PABRA Theses

Permanent URI for this collectionhttps://hdl.handle.net/10568/96162

Browse

Recent Submissions

Now showing 1 - 12 of 12
  • Thumbnail Image
    Item
    Characterization of Pseudocercospora griseola, identification of local sources of resistance and effectiveness of gene pyramiding in controlling angular leaf spot in common bean
    (Journal Article, 2016) Ddamulira, Gabriel
    Angular leaf spot (Pseudocercospora griseola) is a major disease of common bean (Phaseolus vulgaris L.) globally and accounts for 50% yield loss in Uganda. High levels of variety resistance to the disease would minimise yield losses. This study was conducted to; determine the distribution and variability of angular leaf spot (ALS) pathogen, identify new sources of resistance and their inheritance, and elucidate the effectiveness of pyramided genes in improving ALS resistance. A survey was conducted in ten districts of Uganda to determine the distribution of P. griseola, and angular leaf spot differential cultivars and molecular makers were used to define the variability of P. griseola. On the other hand, eighty bean genotypes were screened with four P. griseola isolates to identify new sources of ALS resistance. Futhermore crosses were made between the identified resistant source (U00297) with susceptible parents (K132, K131 and Kanyebwa) as well as other resistant parents (G5686, AND277 and Mexico 54) to generate F1, F2 and back crosses. The parents with their progenies were inoculated with P. griseola isolates 61:63, 21:39 and 17:39 to determine the inheritance of ALS resistance and allelic relationship between resistance genes. Similarly, ALS resistant genes in Mexico 54, AND277 and G5686 were pyramided into single genotypes using a cascading scheme to generate single cross (SC), triple cross (TC) and four parent cross (FPC). The SC, TC and FPC were then crossed with susceptible parents (Kanyebwa and K132) to generate F1 and F2. The F1, F2 with their parents were screened with P. griseola isolate 61: 63 to determine the effectiveness of the pyramided genes in improving ALS resistance. Results showed that angular leaf spot was widely distributed in all districts and altitudes surveyed. The highest disease incidence (68.5%) and severity (46%) were recorded in Dokolo district and the lowest incidence (29%) and severity (11.2%) in Kisoro. Both disease incidence (60%) and severity (45%) were higher in low altitude areas than incidence (33.6%) and severity (20.7%) in high altitude areas. The pathogen was highly variable with 12 pathotypes and 30 haplotypes, defined by ALS differential cultivars and molecular markers, respectively. Pathotype 17:39 and 61:63 were observed to be the most prevalent and virulent in Uganda. U00297 was resistant to all the four pathotypes and regarded as a new source of ALS resistance in Uganda. Segregation ratios of F2 populations indicated that U00297 resistance to pathotype 17:39 was conferred by a dominant gene, while digenic epistatic gene interaction was were responsible for its resistance to pathotypes 61:63 and 21:39. In addition, the dominant gene in U00297 was independent of resistance genes harboured in AND277 and G5686. The pyramided genes showed varying segregation ratios depending on the type of cross. The SC, TC and FPC crosses best fitted for 15:1, 61:3 249:7 ratios, suggesting that SC, TC and FPC segregated for two, three and four genes, respectively. The pyramided genotype (FPC) exhibited the highest level of ALS resistance to the most virulent pathotype 61:63 indicating that crosses with combined resistance genes were more effective in transferring ALS resistance to susceptible bean cultivars.
