GUAVA DECLINE: EVIDENCE OF NATIONWIDE INCIDENCE IN BRAZIL

作者：Gomes Vicente Martins; Souza Ricardo Moreira^*; Midorikawa Glaucia; Miller Robert; Almeida Alexandre Macedo

来源：Nematropica, 2012, 42(1): 153-162.

• complex disease
• Fusarium solani
• guava root-knot nematode
• Meloidogyne enterolobii
• Psidium guajava

In Rio de Janeiro State (Brazil), guava decline is a complex disease in which parasitism by Meloidogyne enterolobii predisposes Fusarium solani-immune trees to extensive root decay caused by this fungus. On the shoot, the symptoms include chlorosis, wilting, scorching of leaf margins and leaf drop, yield reduction, and plant death within months. Since in many States M. enterolobii-infested orchards have been decimated with the same symptoms, this study aimed to assess the incidence of guava decline nationwide. Root samples from declining, nematode-infested orchards were received from Southern, Northeastern and Midwestern Brazil. Of the 682 root fragments processed for fungal isolation, about half were positive for Fusarium sp., and only 5% were positive for other fungi. Sixty-nine Fusarium sp. isolates were established as representatives of those Brazilian regions. To expedite the evaluation of virulence to guava of all these isolates, a growth chamber assay was developed using as reference 11 Fusarium sp. isolates whose virulence to guava plants had been assessed in previous microplot experiments. Of the 69 Fusarium sp. isolates assessed, 87% - from all Brazilian regions - were virulent to stem cuttings used in the growth chamber assay, with 42% of these being classified as highly virulent. All virulent isolates were preliminarily identified as F. solani through morphological characterization. To confirm this, 12 representatives from different Brazilian regions were selected for molecular identification through ITS4 and ITS5 gene sequencing, which confirmed their identity as F. solani.

• 出版日期2012-6