Changes induced by virus and phytoplasma
in sugarcane leaf cells.
Esther Lilia Peralta’,
Sumac Sinchez’.
infections
Odelsa Ancheta2, Maria Elena Ramos2, Ima-
*Plant Virology Department, National Center for Animal and Plant Health (CENSA),
Apdo 10, San Jose de las Lajas, Havana, Cuba.
*National Center of Scientific Research, CubanacBn, C. de la Havana, Cuba.
Mosaic virus (SCMV, potyvirus), bacilliform virus (SCBV, badnavirus),
Fidji (FDV, phytoreovirus) and grassy shoot (GSD, phytoplasma) are important
diseases of sugarcane with quarantine interest for Cuba.
Ultrathing sections of sugarcane leaves infected by the above mentioned
pathogens were studied by transmission electron microscopy [ 1] for determining disease
associated changes in the host. Comparisons were made with healthy leaf sections.
Modifications of chloroplast structure in mesophyll and vascular
parenchyma cells; presence of virus aggregates and cytoplasm inclusions (Figure 1-A
and 1-B) belonging to subdivision III [2], were the most important changes in SCMV
infected cells.
Typical particles of SCBV were randomly distributed in the cytoplasm,
without arranges or crystal formation. Infected cells showed structural changes in
mitochondria and chloroplasts as well as the formation of perinuclear spaces.
Filamentous inclusions were observed in nucleus (Figure 1-C) that can be considered as
an evidence of virus replication site. Additional alterations, such as increase of
ribosomes and P plastids number and changes in the cytoplasm appearance, were also
present.
FDV typical particles were found mostly in abnormal gall cells. They were
observed disperse in the cytoplasm; grouped and organised but not as a perfect crystal
structure; in the vacuoles, vesicles or phagocytes structures and in tubules or channels.
Viroplasmas were seen in xylema and phloema gall cells, with not mature virus particles
at the interior of it and mature ones at the periphery of viroplasmas. Nucleus of infected
cells were deformed and lost or degeneration of organelles were also evidenced.
Increase of P plastid number and virus association with endoplasm reticule,
mitochondria and Golgi complex were additionally observed in cell of the mature galls.
Phloem cells of GSD infected leaves contained numerous phytoplasma type
structures with variable size and morphology. Different reproduction forms of these
organisms as well as their pass through plasmodesmata (Figure l-D), as an evidence of
their movement from cell to cell were observed. Lost or degeneration of chloroplasts
(Figure 1-E and 1-F) as well as severe modifications in nuclear organisation were the
most important effects associated to this disease.
Most of the observed cell effects can be related with typical external
symptoms of these diseases as well as with some of the most important metabolic
changes they induced in the host.
References
1. Ancheta,Odelsa;Ramos,Maria E.; de la Rosa, Maria C. and Rodriguez, Sandra.,
Biotecnologiu
Aplicada, 13 (1996): 195-196.
2. Edwarson, J.R.; Christie, D.E.; Purcifbll, D.E. and Petersen, A. In Diagnosis of plant virus disease.
CRC. Press. Inc. Florida (1993):101-126.
Fig. 1, Changes associated with virus and phytoplasma infections in sugarcane leaf cells. (A)Pinwheel
and (B) lamim aggregates induced by sugarcane mosaic potyvbus (x 20 000 and 15 000). (C) Nuclear
filamentous inclusion in cells infected by sugarcane bacilliform badnavims (x 10 000). (D) Phytoplasma
particles in phloem cells of sugarcane leaves infected by grassy shoot disease. Note their pass through
plasmodesmata. (x 5 000). (E) C3 and C4 chloroplasts in healthy sugarcane leaf (control) (x 10 000 and 8
000) and in GSD infected one (F) (x 8 000).