Applied Plant Sciencehttps://repository.maseno.ac.ke/handle/123456789/7002024-03-29T11:07:30Z2024-03-29T11:07:30ZGeneral and specific combining ability for grain and yield components in a diallel cross among selected nine inbred lines of maize (Zea mays L)MUREITHI, Gladys Wanjikuhttps://repository.maseno.ac.ke/handle/123456789/59252023-12-21T13:27:01Z2023-01-01T00:00:00ZGeneral and specific combining ability for grain and yield components in a diallel cross among selected nine inbred lines of maize (Zea mays L)
MUREITHI, Gladys Wanjiku
Analysis of combining ability plays an important role in identifying elite parents and crosses which can give best combinations based on the performances of their offspring. Hybrid variety production requires broad genetic base among the germplasm as materials to be used as parents because their increase heterosis which can be exploited. There is little knowledge on general and specific combining ability of inbred lines developed by Maseno University maize breeding programme which lead to development of inferior parent and crosses, also knowledge on inbred lines make breeding process more effective as save breeding cost and time. The general objective of this study was to identify parents and crosses with desirable combining ability in order to contribute to increased grain yield. The specific objectives were to analyze general and specific combining ability among selected maize inbred lines and their hybrids for grain yield and yield components among selected inbred lines and their hybrids, assessment of heterosis for F1 hybrids involving selected inbred lines of maize. The study was carried out in the Maseno University demonstration farm between 2019-2021 The study involved making crosses among nine inbred lines in half diallel method II model I to obtain 36 F1 hybrids and evaluating them. The nine inbred lines and their 36 hybrids were planted in randomized complete block design with three replications. The crosses were used to estimate general combining ability (GCA) and specific combining ability (SCA) effects on grain weight, yield related traits and assess heterosis for the F1 hybrids in order to select suitable parents for hybridization and identify superior and promising hybrids. The eight traits measured included days to 50% flowering, days to 50% silking, plant height, ear height, cob length, and cob width, number of rows per cob and grain weight. The data were subjected to Analysis of variance (ANOVA) and means separated using the Least Significant difference at p< 0.05. Mean squares for genotype, SCA and GCA were found to be significantly different. Inbred lines F620R, Cy441/2 and RC 9 were found to be good general combiners for most of the traits hence they can be useful for hybrids development. Crosses F620R X Ex 389, Ex614P X F620R, Ex614P X F-white, F-white X Cy441/2 and Cy441/2 X RC 9 had high positive and significant SCA for grain weight and most of yield related traits hence can be used to develop superior hybrids. Specific combining ability based on yield was used to indicate heterotic grouping of crosses. GCA: SCA ratio were high for days to 50% flowering, days to 50% silking, plant height and number of rows per cob while it was low for ear height, cob width, cob length and grain weight. This shows the importance of both GCA and SCA in inheritance of yield and yield related traits. Among 36 F1s all crosses exhibited high heterosis for grain yield except Ex 614P X Ex bear, Ex 614P X Ex 389, Ex 389 X Bear614 and F620R X Cy441/2 which exhibited low heterosis values. Identified parents and crosses with high GCA and low SCA values could be used in development of superior hybrids and synthetic varieties. There was significance difference in GCA, SCA and heterosis among genotypes hence they is genetic difference which can be exploited further.
Master's Thesis
2023-01-01T00:00:00ZCharacterization of the Genetic Diversity of Cercospora Zeina in Kenya and Mapping the QTL for resistance to Gray Leaf Spot and Turcicum Leaf Blight in MaizeOMONDI, Dennis Oduorhttps://repository.maseno.ac.ke/handle/123456789/53342022-08-23T06:21:51Z2022-01-01T00:00:00ZCharacterization of the Genetic Diversity of Cercospora Zeina in Kenya and Mapping the QTL for resistance to Gray Leaf Spot and Turcicum Leaf Blight in Maize
OMONDI, Dennis Oduor
