Correlation of genome methylation of fig tree accessions with natural nematode and rust incidence / Correlação entre a metilação genômica de acessos de figueira e a incidência natural de nematoides e ferrugem

Commercial fig tree cultivation in Brazil involves a single cultivar, 'Roxo-de-Valinhos'. The use of a single cultivar results in serious diseases and related problems. The aim of this study was to characterize fig accessions by analyzing the natural root-knot nematode and leaf rust incidence in relation to the epigenomic profile of the plant, since epigenetic variations affect plant-pathogen interactions. All plants were attacked by nematodes, indicating susceptibility; Meloidogyne incognita was the root-knot nematode species involved. Joint analysis of data showed that methylation and leaf rust incidence were correlated when observed in the same phenological phase, presenting initial evidence of the same factorial pressure loads in genotypes, suggesting similar behavior within these genotypes.

O Brasil é o maior produtor de figos da América do Sul, porém o cultivo comercial brasileiro da figueira baseia-se na plantação de uma única cultivar, o Roxo-de-Valinhos, resultando em sérios problemas relativos a pragas e doenças. Uma vez que há variações epigenéticas na interação planta-patógeno, principalmente por meio da regulação gênica, o presente trabalho objetiva realizar a caracterização in vivo de acessos de figo, por meio da análise de incidência natural de nematoides formadores de galha e de incidência natural de ferrugem, correlacionada ao seu perfil epigenômico, a fim de subsidiar trabalhos de conservação, melhoramento genético e produção da cultura. A análise dos componentes principais dos dados da caracterização dos acessos foi realizada por meio da matriz de correlação residual obtida pela análise de variância conjunta utilizando o programa GENES. Pôde-se constatar que todas as plantas foram atacadas por este patógeno, evidenciando que são suscetíveis ao mesmo. Já a análise conjunta dos dados demonstrou que a metilação e a incidência de ferrugem em folhas, quando observadas na mesma fase fenológica da planta, se correlacionam, apresentando evidências iniciais de mesmas cargas fatoriais de pressão nos genótipos, com a premissa de comportamento semelhante nos mesmos, indicando que, além do fator genético, fatores abióticos também são responsáveis pelas alterações no fenótipo das plantas, evidenciando a plasticidade fenotípica das mesmas.

Correlation of genome methylation of fig tree accessions with natural nematode and rust incidence.

Commercial fig tree cultivation in Brazil involves a single cultivar, 'Roxo-de-Valinhos'. The use of a single cultivar results in serious diseases and related problems. The aim of this study was to characterize fig accessions by analyzing the natural root-knot nematode and leaf rust incidence in relation to the epigenomic profile of the plant, since epigenetic variations affect plant-pathogen interactions. All plants were attacked by nematodes, indicating susceptibility; Meloidogyne incognita was the root-knot nematode species involved. Joint analysis of data showed that methylation and leaf rust incidence were correlated when observed in the same phenological phase, presenting initial evidence of the same factorial pressure loads in genotypes, suggesting similar behavior within these genotypes.

First Report of a Lettuce-Infecting Sequivirus in Chile.

Sequiviruses are isometric aphidborne plant viruses. Dandelion yellow mosaic virus (DaYMV), genus Sequivirus, was isolated from dandelion and lettuce in Europe. Lettuce mottle virus (LeMoV), a putative sequivirus, is often found in mixed infections with Lettuce mosaic virus (LMV) in Brazil (3). DaYMV, LeMoV and LMV cause similar mosaics in field-grown lettuce. Differences in biology and sequence suggest that DaYMV and LeMoV are distinct species (2). Forty-two and 101 lettuce samples with mosaic symptoms collected from two locations near Santiago during a survey of lettuce viruses in Chile in 2002 and 2003, respectively, were analyzed for the presence of LeMoV using reverse transcription polymerase chain reaction (RT-PCR). Total RNA was extracted (1) and used for RT-PCR with the specific LeMoV primers pairs Lmo3 (5' ACATGAGCACTAGTGAGG 3') and Lmo4 (5' AGATAGAGCCGTCT GGCG 3') (2). One of the 42 and three of the 101 samples produced the expected 300-bp fragment. Isometric particles of 30 nm diameter, typical of a sequivirus, were visualized by transmission electron microscopy. These samples were tested using RT-PCR for the presence of LMV and Cucumber mosaic virus (CMV), but no mixed infections were observed. One isolate, Ch36, was reamplified with the degenerate primer pairs DALE 1 (5' GARTTCAACATGCACGCCAG 3') and DALE 2 (5' TTTTTCTCCCCATYCGTCAT 3') which amplify part of the putative replicase gene (2) and produced a 563-bp fragment that was cloned on pGEM-T Easy (Promega, Madison, WI) and sequenced. The Ch36 product (EMBL Accession No. AM039965) showed 97% amino acid identity with LeMoV from Brazil, 79% with DaYMV, 72% with the sequivirus Parsnip yellow fleck virus, and 34% with the waikavirus Maize chlorotic dwarf virus. To our knowledge, this is the first report of a sequivirus in field lettuce in Chile, and although the virus was found at low incidence, this report extends the range of LeMoV to the western side of the Cordillera de Los Andes. The impact of LeMoV needs to be further analyzed in Chile, Brazil, and possibly other South American countries. References: (1) Y. D. Bertheau et al. DNA amplification by polymerase chain reaction (PCR) 1998. In: Methods for the Detection and Quantification of Erwinia carotovora subsp. atroseptica on potatoes. M. C. N. Perombelon and J. M. van der Wolff, eds. Scott. Crop Res. Inst. Occasional Publ., Dundee, 1998. (2) A. S. Jadão. Caracterização parcial e desenvolvimento de oligonucleotídeos específicos para detecção de sequivirus infectando alface. Ph.D. thesis. FCA-UNESP-Botucatu, Brazil, 2004. (3) O. Stangarlin et al. Plant Dis. 84:490, 2000.