Marker assisted pyramiding genes conferring resistance against major bacterial and fungal diseases into popular common bean varieties (Phaseolus vulgaris L.) with food and market value for Ethiopia


Dr Yayis Rezene overseeing the on-farm variety verification trials (VVT) for advanced breeding lines resistant to angular leaf spot (ALS) and common bacterial blight (CBB). Gofa, Ethoipia, 2022.
PROJECT OVERVIEW
Background
Common bean is the principal food and nutrition security legume crop in Ethiopia, providing dietary protein and a source of cash income for resource-poor farmers Angular leaf spot (ALS), common bacterial blight (CBB) and anthracnose (ANT) are the most economically important diseases of common bean in the country.

The SARI team members, left to right: Mr Tukie, Dr Rezene, Ms Firew and Ms Tadesse, 2021.
Objectives
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Enhancing the trait performance of common bean varieties by combining and assembling two or more complementary genes against major fungal and bacterial diseases of common bean in Ethiopia.
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Characterise pathogenic, genetic variability and geographic distribution of major foliar fungal (ANT) and bacterial (HB) pathogens in Ethiopia and identify new sources of resistance to use in the breeding program.
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Capacity building and training scientist with modern molecular techniques.
Progress to date
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Advanced backcross lines with Redwolaita (17 backcrossed lines) from the Mesoamerican genepool & Ibado (20 backcrossed lines) background which was developed through MAS in the previous project (phase-I) were evaluated at multiple locations (Awassa, Gofa and Areka). This was a prerequisite and requirement for formal release. Variety verification trials planted in 2022 in three locations: Gofa, Areka and Hawassa.
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Nursery trials of improved multiple disease resistance breeding lines derived from Hawassadume (48) and Remeda (68) were carried out to obtain preliminary data under field condition and to obtain sufficient seed for multi-location evaluations.
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Pathogen characterisation for major common bean diseases (ALS, CBB, & ANT) were studied with isolates collected from major bean growing areas.
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Four postgraduate students supported with KT scholarship grants completed their studies.

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Red woylata (i) and Ibado (ii), two of the Ethiopian bean varieties targeted for improvement by the SARI breeding programme; Ms Mihiret Tadesse using the laminar flow hood designed and supplied by KT (iii); the SARI team working in the greenhouse (iv).
PROJECT TEAM MEMBERS

Dr Yayis Rezene
Principal Investigator, the Southern Agricultural Research institute (SARI), Hawassa, Ethiopia.
Dr Rezene has led the Kirkhouse Trust (KT)-funded common bean improvement programme in Ethiopia since its inception in 2013. A KT PhD scholar, he completed his doctorate in 2018. The title of his thesis project was "Genome Wide Marker Trait Association Study, Molecular Characterization and Pathogenic Variability Among Pseudocercospora griseola (Sacc.) Crous & Braun Isolates, the Causal Agent of Angular Leaf Spot Disease of Common Bean in Ethiopia".

Mr Musa Tukie
Laboratory technician, molecular breeding

Ms Mihiret Tadesse Laboratory technician, pathology

Mr Yisahak Tsegaye,
MSc student, University of Hawassa, Ethiopia

Ms Tigist Firew MSc student, University of Hawassa, Ethiopia

Mr Muhammed Sitote
MSc student, Jimma University, Ethiopia Past team member, graduated 2021

Mr Melese Lema
MSc student, University of Hawassa, Ethiopia
Past team member, graduated 2019

Mr Misgana Mitiku Shertore
MSc student, University of Hawassa, Ethiopia
Past team member, graduated 2018
STUDENT PROJECTS
Survey and virulence characterization of the Uromyces appendiculatus, the cause of common bean rust, in major bean growing areas of Southern Ethiopia
Mr Yisahak Tsegaye
MSc in Plant Breeding, University of Hawassa, Ethiopia.
Supervisors: Professor Alemayehu Chala and Dr Yayis Rezene.
Project objectives
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To map the distribution of common bean rust pathogen in production areas of southern Ethiopia.
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To determine the prevalence and severity of the disease.
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To assess virulence variability of the pathogen and identify the most virulent races.
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To identify the resistant bean lines for further breeding programme.

Mr Yisahak Tsegaye preparing the seed for the screening trial.

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Bean rust infected bean plant (i).
Genetic characterisation of angular leaf spot (ALS) resistance in selected common bean (Phaseolus vulgaris l.) cultivars in Ethiopia
Ms Tigist Firew
MSc in Plant Breeding, University of Hawassa, Ethiopia.
Supervisors: Professor Hewan Demissie and Dr Yayis Rezene.