  • Thumbnail Image
    Item
    Introgressing resistance to fusarium root rot in selected farmer preferred Andean bean genotypes from Meso-American line and mapping of associated resistance quantitative trait loci
    (Thesis, 2010) Kamfwa, Kelvin
    The common bean (Phaseolus vulgaris L.) is a primary protein source in the diet of many low-income populations worldwide. Bean root rots have been reported to occur in most bean fields throughout the world. In Uganda, bean root rot is one of the major constraints to bean production, with that caused by Fusarium solani (Mart.) f.sp. phaseoli (Burkholder) (N.C. Snyder & H.N. Hans) resulting in substantial yield losses. The use of resistant varieties is probably the most effective control measure against Fusarium root rot, especially for small-scale farmers with limited access to fungicides. Sources of resistance to Fusarium root rot exist in common beans and have been reported to occur in Africa. Most of the developed and identified resistant genotypes are either late-maturing and small or black-seeded, with a climbing growth habit. None of the commercial Andean bean varieties currently grown in Uganda are resistant to this pathogen. Genetic resistance to Fusarium root rot is polygenic and is strongly influenced by environmental factors. Response to selection for quantitative traits, such as root rot resistance, is slow due to the genetic complexity of the trait and the difficulty in evaluating resistance. Indirect selection for Fusarium root rot resistance based on genetic markers linked to the quantitative trait loci (QTL) for resistance would facilitate improvement, given the limitations of field selection, which are expensive, not consistent across environments and require destructive sampling. The overall objective of this study was to develop approaches based on quantitative trait loci for improving resistance in common beans to Fusarium root rot. The specific objectives were: (i) to confirm the usefulness of a Meso-american source (MLB 49-89A) in transferring resistance to Fusarium solani f.sp. phaseoli into locally adapted Andean types (K20 and K132); (ii) to identify quantitative trait loci that condition resistance to Fusarium root rot in common beans. Two populations of 90 and 78 F4:5 recombinant lines from K20 x MLB-49-89A and K132 x MLB-49-89A respectively, were used to confirm the usefulness of a Meso-american source (MLB 49-89A) in transferring resistance to Fusarium solani f.sp. phaseoli into locally adapted Andean types (K20 and K132). Both K20 and K132 are susceptible to Fusarium root rot, while MLB-49-89A is resistant. The two populations and their parents were evaluated for Fusarium root rot in a screenhouse using a randomised complete block design with two replications in wooden trays measuring 0.74 x 0.42 x 0.115 m. The K20 x MLB-49-89A population was skewed toward resistance while K132 x MLB-49-89A was skewed toward susceptibility. These results therefore clearly show differences in parental effects of K20 and K132 on the resistance to Fusarium root rot. Such differences in means and distributions between the two populations suggest that K20 possesses one or more genes that interact in an epistatic manner with two or more resistance loci in MLB-49-89A. In contrast, K132 apparently lacks the beneficial allele that is present in K20, or has an alternate allele that enhances susceptibility. The frequency distributions for both populations were bimodal, suggesting that a major gene was involved in resistance. A number of lines that had very good resistance levels to Fusarium root rot were identified from both populations. Both the narrow and broad sense heritabilities obtained for K132 x MLB-48-89A in this study were very high (h2B=0.99; h2N=0.98, referenced to additive variance in the F2, reported on a line-mean basis from 2 replications). On the same basis, heritability estimates in K20 x MLB-48-89A were also high (h2B=0.86; h2N=0.81). The heritability estimates obtained in this study and in previous studies by Mukankusi (2007) indicate that improvement of the Andean varieties for resistance to Fusarium root rot using the Meso-american line MLB-49-89A should be possible. The results of this study have shown that when when using MLB-49-89A, it would be easier to improve K20 than K132 for Fusarium root rot resistance. The cross of K132 x MLB 49-89A was emphasized for the mapping study. A total of 35 SSR markers were screened for polymorphism in the parents. Fifteen of the 35 SSR markers were polymorphic, representing 42% of the tested SSR markers. Twelve of the SSR markers gave clearly distinguishable bands and were therefore used for analysis. A mapping population of 62 F4:5 recombinant inbred lines of K132 x MLB 49-89A was used for identifying quantitative trait loci conditioning resistance to Fusarium root. A linkage map was constructed by placing nine of the polymorphic SSR markers into three partial-linkage groups, each with three SSR markers. The other three markers did not connect to these three linkage groups. Using single marker analysis, two SSR markers that were closely linked to each other (PVBR87 and PVBR109) were significantly associated with Fusarium root scores (p<0.0001) in K132 x MLB-49-89A population. Another SSR marker, PVBR255, showed significant effects on Fusarium root rot scores, but at a reduced significance level (p≤0.05). The other nine SSR markers showed no significant effects. Composite interval mapping detected a major QTL in K132 x MLB-49-89A population between PVBR87 and PVBR109 with a LOD score of 6.1 and coefficient of determination (R2) of 34% and did not assign independent significance to the distantly-liked marker, PVBR255. Therefore, only one QTL was detected in the present study, but it is a major QTL, as indicated by the large R2. The two markers associated with the QTL (PVBR87 and PVBR109) are found on linkage group B3 of the common bean core map, close to the region where resistance to root rots, anthracnose, common bacterial blight and bacterial brown spot have been previously mapped. Only four SSR markers (PVBR87, PVBR109, BM156 and BM172) were used in the K20 x MLB 49-89A population because of resource constraints. The two SSR markers (PVBR87 and PVBR109) that were significantly associated with Fusarium root rot resistance in K132 x MLB-49-89A population, also showed significant associations (R2 = 14%, P < 0.001) in the K20 x MLB-49-89A population. This is a confirmation of the presence of a QTL identified on linkage group B3 close to these two markers in the K132 x MLB-49-89A population. The association of this major QTL with resistance in both populations suggests that this QTL may be useful more broadly. There is need to determine whether this QTL is also present in different sources of resistance and whether the two associated SSR markers are useable for marker-assisted selection in a wider range of materials. Fine-resolution mapping could be achieved by using additional markers near the identified markers, enhancing the efficiency of marker-assisted selection and revealing whether this is indeed a single QTL or whether it is made up of several linked QTL, each with a small effect. The detection of this major QTL for resistance to Fusarium provides good prospects for using QTL--based approaches to introgress resistance to Fusarium root rot from Meso-american genotypes into locally adapted Andean bean genotypes.
