170 Records out of 22207 Records

Field ecology of western flower thrips, Frankliniella occidentalis in french bean agroecosystems in Kenya

Author: Ounya, Johnson Nyasani

Awarding University: Leibniz Universitat Hannover, Germany

Level : PhD

Year: 2012

Holding Libraries: Kenya Agricultural Research Institute Headquarters Library ;

Subject Terms: Western Flower Thrips ; Beans ; Phaseolus vulgaris ; Frankliniella occidentalis ; Ecology ; Integrated pest management ; Cucurbita pepo ; Megalurothrips sjostedti ; Thrips ; Weeds ; Galinsoga parviflora ;

Abstract:

Western flower thrips (WFT), [Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae)], is one of the most important pests of French beans (Phaseolus vulgaris L.) in Kenya. Control of WFT is difficult because it has a wide host range, high reproduction rate, cryptic feeding habit, and ability to pupate in soil. Development of sustainable integrated pest management (lPM) strategies against the WFT requires a sound understanding of its field ecology in terms of colonisation pattern, seasonal abundance, and feeding and oviposition behaviour. An understanding of seasonal abundance of WFT is important in predicting when and where economically damaging populations may occur, understanding how crop damage occurs, planning efficient sampling protocols, and in developing effective management programmes that are area specific. Information on feeding and oviposition preference of WFT is a key research need for formulation of IPM strategies based on manipulation of cropping systems. However, the above named aspects have not been studied in details within French bean fields in Kenya. Therefore, the objectives of this study were to determine (1) seasonal abundance ofWFT and its natural enemies in French bean agroecosystems in Kenya, (2) the effect of intercrops on thrips species composition and population density on French beans, and (3) feeding and oviposition preference of WFT for crops and weeds encountered in French bean fields in Kenya. To determine the seasonal abundance of WFT and its natural enemies in field-grown French beans in Kenya, Field studies were conducted in two major French bean agroecological zones in Kenya from January 2009 to December 2009. French beans were sampled every two weeks for WFT and natural enemies. Colonisation of French beans with WFT in both small and large scale farms in high and mid altitude zones started at 2- and 3-leaf stage, respectively. There was an increase in the number of WFT from budding stage to podding/flowering stage. A decline in population density of WFT was at crop senescence. Two natural enemies of thrips, [Orius spp. (Hemiptera: Anthocoridae) and Ceranisus menes (Walker) (Hymenoptera: Eulophidae)], were recorded on French beans in all agroecological zones and their population grew in tandem with the population of WFT. Temperature and relative humidity were weakly correlated with the population density of WFT, while rainfall had a negative effect on the population density of WFT. Overall, the population density of WFT was least in the first growing season (January - April) which was in the long rains season. Higher population densities of WFT on French beans in all farm sizes and agroecological zones were recorded in the third growing season (September - December) which was in the short rains season. Results from this study suggest that seasonal abundance of WFT in the two agroecological zones is influenced by rainfall (depending on amount), phenological stage of French beans and surrounding host plants (where infestations on French beans arise from). To study thrips species composition and thrips population density on French beans planted as a sole crop and as an intercrop with either sunflower, Irish potato, or baby com, in different combinations field experiments were conducted in two seasons. French beans hosted four thrips species, Megalurothrips sjostedti (Trybom), Frankliniella schultzei (Trybom),F. occidentalis (Pergande), and Hydatothrips adolfifriderici (Kamy) in order of decreasing abundance. The main thrips species on Irish potato and sunflower was F. schultzei. Baby com hosted only Frankliniella williamsi (Hood) and Thrips pusillus (Bagnall). A mono crop of French bean hosted more thrips than a French bean intercrop mix. Plots with French bean alone had about 1.4 times higher yields compared to intercropped plots of French bean with sunflower and French bean with baby com. However, the percentage of pods that could get rejected on the market due to thrips d

Effect of compliance with food safety standards on soil fertility in smallholder french bean farms in Kirinyaga County

