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ARS Home » Southeast Area » Mayaguez, Puerto Rico » Tropical Crops and Germplasm Research » Research » Publications at this Location » Publication #330838
Title: Characterization of the common bean host and Pseudocercospora griseola the causative agent of angular leaf spot disease in Tanzania

Author
item CHILAGANE, LUSEKO - Sokoine University Of Agriculture
item NCHIMBI-MSOLLA, SUSAN - Sokoine University Of Agriculture
item KUSOLWA, PAUL - Sokoine University Of Agriculture
item Porch, Timothy - Tim
item SERRATO-DIAZ, LUZ - University Of Puerto Rico
item MUHAMBA-TRIPHONE, GEORGE - Sokoine University Of Agriculture

Submitted to: African Journal of Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/15/2016
Publication Date: 11/24/2016
Citation: Chilagane, L.A., Nchimbi-Msolla, S., Kusolwa, P.M., Porch, T.G., Serrato-Diaz, L.M., Muhamba-Triphone, G. 2016. Characterization of the common bean host and Pseudocercospora griseola the causative agent of angular leaf spot disease in Tanzania . African Journal of Plant Science. doi: 10.5897/AJPS2016.1427.

Interpretive Summary: Angular leaf spot (ALS) is one of the most important diseases of common bean in Tanzania. Breeding for resistance to this disease is complicated by the variable nature of the pathogen. In Tanzania no thorough analysis of the variability of this pathogen has been completed which limits proper strategies for breeding for durable resistance. This work aimed at characterizing ALS in relation to its host in Tanzania. A sample collection of both pathogen and host was conducted in 2013/2014 growing seasons in nine bean growing regions. Single spore isolation was performed for isolates followed by DNA extraction from both the ALS mycelium and from the leaves of the beans where the pathogen was taken. For host characterization, the Phaseolin protein marker, and for the pathogen, the Internal Transcribed Spacer region (ITS) and Actin markers, were used for amplification of the desired regions followed by direct sequencing of the PCR products. Phylogenetic analysis showed the presence of both Andean (69.7%) and Mesoamerican (30.3%) groups of the pathogen which was also the case for the common bean genotypes, Andean (84.2%) and Mesoamerican (15.8%) as revealed by the Phaseolin marker. In both cases, Andean strains of the pathogen and Andean bean genotypes outnumbered Mesoamerican. In relation to the genotypes, Andean genotypes were more susceptible to ALS as compared to Mesoamerican genotypes. There were a few strains that were of Andean origin but were pathogenic on Mesoamerican common bean genotypes, this group has previously been discovered and named Afro-Andean. Most of the regions of Tanzania had only Andean strains except for Kagera where most of the isolates were Mesoamerican strains (60%), followed by Arusha (50%) and Tanga (33%). The findings of this study are important for setting breeding objectives for angular leaf spot disease in Tanzania.

Technical Abstract: Angular leaf spot (ALS) caused by the fungus Pseudocercospora griseola is one of the most important diseases of common bean in Tanzania. Breeding for resistance to this disease is complicated by the variable nature of the pathogen. In Tanzania no thorough analysis of the variability of this pathogen has been completed which limits proper strategies for breeding for durable resistance. This work aimed at characterizing P. griseola in relation to its host in Tanzania. A sample collection of both pathogen and host was conducted in 2013/2014 growing seasons in nine bean growing regions. Single spore isolation was performed for P. griseola isolates followed by DNA extraction from both the P. griseola mycelium and from the leaves of the beans where the pathogen was taken. For host characterization, the Phaseolin protein marker, and for the pathogen, the Internal Transcribed Spacer region (ITS) and Actin markers, were used for amplification of the desired regions followed by direct sequencing of the PCR products. Phylogenetic analysis showed the presence of both Andean (69.7%) and Mesoamerican (30.3%) groups of P. griseola which was also the case for the common bean genotypes, Andean (84.2%) and Mesoamerican (15.8%) as revealed by the Phaseolin marker. In both cases, Andean strains of the pathogen and Andean bean genotypes outnumbered Mesoamerican. In relation to the genotypes, Andean genotypes were more susceptible to ALS as compared to Mesoamerican genotypes. There were a few strains that were of Andean origin but were pathogenic on Mesoamerican common bean genotypes, this group has previously been discovered and named Afro-Andean. Most of the regions of Tanzania had only Andean strains except for Kagera where most of the isolates were Mesoamerican strains (60%), followed by Arusha (50%) and Tanga (33%). The findings of this study are important for setting breeding objectives for angular leaf spot disease in Tanzania.