RESUMEN
The diversity of endophytic filamentous fungi from leaves of transgenic imidazolinone-tolerant sugarcane plants and its isoline was evaluated by cultivation followed by amplified rDNA restriction analysis (ARDRA) of randomly selected strains. Transgenic and non-transgenic cultivars and their crop management (herbicide application or manual weed control) were used to assess the possible non-target effects of genetically modified sugarcane on the fungal endophytic community. A total of 14 ARDRA haplotypes were identified in the endophytic community of sugarcane. Internal transcribed spacer (ITS) sequencing revealed a rich community represented by 12 different families from the Ascomycota phylum. Some isolates had a high sequence similarity with genera that are common endophytes in tropical climates, such as Cladosporium, Epicoccum, Fusarium, Guignardia, Pestalotiopsis and Xylaria. Analysis of molecular variance indicated that fluctuations in fungal population were related to both transgenic plants and herbicide application. While herbicide applications quickly induced transient changes in the fungal community, transgenic plants induced slower changes that were maintained over time. These results represent the first draft on composition of endophytic filamentous fungi associated with sugarcane plants. They are an important step in understanding the possible effects of transgenic plants and their crop management on the fungal endophytic community.
Asunto(s)
Ascomicetos/aislamiento & purificación , Hongos/aislamiento & purificación , Hojas de la Planta/microbiología , Plantas Modificadas Genéticamente/microbiología , Saccharum/microbiología , Ascomicetos/clasificación , Ascomicetos/efectos de los fármacos , Ascomicetos/genética , Biodiversidad , ADN de Hongos/genética , ADN Ribosómico/genética , ADN Espaciador Ribosómico/genética , Hongos/clasificación , Hongos/efectos de los fármacos , Hongos/genética , Herbicidas/farmacología , Filogenia , Análisis de Secuencia de ADNRESUMEN
The Alternaria brown spot (ABS) is a disease caused in tangerine plants and its hybrids by the fungus Alternaria alternata f. sp. citri which has been found in Brazil since 2001. Due to the recent occurrence in Brazilian orchards, the epidemiology and genetic variability of this pathogen is still an issue to be addressed. Here it is presented a survey about the genetic variability of this fungus by the characterization of twenty four pathogenic isolates of A. alternata f. sp. citri from citrus plants and four endophytic isolates from mango (one Alternaria tenuissima and three Alternaria arborescens). The application of two molecular markers Random Amplified Polymorphic DNA (RAPD) and Amplified Fragment Length Polymorphism (AFLP) had revealed the isolates clustering in distinct groups when fingerprintings were analyzed by Principal Components Analysis (PCA). Despite the better assessment of the genetic variability through the AFLP, significant modifications in clusters components were not observed, and only slight shifts in the positioning of isolates LRS 39/3 and 25M were observed in PCA plots. Furthermore, in both analyses, only the isolates from lemon plants revealed to be clustered, differently from the absence of clustering for other hosts or plant tissues. Summarizing, both RAPD and AFLP analyses were both efficient to detect the genetic variability within the population of the pathogenic fungus Alternaria spp., supplying information on the genetic variability of this species as a basis for further studies aiming the disease control.
A mancha marrom ou mancha de Alternaria é uma doença causada pelo fungo Alternaria alternata f. sp. citri, encontrada no Brasil desde 2001 em plantas de tangerina e seus híbridos. Por se tratar de uma doença recente no Brasil, a epidemiologia e variabilidade genética deste patógeno compõem importantes pontos a serem estudados. Este trabalho teve como objetivo avaliar a variabilidade genética deste patógeno por meio da caracterização de vinte e quatro isolados de A. alternata f. sp. citri de plantas de citros juntamente com quatro isolados endofíticos de manga, sendo um deles identificado como Alternaria tenuissima e outros três como Alternaria arborescens. A análise de componentes principais (PCA) do perfil de bandas obtidos pela aplicação de duas técnicas de marcadores moleculares, Amplificação Aleatória de Polimorfismos de DNA (RAPD) e Polimorfismo de Comprimento de Fragmentos Amplificados (AFLP), mostrou a formação de quatro grupos distintos. Apesar do mais amplo perfil de análise por meio da técnica de AFLP, não foi observado nenhuma modificação significativa dentro dos grandes grupos obtidos quando comparado ao RAPD, exceto no posicionamento dos isolados LRS 39/3 e 25M. Além disso, em ambas as análises, somente os isolados de plantas de limão agruparam entre si. Considerando outros hospedeiros ou tecidos de planta não foi possível encontrar grupos específicos. Concluindo, ambas as análises (RAPD e AFLP) são eficientes no estudo de variabilidade genética de Alternaria spp., fornecendo informações sobre a diversidade genética desta espécie, servindo como base para futuramente correlacionar este estudo com estudos adicionais objetivando o controle da doença.
RESUMEN
The Alternaria brown spot (ABS) is a disease caused in tangerine plants and its hybrids by the fungus Alternaria alternata f. sp. citri which has been found in Brazil since 2001. Due to the recent occurrence in Brazilian orchards, the epidemiology and genetic variability of this pathogen is still an issue to be addressed. Here it is presented a survey about the genetic variability of this fungus by the characterization of twenty four pathogenic isolates of A. alternata f. sp. citri from citrus plants and four endophytic isolates from mango (one Alternaria tenuissima and three Alternaria arborescens). The application of two molecular markers Random Amplified Polymorphic DNA (RAPD) and Amplified Fragment Length Polymorphism (AFLP) had revealed the isolates clustering in distinct groups when fingerprintings were analyzed by Principal Components Analysis (PCA). Despite the better assessment of the genetic variability through the AFLP, significant modifications in clusters components were not observed, and only slight shifts in the positioning of isolates LRS 39/3 and 25M were observed in PCA plots. Furthermore, in both analyses, only the isolates from lemon plants revealed to be clustered, differently from the absence of clustering for other hosts or plant tissues. Summarizing, both RAPD and AFLP analyses were both efficient to detect the genetic variability within the population of the pathogenic fungus Alternaria spp., supplying information on the genetic variability of this species as a basis for further studies aiming the disease control.