Population typing of the causal agent of cassava bacterial blight in the Eastern Plains of Colombia using two types of molecular markers.

Silvia Restrepo,Lucie Poulin,Nathalia Arias-Rojas,César A Trujillo,Anibal Tapiero,Ralf Koebnik,Adriana J Bernal,César A Medina

doi:10.1186/1471-2180-14-161

Abstract

BackgroundMolecular typing of pathogen populations is an important tool for the development of effective strategies for disease control. Diverse molecular markers have been used to characterize populations of Xanthomonas axonopodis pv. manihotis (Xam), the main bacterial pathogen of cassava. Recently, diversity and population dynamics of Xam in the Colombian Caribbean coast were estimated using AFLPs, where populations were found to be dynamic, diverse and with haplotypes unstable across time. Aiming to examine the current state of pathogen populations located in the Colombian Eastern Plains, we also used AFLP markers and we evaluated the usefulness of Variable Number Tandem Repeats (VNTRs) as new molecular markers for the study of Xam populations.ResultsThe population analyses showed that AFLP and VNTR provide a detailed and congruent description of Xam populations from the Colombian Eastern Plains. These two typing strategies clearly separated strains from the Colombian Eastern Plains into distinct populations probably because of geographical distance. Although the majority of analyses were congruent between typing markers, fewer VNTRs were needed to detect a higher number of genetic populations of the pathogen as well as a higher genetic flow among sampled locations than those detected by AFLPs.ConclusionsThis study shows the advantages of VNTRs over AFLPs in the surveillance of pathogen populations and suggests the implementation of VNTRs in studies that involve large numbers of Xam isolates in order to obtain a more detailed overview of the pathogen to improve the strategies for disease control.

Highlights

Molecular typing of pathogen populations is an important tool for the development of effective strategies for disease control
These studies showed that Xanthomonas axonopodis pv. manihotis (Xam) populations from the Caribbean and Eastern Plains were dynamic and presented a higher genetic diversity when compared with populations from Cauca [8,9,14]
A large number of isolates was obtained from cassava producing areas in the Eastern Plains of Colombia A total of 101 isolates were collected at four locations in the Eastern Plains of Colombia

Summary

Introduction

Molecular typing of pathogen populations is an important tool for the development of effective strategies for disease control. The development of durable resistance becomes more challenging with this kind of pathogens Factors such as the genetic flow between pathogen populations and processes that increase the Xanthomonas axonopodis pv. Xam populations have been characterized in different countries in South America and Africa, starting in the 1980s These studies showed that the South American populations were more diverse than those from Africa [9,11,12,13,14]. We monitored populations of the pathogen in the Caribbean region, where three cassava varieties are intensively and extensively cultivated. These studies were performed using AFLPs and sequences of genes coding for Type Three Effectors proteins (T3Es). It is pertinent to characterize populations outside of the studied regions and to establish their dynamics and to which extent those dynamics may have an impact on the crop

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