March 24, 2006
From: ProMED-mail<promed@promedmail.org>
In this posting:
[1] Chili pepper - India: 1st Report
[2] Pigeon pea - India: 1st Report
[1] Chili pepper - India: First Report
Date: 24 Mar 2006
From: ProMED-mail <promed@promedmail.org>
Source: British Society for Plant Pathology, New Disease
Reports, Vol. 13 [edited] <http://www.bspp.org.uk/ndr/july2006/2006-18.asp>
M.S. Khan and S.K. Raj*, Molecular Virology, National Botanical
Research Institute, Lucknow-2260 01, India *<skraj2@rediffmail.com>
Accepted for publication 20 Mar 2006
Chilli (_Capsicum annuum_; family _Solanaceae_) is an important
spice crop, being cultivated over large areas in Asia, Africa,
South and Central America, parts of USA and Southern Europe.
India is the largest chilli
producer in the world, producing 1.2 million tonnes of dry
chilli, from an area of about 880 000 hectares. During the
winter of 2004, a severe phytoplasma-like disease of chilli was
noticed in the Bahraich district of Uttar Pradesh with a low
incidence (ca. 5 percent of plots showed some infection). The
symptom of the disease consisted of shortening of leaves,
petioles & internodes and crowding of leaves and stunting of
whole plant (Fig. 1).
Figure 1: Diseased chilli plant showing phytoplasma-like
symptoms
[<http://www.bspp.org.uk/ndr/july2006/2006-18-1th.jpg>
- Mod.JAD]
For molecular detection of the causal pathogen, the total DNA of
plant samples with or without symptoms was isolated using the
protocol of Ahrens & Seemüller, 1992. Direct PCR was carried out
using the universal 16S
rDNA-specific primers P1/P6 (Deng & Hiruki, 1991), which
resulted in the production of a approx. 1.5-kb product from
diseased samples but not symptomless ones. Nested-PCR was
further performed with primers R16F2n/R16R2 (Gundersen & Lee,
1996) which gave an amplicon of the expected size approx. 1.2 kb
DNA. This product was cloned, sequenced and the data deposited
in Genbank (Accession DQ343288). A blast search revealed the
highest level of sequence identities (98 percent) with 16SrI
Aster yellows group members, such as Barley deformation
phytoplasma (AY734453), Aster yellows phytoplasma (AY665676),
Valeriana yellows phytoplasma (AY102274), Onion yellows
phytoplasma (AP006628) and Silene virescence phytoplasma
(AY744070).
Previously a phytoplasma associated with chilli little leaf
disease has been detected in India by graft transmission and
electron microscopy (Singh & Singh 2000), but the causal
pathogen was not characterised at the molecular level. To our
knowledge, this is the first report of molecular detection of an
isolate of Aster yellows phytoplasma (_Candidatus Phytoplasma
asteri_) infecting chilli in India.
References
Ahrens U, Seemueller E, 1992. Detection of DNA of plant
pathogenic mycoplasma like organism by a polymerase chain
reaction that amplifies a sequence of the 16S rRNA gene.
Phytopathology 82, 828-832.
Deng S, Hiruki D, 1991. Amplification of 16S rRNA genes from
culturable and nonculturable mollicutes. Journal of
Microbiological Methods 14, 53-61.
Gundersen DE, Lee IM, 1996. Ultrasensitive detection of
phytoplasmas by nested-PCR assays using two universal primer
pairs. Phytopathologia Mediterranea 35, 144-151.
Singh D, Singh SJ, 2000. Chilli little leaf - a new phytoplasma
disease in India. Indian Phytopathology 53, 309-310 [Map:
Bahraich district of Uttar Pradesh, India <http://www.maplandia.com/india/uttar-pradesh/bahraich/>
-Mod.JAD]
[2] Aster yellows phytoplasma, pigeon pea -
India: 1st Report
Date: 24 Mar 2006
From: ProMED-mail <promed@promedmail.org>
Source: British Society for Plant Pathology, New Disease
Reports, Vol. 13 [edited]
<http://www.bspp.org.uk/ndr/july2006/2006-15.asp>
S.K. Raj1*, M.S. Khan1, S.K. Snehi1, S. Srivastava2 and H.B.
Singh2, 1
Molecular Virology and 2 Plant Pathology, National Botanical
Research Institute, Rana Pratap Marg, Lucknow-226001, U.P.,
India
*<skraj2@rediffmail.com>
Accepted for publication 7 Mar 2006
Pigeon pea (_Cajanus cajan_; family Fabaceae) is a protein-rich
pulse crop, cultivated for its nutritive value. India
contributes over 80 percent of world production and 77.5 percent
of the global hectarage (Ahlawat et al.,
2005). Pigeon pea plants growing in an experimental field at
NBRI, Lucknow in 2005 were found with typical phytoplasma
symptoms that included little leaves, shortening of internodes
and petioles giving a bunchy appearance and whole plant
stunting.