  • Thumbnail Image
    Item
  • Thumbnail Image
    Item
    Improvement of resistance to fusarium root rot through gene pyramiding and validation of SSR PVBR87 marker in common bean
    (Thesis, 2011) Obala, Jimmy
    Fusarium root rot caused by Fusarium solani f. sp. phaseoli is among the most serious diseases of the common bean in Uganda causing total crop loss in susceptible cultivars. Studies have indicated that 2-9 genes located at different loci govern resistance to Fusarium root rot among different resistance sources. Accumulation of several of these genes from the different sources into a single genetic background has been proposed to result in an increased level of resistance to Fusarium root rot, and more effective transfer of this resistance into consumer-preferred cultivars. Use of molecular markers together with phenotypic selection could speed up breeding progress for Fusarium root rot resistance. A simple sequence repeat (SSR) PVBR87 marker linked to Fusarium root rot resistance quantitative trait loci (QTL) was identified in a previous study but its use in identifying resistant genotypes outside the original two mapping populations has not been determined. This study estimated the number of pyramided Fusarium root rot resistance genes from four sources of resistance, their interaction and effectiveness in improving Fusarium root rot resistance levels. The study also validated the association of the SSR PVBR87 marker with resistance to Fusarium root rot in an additional population. The study was conducted at the International Centre for Tropical Agriculture (CIAT) based at the National Agricultural Research Laboratories – Kawanda, Uganda. Four Fusarium root rot resistant (R) inbred lines: MLB-48-89A (48), MLB-49-89A (49), G2333 (G2) and G685 (G6), and two susceptible (S) lines: K20 and Kanyebwa (Kan) were used in the study. A double cross (DC) was developed from the four resistant parents. The DC F1 and each resistant parent were crossed to the two susceptible cultivars to form five-parent crosses and single crosses, respectively. Parental, F1 and F2 populations were subjected to Fusarium solani f. sp. phasoeli isolate-3. Twenty one days xi after planting, symptom severity was assessed on a scale of 1-9 (varied at 1,2,3,4,5,6,7,8,9). Plants of each cross were grouped into resistant (score 1-4) and susceptible (score 5-9). F2 plants of K20 x G2 and 49 x Kan were screened with SSR PVBR87 marker. The estimated number of genes and gene interactions were determined using X2 goodness-of-fit test (P = 0.05) and means were compared by “Students t-test” (P = 0.05). The association of SSR PVBR87 marker to Fusarium root rot resistance was determined using X2 test of independence and single marker regression analysis (P = 0.05). Two to three genes segregated in the R x R single crosses and at least four genes segregated in the double cross population indicating three of the four resistant parents differed from each other by at least one gene and two of the four parents have at least one gene in common. Genetic effects among the crosses included additive and dominance effects and epistatic interactions. Five-parent crosses performed better than the single crosses, demonstrating the potential of using combined resistance in improving resistance to Fusarium root rot in susceptible bean cultivars. The SSR PVBR87 marker showed significant association to Fusarium root rot resistance in both K20 x G2 and Kan x 49 indicating its stability in different genetic background but still requires further validation in different environments and in additional genetic backgrounds to determine its use for marker-assisted breeding for improving resistance to Fusarium root rot. The genes responsible for the higher levels of Fusarium root rot resistance in the pyramids are not specifically known. It is necessary that these resistance genes be tagged with molecular markers. Tagging of the genes with molecular markers would provide knowledge of their genomic locations, the nature of their interactions and also facilitate the transfer of these genes or alleles, through molecular marker-assisted gene introgression, into other agronomically superior, but Fusarium root rot susceptible cultivars. Since no selection for Fusarium root rot resistance or any other desirable agronomic traits was practiced in this study, there is need to select between and within families from among the five-parent cross populations and the single crosses for resistance to Fusarium root rot. However, the predominance of non-additive gene effects for Fusarium root rot resistance, especially in the five-parent crosses suggests that selection for resistance would be more effective at advanced generations of selfing. The bean parents used in constructing the five-parent cross populations are of diverse seed character, growth habit, maturity period, and have varied response to several abiotic and biotic constraints. There is also need to select for these traits in the populations developed in this study as these traits eventually affect acceptability of any potential new variety. The amounts of phenotypic variation explained by the SSR PVBR87 in two populations were low; hence, there is still need to further validate the marker in additional populations and in several environments to determine its efficacy for marker-assisted breeding for Fusarium root rot resistance.