Author: Mnyambo, Clarice Gombe

Awarding University: University of Nairobi, Kenya

Level : MSc

Year: 2012

Holding Libraries: University of Nairobi Jomo Kenyatta Memorial Library ;

Subject Terms: Beans ; Soil acidity ; Fertilizers ; Kirinyaga County ;

Abstract:

Compliance with Food Safety Standards (FSS) for production of export vegetables involves application of manure, agro-chemicals and other inputs which influence soil quality. A study was conducted in Kirinyaga County, Central Kenya to investigate the effect of compliance with FSS for production of French beans on soil quality in smallholder farms. The study area was divided into three agro-ecological zones; upper (Gichugu), middle (Ndia) and lower (Mwea) zones. Soil samples were collected from farmers in the three zones based on compliance levels: compliant with FSS, non-compliant with FSS and non-French bean growers. Compliance with FSS was following the guidelines stipulated in the GlobalGAP for production of French beans. Surface soil (O-30cm) samples were collected from 230 farms, of which 76 were compliant, 87 non- compliant and 67 non-French bean growers. To assess soil quality, samples were subjected to analysis of selected chemical properties in the laboratory. The data were analyzed using GenStat 13th Edition at 5% level of significance. In all three zones, French beans are grown in intensive mixed farming systems, and frequently as intercrop in 0.16- 0.18 hectares of land. The main organic fertilizer applied is cattle manure at the rates of 6.25 to 9.3 tlha. The main inorganic fertilizers applied are DAP during planting and CAN as top dressing; at the rates ranging from 110 to 170 tlha, and 135 to 150 tlha respectively. Both organic and inorganic fertilizers are applied below recommended rates. Chemical analysis results show that soil pH for Gichugu and Ndia is strongly acid (5.35-5.51), while for Mwea it is medium acid (5.83-5.97), but not significantly different among compliance levels. In all three zones and compliance levels, carbon (1.49-1.86%) and total nitrogen (0.16-0.18%) contents were not significantly different. However, Mwea had relatively higher levels of carbon content, which can be attributed to the high amounts of manure applied compared to Gichugu and Ndia. Phosphorus and potassium contents were medium to high, but not significantly different among zones and compliance levels. Mwea had the highest content of soil P and potassium due to application of relatively higher amounts of DAP, NPK and manure. Calcium content in the soil was medium whereas magnesium content was high in all the zones and compliance levels as a result of continuous use of manure. In Mwea, the high levels can be attributed to parent material of the soil in addition to manure application. Low nitrogen levels in the soil can be attributed to continuous cultivation of crops, high uptake of N due to frequency of growth, crop harvest removal and application of N fertilizers below recommended levels. Compliant farms had higher levels of copper, iron and manganese in the soil. French bean farmers complying with FSS apply foliar sprays to supply micro nutrients to the crop. Micronutrients uptake from the soil is low thus most of the micronutrient needed by the plant is supplied through foliar feeds. This results to micronutrients level in the soil being high. The results show that compliance with FSS had no significant effect on soil quality within the current farming and management systems. This would be explained by the prevalent practice of random crop rotations, intercropping and application of varying amounts of both organic and inorganic fertilizers. It is recommended that farmers adopt defined cropping calendars, rotations and intercrops, and also increase fertilizer amounts (CAN, NPK and manure) to recommended rates based on nutrient levels in soil and intensity of cropping for each agro-ecological zone.

Impact of soil fertility management practices on major insect pests of Beans (phaseolus vulgaris L.) and yield in Taita District, Kenya

Author: Ochilo, Willis Ndeda

Awarding University: University of Nairobi, Kenya

Level : MSc

Year: 2011

Holding Libraries: University of Nairobi Jomo Kenyatta Memorial Library ;

Subject Terms: Beans ; Phaseolus vulgaris ; Pest control ; Ophiomyia ; Aphis fabae ; Insects ; Black bean aphid use Aphis fabae ; Soils ; Fertilizers ; Taita District ;

Abstract:

