TITLE:
Mycosphaerella areola—The Teleomorph of Ramularia areola of Cotton in Brazil, and Its Epidemiological Significance
AUTHORS:
Yeshwant R. Mehta, Rafael Galbieri, Mariana S. Marangoni, Leandro Camargo Borsato, Heloisa Poliselo Rodrigues, Jéssica Pereira, Angela Mehta
KEYWORDS:
Gossypium hirsutum, Ramularia Leaf Blight, Sexual Morph, ITS rDNA Sequence Analysis
JOURNAL NAME:
American Journal of Plant Sciences,
Vol.7 No.10,
July
22,
2016
ABSTRACT: While Ramularia leaf blight of cotton caused by Ramularia areola is of top most importance for Brazil, information
is lacking regarding the survival mechanism of this pathogen during the cotton-free
period. The teleomorph of R. areola is expected to belong to the genus Mycosphaerella.
In the present study attempts were made to verify occurrence of this teleomorph
in the State of Mato Grosso, Brazil. Decaying cotton leaves were collected two
months after harvest of 2014 from 44 commercial and experimental fields where
aerial fungicidal applications were made or not during the crop cycle to
control the Ramularia leaf blight. Examination of the decaying cotton leaves revealed
presence of abundant sclerotia, spermagonia and ascoma of Mycosphaerella sp. intermingled with each other during the
cotton-free period in most of the leaf samples. Mono-ascospore isolations were
obtained from the ascoma and considering their cultural, morphological, pathological
and DNA sequence analysis they were identified as Mycosphaerella areola. M. areola and R. areola isolates produced similar symptoms under glasshouse
inoculations. Reisolation of the pathogen from the symptoms produced by M. areola isolates yielded R. areola. Some cotton leaves showing
such symptoms were kept on the soil surface on plastic trays for two months
under natural field condition. After this period the decaying leaves showed
abundant perithecia identical to their original M. areola. ITS rDNA sequence analyses revealed identical sequences
from M. areola and R. areola isolates. Occurrence and the
viability of the perfect stage M. areola during the cotton-free period on the left-over stubble from one season to
another were interpreted as the survival mechanism of the pathogen and were considered
responsible for the Ramularia blight epidemics in the State of Mato Grosso.
Disease management practices for the State of Mato Grosso are discussed. This
is the first report about the occurrence of the M. areola in Brazil.