  • Thumbnail Image
    Item
    Agronomic performance and farmer preferences of selected bean varieties in uganda, hoima and rakai districts
    (Thesis, 2015) Awio, Bruno
    Genetic resources are one of the key strategies with which farmers respond to occurring and unpredicatable weather patterns. This study was aimed at testing the performance of farmer-acceptable improved multiple stress tolerant bean varieties and assessing farmers perceptions through participatory variety selection approach in the districts of Rakai and Hoima in Uganda. The specific objectives of the study were to determine the agronomic pefromance for yield and disease reaction of the bean varieties in multi-environment trials, and to understand variety selection criteria of farmers and compare it with that used by breeders to determine where there is convergence/divergence and its implications for breeding and the selection of varieties for future participatory variety selection studies. The study was conducted with nine selected farmer groups in Hoima and Rakai district. These districts were identified to experience contrasting climatic conditions, degraded soils and declining soil fertility by the Climate Change, Agriculture and Food Security programme (CCAFS) of the Consultative Group for International Agricultural Research (CGIAR). Fifteen bean varieties bred for different traits were tested in six villages to determine their performance for yield and yield components, and reaction to diseases and in nine villages for farmer preference. Each trial was planted in split plot design with two replicates. Finlay and Wilkinson (FW), the Additive Main Effect and Multiplicative Interaction (AMMI) analysis and Genotype + Genotype interaction (GGE) biplot were used to assess G x E effects on performance for key agronomic traits of the fifteen varieties in six locations. Researchers selection index were derived from the traits measured in the trials and compared with the farmers’ preference index using spearman rank correlation. The result indicates that the six environments under evaluation could best be classified in two mega-environments based on the yield output of clean seed. Mega-environment 1 consisted of Gosola village in Rakai, and three villages in Hoima district; Butimba, Butyamba and Kyakamese village while mega-environment 2 consisted of two villages; one in Rakai; Ninzi and another in Hoima, Mpalangasi village. Varieties NABE 2 and NABE 14 performed best in one mega-environment while varieties ROBA 1 and NABE 2 were the best in the second mega-environment. Based on Finlay and Wilkinson and AMMI, varieties Masindi Yellow Long, NABE 17 and CAL 143 were the most stable while varieties ROBA 1, NABE 2 and RWR 719 were high yielding but unstable in clean seed weight. The latter varieties (viz. ROBA 1, NABE 2 and RWR 719) were also highly responsive to environment difference in number of pods and in reaction to the three diseases, namely, ALS, bean rust and CBB disease severity. The number of pods per plant and reaction to disease were the traits less influenced by genotype-by-environment interaction. A significant but negative spearman rank relationship was observed between choices of researcher and that of farmers’ for varieties. Varieties RWR 719, NABE 2, NABE 14 and ROBA 1 were the best based on researcher ranking. While Masindi Yellow Long, Farmers’ seed and NABE 17 were farmer preferred varieties. Some of the introduced varieties were as well liked as the local varieties. The exotic varieties of choice included KAT B1, KATX 69, KATX 69 and KATX 56. Early maturity, seed size and colour (KAT B1) are attributes that could have favoured the varieties selection by farmers. These findings imply that Masindi Yellow Long was the most popular variety and produced stable clean seed yield across locations. The variety however, was found highly susceptible to diseases. Thus, improvement of Masindi Yellow Long by researchers would improve food security situations in the CCAFS selected sites and in the whole of Uganda. Furthermore, strong researcher-farmer collaboration will be required in the futur for selection and development of improved varieties to ensure high likelihoods of adoption of varieties that are resilient to stresses influenced by the changing seasonal weather patterns
  • Thumbnail Image
    Item