The common bean (Phaseolus vulgaris L.) is an important food and cash crop in Africa. It is estimated that it provides food for more than 100 million people and is a critical source of income for rural households. Despite its importance, common bean yields in parts of Africa have dropped in the last ten years by as much as 50 percent. This decline is attributed to low soil fertility, poor crop management, diseases and high incidences of insect pests. Key among the major insect pests of beans are the bean stem maggot (Ophiomyia spp), and the black bean aphid (Aphis fabae) accounting for yield losses ranging from 8 to 100% and 37 to 90% respectively. To overcome the insect pest problems of beans, insecticides were and are still used. However, problems have arisen, some quite serious to detract from the benefit realised from insecticides use. Consequently, it has become absolutely imperative that fresh approaches to pest control be undertaken. It is on this premise that the study sought to evaluate alternatives to the use of insecticides in controlling incidences of the bean stem maggot (Ophiomyia spp.) and the black bean aphid (Aphis fabae), and their impact on beans yield. Field trials were undertaken in Taita District where agriculture contributes to 95% of household income with very little or no fertility inputs in farms. In the study, the following were tested: two kinds of fertilizers, farmyard manure and Trichoderma seed coatings. Planting was done during the long rains. Field survey of Ophiomyia spp and Aphis fabae were conducted four weeks after bean emergence and at harvest to determine their incidence and prevalence. Plant mortality, plant survival, and yield were used as criteria for assessing crop loss. The addition of soil amendments had no influence on the levels of infestation of the bean stem maggot and the black bean aphid, and their associated plant mortality. However, soil fertility management positively influenced yield parameters such as the number of pods per plot, dry-seed, and bean-straw. Three treatments, namely Mavuno + Trichoderma, TSP + CAN and Mavuno were able to improve yield by 52.9, 48.9 and 46.7% respectively. These findings point to the fact that as much as soil fertility interacts with beans in a wide variety of ways including capacity to produce yield despite pest attack; soil amendments should not be used as a standalone means for improving productivity of cropping systems, since their influence on incidences of insect pests is minimal. Subsequently, in order to maximise yield, there is still a strong need to adopt holistic management approaches that integrates, not only, soil fertility management and pest management but also incorporates other agronomic best management practises.

Antifungal activity of selected crude plants extracts on bean rust (Uromyces appendiculatus) and their effects on physiological activitiesof french beans

Author: Nyasetia, Dominic Menge Shane

Awarding University: Jomo Kenyatta University of Agriculture and Technology, Kenya

Level : MSc

Year: 2011

Holding Libraries: Jomo Kenyatta University of Agriculture and Technology Library ;

Subject Terms: French beans ; Phaseolus vulgaris ; Uromyces appendiculatus ; Pest control ; Maesa lanceolata ; Tithonia rotundifolia ; Aloe secundiflora ; Carissa edulis ; Urtica dioica ; Boscia angustifolia ; Zanthoxylum chalybeum ; Melia volkensii ;

Abstract:

