Angular leaf spot disease status and characterization of the causative pathgen (P. Griseola) in Tanzania

Authors: CHILAGANE, L - Sokoine University Of Agriculture; NCHIMBI-MSOLLA, SUSAN - Sokoine University Of Agriculture; KUSOLWA, PAUL - Sokoine University Of Agriculture; SERRATO-DIAZ, LUZ - University Of Puerto Rico; Porch, Timothy - Tim

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 1/11/2016
Publication Date: N/A
Citation: N/A

Interpretive Summary: Angular leaf spot 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 no thorough attempt has been completed to evaluate the variability of this pathogen which limits proper strategies for breeding for durable resistance. This work aims at evaluating ALS disease status and elucidating the variability of the causative pathogen in the country. A survey was conducted in two bean growing seasons, 2013 and 2014, in nine main bean growing regions of Tanzania for disease severity evaluation and disease sample collection. Isolation was completed and DNA was extracted for molecular characterization through sequencing the ITS region and the actin gene. The results indicated the presence of the disease in all the regions of Tanzania, while Kagera and Mbeya had the highest severity (score of 7), and Rukwa and Manyara had the lowest (score of 4). Phylogenetic analysis shows the presence of the Andean and Mesoamerican groups of P. griseola. Most of the isolates from the Kagera region were Mesoamerican (60%) and a lower proportion of Mesoamerican isolates were collected from Arusha (50%) and Tanga (33%). All other regions presented only Andean isolates. More work is underway on pathogenicity testing. This knowledge on the variability and distribution of the pathogen is crucial for directing breeding efforts for ALS disease resistance in Tanzania.

Technical Abstract: Angular leaf spot 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 no thorough attempt has been completed to evaluate the variability of this pathogen which limits proper strategies for breeding for durable resistance. This work aims at evaluating ALS disease status and elucidating the variability of the causative pathogen in the country. A survey was conducted in two bean growing seasons, 2013 and 2014, in nine main bean growing regions of Tanzania for disease severity evaluation and disease sample collection. Isolation was completed and DNA was extracted for molecular characterization through sequencing the ITS region and the actin gene. The results indicated the presence of the disease in all the regions of Tanzania, while Kagera and Mbeya had the highest severity (score of 7), and Rukwa and Manyara had the lowest (score of 4). Phylogenetic analysis shows the presence of the Andean and Mesoamerican groups of P. griseola. Most of the isolates from the Kagera region were Mesoamerican (60%) and a lower proportion of Mesoamerican isolates were collected from Arusha (50%) and Tanga (33%). All other regions presented only Andean isolates. This knowledge on variability and distribution of the pathogen is crucial in planning for breeding. More work is underway on pathogenicity testing.