LIBRO-CONGRESO-CITRUS

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infected trees, while bark scaling was found to be common in some citrus cultivars infected by viroids. CTV,
CEVd and HSVd were also detected in 45-79% of citrus seedlings imported from Syria, Lebanon, India, Jordan,
Pakistan and Egypt. This provides evidence for circulation of CTV and citrus viroids via seedlings originating
in these countries. Cloning and sequencing the CP gene of 6 isolates of CTV showed that the isolates have
96-99% identity with representative isolates from other parts of the world. Phylogenetic analysis of the CTV
isolates provided evidence that 4 isolates belong to CTV Group 4. However, 2 isolates formed a clade and were
separated from all other CTV groups with 100% bootstrap support, which suggests that the two isolates from
Oman constitute a new CTV phylogenetic group. Work is in progress to characterize phylogenetic relationship
of citrus viroids from Oman with viroids from other parts of the world.
S14P31
Recent trends in diagnosis, characterization, and management of major virus and virus-like
pathogens infecting citrus in India
Ghosh D.K.
Plant Virology Laboratory, NRC for Citrus, Nagpur (44000), Maharashtra, India. ghoshdk@hotmail.com
The field of citrus virology has expanded in the past couple of decades due to the discovery of various virus
and virus-like pathogens. The economic importance of these pathogens derives largely from their ability
to cause systemic diseases and to persist in vegetative parts of the plants for as long as the trees remain
alive. Hence losses are not confined to the season in which infection occurs, but continue as long as the
infected plants are in culture. In India about sixteen such pathogens are reported to infect citrus plants among
which Citrus tristeza virus (CTV), Indian citrus ringspot virus (ICRSV), Citrus yellow mosaic virus (CiMV), Citrus
exocortis viroid (CEVd) and the Citrus Greening bacterium (HLB) are of major concern. Nagpur mandarin (Citrus
reticulata), acid lime (Citrus aurantifolia) and mosambi (Citrus sinensis) are three important commercial crops
in India and are infected by these pathogens resulting in gradual decline of citrus orchards. These pathogens
can be diagnosed by conventional bio-diagnosis that has its own limitations. Today a multitude of PCR
based techniques, viz. PCR, RT-PCR, IC-PCR, multiplex PCR etc., and protein based diagnosis using pathogen
specific polyclonal and monoclonal antibodies are being used routinely for detection of these pathogens in
citrus plant samples either as single or as mixed infections. Genomes of these pathogens have been cloned,
sequenced and their phylogenetic relationships established. One important component for integrated disease
management is to implement a citrus budwood certification program to provide planting material free from
the major graft transmissible pathogens. Accordingly by using the standardized biological, serological, and
molecular techniques, a citrus budwood certification program has been implemented in India to provide one
million virus free citrus plants annually to the citrus growers.
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The citrus nursery tree certification program in Spain
Pina J.A. 1 , Chomé P. 2 , Vives M.C. 3 , and Navarro L. 3
1 Consellería de Agricultura, Pesca, Alimentación y Agua (CAPAA), Servicio de Sanidad Vegetal, Spain; 2 Ministerio de Agricultura,
Alimentación y Medio Ambiente (MAGRAMA), Oficina Española de Variedades Vegetales, Spain; and 3 Instituto Valenciano de
Investigaciones Agrarias (IVIA), Centro de Protección Vegetal y Biotecnología, Moncada, Valencia, Spain. pina_jos@gva.es
This program includes four blocks of trees: 1) The protected foundation block, that is maintained at IVIA and
includes healthy plants recovered by shoot-tip grafting in vitro (STG) from local or foreign varieties. Plants
are grown in containers inside insect-proof screenhouses. 2) Foundation blocks propagated with budwood
from the protected foundation block and also grown inside screen- or greenhouses. They belong to individual
nurseries or nursery groups. 3) Budwood increase blocks including plants propagated directly from foundation
trees to increase the number of buds for propagation of certified trees. They are also maintained inside
screen- or greenhouses at each nursery. 4) Certified nursery trees are propagated with budwood from the
increase blocks. Certified trees are produced in the open field, in screenhouses or in greenhouses. Plants of
each block are periodically indexed by different methodologies according to the regulations. The program
is operating with this outline since 1979, when the first healthy plants recovered by STG were released to
250 - VALENCIA CONFERENCE CENTER, 18th-23rd NOVEMBER 2012