Pathogen Variability and New Sources of Resistance to Angular Leaf Spot Among Bean Landraces in Uganda

Ddamulira, G.

doi:10.18697/ajfand.84.blfb1006

Cited by 10 publications

(15 citation statements)

References 22 publications

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“…The exception was revealed by the STRUCTURE analysis of the breeder-selected and household collection samples, which identified a fourth distinct population, based on the Evanno et al (2005) test, indicating more complex population structure in household seed stocks relative to the global germplasm collection (Figure 5). Control genotypes, visual inspection of seed morphological traits, and prior information obtained from previous molecular analyses (Gepts, 1988; Ddamulira et al, 2014; Okii et al, 2014), provided additional empirical support for characterization of the K = 4 populations. The fourth population was primarily composed of Andean seed samples that household members consistently referred to as “Seed Engufu” (translated from the local Bantu language, Runyoro or Nyoro, as “short seed”).…”

Section: Resultsmentioning

confidence: 89%

Genetic Patterns of Common-Bean Seed Acquisition and Early-Stage Adoption Among Farmer Groups in Western Uganda

et al. 2018

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Widespread adoption of new varieties can be valuable, especially where improved agricultural production technologies are hard to access. However, as farmers adopt new varieties, in situ population structure and genetic diversity of their seed holdings can change drastically. Consequences of adoption are still poorly understood due to a lack of crop genetic diversity assessments and detailed surveys of farmers' seed management practices. Common bean (Phaseolus vulgaris) is an excellent model for these types of studies, as it has a long history of cultivation among smallholder farmers, exhibits eco-geographic patterns of diversity (e.g., Andean vs. Mesoamerican gene-pools), and has been subjected to post-Columbian dispersal and recent introduction of improved cultivars. The Hoima district of western Uganda additionally provides an excellent social setting for evaluating consequences of adoption because access to improved varieties has varied across farmer groups in this production region. This study establishes a baseline understanding of the common bean diversity found among household producers in Uganda and compares the crop population structure, diversity and consequences of adoption of household producers with different adoption practices. Molecular diversity analysis, based on 4,955 single nucleotide polymorphism (SNP) markers, evaluated a total of 1,156 seed samples that included 196 household samples collected from household producers in the Hoima district, 19 breeder-selected varieties used in participatory breeding activities that had taken place prior to the study in the region, and a global bean germplasm collection. Households that had participated in regional participatory breeding efforts were more likely to adopt new varieties and, consequently, diversify their seed stocks than those that had not participated. Of the three farmer groups that participated in breeding efforts, households from the farmer group with the longest history of bean production were more likely to conserve “Seed Engufu”, a local “Calima”-type variety of the Andean bean gene pool, and, at the same time, introduce rare Mesoamerican gene pool varieties into household seed stocks.

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Section: Resultsmentioning

confidence: 89%

Genetic Patterns of Common-Bean Seed Acquisition and Early-Stage Adoption Among Farmer Groups in Western Uganda

et al. 2018

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“…Moreover, progress in breeding for ALS resistance has been slow, mainly because of the high diversity of ALS pathogen races found in East Africa (Wagara et al, 2011;Ddamulira et al, 2014b;Leitich, 2016;Kijana et al, 2017). Research on ALS in East Africa has focused on the identification and genetic characterization of new sources of resistance in local landraces and released varieties (Ng'ayu-Wanjau, 2013;Ddamulira et al, 2014a;Leitich, 2016;Kijana et al, 2017). In these studies, Mexico 54 was found to be resistant to most races of P. griseola, and this cultivar is the most common source of ALS resistance in breeding in Uganda and East Africa (Namayanja et al, 2006;Chilagane et al, 2013;Ng'ayu-Wanjau, 2013;Ddamulira et al, 2015;Miller et al, 2018).…”