    Quantitative trait loci underlying drought tolerance in the (brb 191 x seq 1027) f5 recombinant inbred line population of common bean (Phaseolus vulgaris l.) in Uganda
    (Thesis, 2017) Nabateregga, Mabel
    The common bean (Phaseolus Vulgaris L.) is the most important food legume crop for direct consumption in the world. The crop is a primary protein source in the diet of many low-income populations globally. However, drought has become a major constraint affecting over 60% of dry bean production worldwide causing crop failure, hunger and poverty especially in Uganda. Development of drought tolerant cultivars is the most effective control measure in mitigating effects of drought on dry bean production. Significant research efforts have been made over the past two decades to improve common bean adaptation to drought. Consequentially, sources of drought tolerance have been identified; however, the genetic diversity and mechanistic behavior of drought tolerance within the common bean is still not fully understood. Drought tolerance is a physiologically complex process integrating several mechanisms and quantitative traits, which has made breeding for drought tolerance in the common bean very problematic. Furthermore, evaluation for drought tolerance is very laborious, time consuming and employs destructive sampling, which has further slowed efforts of improving the common bean. Therefore, marker assisted selection using genetic markers that are tightly linked to quantitative trait loci (QTL) controlling drought tolerance traits is the most feasible solution. The aim of this study was to identify phenotypic traits and quantitative trait loci underlying drought tolerance in the common bean. More specifically this research study aimed at (i) identifying key phenotypic traits and sources of drought tolerance in the intra-gene pool Andean cross (BRB 191 x SEQ 1027) population, (ii) Mapping QTL controlling drought tolerance in the genome and markers flanking these QTLs. The BRB 191 x SEQ 1027 population derived from drought tolerant lines BRB 191 and SEQ 1027 was evaluated for two years and I year under field and greenhouse conditions respectively at Kawanda in Uganda. The F5 RIL population comprising of 128 lines was assessed under drought stress (DS) and non-stress (NS) environments for twenty (20) drought related traits which included agronomic, morphological, phenological, and physiological components. Viable sources of drought tolerance were identified in the (BRB 191 x SEQ 1027), namely: lines114, 117, 91 and 41. Also, BRB 191 was affirmed as a viable source of drought tolerance. Drought stress in the field significantly affected all measured traits except harvest index (HI) and stem biomass reduction (SBR) (P˂0.001). However, chlorophyll content (SCMR), canopy temperature (CT), stem biomass reduction (SBR) and 100 seed weight (100SW) remained significantly stable under season by genotype by environment (Sn. Gen. E) interactions and genotype by environment (G x E) interactions as well (P˂0.001). Stability of these traits highlighted their usefulness in selecting for drought tolerance across different environments. Furthermore, pod partitioning index (PPI), harvest index (HI), chlorophyll content (SCMR) and stem biomass reduction (SBR) remained significantly stable under G x E effects. Significant correlations (P˂0.001) were also maintained between HI and PPI with seed yield under drought stress for 2 years in the field indicating the viability of photosynthate remobilization in increasing yield potential under drought stress conditions. A linkage map spanning 204.7 cM with an average distance of 3.4 cM between marker intervals was constructed using 60 single nucleotide polymorphic (SNP) markers in this study. Inclusive composite interval mapping (ICIM) revealed thirty six (36) major QTL from field (29 qtl) and greenhouse (9 qtl) evaluations (LOD≥3.0). Co-localization and clustering of a large number of QTL was detected on pv02 at 4 major chromosome positions. A major seed yield QTL SY2.1BS on pv02 was tightly linked to five major QTL associated with pod partitioning and phenology. Pleiotropy was also detected in the greenhouse between leaf biomass and phenology. QTL associated with seed weight and phenology mapped near previously reported QTL. The above findings provide a possibility for marker assisted breeding using markers tightly linked to photosynthate remobilization.