Rust (Uromyces appendiculatus) is a major foliar disease that reduces yields and pod quality in beans. There is need to introduce effective and environmentally friendly pest control products. The objective of this study was to evaluate the performance of commercial fungicide (Kocide DF) and antifungal plant extracts in the control of this disease. A total of 9 plants belonging to different genera were selected from native flora of Eastern, Western and Rift Valley provinces in Kenya. The antifungal activities against U. appendiculatus by the crude extracts of selected plants were studied in vitro and in vivo experiments. French bean (Phaseolus vulgaris L.) variety Amy that is susceptible to bean rust (U. appendiculatus) was used in evaluation. In vitro evaluations was performed on extracts from Maesa lanceolata, Tithonia rotundifolia; Aloe secundiflora, Carissa edulis, Urtica dioica. Boscia angustifolia, Zanthoxylum chalybeum, Melia volkensii and Kocide DF as treatments. A field trial was established at JKUAT-Kenya in a Completely Randomized Block Design replicated 4 times. The plots were 3 x 4 m with 0.5 m paths between plots and 1.5 m between blocks. Variety Amy was planted at a spacing of 30 x 10 em within and between rows. Single plant extracts and combinations of Boscia angustifolia; Zanthoxylum chalybeum and Melia volkensii were used to evaluate their effect on U appendiculatus in the field. The treatments were applied once in every week. Major carotenoids from the pods of French beans were isolated and profiled using High Performance Liquid Chromatography (HPLC) peaks to determine the consistency of the compounds in the pods. Physiological responses such as carbon dioxide assimilation, Photosynthetic active radiation (PAR), Transpiration, Stomatal conductance (gs), leaf temperature and Photosynthetic rate (Pn) of French beans treatments were examined using Infrared gas analyzer (IRGA) in all treatments. Differences were found between the inhibitory effects in vitro and in vivo. B. angustifolia, Z. chalybeum and M. volkensii inhibited efficiently spore germination of U. appendiculatus. Extracts of B. angustifolia, Z. chalybeum and M. volkensii showed significant levels (p<O.05) of disease inhibition activities against U. appendiculatus on bean leaves and pods. The most effective treatment was M volkensii followed by B. angustifolia- Z. chalybeum. There were significant differences among treatments in marketable yields. The high regressions between stomatal conductance and rate of transpiration in the all treatments indicated that stomatal conductance and rate of transpiration' were interdependent and it was interpreted to mean that stomatal conductance enhanced rate of transpiration at different times of the day. A total of eight treatments were used in the study. A combination of Z. chalybeum and M. volkensii appeared to have caused reduction in bacterial population. M. volkensii and B. angustifolia - Z. chalybeum treatments caused significant increase in fungal population. In general, results revealed bioactive potential of the flora from M. volkensii and a combination between B. angustifolia and Z. chalybeum to produce metabolites with potential applications as botanical pesticides.

The potential of castor bean (Ricinus communis) to rejuvenate livelihoods in arid and semi-arid lands : the case of Tharaka and Mbeere Districts, Kenya

Author: Muchoka, James Peter

Awarding University: Kenyatta University, Kenya

Level : MES

Year: 2011

Holding Libraries: Kenyatta University Moi Library ;

Subject Terms: Ricinus communis ; Tharaka District ; Mbeere District ; Castor beans USE Ricinus communis ;

Abstract:

Ricinus communis L., (Castor bean plant) is among the many neglected industrial plants that could significantly change the lives of many rural communities in developing countries. Commercial production is cited in many countries in the world, but production in Kenya has been on the decline. This study sought to assess the contribution that castor bean could offer to the livelihoods of people living in the semi-arid Tharaka and Mbeere districts that are considered by the Ministry of Agriculture as traditional producers of the bean in Eastern province of Kenya. The target population was the household. Using Purposive Sampling Method, two administrative divisions were selected. one in Tharaka district and the other in Mbeere district. Eventually, a representative sample of households from the locations in the selected divisions was obtained through snow balling, starting from the Chiefs' camp. In each sample division 100 sample households were selected. Based on a list of registered/organized groups obtained at the Social Development Officer in the division of study, 15 office bearers from different groups were randomly sampled in each division. Similarly, 15 village sub unit heads were randomly sampled based on the list provided by the District Officer making another 30 households of local leaders from each division. A total sample of 260 households was obtained. Data collected was coded and the computer software (Statistical Package for Social Sciences) was used to analyze the data. The study found out that there was need to revise land ownership laws in Tharaka and Mbeere districts to give the youthful farmers a chance to practice more innovative farming methods and engage in the right enterprise mix. Age was a significant factor in domesticating castor (n=260, p=O. 01, r=-O .220**). Over 80% of the sampled respondents indicated that castor was useful. But even though useful, only 2.7% of the respondents grew it as a commercial crop. Lack of information on many technical issues largely contributed to this dismal performance. Indeed, 34.6% of respondents requested for backstopping in all technical areas whereas a paltry 4.2% of initial knowledge held by respondents came from extension workers and therefore enhancing the argument that extension workers also needed skillsin producing castor beans. Different castor accessions are grown in the study area and may possess varied ricin content, with 85% of the respondents indicating that they are not poisonous: An overwhelming 92.7% of the respondents were willing and ready to plant castor for commercial purposes if the necessary support structures are put into place. Policy guidelines on the production of castor were lacking, making growth of castor a risky business. Urgent enactment of castor policy is needed not only to broaden the range of castor products in the market but also to boast its national value compared to other competing cash crops. This study is useful to policy makers, staff and farmers working in the agricultural sector.

