Os estudos apresentados neste trabalho contribuiram para aumentar o conhecimento sobre os mecanismos celulares e moleculares de resistência do cafeeiro (HDT 832/2 e Sarchimor) a Hemileia vastatrix, bem como da interacção não hospedeira cafeeiro-Uromyces vignae usada como modelo comparativo. As interacções hospedeira e não hospedeira estudadas foram caracterizadas por uma resistência do tipo pré-haustorial, associada à reacção de hipersensibilidade, à acumulação de fenóis e à activação de genes de reconhecimento/sinalização e de genes envolvidos nas respostas de defesa por intermédio das vias do ácido salicílico e do jasmonato. Na interacção não hospedeira verificou-se contudo uma menor intensidade na expressão de genes, o que poderá decorrer da menor percentagem de uredóporos germinados (resultando num menor número de infecções). A resistência pré-haustorial dos cafeeiros HDT 832/2 e Sarchimor a H. vastatrix raça II constitui uma excepção relativamente ao que é típico das interacções hospedeiro-ferrugem, que são normalmente do tipo pós-haustorial. A resistência pré-haustorial, próxima da resistência não hospedeira, tem-se revelado mais difícil de “quebrar” do que a resistência pós-haustorial, o que poderá explicar a maior durabilidade de resistência verificada em HDT 832/2, e no seu descendente Sarchimor, do que noutros genótipos onde se tem vindo a observar quebra de resistência. Este estudo insere-se numa investigação mais alargada que visa a análise do comportamento de diversos genótipos de cafeeiro em resposta a novas raças de H. vastatrix, de forma a tentar inferir sobre a natureza e a durabilidade da sua resistência.
Por comparação com o verificado na interacção hospedeira, a rapidez na diferenciação de estruturas de infecção de U. vignae e de respostas dos cafeeiros (interacção não hospedeira), em conjunto com a reduzida expressão génica registada nos primeiros tempos após inoculação estudados, sugere o interesse de se proceder a amostragens em intervalos mais curtos que os utilizados neste estudo. Essa amostragem poderá permitir identificar a expressão de genes como rlk, wrky1, pal, gt, pr1 e pr10 em resposta às primeiras fases da infecção, tal como verificado na interacção hospedeira.
Com base nestes resultados serão seleccionados os tempos 21-24 h.a.i. e 9-12 h.a.i., respectivamente para a interacção hospedeira e não hospedeira (quando se verifica maior frequência da activação dos genes analisados), para sequenciação dos respectivos transcritomas, por pirosequenciação. Esta análise permitirá identificar e comparar de forma exaustiva os genes de cafeeiro expressos em resposta às duas ferrugens, potencialmente revelando determinantes genéticos de resistência que poderão ter interesse no melhoramento do cafeeiro para resistência à ferrugem, bem como na identificação de factores que presidem à interacção gene-a-gene com H. vastatrix.
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