Avaliação da segregação do gene da Oxalato Descarboxilase e da resistência ao Fusarium oxysporum na geração T1 de fumo transformado com OXDC

Abstract

Since the domestication of plants for human use, the diseases are causing major production losses. Pathogenic fungi such as Sclerotium rolfsii, Botrytis cinerea, Sclerotinia sclerotiorum and Fusarium oxysporum are capable of infecting various plant species. Infection by these fungi leads to considerable losses at harvest. The initial phase of the infection involves the production and accumulation of large amounts of oxalic acid (OA), which seems to be one of the biggest determinants of pathogenicity. Fusarium oxysporum is the most common species of the genus and causes vascular wilt in different plant species. This fungus causes severe losses in many crops such as cotton, tobacco, bananas, coffee, strawberry and sugar cane. Genes that confer resistance to pathogens become of agronomic importance as resources for improvement. Among these we highlight the enzyme oxalate decarboxylase (OXDC) capable of catalyzing the degradation of OA in formic acid and carbon dioxide, decreasing the infectivity of the fungus. In the T0 generation of tobacco transformed with OXDC gene four resistant fungal strains were obtained, they were analyzed in T1. The objective of this study was to evaluate the segregation of the transgene OXDC for T1 generation of smoke and assess whether the T1 generation of transformed plants are able to resist the pathogen Fusarium oxysporum. Thirty T1 plants of each line of tobacco transformed with OXDC were evaluated by PCR for the presence of HPTII. These four strains were analyzed showed a segregation ratio of 3:1. A positive PCR plant of each strain was subjected to bioassays to verify resistance to the fungus and the OA. In the test of resistance to the fungus Fusarium oxysporum, this was not able to infect the transgenic lines , showing an increase of the resistance of T1 relative to T0 when the results were compared. The levels of transgene expression were assessed by RT-PCR. T1, T4 and T6 strains showed similar levels of expression, the T2 strain showed lower expression level than other strains , so that this result can be correlated with lower resistance to OA. Based on these results it can be concluded that the enzyme Oxalate Descarboxylase demonstrated to be effective in combating the pathogen Fusarium oxysporum and potentially efficient against other fungi which also use OA in the infection process.