  • Thumbnail Image
    Item
    Inheritance and characterization of cooking time, seed iron and zinc content in selected African common bean germplasm
    (Thesis, 2017) Mukai Mughi, Irene
    Long cooking time for beans continues to be a major hindrance to the widespread consumption of beans. Prolonged cooking time leads to structural changes at the grain cellular level, resulting in a loss of nutrients such as Iron (Fe) and Zinc (Zn) which are important nutrients in addressing micronutrient malnutrition (“hidden hunger”). The aim of this study was to evaluate the diversity for cooking time, iron and zinc content in a total of 152 genotypes from around eastern Africa, including Kenya, Uganda, Tanzania, Ethiopia, and Rwanda, and to determine the mode of inheritance for cooking time, Fe and Zn content in common bean genotypes. A total of 152 common bean genotypes released by the Pan-Africa Bean Research Alliance (PABRA) across Eastern Africa were planted in the field at International Centre for Tropical Agriculture (CIAT) farm at Kawanda, 13km from Kampala city, during two rainy seasons of 2015 B (April – July) and 2015D (September – December). Data collected included soil nutrient composition for the site used in each season, agronomic data and disease data. Six parental genotypes were crossed in a screen house at CIAT-Kawanda, using a 6 x 6 half diallel mating design. The F1’s were advanced to F2 generation which was subjected to cooking time, Fe and Zn content tests. Cooking time test was carried out at CIAT-Kawanda on plot basis using the standardized Matson cooker method. Fe and Zn analysis was carried out at Rwanda Agricultural Board (RAB) research station in Rubona using the X-Ray Fluorescent (XRF) platform. Across the two seasons, among the 152 genotypes studied, 5 had a cooking time of <45 minutes, 55 genotypes cooked for 46-60 minutes and 92 genotypes cooked for >61 minutes. In response to Fe and Zn seed content, 8.7% were high in Fe (>70 mg/kg) whereas 69.1% were high Zn (>30 mg/kg). A total of 15 genotypes (Amahunja, Awash melka, Bihogo, CAB 2, ECAPAN021, G858, Icaquimbaya, KK20, NABE12C, NABE4, NABE6, ROBA-1, RWR1873, RWV3006) were consistent in short cooking time for the two seasons and had a Fe content above the low Fe check (CAL96 – 55mg/kg). Analysis of variance showed a highly significant variation among genotypes, general combining ability (GCA) and specific combining ability (SCA) components in the F2 for cooking time, Fe and Zn content, indicating that additive variance predominated with non-additive gene effects contributing a considerable amount of variations. Awash melka had the desired GCA combination for cooking time, Fe and Zn content. Significant SCA effect for cooking time and high Fe content were observed in NgwakuNgwaku x KATX56 identifying it as a good cross for combining short cooking with high Fe and Zn content.
  • Thumbnail Image
    Item
    Inheritance of resistance to common bacterial blight (xanthomonas campestris pv. phaseoli) disease and yield of common bean
    (Thesis, 2015) Divage, Belarmino
    The common bean (Phaseolus vulgaris L.) is a legume grain crop with great importance in East Africa, being a source of food and income for most rural households. In Uganda, common bean is a major source of food security being a readily available and popular food to both the urban and rural population. However, productivity of the crop is limited by many diseases, common bacterial blight (CBB) caused by Xanthomonas campestris pv phaseoli (Xcp) being one of them. The use of natural resistance to CBB is the most effective and environmentally sound approach among others to control this disease. This study aimed at i) identifying new resistance genes to CBB and ii) understanding the mode of inheritance in the newly identified sources of resistance. Eighty genotypes (65 lines from the PABRA regional nutritional nursery, 10 interspecific lines (P. coccineus x P. vulgaris) coded ALB, five docummented sources of CBB resistances coded VAX and 24 newly developed resistance lines coded ACC were screened for CBB resistance in a screen house at CIAT Uganda. A Fuscans (Xcpf ) variant of Xanthomonas campestris pv. phaseoli (Xcp ) isolate named “Kawempe 1” was used. From the screening, six genotypes namely JESCA, RWV 2070, RWR 2154, MIB 456, NUA 45 and MCM 2001 were found to have good resistance to CBB. To determine the mode of inheritance of the identified resistance in these six genotypes, crosses with locally prefered genotypes were made, two landraces; Masindi Yellow (large seeded yellow) and Kanyebwa (medium sized red speckled sugar bean), and two released varieties; K131 (small seeded carioca seed type) and K132 (large seeded red mottled) using North Carolina Design II matting design. All the F1 seed available was planted and F1 progenies were advanced to F2 generations in screen house and evaluated for resistance to Xcp using Xanthomonas campestris