INVESTIGADORES
PERELLO Analia Edith
artículos
Título:
Fisrt report of Alternaria infectoria on amaranth (Amaranthus caudatus spp mantegazzianus) in Argentina
Autor/es:
NOELTING, C; MOLINA, N; MÓNACO, C; PERELLÓ, A
Revista:
New Diseases Reports
Editorial:
British
Referencias:
Lugar: British Society of Plant Pathology; Año: 2012 vol. 25 p. 11 - 11
ISSN:
2044-0588
Resumen:
Amaranth is an ancient crop originating in the Americas that can be used
as a high-protein grain (12-17%) or as a leafy vegetable, and has potential
as a forage crop (Putnam et al., 1989). Grain amaranth species have been
important in different parts of the world and at different times for several
thousand years (Meyers & Putnam, 1988). At the end of December 2009
the presence of discoloured panicles and seeds of amaranth (Amaranthus
caudatus ssp. mantegazzianus) was recorded at the Instituto Fitotécnico of
Santa Catalina, Llavallol locality, Buenos Aires Province, Argentina. Up
to 100% of the surface area of seeds was affected by the disease (Fig. 1).
Fungal isolates with morphological characteristics similar to those of A.
infectoriawere collected from diseased grains and cultured on potato carrot
agar (PCA) medium, then incubated at 20 ± 2 °C under a light/dark cycle
(12/12 h). After seven days, light grey coloured colonies reaching 35 mm
in diameter were observed. Conidia were formed on the surface of the
agar. The average conidial size on PCA was 32-40 x 9.6 μm with a
conidial beak length of 16-48 μm, and four transverse septa. The presence
of a longitudinal septum was recorded in 18% of the conidia with 2%
having two partitions (Fig. 2). In general, these measurements are within
the size range determined by Simmons (2007) for A. infectoria.
An isolate (CN-2364) was evaluated for its pathogenicity by spraying a
suspension of conidia (1 x 105 spores/ml) on 400 surface-sterilised and
healthy seeds and panicles. Control panicles and seeds were sprayed only
with water. The inoculated panicles and seeds were placed on moistened
cotton and paper in plastic trays (22 x 12 x 8 cm) and incubated in growth
chambers at 20 ± 2 °C with an 8 h photoperiod for seven days. After this
period, discolouration similar to the original symptoms developed on the
inoculated panicles and seeds. In addition, a high proportion of abnormal
seedlings sprouting from the inoculated seeds displayed swollen roots,
folded cotyledons, or stunted roots (Fig. 3). In the case of inoculated
panicles, the entire destruction of the axes was observed. No symptoms
were observed on non-inoculated panicles or seeds. Koch´s postulates
were confirmed by re-isolation of A. infectoria from the infected material.
The culture has been deposited at the La Plata Spegazzini Colección de
Cultivos under accession number 1077. There are previous reports
of Alternaria species(A. alternata and A. chlamydospora) associated with
discolouration of amaranth seeds (Noelting et al., 2009a, 2009b) but to our
knowledge, this is the first documented report of A. infectoria affecting
panicles and seeds of amaranth in Argentina. To the authors' knowledge,
A. infectoria has not been detected in an amaranth crop at other localities.
Alternaria infectoria has been reported on wheat in Argentina (Perelló et
al., 2007). This disease could significantly reduce the production and the
quality of amaranth due to seed transmission and its possible effects on
other plant parts.