Effect of Arbuscular mycorrhizal fungi (AMF) inoculation and management of indigenous AMF population on the ex-situ performance of maize and beans in Embu and Taita Districts , Kenya

Author: Mwangi, John Nyaga

Awarding University: Jomo Kenyatta University of Agriculture and Technology, Kenya

Level : MSc

Year: 2011

Holding Libraries: Jomo Kenyatta University of Agriculture and Technology Library ;

Subject Terms: Embu District ; Taita District ; Mycorrhizas ; Fungi ; Maize ; Zea mays ; Beans ; Phaseolus vulgaris ; Manures ; Soil fertility ;

Abstract:

Many experiments examining the effect of Arbuscular Mycorrhizal Fungi (AMF) on crops are ambiguous and many of those demonstrating positive effects have been carried out in the greenhouse using simplified systems rendering the results not easily reproducible in the field. Therefore field experiments become necessary considering gaps in understanding of the Arbuscular Mycorrhizal (AM) association, importance of AMF species diversity and the effect of different agronomic practices on the ecology and function of AMF. The study demonstrated the importance of mycorrhizae in agricultural production systems in tropical landscapes, through establishing effects of various soil fertility management practices such as use of different fertilizers, use of manure, and slow releasing rock phosphate (mijingu) on AMF. Effect of direct AMF inoculation in the field and management of indigenous population and the performance of maize and bean were also evaluated. Soil from Below Ground Biodiversity (BGBD) test strips and demonstration blocks under FP (combination of TSP and CAN), mijingu, manure and mavuno (organic fertilize) application were sampled. The effects of existing AMF and AMF introduced across management practices were evaluated and compared to plant growth and yield. Mycorrhizal density and prevalence was determined over a period of two cropping seasons and the experiment replicated in the two benchmark sites namely Embu in the highlands of central Kenya and the coastal highlands in TaitaTaveta. This constituted the on-farm experiments of the project. On-station experiments were also set up and direct inoculation of AMF was done on common bean (phaseolus vulgaris L) and maize (Zea mays L) intercrop; effects on crop performance were determined. Field inoculation with AMF has been demonstrated to positively affect the yield of maize and bean at Embu experimental site though not significantly different with application of the different soil fertility amendments. The use of inorganic and organic fertilizers enhanced AMF utilization; the addition of these fertilizers to AMF led to higher crop yield as well as root colonisation compared to plots under AMF applied alone. A total of 15 AMF morphotypes were isolated and described from both Taita and Embu sites, majority being Gigasporaceae (9), followed by Acaulosporaceae (4) and Glomaceae (2). The highest species count was obtained from 0-10cm depth. Inoculation of plots with AMF was found to increase the total AMF abundance in the soil. However there was no significant (p 2: 0.05) difference in spore abundance at onstation experiments with use of different soil fertility amendment practices in the first season but varied less significantly (p :::: 0.05) after the second season but a marked reduction in AMF population was recorded with passage of each cropping season. Onfarm experiments (test strips) also recorded a reduction in AMF population with subsequent season. The spore abundance showed no significant difference with application of the different soil amendments. This was also the case with species richness in the soil during the two seasons. In demonstration plots, there were significant (p :::: 0.05) differences in spore abundance among the different soil fertility amendment practices. Also a marked decrease in AMF population in subsequent cropping season was recorded There was higher root colonisation as well as spore abundance in the soil under manure application with subsequent average maize and bean production. Manure application was found to be the best method to conserve AMF population in the soil and thus recommended as a cheap and an environmentally friendly method of soil fertility management.