Ms Tigist Firew
Achievements
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Two independent populations were developed by crossing SPS-50 HB with susceptible parent Redwoliata (RW) as the female parent to generate F1 populations. For the allelism test, SPS-50 HB was crossed with the resistant Mex 54 to determine the allelic relationship between Phg-2 resistance gene in Mex 54 and resistance in SPS-50HB common bean cultivar.
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The populations developed have been evaluated in field conditions. SSR, RAPD and SCAR markers linked to Phg-2 resistance gene are being tested on the parental lines to identify polymorphis
Project objectives
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Study the inheritance pattern of ALS resistance in the common bean cultivar SPS 50 HB by using segregating populations derived from crossing SPS 50 HB with the susceptible cultivar Red woylata.
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Establish the relationship between ALS the resistance genes in SPS 50 HB and the previously characterized in Mesoamerican source, Mex 54.
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Identify molecular markers linked to these resistance gene(s) to facilitate their introgression into preferred common bean cultivars.
Mex-54

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Mex-54
Rw
SPS-50 HB

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Bean varieties for the mapping population growing the the greenhouse (Red woylata (RW), Mex 54 and SPS-50 HB; i); Ms Firew and Ms Tadesse making crosses in the greenhouse (ii); Ms Firew working in the lab (iii); SPS-50 HB populations grown in field conditions for evaluation to disease resistance (iv).
Marker-assisted introgression of the anthracnose (ANT) resistance gene to common bean (Phaseolus vulgaris L.)
Mr Muhammed Sitote
MSc in Plant Breeding, University of Jimma, Ethiopia, 2021.
Supervisors:Professor Professor Kassahun Bantte and Dr Yayis Rezene
Project overview
The objectives of the project were to introgress the gene conferring resistance to ANT (Co-14) from the donor variety KT-RWA77 into the bean cultivar KT-IBMV4, which is susceptible to ANT but resistant to angular leaf spot (ALS) and common bacterial blight (CBB).

Mr Muhammed Sitote
Achievements
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A backcross BC2F2 population has been developed. The CV542014 marker was used to tag resistance to ANT in segregating populations, which was confirmed by artificial inoculation of selected lines. The selection of individuals for the advancement of population was also based on seed attributes (colour and size) and plant vigour.
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The agronomic attributes of selected BC2F2 were characterised in the greenhouse after the artificial inoculation of plants with 3 different ANT races, with the parental cultivars and 2 released bean varieties (Ibadu and Tatu) as controls. Treatments were laid down in completely randomized design (CRD) with four replications. Four promising BC2F2 were selected for further characterisation and advancement.

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Bean leaf showing the symptoms of ANT infection (i); the detached leaf methods for assessing disease susceptibility to ANT phenotypically: after artificial inoculation with the pathogen, the leaves from resistant plats remain green, while leaves from susceptible plants turn yellow and then brown (ii); BC2F2 populations in the greenhouse (iii). Only the plants identified as resistant to ANT in the detached leaf assay and containing the CV542014 ANT marker were selected for advancement to the next stage of the breeding programme.
Introgression of genes conferring resistance against angular leaf spot (Pseudocercospora griseola) and anthracnose (Colletotrichum lindemuthianum) into common bean (Phaseolus vulgaris L.) using marker assisted selection
Mr Melese Lema
MSc in Plant Breeding, University of Hawassa, Ethiopia, 2019.
Supervisors: Professor Hewan Demissie, University of Hawassa, Dr Yayis Renzene, SARI, Ethiopia.
Project overview
Angular leaf spot (ALS), anthracnose (ANT) and common bacterial blight (CBB) are important diseases of common bean in Ethiopia that can cause severe yield reduction. This study, for a MSc in Plant Breeding at the University of Hawassa, was conducted to combine resistance genes for ALS and ANT diseases into advanced breeding lines (with Red woylata as the recurrent parent) using marker assisted selection in combination with phenotypic selection. High correlation values, for ALS (r = -0.65) and for ANT (r=-0.73) were obtained between phenotypic and molecular data respectively, indicating high reliability of the markers used. Eight breeding populations were developed and assessed for their response to ALS, ANT and CBB after artificial infection. Three advanced breeding lines carrying the four target disease resistance genes were identified and selected for advancement in the breeding programme.
Since his graduation in 2019 Mr Lema is working as a cereal breeder for the Arba Minch' Agricultural Research Center, Gamo Gofa, Ethiopia.

