Browsing by Author "Kusolwa, Paul Mbogo"

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Characterization of the common bean host and Pseudocercospora griseola, the causative agent of angular leaf spot disease in Tanzania
(African Journal of Plant Science, 2016) Chilagane, Luseko Amos; Msolla, Susan Nchimbi; Kusolwa, Paul Mbogo; Porch, Timothy Gabriel; Diaz, Luz Miryam Serrato; Tryphone, George Muhamba
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.
Genetic characterization of angular leaf spot resistance in selected common bean landraces from Tanzania
(African Journal of Biotechnology, 2015-10-28) Tryphone, George Muhamba; Chilagane, Luseko Amos; Nchimbi-Msolla, Susan; Kusolwa, Paul Mbogo
Angular leaf spot disease (ALS) caused by Pseudocercospora griseola is one of the most important bean diseases in Tanzania. The bean landraces Beti-10, Nanka, Nanavala and Nkanamna used in this study have been identified as resistant to ALS but the nature of inheritance and mechanisms of resistance against ALS in those potential sources has not been elucidated. This information is crucial and a necessary first step for a successful breeding programme. The objective of this work was to study the inheritance of ALS resistance in those landraces and to identify the mechanisms of genetic resistance using Simple Sequence Repeat (SSR) markers. Crosses were made between resistant bean landraces and a susceptible bean cv Kablanketi. The parents, F1, F2 and backcrosses derived plants were used for inheritance studies and for molecular marker screening using 30 SSR markers. Results indicate that, a single dominant gene control resistance against ALS in each of the four landraces; also the SSR marker Pv-ag004 was found to be polymorphic between Beti-10 and Kablanketi and linked to the disease resistance. The resistance were validated by checking the F2 population of the cross between Kablanketi × Beti-10. Therefore, since marker Pv-ag004 is polymorphic and linked to ALS resistance, the Beti-10 landrace might be a potential source of ALS resistance. However, a detailed study with more markers need to be done on these landraces with a view to opening the possibilities of identifying new markers linked to ALS resistance and mapping of genes associated with resistance to ALS.
Incorporation of resistance to angular leaf spot and bean common mosaic necrosis virus diseases into adapted common bean (Phaseolus vulgaris L.) genotype in Tanzania
(African Journal of Biotechnology, 2012-07-03) Chilagane,Luseko Amos; Tryphone,George Muhamba; Protas, Deogracious; Kweka, Elisiana; Kusolwa, Paul Mbogo; Nchimbi-Msolla, Susan
Angular leaf spot (ALS) caused by the fungus Pseudocercospora griseola and Bean common mosaic and necrosis virus (BCMV/BCMNV) are important diseases of common bean in Tanzania that can cause severe yield reduction when uncontrolled. This study was conducted to incorporate resistant genes for ALS and BCMV/BCMNV diseases into adapted, market class and farmers and consumers preferred bean genotype using marker assisted selection. The parents Mexico 54 and UBR(25)95 donor of Phg-2 and I/bc-3 genes for ALS and BCMV/BCMNV, respectively were used for the recipient being Kablanketi. In selection, SCAR markers SNO2, ROC11 and SW13 linked to Phg-2, bc-3 and I gene, respectively were used. A parallel backcrossing (modified double cross) procedure was used. The F1, F2 and backcrosses from single crosses were characterized. The Chi square values for ALS were 0.081 (P<0.776) and 0.017 (P<0.896) and for BCMNV were 1.609 (P<0.205) and 1.2 (P<0.273) for molecular and phenotypic screening, respectively. The resistance to ALS and BCMNV was found to be monogenic and the genes involved are dominant and recessive, respectively. The heritability of ALS was found to be high (0.772) implying that selection for ALS can be done early in segregating populations. High correlation values, r = 0.741 and 0.624 for ALS and BCMNV, were obtained between phenotypic and molecular data, indicating high reliability for markers. In selection, it was possible to select lines with multiple disease resistances. This work signified the use of MAS for multiple gene screening.
