Characterization of the common bean host and Pseudocercospora griseola, the causative agent of angular leaf spot disease in Tanzania
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Date
2016
Journal Title
Journal ISSN
Volume Title
Publisher
African Journal of Plant Science
Abstract
Angular leafspot (ALS), caused by the fungus, Pseudocercospora griseola, is one of the most important
disease of common bean in Tanzania. Breeding for resistance to this disease is complicated by the
variable nature of the pathogen. In Tanzania, a thorough analysis of the variability of this pathogen is
lacking which limits breeding for durable resistance. This work aimed at characterizing P. griseola in
relation to its host in Tanzania. A sample collection of both P. griseola and common bean was
conducted in the 2013 and 2014 growing seasons from nine regions. Single spore isolation was
performed for P. griseola isolates and DNA was extracted from both P. griseola mycelium and bean
leaves from which the pathogen was collected. For characterization of the gene pool origin of the host,
Phaseolin DNA marker was evaluated and for the pathogen, the Internal Transcribed Spacer region (ITS)
and the Actin gene sequences were evaluated. Phylogenetic analysis showed the presence of 69.7%
Andean and 30.3% Mesoamerican strains of P. griseola in Tanzania. The common bean host genotypes
showed a similar distribution with 84.2% Andean and 15.8% Mesoamerican. In both cases, Andean
strains of the pathogen and Andean bean genotypes outnumbered Mesoamerican. In relation to the
common bean genotypes, Andean genotypes were more susceptible to ALS as compared to
Mesoamerican genotypes. There were few strains that were of Andean origin but were pathogenic on
Mesoamerican common bean genotypes, a group that has previously been termed Afro-Andean.
Geographically, most of the regions of Tanzania had only Andean strains except for Kagera where 60%
were Mesoamerican strains, and in Arusha and Tanga, where 50 and 33% were Mesoamerican,
respectively. Only three regions, Kagera, Mbeya and Rukwa, were found to grow Mesoamerican beans.
The findings of this study are important in setting basic objectives for breeding for angular leaf spot
disease in Tanzania.
Description
Journal article
Keywords
Actin gene, Angular leaf spot (ALS), Internal Transcribed Spacer region (ITS), Phaseolin protein, Phaseolus vulgaris