Analysis of flavour and molecular diversity of Kenyan lablab bean (lablab purpureus (L.) sweet) accessions

Author: Kimani, Esther Nyambura

Awarding University: Egerton University, Kenya

Level : MSc

Year: 2010

Holding Libraries: Kenya Agricultural Research Institute Headquarters Library ;

Subject Terms: Lablab beans/Lablab purpureus/Genetics/ ;

Abstract:

The legume species Lablab purpureus L. Sweet grows in most tropical environments. It is used as a cover crop and green manure and provides a high-protein food for humans and livestock feed. The study was carried out to analyse flavour components and molecular diversity of Kenyan lab lab accessions. Twenty four accessions from the National genebank and farmers were evaluated for odour and bitter taste intensities using sensory tests. Analysis of cyanogenic glycosides was carried out using the picrate method and volatile compounds were isolated and separated using gas chromatography. The genetic diversity of 50 accessions was studied using Amplified fragment length polymorphism (AFLP) markers. The sensory evaluations showed significant (p::::0.05) differences for the bitter taste but none for odour. Accession 10706 and 13096 exhibited the highest and lowest means respectively for both bitter and odour taste. The levels of cyanogenic glycosides were not different for the 24 accessions, but significant (p::::0.05) differences were observed in the volatile compounds isolated from the accessions with upto 89% similarity of the accessions. Two hundred and sixty two volatile compounds were identified using literature databases. The molecular study revealed a total of 180 polymorphic bands. The overall mean expected heterozygosity (He) for all the populations was 0.189. The Eastern population had the highest He of 0.297. The plot of the first and second principal coordinates for cluster analysis revealed an overlap of the accessions forming a tight cluster, with the exception of four; namely Mwingi-3 and 12000 from Eastern population, 12187R3 and 10706Rl from Coast and Rift Valley populations. The Unweighted pair group using mathematical arithmetic averages (upGMA) cluster analysis generated from the distance matrix revealed three major groups. Group 1 had accessions 10706Rl and Mwingi-J, group 2 had accessions 12187R3 and 12000, while group 3 had the rest of the accessions. The low diversity revealed from these results may be due to the narrow genetic base for breeding stocks, and exchange of germplasm across the country. Results obtained from this study will be of great help in lab lab accession management by ensuring maximization of exploitation of this vital resource as well as in developing breeding strategies for Lablab purpureus.

Nature of genetic control and inheritance of resistance to Pythium root rot in bean genotypes

Author: Otsyula, Reuben Masheti

Awarding University: Makerere University, Uganda

Level : PhD

Year: 2010

Holding Libraries: Kenya Agricultural Research Institute Headquarters Library ;

Subject Terms: Beans ; Phaseolus vulgaris ; Pythium root rot ; Genetics ; Pythium ultimum ; Vihiga District ; Kawanda Research Station, Kampala, Uganda ;

Abstract:

Pythium root rot induced by several fungal species of Pythium causes up to 70% yield loss in commercial bean (Phaseolus vulgaris L) cultivars in East and Central African region. Host resistance is the least costly and most effective strategy for managing Pythium root rot, particularly for smallholder farmers. Resistant varieties have been identified but the nature of genetic control and inheritance mechanism of resistance to Pythium root rot in beans is not known. This research work was undertaken to a) determine the nature of genetic control of resistance to Pythium root rot in bean genotypes. b) Establish the inheritance of resistance mechanism to Pythium ultimum in beans, c) elucidate the relationship between root rot resistant, moderately resistant and susceptible bean genotypes to Pythium root rot and d) incorporate Pythium root rot resistance into commercial cultivar GLP 2 grown in Kenya and Uganda. The first part of this study involved analysis of genetic control of resistance in bean genotypes to various species of Pythium occurring in East and Central Africa. Sixty bean genotypes were evaluated against 10 isolates of 7 different Pythium species in the screen house at the International Centre for Tropical Agriculture (CIAT). There were no significant differences in resistance (1-3 CIA T scale), moderately resistance (4-7) and susceptible (8-9) reaction of different bean genotypes to different isolates of Pythium indicating that different species were controlled by the same resistant gene. In a follow up study a sample of genotypes with different disease reaction were evaluated for disease development using area under disease progress curve (AUDPC). Significant AUDPC values (4-5) observed showed that disease developed but did not progress in some varieties (resistance); developed but progressed slowly (29 & 30) in some varieties (moderately resistance) and; developed and progressed very fast (65- 70) (high susceptibility) in others indicating that different genes are responsible for resistance, moderate resistance and susceptibility to Pythium root rot in the genotypes studied. The result of analysis of genetic control showed that there are two distinct modes of genetic mechanisms that are responsible for resistance, and moderately resistant reaction to Pythium root rot in bean varieties. There was an indication from this study the mresponsibte ne of suggests that: the major and minor genes had broader activity and therefore could be used to protect root rot commercial varieties grown in different locations in East and Central Africa and the varieties had a potential to be used for development of populations that could be used to produce resistant varieties for host resistance management of root rot in beans. The second part of the study which determined the inheritance of resistance mechanism to in bean genotypes used segregating populations developed between four commercial susceptible and five resistant bean cultivars. The genotypes were evaluated in the screen house at the International Centre for Tropical Agriculture (CIA T) at Kawanda research station in Kampala and on root rot hot spot nursery in Vihiga district of Western Kenya. Evaluations of inheritance F F2 and backcross populations revealed that resistance to root rot was conditioned by a single dominant gene. No segregation was observed in resistant x resistant parent crosses, revealing that resistance to in all five genotypes was controlled by the same gene. The third part of the study which elucidated the relationship between root rot resistant, tolerant and susceptible bean genotypes used amplified fragment length polymorphism. There was no significant variation among bean genotypes resistant to root rot. There was however, notable variation between genotypes originating from Central America and the genotypes that originated from Africa. The genotypes that had their origin in Africa lacked root rot resistance. Close similarity of genotypes origi

Effects of inter-specific interaction of nitrogen fertilizer and bean-maize cropping systems on seed quality of beans in Western Kenya

Author: Ogutu, Maurice Oyugi

Awarding University: Moi University, Kenya

Level : MPhil

Year: 2010

Holding Libraries: Kenya Agricultural Research Institute Headquarters Library ;

Subject Terms: Beans ; Phaseolus vulgaris ; Fertilizers ; Maize ; Zea mays ; Kibos, Kenya ; Kisii, Kenya ; Nitrogen ;

Abstract:

Common bean (Phaseolus vulgaris) seed qualities are often affected by soil deficient nutrients and sub-optimal intercropping systems practiced by farmers. Combined effects : of nitrogen fertilizer at 0 kg N ha-1, 50 kg N ha-1 and cropping systems consisting of four patterns namely Research, Farmers, Mbili mbili and Pure bean stand practices were studied and evaluated in an intercrop involving beans and maize (Zea mays) in the year 2006. Objectives of this study were, to determine the effects of cropping systems and nitrogen fertilization at different locations on seed qualities of beans. Two field experiments were conducted at KARI-Kibos and KARI-Kisii. Maize hybrid 614D and bean variety KK 8 were used as test crops. The experiment composed of 4 cropping systems and two nitrogen fertilizer levels in a Randomized Complete Block Experimental Design. The results from the study, showed that mbili system significantly (p::S0.05) increased the seedling dry matter and seed vigour by 42% and 42% respectively, while the research method increased the seed germination percentage by 10.6%. However bean seed qualities parameters like seedling growth rate, shoot length and seed sizes were not affected by the intercropping systems. Addition of nitrogen fertilizer increased the Thousand Seed Weight (TSW) at Kisii by 4.5%, while at Kibos it reduced the shoot length by 42%. Effects due to location revealed that TSW, seed germination and shoot length were of better quality in Kisii, than in Kibos while cropping system> N fertilizer x location interactions showed that seedling growth rate and vigour were increased by 20% and 18% respectively. Seed vigour which is one of the physiological characters of seed can be used as the best indicator to determine the performance of field crops under adverse conditions of temperature, water stress, weeds, and pathogens. Key words: Inter-specific interaction, Cropping system, Nitrogen and Seed quality.