Gray leaf spot (GLS) caused by Cercospora zeina in Africa and Turcicum leaf blight (TLB) caused by Exserohilum turcicum are a major threat to maize production due to the associated grain yield losses. Resistance in the currently grown maize hybrids could be overcome by high levels of genetic diversity that characterize C. zeina and E. turcicum populations. However, little is known concerning the population structure and diversity of C. zeina in Kenya. The objectives of this study were first to characterize the genetic diversity of C. zeina. Secondly to map the quantitative trait loci (QTL) conditioning resistance to GLS and TLB in the double haploid (DH) population from CML511×CML546. The genetic diversity of C. zeina and the role of sexual recombination in this population was determined by collecting GLS infected maize leaves from four counties in Kenya. The genomic DNA for the 129 successful isolates were assayed using previously designed mating type (MAT) primers and genotyped using 11 microsatellite markers. The CTB7 (cercosporin toxin biosynthesis 7) test confirmed that all the isolates sampled were C. zeina as they all produced PCR products of 618 bp. The population exhibited high levels of gene diversity (He=0.445), slightly high gene flow (Nm=3.85) and high level of polymorphism. In addition, the four counties were characterized by nearly equal distribution of the two mating types, providing evidence that it could be undergoing sexual recombination. Occurrence of sexual recombination could be responsible for the high genetic diversity. STRUCTURE analysis revealed that the population clustered into four sub-groups according to the four counties. The PhiPT value of 0.15 (p=0.001) corroborated with AMOVA tests was significant to provide evidence for partial population differentiation. QTL mapping was achieved by evaluating the DH population in Maseno and Kabianga in a 5×46 alpha lattice design during the long rains of 2018 and 2019. The disease incidence for the plots were scored on a scale of 1-9 and the best linear unbiased predictions determined using META-R statistical software. Marker genotyping of the population was performed using 1250 markers in diversity arrays technology (DArTseq). Linkage map construction and QTL analysis were conducted in QTL IciMapping v4.1. Nine GLS resistance QTLs were mapped on the chromosomal bins 1.06, 1.07, 1.11, 2.04, 2.06, 3.04, 3.05, 4.1 and 7.04. Fourteen TLB resistance QTLs were detected on the chromosomal bins 1.02, 1.08, 2.05, 2.06, 2.07, 3.01, 3.04, 4.02, 4.08, 5.03, 6.05, 7.03, 8.08 and 10.04. The QTLs were detected in at least two environments. The highest phenotypic variance was conditioned by qGLS1_190 (16.60%) for GLS and qTLB8_171 for TLB (13.65%). Disease resistance was negatively correlated with flowering time suggesting higher resistance in the late maturing genotypes. These findings will enhance proper identification of the pathogen causing GLS and GLS management programs. The identified QTLs and their flanking markers could be validated and fine mapped in future work for use in breeding for resistance to GLS and TLB.
Masters Theses
2022-01-01T00:00:00ZDetermination of Agricultural Production Constraints and Optimal Enterprise. Mix in an Irrigation Scheme: The Case of HOLA Irrigation Scheme in KenyaAYOO, C.A.A.https://repository.maseno.ac.ke/handle/123456789/51142022-03-24T07:07:55Z1992-01-01T00:00:00ZDetermination of Agricultural Production Constraints and Optimal Enterprise. Mix in an Irrigation Scheme: The Case of HOLA Irrigation Scheme in Kenya
AYOO, C.A.A.
This study arose out of the need to address the problem of poor performance of Kenya's large scale irrigation schemes. The poor performance has been
evidenced by the negative cash flows that these schemes have consistently recorded since their inception (with the exception of the Mwea Tabere Rice Irrigation Scheme in Kirinyaga district) and the low incomes received by the tenant farmers. The study focused on the Hola Irrigation Scheme which was chosen because of its locat icon in the Tana River Basin which possesses the greatest. potential for irrigation development in the country. The scheme's farm plans were investigated
under the null hypothesis that poor enterprise
combinations and resource misallocation were the primary sources of its poor performance. Both primary and
secondary data were gathered on inputs, outputs, prices and family characteristics, among others. The gross margins of the various crop enterprises were then
computed as a basis for determining the relative
profitabi1ity. The computed gross margins were also
used to formulate an objective function which was an integral component of linear programming, the analytical technique that was employed. A linear programming
problem matrix was then constructed and fed into a
computer to determine the optimal farm plans. These were
/
compared with the existing farm plans and were found to
- i< 1 -
differ significantly. It was therefore
inferred that
- x it -
the existing enterprise combinations and resource
allocation patterns were inefficient and that farm
incomes could therefore be increased through resource real location. From the dual values, the constraints to increased farm incomes were deduced to be April labour, November labour, capital and subsistence requirements. A marketing constraint was also identified as the cause of the wide fluctuations in commodity prices, especially for onions and tomatoes and lack of adequate storage.
The conclusions of the study were that resource use
patterns be altered by adapting the optimal farm plans and that the existing structural and institutional
constraints be eased to make the change possible. Such constraints include transport infrastructure, credit and storage.
