Abstract
Genotypic and phenotypic variation among 16 isolates of Ramularia areola of Gossypium hirsutum collected from five different geographical regions of Brazil was studied through virulence spectrum on three cultivars in the glasshouse and through ERIC- and REP-PCR and ITS1-5.8S-ITS2 rDNA analysis. Difference in virulence spectrum and molecular analysis of some isolates was observed. ERIC- and REP-PCR showed similar results and revealed a high level of diversity among the isolates. A unique profile for both ERIC and REP was obtained for most isolates. On the other hand, the ITS rDNA analysis did not show different PCR-RFLP patterns. While some isolates differed among each other considering genotypic and phenotypic reactions, no clear cut evidence was found about the existence of genetic lineages of R. areola in Brazil. Identification of genetic variability among the R. areola isolates originated from different geographic regions would permit screening of Brazilian germplasm and achieve sources with a wide spectrum of resistance. This is the first report of the genotypic and phenotypic variability among the R. areola isolates originated from five cotton growing regions of Brazil.
Highlights
Leaf blight of cotton caused by Ramularia areola is economically important especially for Brazil, causing heavy yield losses [1,2,3,4]
Genotypic and phenotypic variation among 16 isolates of Ramularia areola of Gossypium hirsutum collected from five different geographical regions of Brazil was studied through virulence spectrum on three cultivars in the glasshouse and through Enterobacterial Repetitive Intergenetic Consensus (ERIC)- and Repetitive Extragenic Palindromic Sequence (REP)-PCR and ITS1-5.8S-ITS2 rDNA analysis
This is the first report of the genotypic and phenotypic variability among the R. areola isolates originated from five cotton growing regions of Brazil
Summary
Leaf blight of cotton caused by Ramularia areola is economically important especially for Brazil, causing heavy yield losses [1,2,3,4]. In Brazil, some years ago it was considered as a secondary and late season disease, in recent years the disease is of principal concern especially because it attacks cotton during the entire crop cycle. In the Cerrado region of Brazil the yield losses caused by this disease are estimated to be around 30% but in severe cases they can be up to 75% in the State of Mato Grosso [1,2,4]. At present the disease is partially controlled in Brazil by 5 - 8 applications of fungicides thereby adding to the cost of cultivation and at the same time making the intensive use of fungicides almost unsustainable in the course of time. Resistance of some genotypes was detected under field conditions but their resistance was not found to be consistent presumably because of the genetic variability among the patho-
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