Identification of Phenotypic and Genotypic Variability among the Isolates of Ramularia areola of Brazilian Cotton 1897
The size of the amplified DNA was around 580 bp.
None of the restriction enzymes was informative. Only
the enzyme Hinf 1 was able to cut the DNA of all the pa-
thotypes in three parts but identical banding pattern was
observed for all the isolates (Figure 5). Lack of differen-
tiation between the isolates in this analysis perhaps indi-
cates that the minor genes for resistance are not involved.
While some isolates differed among each other con-
sidering genotypic and phenotypic reactions, no clear cut
evidence was found about the existence of genetic line-
ages of R. areola in Brazil. It is quite understandable that
genetically similar isolates may differ in their phenotypic
reactions and vice versa. There are some reports in the
literature about the use of molecular techniques to distin-
guish races or pathotypes of fungal and bacterial patho-
gens [9,11]. However, in general, in several other patho-
systems no relationship between phenotypic reaction and
genetic diversity was observed based on DNA sequences
Identification of existence of variability among the
isolates of the pathogen would orient the breeding pro-
cedures to create new cultivars with a broader spectrum
of resistance against this pathogen. Although we tested
only 16 isolates of R. areola, the results would serve as a
basis for future studies in this area. More detailed infor-
mation is required to comprehend the virulence fre-
quency and the existance of the genetic lineages if any,
using a wider range of cultivars and isolates originating
from different cotton growing areas of Brazil. It is possi-
ble that other molecular techniques may also show genetic
differences among the isolates and assist in identification
of distinct genetic lineages of R. areola in Brazil. This
100 bp 12.8 13.2 17.5 22.3 44.1 58.4 63.3
Figure 5. Sample gel showing amplification products of the
Ramularia areola isolates using restriction enzyme Hinf I.
100 bp = Molecular marker; 12.8 through 63.3 randomly
selected isolates of R. areola.
would assist screening cotton germplasm for resistance
against genetic lineages/pathotypes showing perhaps both
phenotypic and genotypic variability. Resistance sources
identified in this way would remain stable for a longer
period of time. Such studies would also assist in estab-
lishing differential set of cotton cultivars to identify field
strains of R. areola in Brazil. This is the first report on
the identification genotypic differentiation among the
Brazilian isolates of R. areola and its relationship with
the virulence spectrum.
Considering the UPGMA cluster analysis formed by
ERIC and REP-PCR, it may be concluded that the 16
isolates of R. areola fell into three major groups belong-
ing to broadly separated geographical regions. While there
existed genotypic and phenotypic variability among the
isolates, so far no clear indication was observed as re-
gards the existence of genetic lineages of R. areola in
Brazil. Results indicate the necessity of using different
isolates for screening the germplasm aimed at creating
new cultivars with broad spectrum resistance.
Genetic seed material of the cotton genotypes was pro-
vided by Camilo de Lelis Morello (Embrapa Algodão
Campina Grande, PB, Brazil) and Paulo H. Aguiar (Fun-
dação MT, Rondonópolis, MT, Brazil). The present re-
search was conducted under the financial support of IMA,
MT, Brazil. Thanks are also due to Bonnie Vieira and
Mariane Vieira for technical assistance.
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