Figure 1: Symptoms of little leaf disease on pigeon pea (left &
right), with an uninfected plant (centre)
[<http://www.bspp.org.uk/ndr/july2006/2006-15-1a.jpg>
<http://www.bspp.org.uk/ndr/july2006/2006-15-1b.jpg>
<http://www.bspp.org.uk/ndr/july2006/2006-15-1cth.jpg>
- Mod.JAD]
DNA was extracted from infected leaves (0.5 g) and used in a
simple PCR with phytoplasma 16S rDNA primers P1/P6 (Deng &
Hiruki, 1991). This resulted in the production of a band of
approximately 1.5 kb, from all 3
samples with symptoms but not from an apparently healthy sample.
The PCR products were used as templates in a nested PCR using
primers R16F2n/R16R2 (Gundersen & Lee, 1996) giving a product of
around 1.2 kb. This amplicon was cloned, sequenced, with the
sequence deposited in Genbank (Accession No. DQ343287). Blast
analysis showed the highest (99 percent) similarities with Ash
witches'-broom (AY566302), Hydrangea phyllody (AY265219), Maize
bushy stunt (AY265208), Epilobium phyllody (AY101386) and Onion
yellows (AP006628); all members of the 16SrI Candidatus
phytoplasma asteris group (IRPCM Phytoplasma/Spiroplasma Working
Team-Phytoplasma taxonomy group, 2004). The isolate did not
share any similarity with members of the phytoplasma 16SrIX
(Pigeon pea witches'-broom) gro! up. This is the first record of
pigeon pea little leaf disease in India and
the first report of an isolate of '_Candidatus Phytoplasma
asteris_' infection of pigeon pea.
References
Ahlawat IPS, Gangaiah B, Singh IP, 2005. Pigeon pea (Cajanus
cajan) research in India - an overview. Indian Journal of
Agricultural Sciences 75, 309-320.
Deng S, Hiruki D, 1991. Amplification of 16S rRNA genes from
culturable and nonculturable mollicutes. Journal of
Microbiological Methods 14, 53-61.
Gundersen-Rindal DE, Lee IM, 1996. Ultrasensitive detection of
phytoplasmas by nested-PCR assays using two universal primer
pairs. Phytopathologia Mediterranea 35,144-151.
IRPCM Phytoplasma/Spiroplasma Working Team-Phytoplasma taxonomy
group, 2004. Candidatus Phytoplasma, a taxon for the wall-less,
non-helical prokaryotes that colonize plant phloem and insects.
International Journal
of Systematic and Evolutionary Microbiology 54, 1243-1255.
[Map: Lucknow, India
<http://www.tageo.com/index-e-in-v-36-d-m2919422.htm>
- Mod.JAD]
--
ProMED-mail
<promed@promedmail.org>
[The crop plants pigeon pea (_Cajanus cajan_) and chili pepper
(_Capsicum annuum_) in Uttar Pradesh, India are shown here to be
afflicted with symptoms attributed to Phytoplasma diseases of
plants. Symptoms in both
hosts included shortening of internodes and petioles giving a
bunchy or crowded appearance and whole plant stunting. The
pathogen in India causing these 2 infections has been shown for
the 1st time to be the aster yellows Phytoplasma (_Candidatus
Phytoplasma asteri_). The 2 hosts examined by this laboratory
are not frequently mentioned in articles on aster yellows
Phytoplasma, making these noteworthy reports. There are over 70
posts in ProMED-mail archives for the search term Phytoplasma,
and the ones listed in "see also:" contain reference to the
aster yellows Phytoplasma.
Phytoplasmas are a group of prokaryotic, microscopic plant
pathogens that cause over 700 diseases of food, fiber and
ornamental plants. They are found mainly in the phloem sieve
tubes of their plant hosts and in certain
sucking insects, which can act as vectors. These included
leafhoppers (aster yellows Phytoplasma vector), planthoppers and
psyllids. They can also be spread by grafting, by parasitic
plants or by seed transmission.
Detection of phytoplasmas is by grafting to susceptible host
plants, microscopy, serology (ELISA), nucleic acid hybridization
or DNA amplification using the polymerase chain reaction (PCR).
Symptoms displayed by plants infected with phytoplasmas include
foliage yellowing, petal greening, shoot proliferation,
stunting, little leaf formation, necrosis and a decline of vigor
leading to death.
Links:
<http://plantpathology.tamu.edu/Texlab/Multicrop/asteryellows.html>
<http://www.agr.gov.sk.ca/DOCS/crops/integrated_pest_management/disease/asteryellows01.asp>
- Mod.JAD]
[see also in the
archive:
Phytoplasma, new, potato - USA: 1st report 20060223.0585
2005
----
Barley phytoplasma - Lithuania: 1st report 20050318.0782
2004
----
Big bud disease, potato - Bolivia 20041127.3174
Parsley leaf disease, tomato - Bolivia: 1st report 20041126.3167
Aster yellows phytoplasma, grapevine - Tunisia 20040512.1280
Potato purple top disease - USA (WA, OR) 20040415.1041
Grapevine yellows phytoplasmas, new data, EPPO 20040104.0037
2003
----
Elm yellows phytoplasma, grapevine - Serbia 20030523.1261
2002
----
Phytoplasma, oat - Lithuania 20020516.4224
2000
----
Lime witches' broom phytoplasma - India 20000125.0129]
