province.
Nearly 10% of the plants were infected and showed yellow vein clearing of lateral veins, shrinking, watersoaked,
and boat-shaped leaves. The symptoms were more severe on spring and autumn leaves than
in summer leaves. This disease was transmitted by grafting from infected Eureka lemon to six lemon
(Femminello, Fino, Villafranca, Verna, Kutdiken and Monachello) and two sour orange (Daidai and Morocco)
varieties inducing similar symptoms. Variable symptoms were observed in other hosts ranging from severe
yellowing and vein clearing on Dweet tangor, slight vein clearing on Tongshui 72-1 sweet orange and Marsh
grapefruit, to no symptoms on Etrog citron, Mexican lime and Ponkan seedlings. Eight herbaceous plants
were tested for mechanical transmission of the disease. While Vigna unguiculata and Capsicum frutescens
showed conspicuous symptoms, Lycopersicum esculentum, Nicotiana benthamiana, Momordica charantia,
Solanum melongena, Cucumis sativus and Sesamum indicum remained symptomless. Symptom expression
was influenced by temperature, being intense between 18 and 24ºC but disappearing over 32ºC. Furthermore,
crude extracts from young lemon leaves with yellow vein clearing were examined by transmission electron
microscopy and showed filamentous virus particles measuring 13-15×400-1000 nm. Based on the above
results, this disease is likely to result from Citrus yellow vein clearing virus (CYVCV).
S14P30
Virus and virus-like diseases of citrus in Oman
Al-Sadi A.M. 1 , and Al-Harthi S.A. 2
1 Sultan Qaboos University (SQU), Crop Sciences, Oman; and 2 Royal Court Affairs (RCA), Royal Gardens and Farms, Oman.
alsadi@squ.edu.om
A study was conducted to investigate virus and virus-like diseases of citrus in Oman. A survey over 2009 to
2011 showed that Citrus tristeza virus (CTV), Citrus exocortis viroid (CEVd) and Hop stunt viroid (HSVd) are
common in various regions of the country. These agents were detected in acid lime, sweet orange, sour
orange, grapefruit, lemon and other citrus species. Stem pitting symptoms were found to be common for CTV
XII INTERNATIONAL CITRUS CONGRESS 2012 - 249
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