Section: Breeding For Angular Leaf Spot Resistance In East Africamentioning

confidence: 99%

A Review of Angular Leaf Spot Resistance in Common Bean

et al. 2019

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Angular leaf spot (ALS), caused by Pseudocercospora griseola, is one of the most devastating diseases of common bean (Phaseolus vulgaris L.) in tropical and subtropical production areas. Breeding for ALS resistance is difficult due to the extensive virulence diversity of P. griseola and the recurrent appearance of new virulent races. Five major loci, Phg‐1 to Phg‐5, conferring ALS resistance have been named, and markers tightly linked to these loci have been reported. Quantitative trait loci (QTLs) have also been described, but the validation of some QTLs is still pending. The Phg‐1, Phg‐4, and Phg‐5 loci are from common bean cultivars of the Andean gene pool, whereas Phg‐2 and Phg‐3 are from beans of the Mesoamerican gene pool. The reference genome of common bean and high‐throughput sequencing technologies are enabling the development of molecular markers closely linked to the Phg loci, more accurate mapping of the resistance loci, and the comparison of their genomic positions. The objective of this report is to provide a comprehensive review of ALS resistance in common bean. Furthermore, we are reporting three case studies of ALS resistance breeding in Latin America and Africa. This review will serve as a reference for future resistance mapping studies and as a guide for the selection of resistance loci in breeding programs aiming to develop common bean cultivars with durable ALS resistance.

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“…The major diseases constraining common bean productivity in Eastern and Central Africa include angular leaf spot (ALS) caused by Pseudocercospora griseola (Sacc.) (Ddamulira et al, 2014;Leitich et al, 2016) and anthracnose (Colletotrichum lindemuthianum (Sacc. and Magn.…”

Section: Marker-assisted Gamete Selection For Multiple Disease Resistmentioning

confidence: 99%

“…First, is the occurrence of new races and strains of disease pathogens, such as ALS, anthracnose, root rots, and BCMV (Leitich et al, 2016;Mwaipopo et al, 2017). In addition, there is insufficient identification and deployment of new sources of resistance to the emerging pathotypes (Ddamulira et al, 2014;Mukankusi et al, 2018), as well as a narrow genetic base within existing breeding populations, especially for grain yield potential and disease resistance. This threatens progress towards improvement for these traits (Kimani et al, 2005b;Asfaw et al, 2009).…”

Section: Marker-assisted Gamete Selection For Multiple Disease Resistmentioning

confidence: 99%

Validation of effectiveness marker-assisted gamete selection for multiple disease resistance in common bean

Mondo¹,

Kimani²,

Narla³

2019

Afr. Crop Sci. J.

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Plant breeding is the most cost-effective, practical and environmentally friendly strategy for reducing losses associated with bean diseases, especially in low-input agricultural systems because no additional investment is required from farmers. However, incorporating resistance to one pathogen may not result in a significant change because several diseases co-infection beans at the farm level. Consequently, breeding varieties with multiple disease resistance is a more appropriate, reliable and sustainable approach. In such context, gamete selection is the more appropriate breeding method because it allows simultaneous selection for multiple traits; though as originally proposed and validated, it is largely based on phenotypic evaluation for agronomic traits, which leads to delay in variety development and strong dependence on erratic weather conditions. The objective of this study was to validate 26 F 1.8 elite bean lines selected for resistance to angular leaf spot (ALS), anthracnose, root rots, common bacterial blight (CBB) and bean common mosaic virus (BCMV), from inter-racial and inter-gene pool populations developed using molecular markers on the gamete selection method in early generations. Pathogens were isolated from diseased plants collected from various locations in central Kenya, multiplied on appropriate media and used to inoculate the test lines in a greenhouse at Kabete Field Station, University of Nairobi. Data on disease incidence and severity were collected at 14, 21, 28 th days after inoculation, using the 1-9 CIAT scale; except for the root rot experiments for which data were recorded once at 21 st day after seedling emergence. Results showed that five of the 26 elite lines possessed multiple resistance to five pathogens, eight to four pathogens, nine to three pathogens, three to two pathogens and one was resistant to one pathogen. This implied that markers, used in early generations, were effective in the identification and transfer of resistance genes to susceptible commercial varieties. However, there were no significant correlations in the reaction of tested genotypes to pathogens in this study, except between BCMV and ALS (r=0.3942*). This suggests that resistance genes are in different chromosomes and are assorted independently. The presence of genotypes with multiple disease resistance among test elite lines, confirms the effectiveness M.J. MONDO et al. 586 of inter-racial crosses and marker-assisted gamete selection to concurrently improve the resistance to common bean major diseases in Eastern Africa.

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Pathogen Variability and New Sources of Resistance to Angular Leaf Spot Among Bean Landraces in Uganda

Cited by 10 publications

References 22 publications

Genetic Patterns of Common-Bean Seed Acquisition and Early-Stage Adoption Among Farmer Groups in Western Uganda

Genetic Patterns of Common-Bean Seed Acquisition and Early-Stage Adoption Among Farmer Groups in Western Uganda

A Review of Angular Leaf Spot Resistance in Common Bean

Validation of effectiveness marker-assisted gamete selection for multiple disease resistance in common bean

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