Genetic studies on host-plant resistance to bean fly (Ophiomyia spp.) and seed yield in common bean (phaseolus vulgaris) under semi-arid conditions

Author: Ojwang', Pascal Peter Okwiri

Awarding University: University of KwaZulu-Natal, South Africa

Level : PhD

Year: 2010

Holding Libraries: Kenya Agricultural Research Institute Headquarters Library ;

Subject Terms: Ophiomyia ; Phaseolus vulgaris ; Beans ; Arid and semi-arid regions ; Pest control ; Genetics ;

Abstract:

Bean fly (Ophiomyia spp.) is a major pest of common bean (Phaseolus vulgaris L.) throughout eastern and southern Africa. In the semi-arid areas, apart from drought, the insect pest is reported to cause high crop losses up to 100%, particularly when drought occurs and under low soil fertility. Host-plant resistance is part of the integrated pest management strategies that have been widely employed against major insect pests of tropical legumes. However, information regarding its use in control of bean fly in common bean is limited. Therefore, the objectives of this study were to: (1) validate farmers' perceptions of major constraints responsible for yield losses, particularly the major insect pests of beans; (2) asses the level of adoption of improved bean varieties and determine factors that influence farmers' preferences of the varieties and criteria for selection; (3) identify sources of resistance to bean fly available in landraces; (4) determine the nature of gene action controlling bean fly resistance and seed yield in common bean; (5) describe a procedure for generating optimal bean fly populations for artificial cage screening for study of the mechanisms of resistance available in common bean against bean fly. Farmers considered drought and insect pest problems as main causes for low yields. The adoption rate for improved varieties was high but self-sufficiency in beans stood at 23% in the dry transitional (OT) agro-ecology and at 18% in the dry mid-altitude (OM) agroecology, respectively. Drought, earliness, yield stability, and insect pest resistance were the factors determining the choice of varieties by farmers. Bean fly (Ophiomyia spp.), African bollworm (Helicoverpa armigera) and bean aphid (Aphis fabae) were identified as key crop pests of beans limiting yield. The study to identify new sources of resistance included 64 genotypes consisting of land races, bean fly resistant lines and local checks. The experiment was done under drought stressed (OS) and non-stressed (NS) environments and two bean fly treatments (insecticide sprayed and natural infestation) for three cropping seasons between 2008 and 2009. Genotypes differed in their reaction to natural bean fly attack under drought stressed (OS) and non-stressed environments (NS) over different cropping seasons. However, the effect of bean fly appeared to vary between the long rains (LR) and short rains (SR). It was observed that an increase in the number of pupae per stem resulted in a higher plant mortality. The range of seed yield was from 345 t01704 kg ha' under natural infestation and from 591 to 2659 kg ha' under insecticide protection. Seed yield loss ranged from 3 to 69 %. The resistance of most of the bean fly resistant lines seemed to be ineffective in presence of OS. To determine the nature of gene action controlling the inheritance of resistance to bean fly, four parents with known reaction to bean fly were crossed with four locally adapted genotypes in an 8 x 8 half-diallel mating design. Similarly, two resistant and two susceptible parents were selected and crossed to produce populations for generations means and variance components analysis. Results revealed that both general combining ability (GCA) and specific combining ability (SCA) mean squares were significant (p s 0.05) for all four traits studied, except SCA for stem damage during one cropping season. Among the parents, GBK 047858 was the best general combiner for all the traits studied across seasons except for stem damage during LR 2009. Genotypes GBK 047821 and Kat x 69 (a locally adapted variety) were generally good general combiners for resistance traits as well as seed yield. General predictability ratio values ranging from 0.63 to 0.90 were obtained for plant mortality, stem damage, pupae in stem and seed yield across cropping seasons. These results established the predominance of additive gene effects (fixable variation) over the non-additive effects in controlling the traits.