Inheritance of Angular Leaf Spot [Phaeoisariopsis griseola (Sacc.) Ferr] Resistance in Common Bean (Phaseolus vulgaris L.) Population Developed from Kablanketi Mexico 54
(Journal of Agricultural Science and Technology, 2012-07-20) Tryphone, George Muhamba; Chilagane, Luseko Amos; Kusolwa, Paul Mbogo; Nchimbi-Msolla, Susan
The genetic resistance to angular leaf spot (ALS) caused by Phaeoisariopsis griseola in the common bean cultivar Mexico 54 was investigated on disease reactions in parental, F1, F2 and backcross generations derived from crosses between a resistant cultivar Mexico 54 and a susceptible cultivar Kablanketi under screen house conditions. The heritability (h2) estimate was as high as 0.719 indicating a successful transfer of ALS resistance among progenies and thus selection can be performed in early generation. High heritability coupled with high expected genetic advance of 39.5% is considered to be more useful in predicting the outcome of selecting the best individuals. Chi-square values were computed to determine whether the observed ratios for disease reactions deviated from expected Mendelian ratios for a single, dominant gene controlling resistance to angular leaf spot in common bean. Based on the resistance of the F2, and the backcross generation to the resistant parent, a 3 resistant: 1 susceptible segregation ratio in the F2 and a 1 resistant: 1 susceptible segregation ratio in the backcross generation to the susceptible parent was obtained implying that resistance to the isolate of Phaeoisariopsis griseola is governed by a single, dominant gene.
Inheritance of angular leaf spot [Phaeoisariopsis griseola (Sacc.) Ferr] resistance in common bean (Phaseolus vulgaris L.) population developed from Kablanketi x Mexico 54
(David Publishing, 2012-07-20) Nchimbi-Msolla, Susan; Tryphone, George Muhamba; Chilagane, Luseko Amos; Kusolwa, Paul Mbogo
The genetic resistance to angular leaf spot (ALS) caused by Phaeoisariopsis griseola in the common bean cultivar Mexico 54 was investigated on disease reactions in parental, F1, F2 and backcross generations derived from crosses between a resistant cultivar Mexico 54 and a susceptible cultivar Kablanketi under screen house conditions. The heritability (h2 ) estimate was as high as 0.719 indicating a successful transfer of ALS resistance among progenies and thus selection can be performed in early generation. High heritability coupled with high expected genetic advance of 39.5% is considered to be more useful in predicting the outcome of selecting the best individuals. Chi-square values were computed to determine whether the observed ratios for disease reactions deviated from expected Mendelian ratios for a single, dominant gene controlling resistance to angular leaf spot in common bean. Based on the resistance of the F2, and the backcross generation to the resistant parent, a 3 resistant: 1 susceptible segregation ratio in the F2 and a 1 resistant: 1 susceptible segregation ratio in the backcross generation to the susceptible parent was obtained implying that resistance to the isolate of Phaeoisariopsis griseola is governed by a single, dominant gene.
Introgression of common bacterial blight (xanthomonas axonopodis pv. phaseoli) resistance to common bean (phaseolus vulgaris L.) adapted to Tanzania facilitated by marker assisted selection
(International Scholars Journals, 2012-10-09) Tryphone, George Muhamba; Chilagane, Luseko Amos; Protas, Deogracious; Kusolwa, Paul Mbogo; Msolla, Susan Nchimbi
Common bacterial blight (CBB) caused by Xanthomonas axonopodis pv phaseoli (Xap) is an important disease of common bean in Tanzania causing severe damage. This study was carried out to introgress resistance to CBB to the adapted common bean in Tanzania with the facilitation of molecular markers along with determining the inheritance and heritability of the disease. Crosses were made between the adapted parent Kablanketi and the resistant parent Vax 4 and their F1, F2 and the backcrosses to both parents generated. The phenotypic evaluation was carried out after inoculation with Xap and the molecular marker was applied on the F2 generations using the SCAR marker SAP 6 linked to a QTL for CBB resistance. The result shows no significant deviation from the expected 3:1 (χ2 = 0.47; P>0.05) in the F2 population and 1:1 for the backcross to the susceptible parent. These results that resistance in Vax 4 to Xap is conditioned by the presence of dominant genes. The moderate heritability of 0.32 was estimated implying that resistance is conditioned by one major gene which has effects of partial resistance. There were significant correlation between the phenotypic reaction and molecular marker screening (resistant QTL) (r = 0.502; p<0.05). This indicates there are greater chances of selecting resistant individuals using molecular markers which also exhibited resistance under field conditions .