1992-01-01T00:00:00ZGenetic Diversity of Legume Nodulating Bacteria and the Effect of Nitrogen Sources on the Yield of Common Bean in Western KenyaKawaka, Fanuelhttps://repository.maseno.ac.ke/handle/123456789/9812019-10-24T06:59:24Z2016-01-01T00:00:00ZGenetic Diversity of Legume Nodulating Bacteria and the Effect of Nitrogen Sources on the Yield of Common Bean in Western Kenya
Kawaka, Fanuel
Declining soil fertility in general and nitrogen (N) in particular limit crop production on many smallholder farms in western Kenya. Soil N deficiency is usually ameliorated with inorganic N fertilizers but their high costs preclude their use by resource poor smallholder farmers. In addition there are concerns that increased use of inorganic fertilizers could lead to environmental degradation. Organic inputs offer sustainable alternatives to expensive inorganic N fertilizers but the common organic materials on smallholder farms are not available in adequate amounts. The use of none traditional organic materials such as water hyacinth has been reported to supply plant nutrients but has not been adequately tested. Integration of legumes such as the common bean in cropping systems is another option that has the potential to contribute soil N through symbiotic nitrogen fixation. However there is paucity of information on the abundance, symbiotic effectiveness and identity of native bacterial strains from soils in western Kenya thus making it difficult to make informed decisions on the inoculation need. This study was conducted to compare the response of common bean to water hyacinth compost, inorganic N fertilizer and determine the abundance, symbiotic efficiency (SE) and identity of the native bacteria nodulating legumes. Soil sampling was carried out in three farms that had been used for growing common bean for at least two seasons and one fallow land with no known history of growing common bean or inoculation in Kisumu and Kakamega. The abundance of soil bacteria and symbiotic efficiency (SE) were determined in a greenhouse experiment. Deoxyribonucleic acid (DNA) was extracted from the bacteria and the 16S rRNA gene sequenced to establish their identity. Field experiments were laid out in a randomized complete block design (RCBD) replicated four times at Masinde Muliro University of Science and Technology and Kisumu for two consecutive seasons during the short rains of October to December, 2013 and the long rains of April to August, 2014. The treatments consisted of two bean varieties, rhizobium inoculation and non inoculation, with and without phosphorus (P), urea and water hyacinth compost. The population of bacteria ranged from 3.2 × 101 to 3.5 × 104 cells per gram of soil. Cluster analysis of the 16S rRNA gene grouped the native bacterial strains into five genera: Rhizobium, Bacillus, Pantoea, Enterobacter and Klebsiella. The bacterial strains had high SE compared to the first commercial the inoculant, CIAT 899 and ranged from Rhizobium sp (74%) to Klebsiella variicola (170%). The two species of Klebsiella variicola (MUST005 and KSM005) and Enterobacter hormaechei recorded higher SE than strain 446, a second inoculant. These native species should be exploited for the development of inoculation programmes to enhance N fixation in the region. Low levels of P were recorded in fallow soils at the two sites while Aluminium levels were high in Kakamega. Urea significantly improved yields of common bean in the short rain season compared to the other treatments at the two sites. However, in the long rains season water hyacinth compost gave higher yields than urea and control. This study reveals that the use of water hyacinth compost can serve as a substitute for inorganic N source.
PHD Thesis
2016-01-01T00:00:00ZPhenotypic variation in morphology, yield and seed quality in selected accessions of leafy AmaranthsOMONDI, Joshua Otienohttps://repository.maseno.ac.ke/handle/123456789/7502019-11-01T11:07:46Z2017-01-01T00:00:00ZPhenotypic variation in morphology, yield and seed quality in selected accessions of leafy Amaranths
OMONDI, Joshua Otieno
Vegetable amaranths are highly valued for being rich in proteins and micronutrients such as iron, calcium, zinc, vitamin C and vitamin A. In spite of the crop’s exceptional nutritional qualities, very little effort has been put in to improve the foliage yield potential in Kenya. Reports on morphological phenotypic variation analysis in Amaranthus are rare and detailed agronomic recommendations for leaf and seed yields and quality enhancement are scanty. Research on the extent of the phenotypic variation of amaranths is of great significance in the choice of some of the amaranths accessions as progenitors for useful traits. It was on this background that this study assessed the phenotypic variation in morphology, yields and seed quality in five amaranth accessions commonly grown for leaf consumption in Kenya. The specific objectives of the study were; to evaluate growth and morphological variation, evaluate leaf and seed yields and to assess seed quality in the five accessions vegetable amaranths. The five accessions were planted in randomized complete block design (RCBD) with three replicates. The amaranth accessions were provided with uniform agronomic treatments. Data was collected on growth and morphological traits, leaf and seed yields and seed quality parameters from ten plants per plot. Seed moisture content was determined using the fresh weight basis as per the international seed testing association (ISTA) standards. Seed quality as measured by germination was conducted in four replicate samples of 25 seeds each. The seeds were sown on plain agar held in 90mm sterilin petri-dishes and incubated at temperatures of 24-260C. Data collected from the study on the quantitative traits were subjected to analysis of variance (ANOVA) at 5% level of