Mr Melese Lema

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Mr Lema making crosses between the parental lines (i); an elongated pod from a successful cross (ii); Mr Lema working in the lab (iii); isolates of the fungus Colletotrichum lindemuthianum (the pathogen responsible for ANT), grown in culture media in the lab to test for disease resistance in breeding populations by artificial inoculation (iv).
Genotypic and virulence characterisation of Xanthomonas axonopodis pv.phaseoli and Xanthomonas axonopodis pv.phaseoli var. fuscans, and reaction of the backcross four (BC4) common bean population to common bacterial blight (CBB)
Mr Misgana Mitiku Shertore
MSc in in Plant and Horticulture Sciences, Crop Protection, University of Hawassa, Ethiopia, 2018.
Supervisors: Professor Alemayehu Chala, University of Hawassa, Dr Yayis Renzene, SARI, Ethiopia.
Project overview
This study characterised forty common bacterial blight (CBB) isolates collected from seven localities in Ethiopia, in terms of their morphology, genotypic variability within and between populations, pathogenicity and virulence.
The near totality of isolates collected were Xanthomonas axonopodis pv. phaseoli and Xanthomonas axonopodis pv. phaseoli var. fuscans. Isolates differed in aggressiveness and the common bean varieties Red wolayta, Ibado and VAX6 displayed different levels of disease resistance. Three of the common bean lines (KT014, KT018 and VAX6) were found to be resistant to all five (ET515, ET516, ET517, ET534 and ET504) virulent common bacterial blight isolates. The results of this study suggest the existence of diverse isolates in individual populations that should be given prior attention in the future breeding programs. Similar studies should be carried out by collecting isolates from additional common bean producing areas representing the various agro-ecological zones to cunderstand how the common bacterial blight populations vary across the country.

Mr Misgana Mitiku Shertore

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Mr Mitiku Shertore isolating and making pure cultures of Xanthomonas axonopodis, the causal agent of CBB (i); pure cultures of the pathogen (ii); during artificial infestation of plants in the greenhouse to test for disease-resistance (iii); symptoms of disease in susceptible plants after inoculation (iv).
PUBLICATIONS
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Lema, M., Demissie, H. and Rezene, Y., 2021. Marker assisted gene introgression in to common bean (Phaseolus vulgaris l) against angular leaf spot (Pseudosercospora griseola) and anthracnose (Colletotrichum lindemuthianum). Journal of Agricultural Science and Practice 6: 118-129.
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Rezene, Y., 2021. GGE-Biplot Analysis of Multi-Environment Yield Trials of Common Bean (Phaseolus vulgaris L.) in the southern Ethiopia. Journal of Plant Studies, 8(1), pp.1-35.Rezene, Y. and Mekonin, S., 2019. Screening common bean (Phaseolus vulgaris L.) germplasm for resistance against angular leaf spot (Pseudocercospora griseola) disease under field condition. Journal of Plant Studies; Vol, 8(1).
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Rezene, Y., 2019. GGE-Biplot Analysis of Multi-Environment Yield Trials of Common Bean (Phaseolus vulgaris L.) in the southern Ethiopia. Journal of Plant Studies 8(1).
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Rezene, Y., Tesfaye, K., Mukankusi, C., Ratz, B. and Gepts, P., 2019. Marker-assisted Pyramiding Resistance Genes Against Angular Leaf Spot and Common Bacterial Blight Disease into Preferred Common Bean Cultivar. Molecular Plant Breeding, 10. J Biotechnol Biomater 2018, 8:4 DOI: 10.4172/2155-952X.1000286.
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Rezene, Y., Tesfaye, K., Clare, M. and Gepts, P., 2018. Pathotypes characterization and virulence diversity of Pseudocercospora griseola the causal agent of angular leaf spot disease collected from major common bean (Phaseolus vulgaris L.) growing areas of Ethiopia. J Plant Pathol Microbiol, 9(445), p.2.
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Rezene, Y., Tesfaye, K., Mukankusi, C., Arunga, E. and Gepts, P., 2018. Simple and rapid detached leaf technique for screening common beans (Phaseolus vulgaris L.) in vitro against angular leaf spot (Pseudocercospora griseola) disease. African Journal of Biotechnology, 17(35), pp.1076-1081.
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Rezene, Y., Tesfaye, K., Clare, M., Male, A. and Gepts, P., 2018. Rep‐PCR genomic fingerprinting revealed genetic diversity and population structure among Ethiopian isolates of Pseudocercospora griseola pathogen of the common bean (Phaseolus vulgaris L.). J Plant Pathol Microbiol, 9(463), p.2.

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The SARI bean improvement team in 2021, left to right: Dr Yayis Rezene; Ms Mihiret Tadesse; Ms Tigist Firew; Mr Musa Tukie;(i); Mr Musa Tukie (ii); Mr Misgana Mitiku Shertore (iii).
PROJECT LOCATIONS
Locations of the Southern Agricultural Research Institute SARI field sites.