Caracterização da diversidade genética de isolados Amazônicos de Crinipellis perniciosa oriundos de tecido infectado de Theobroma cacao

Abstract

Characterization of the genetic diversity of Amazonian isolates of Crinipellis perniciosa from infected tissues of Theobroma cacao. Witches' broom disease of cacao (Theobroma cacao L.), caused by the basidiomycete Crinipellis perniciosa, devastated the producing region of Southern Bahia, previously cultivated mainly with highly susceptible cultivars, forcing Brazil, a typical exporter country to become a cocoa importer. The loss of resistance of the genotype "Scavina 6", the unique source of resistance against C. perniciosa has been associated with pathogen genetic variability. Thus, the objective of this study was to characterize the genetic diversity of C. perniciosa isolated derived from infected tissues of T. cacao ('green-brooms'), originally collected in the Amazon (Amazonas, Pará and Rondônia states), a region with endemic occurrence of the fungus, using molecular markers. The identification of the genetic relationships among the Amazonian and Bahian isolates, and the possible existence of geographical isolates were also objectives of this work. First, the identification confirmation of the Amazonian isolates was conducted using amplification and digestion of the ITS region of the rDNA and telomeric markers. All isolates evaluated were confirmed as C. perniciosa. The telomeric primer TeloC1, previously shown to discriminate the C biotype, allowed the separation of biotype C from biotypes S and L, but it revealed genetic diversity for isolates from Cametá, PA and Cacaulândia, RO. Using another telomeric marker amplified with TeloA1 primer and ERIC, a large genetic diversity was detected for isolates from the Amazon in comparison to Bahian. Within the Amazonian isolates, more diversity was detected for isolates from Rondônia (Ji-Paraná, Cacaulândia and Ariquemes) and Pará (Cametá), areas with endemic occurrence of wild cacao or historical introduction and cultivation (over 300 years), respectively. Isolates colletected at the Transamazônica roadway,

Avaliação da diversidade genética e associação com patogenicidade de isolados de Moniliophthora perniciosa oriundos da Amazônia Brasileira

“…Por exemplo, entre os isolados do Brasil, os originários de Rondônia foram os mais agressivos ao 'Scavina 6', e marcadores RAPD claramente distinguiram estes isolados de outros coletados no Pará (ANDEBRHAN et al, 1999), sendo que os isolados de Rondônia possuem alelos de locos de microssatélites raros e específicos, demonstrando maior diversidade genética (SILVA, 2007). O estudo de locos de microssatélites também permitiu identificar uma maior diversidade na região Amazônica em isolados de M. perniciosa coletados em Rondônia e Pará (SILVA, 2007).…”

“…Os produtos das amplificações com os iniciadores ITS1-18S e ITS4 foram digeridos separadamente com as enzimas MspI e HinfI, para revelar fragmentos de restrição (ARRUDA et al, 2003b;SILVA, 2007). Para a digestão com cada enzima foi utilizado um volume de 10 µL da reação de amplificação, 2 µL do tampão da enzima e 2 unidades da enzima MspI ou HinfI (Fermentas) num volume total de 20 µL, incubados por uma hora a 37ºC.…”