significance. Clustering was done using agglomerative hierarchical clustering method. This study revealed that there was significant variation among the accessions in most of the growth and morphological characteristics. This could probably be attributed to lack of selection pressure on amaranths. There was also great diversity in leaf and seed yields, the most outstanding being Amaranthus hybridus (AH). An overall multiple regression model indicated significant positive correlation (R2=0.7378) of the growth and morphological characteristics to leaf yield. The model accounted for 73.78% of the variation in leaf yield per plant. This implies that the greater the value of the growth and morphological characteristics the higher the leaf yield. Morphological characteristics thus contributed directly to leaf yield hence selection could be done on these traits to achieve leaf yield improvement. Significant variation was observed in germination tests with accessions AH exhibiting the highest germination percentage. There was also significant differences in the moisture content among the five accessions. Cluster dendogram grouped the accessions into three clusters with agglomerative co-efficient of 0.81. All the landrace variety (LV) were grouped in cluster 1, Evergreen variety (EG), accession from gene bank of Kenya (GBK) and simlaw (SIM) were grouped in cluster 2 and Amaranthus hybridus (AH) grouped in cluster 3. Accessions EG, GBK and SIM clustered together because they are of the same species even though they were sourced from different collections. The study concluded that accession AH is the best source of growth and morphological traits for a breeding programme, the best for selection for both vegetable and seed production and the best producer of quality seeds. Accession AH can thus be recommended to Kenyan farmers as the most suitable cultivar for agro-ecologies similar to Mumias sub-county. Accession AH can also serve as a dual purpose cultivar to farmers in Western Kenya. Landrace variety (LV) was found to contain early maturity traits hence suitable for selection for earliness.
2017-01-01T00:00:00ZIdentification of Maize (Zea Mays L.) Genotypes Resistant to Striga Hermonthica (Del.) and Determination of Genetic Basis for ResistanceMbogo, Peter Okothhttps://repository.maseno.ac.ke/handle/123456789/7012018-10-09T13:21:07Z2017-01-01T00:00:00ZIdentification of Maize (Zea Mays L.) Genotypes Resistant to Striga Hermonthica (Del.) and Determination of Genetic Basis for Resistance
Mbogo, Peter Okoth
The obligate root hemi-parasite, Striga hermonthica (Del.) Benth., native to sub-Saharan Africa causes serious economic constraint to cereal production. There has been limited study to understand the genetics of Striga tolerance or resistance in maize in Kenya and the information on mechanisms of resistance to Striga in maize in very limited. The use of maize (Zea mays L.) genotypes that support reduced Striga hermonthica emergence can form an important basis for developing Striga resistant cultivars. The objective of this study was to contribute to the knowledge of gene action controlling Striga resistance and to improved yield in maize. 28 maize inbred lines sourced from IITA and Maseno University and 9 Maseno university experimental hybrids were evaluated in western Kenya in 2011 and 2012 growing seasons. A generation means analysis was performed using a resistant and a highly susceptible maize inbred line selected from inbred line screening. Highly significant differences (P <0.001) were detected among the inbred lines and hybrids for grain yield, emerged Striga counts and Striga damage rating. A highly significant and negative correlation coefficient was observed between emerged Striga and yield as well as between Striga damage ratings and yield. Inbred lines MSMP1/P2, TZSTR154, TZSTR133, TZSTR139, TZSTR 166 and a resistant check 9450 were identified as the most resistant lines as they consistently performed well in Striga-infested environments. These inbred lines could be used for breeding Striga resistant maize varieties. Maseno experimental hybrids, EH14 and EH12 recorded much better grain yields and stability compared to commercial varieties under Striga infestation and in Striga free fields. National performance trials conducted by KEPHIS confirmed their high yield and yield stability and were released for commercialization. Maseno hybrids had parental lines previously selected from maize landraces from western Kenya, thus suggesting that they are potential sources of Striga weed tolerance genes. Generation means analysis results showed significant differences among generations for emerged Striga, Striga damage rating and maize growth including Plant and Ear height. Most of the additive, dominance, additive x additive, additive x dominance and dominance x dominance effects were significant indicating the importance of the additive, dominance and epistatic modes of gene actions in controlling emerged Striga, Striga damage rating, plant and ear height. Most components conferring Striga tolerance behaved in a qualitative manner. Dominance effects had higher mean values over additive effects. Significant dominant genetic effects (d) for Striga emergence and Striga damage rating suggested preponderance of non-additive genetic effects in the inheritance of Striga tolerance. The results also reveal the involvement of duplicate epistasis where the dominance estimate and dominance x dominance interaction had opposite signs. The presence of duplicate type of gene interaction confirms the importance of dominance gene effects. The identified maize inbred lines with good levels of resistance and different resistance mechanisms can facilitate pyramiding of several resistant alleles to obtain more durable and stable polygenic resistance to Striga hermonthica in maize.
2017-01-01T00:00:00Z