pv. phaseoli var.Fuscans (Xcpf ) variant of Xanthomonas Campestris pv. phaseoli (Xcp ) ―Kawempe 1‖ . Heritabilities estimates and segregations patterns showed that additive effects predominated over non additive ones with quantitative inheritance. Among the six resistant MCM 2001 and RWV 2070 showed the strongest GCA effect hence most effective resistance. Masindi Yellow X RWR 2070, Kanyebwa x RWR 2070, K 132 x MIB 465, K 131 x JESCA and K 131 x MCM 2001, were considered the most desirable crosses for CBB resistance. The crosses K132 x JESCA, K132 x MIB 456 and Masindi Yellow x RWR 2070 had good mean values for all the yield parameters under analysis. Chi-square tests for goodness of fit showed the presence of more than one gene controlling the resistance to CBB on the materials used on this study. Some of the susceptible parents (K132 and Kanyebwa ) were shown to posses factors contributing to CBB resistance. The heritability estimates for broad-sence and narrow sence coefficient of genetic determination was 0.65 for both, because the SCA variance was negligible due to its negative value, the Bakers ratio was 1, with more than one gene involved with epistatic interaction. From the study findings, it is recommended that the characteristics of resistance to CBB should be investigated in every new parental source when they are initially introduced into the breeding programme. It is also recommended that breeding methods such as crossing and selfing or backcrossing that make the best use of additive variance, should be used to transfer CBB resistance into susceptible commercial and preferred varieties, since the additive gene actions were more important than non-additive gene effects. Generations could also be advanced by the single-seed-descent method or F2-derived families harvested in bulk, due to high hereditability estimation value. Later the promising genotypes should be subjected to multi-location trials to test the stability of their performance while enriching findings regarding their gene action. The promising stable varieties identified should be subjected to selection, preferably with participation of farme
  • Thumbnail Image
    Item
    Consumer preference for bean attributes: a study in Kiambu county, Kenya
    (Thesis, 2013) Gitonga, Hannah W.
    Common bean (Phaseolus Vulgaris L.) is an important legume that provides income and food in Kenya. The Kenyan bean market has a bean deficit of 10,800 metric tons. This is despite intensive breeding work that has resulted in bean varieties that are high yielders, superior in withstanding biotic and abiotic stresses. There should be a shift on how beans are produced if Kenya is expected to be self sufficient in bean production. Focus should shift from how much beans can be produced within a given area, as has been the case, to production of what is acceptable in the market by consumers. This study focused on consumer preference for common beans in two districts, Thika East and Thika West of Kiambu County. The two were chosen because of their high population, diverse socioeconomic characteristics of residents since the two districts had both rural and urban living setups. Questionnaires with structured and open ended questions were used to reach 212 consumers and 67 traders. A hedonic price model was used to analyse effect of preferred attributes on price. Results showed that beans were an important part of respondents diet with majority of respondents (86%) consuming beans more than once a week. Rural respondents consumed beans more frequently compared to urban respondents; difference in consumption was statistically significant (0.025). Beans were popular with women (83%) and were consumed by all age groups but there was more consumption in the 31-40 years age group (26.8%). GLP 585 was ranked 1st by 64.7% respondents, GLP 2 was ranked 2nd (43%) and KAT X56 was ranked 3rd (39.8%) respondents. GLP varieties were popular among urban respondents while rural respondents consumed both GLP and KAT varieties. Consumers had preference for Cooking quality, keeping quality, color, taste, low flatulence and grainsize attributes associated with GLP 585, KAT X56 and GLP 2 varieties. Cooking quality and keeping quality were important attributes consumers considered when making purchase decisions. They were willing to pay a premium for color and discount for flatulence of KAT X56. They were willing to pay a premium for taste and discount for grainsize of GLP 585. These results suggest efforts should be focused on improvement of these attributes. Exploration of other factors that effect price consumers would be willing to pay for a variety should be undertaken. Promotion campaigns should be undertaken to create awareness of nutritional value of beans. Value chain analysis of beans to come up with ready to use products with high nutritional value is recommended.
  • Thumbnail Image
    Item
  • Thumbnail Image
    Item
  • Thumbnail Image
    Item