Diversidade e estrutura genética da população de Fusarium decemcellulare isolado de guaranazeiro (Paullinia cupana var sorbilis)

Abstract

Guarana plant (Paullinia cupana var. sorbilis (Mart.) Ducke) is an Amazonian species with great economic potential because of the different chemical properties of pharmaceutical and industrial interest. Brazil is the only of guarana seeds producer and Bahia followed by Amazonas major producers. Pests and diseases caused by fungi are among the main factors responsible for low production in the Amazon region. For many years considered a disease with no economic importance the oversprouting caused by Fusarium decemcellulare that is becoming a serious problem for the guarana culture in the Amazon and was also recently reported in guarana crops in the Bahia state, the disease has at least three characteristic symptoms: oversprouting of vegetative buds, floral hypertrophy and stem galls. This study aimed to analyze the diversity and genetic structure of F. decemcellulare from the main producing area of guarana in the Amazonas by molecular ISSR marker and conduct phylogenetic analysis to determine the occurrence of species complex in guarana plant. We analyzed 300 isolates collected from eight districts of Amazonas state based on 10 ISSR markers that generated 167 polymorphic bands. The number of observed alleles (Na) ranged from 1.48 (Presidente Figueiredo to 1.98 (Manaus) and the effective number of alleles (Ne) was 1.54 (Urucará) and 1.41 (Presidente Figueiredo), the values for heterozygosity (H) and Shannon Index (I) were very similar among the eight populations, with minimal to Rio Preto da Eva (H = 0:29 and I = 0:43) and maximum to Manaus (M = 0:39 and I = 0:48). The analysis of molecular variance (AMOVA) showed high genetic variability within populations (77%). Population genetic analysis by PCO (Principal coodenates analysis) and genetic structure of 300 isolates identified two populations from F. decemcellulare in guarana plant in Amazon. To verify if the different populations identified represent the same phylogenetic species, partial sequencing of the EF-1α was successfully obtained for 275 isolates and based on 19 haplotypes identified in the population 34 isolates were selected to phylogenetic analysis with (rpb1, rpb2 and ITS + LSU rDNA). The concatenated data from four regions grouped isolates in three different cluters suggesting the occurrence of three putative species in guarana plant. The analysis of 34 isoltes with ISSR also revealed the occurrence of three clusters with 54% similarity, although the marker has not been able to differentiate the putative species identified in the phylogeny. In both cases isolates were not grouped by symptoms, geographical origin or mating type, indicating the occurrence of different species can be the main factor to cluster distribution of F. decemcellulare from guarana plant.