Articles
PHYTOPLASMA INFECTION IN ASCLEPIAS PHYSOCARPA
Article number
722_44
Pages
349 – 354
Language
English
Abstract
Asclepias physocarpa (sin. Gomphocarpus physocarpus; Asclepiadaceae) is a
perennial ornamental plant, mainly distributed in tropical and subtropical areas and
it is reported to be infected by a few viruses, such as tobacco streak and tomato
spotted wilt viruses.
In August 2002, plants one and two years old showing severe stunting,
associated with rosette-like symptoms were observed; in other plants symptoms of
yellows and vein yellowing were also present.
High percentages (up to 30-40%) of
diseased plants were present in many fields in Imperia area (Liguria, North-Western
Italy). Mechanical inoculations on herbaceous plants, leaf-dip preparations for
electron microscopy, and DAS-ELISA tests gave negative results for virus presence.
Molecular analyses (PCR/RFLP) were performed on nucleic acid extracted from
phloem tissue collected from symptomatic and asymptomatic plants in November,
and provided evidence of phytoplasma presence in the majority of samples
examined.
RFLP on 16S ribosomal gene indicated that 16SrI-B (aster yellows),
sometimes in mixed infection with 16SrXII-A (stolbur) phytoplasmas, and 16SrIII-B
(clover yellow edge) phytoplasmas were present in symptomatic material; in
asymptomatic plants stolbur phytoplasmas were identified.
This disease is seriously affecting A. physocarpa cultivations and it is likely
that the plants become infected during cultivation cycles since leafhopper presence
was quite spread in all the fields examined.
It was not possible to attribute a certain
phytoplasma or mixture of phytoplasmas to the different symptoms observed, except
for stolbur phytoplasmas detected in single infection only in asymptomatic plants.
Probably, the type of symptoms could be influenced by the plant stage at the
moment of infection: i.e., infected young plants show stunting and rosetting, while
those infected at older stages (2 years) only react with yellows to the presence of the
same pathogen/s.
perennial ornamental plant, mainly distributed in tropical and subtropical areas and
it is reported to be infected by a few viruses, such as tobacco streak and tomato
spotted wilt viruses.
In August 2002, plants one and two years old showing severe stunting,
associated with rosette-like symptoms were observed; in other plants symptoms of
yellows and vein yellowing were also present.
High percentages (up to 30-40%) of
diseased plants were present in many fields in Imperia area (Liguria, North-Western
Italy). Mechanical inoculations on herbaceous plants, leaf-dip preparations for
electron microscopy, and DAS-ELISA tests gave negative results for virus presence.
Molecular analyses (PCR/RFLP) were performed on nucleic acid extracted from
phloem tissue collected from symptomatic and asymptomatic plants in November,
and provided evidence of phytoplasma presence in the majority of samples
examined.
RFLP on 16S ribosomal gene indicated that 16SrI-B (aster yellows),
sometimes in mixed infection with 16SrXII-A (stolbur) phytoplasmas, and 16SrIII-B
(clover yellow edge) phytoplasmas were present in symptomatic material; in
asymptomatic plants stolbur phytoplasmas were identified.
This disease is seriously affecting A. physocarpa cultivations and it is likely
that the plants become infected during cultivation cycles since leafhopper presence
was quite spread in all the fields examined.
It was not possible to attribute a certain
phytoplasma or mixture of phytoplasmas to the different symptoms observed, except
for stolbur phytoplasmas detected in single infection only in asymptomatic plants.
Probably, the type of symptoms could be influenced by the plant stage at the
moment of infection: i.e., infected young plants show stunting and rosetting, while
those infected at older stages (2 years) only react with yellows to the presence of the
same pathogen/s.
Authors
A. Bertaccini, M.G. Bellardi, S. Botti, S. Paltrinieri, P. Restuccia
Keywords
Asclepias physocarpa, stunting, yellows, PCR, RFLP
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