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First report on the occurrence of Cladosporium fulvum strains in Cuba that can overcome the Cf- 9 resistance gene

Primer informe sobre la presencia en Cuba de cepas de Cladosporium fulvum que pueden vencer el gen de resistencia Cf- 9

Dear editor:

Leaf mould of tomato, caused by the fungus Cladosporium fulvum Cooke (syn. Passalora fulva (Cooke) U. Braun & Crous), does hardly occur in outdoor grown tomatoes in Cuba. However, with the recent increase in production of tomato hybrids grown under anti-aphid mesh covers and greenhouses, it has become a major fungal disease, suggesting that the pathogen quickly evolves by accumulating mutations to overcome tomato Cf resistance genes. Globally, many races of C. fulvum have evolved so that can overcome single or sometimes multiple Cf genes present in commercially grown cultivars of tomato. Identification of the virulence spectrum of the C. fulvum population in Cuba is important for effective management of the disease by deployment of tomato hybrids with new Cf genes or combinations thereof. In recent years for this purpose, 36 single conidial strains obtained from diseased tomatoes collected in different provinces of Cuba were inoculated on a defined set of near-isogenic lines (NILs) of the tomato cultivar MoneyMaker carrying no Cf (for Cladosporium fulvum) resistance gene (MM- Cf-0) and the Cf- 9 resistance gene (MM- Cf- 9 =LA3047). Moreover, PCR amplification of the Avr 9 gene was analyzed by using the specific primers described by Stergiopoulos et al. All 36 strains could infect LA3047, indicating that they all can overcome the Cf- 9 gene, which was confirmed through the non-amplification of the Avr 9 gene. This is the first report on the occurrence of C. fulvum isolates in Cuba that can overcome the Cf- 9 resistance gene.






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