Diversidade de bactérias causadoras de podridão mole em hortaliças no estado de Pernambuco

Abstract

The soft rot disease is responsible for causing significant losses in the production of several crops around the world. Our objectives were: i) to identify the bacteria causing soft rot in different vegetables from different climatic zones (forest, intermiediary, semiarid) of the Pernambuco state by sequencing of the 16S rDNA region and multilocus sequence analysis (MLSA) with the genes gapA, icdA, mdh, proA, gyrA, ropS, recA, dnaX, fusA and rplB; (ii) to analyze the genetic structure of the population prevalent in the study (Pectobacterium carotovorum subsp. brasiliensis) using rep-PCR analysis. BLASTn analysis of the 16S rDNA region showed that the collection of 177 isolates, in addition to species and subspecies of Pectobacterium and Dickeya, other genera such as Enterobacter, Kluyvera, Klebsiella, Morganella, Providencia, Rahnella and Raoutella are also associated with soft rot in the state of Pernambuco. Through the MLSA, 64 isolates were identified as P. carotovorum subsp. brasiliensis and 47 as P. aroidearum, demonstrating the prevalence of these bacteria in the state. It was observed high diversity of genera and species of the family Enterobacteriaceae causing soft rot in vegetables in the different climatic zones of the state of Pernambuco. Lettuce is the most susceptible vegetable to the attack of enterobacteria, including bacteria that are pathogenic to man. The first record of the occurrence of soft rot caused by P. carotovorum subsp. odoriferum, D. dadantii subsp. dadantii and D. zeae in lettuce, E. ludwigii, E. massiliensis and E. bugandensis in zucchini, K. pneumoniae subsp. ozone in lettuce, K. michiganensis in lettuce and cabbage, M. morganii subsp. sibonii in Chinese cabbage, R. inusitata in Japanese coriander, R. terrigena in pumpkin and lettuce, L. amnigena in zucchini and K. georgiana in lettuce, eggplant and peppers. Population analysis of P. carotovorum subsp. brasiliensis (n = 64) revealed high variability, high haplotype richness and high genetic diversity of the population. However, evidence of low gene flow was observed among the subpopulations of Zona da Mata, Agreste and Sertão. It was observed absence of recombination in the subpopulations, indicating that possibly the mutation has been the phenomenon that caused the genetic variability observed in the study population. There was no genetic differentiation between the subpopulations and the analysis of molecular variance showed that much of the variation occurred within the subpopulations.