A cultura do feijoeiro apresenta grande importância econômica para o Brasil e especificamente para a região do Sudoeste do Paraná, onde é cultivado principalmente em pequenas e médias propriedades. Constitui-se em um dos alimentos mais ricos consumido pelo povo brasileiro, principalmente para as populações mais pobres. É imprescindível o estudo cientifico dos sistemas de produção e o avanço tecnológico para aumentar sua produtividade e rentabilidade. Entre os gargalos limitantes à cultura, está a necessidade de estudar melhor os níveis populacionais de plantas daninhas que justificam o seu controle atendendo a critérios econômicos, o que resultaria em maior segurança para tomada de decisões de controle e, conseqüentemente, maior economia aos produtores rurais. Nesse contexto, realizou-se um experimento na área experimental da Universidade Tecnológica Federal do Paraná, Campus Pato Branco, com objetivo de verificar o nível de dano econômico e competitivo de Euphorbia heterophylla sob diferentes densidades e épocas de semeadura desta infestante em relação à cultura do feijoeiro. O experimento foi conduzido a campo em delineamento de blocos ao acaso, em parcelas subdivididas, com quatro repetições. Nas parcelas principais foram locadas oito densidades esperadas de E. heterophylla (0, 6, 10, 17, 29, 49, 83 e 142 pl m-2) e nas subparcelas duas épocas de semeadura de E. heterophylla (12 dias antes da semeadura do feijão e simultaneamente a cultura). Foram realizadas avaliações das características agronômicas das plantas de feijão e morfológicas de E. heterophylla e feijão durante o período de desenvolvimento e no momento da colheita da cultura. No cálculo das perdas de rendimento foi empregado o modelo da hipérbole retangular e pelo método de segmentação linear, sendo extraídos os parâmetros “i” (perda percentual por cada planta de E. heterophylla), que foram empregados no cálculo do nível de dano econômico. A antecipação da semeadura de E. heterophylla, bem como o incremento na densidade acarretaram redução da produtividade da cultura do feijão, devido principalmente à redução do número de legumes por planta. A interferência de plantas de E. heterophylla com a cultura do feijão determinou redução da estatura de plantas, índice de área foliar, massa seca, número de trifólios, número de ramificações produtivas, mas houve aumento da altura de inserção de legumes da cultura. A semeadura antecipada de E. heterophylla proporciona maior desenvolvimento desta espécie em relação à época de semeadura simultânea com a cultura do feijão, refletindo-se no aumento da área foliar, da massa seca e da cobertura do solo pela espécie daninha. A perda percentual por planta daninha pode ser estimada adequadamente através dos diferentes modelos utilizados. Tanto o modelo hiperbólico quanto o linear indicam maior perda percentual quando a semeadura de E. heterophylla ocorre antecipadamente à cultura do feijão comum. O modelo hiperbólico superestima os valores de nível crítico de dano em relação ao modelo linear. O aumento na perda de rendimento por unidade de planta daninha, rendimento da cultura, eficiência do herbicida e no valor do produto colhido ocasionam diminuição dos valores dos níveis de dano econômico. No entanto, o aumento do custo de controle de plantas de E. heterophylla aumenta os valores do nível de dano econômico. / Bean crop has great economic importance to Brazil and specifically for the South West of Parana, where it is grown mainly in small and medium farms. It constitutes one of the richest foods consumed by the Brazilian people, especially for the poorest populations. In this context, the scientific study of production systems and technological advances are essential to increase productivity and profitability. Among the factors that limit crop development, is the need to better understand the weed population levels that justify its control attending economic aspects, which would result in better control decision-making and, consequently, lower costs to farmers. In this context, an experiment was carried out at the experimental area of the Federal Technologic University of Paraná, Campus Pato Branco, in order to verify the economic injury level and competitive potential of the Euphorbia heterophylla under different sowing dates and densities of this weed in relation to the bean crop. The experiment was laid out as a randomized blocks arranged in a split-plots design with four replications. At the main plots were located eight expected densities of E. heterophylla (0, 6, 10, 17, 29, 49, 83 and 142 pl m-2) and at the subplots two sowing dates of E. heterophylla (12 days before bean sowing and at the crop sowing day). Evaluations were made on the agronomic characteristics of the bean plants during its development and at the harvest period. Moreover, morphological characteristics of the E. heterophylla and the beans were also evaluated at the same periods. To determine the crop yield losses was used the hyperbolic model and the linear segmentation method, and extracted the parameters "i" (percentage loss per plant of E. heterophylla), which were used in calculating the economic injury level. E. heterophylla sowed before the crop as well as its density increase led to reduced productivity of the bean, mainly due to reduction in the number of pods per plant. Moreover, the interference of the E. heterophylla on the bean crop resulted in lower plants, reduced leaf area index, lower dry weight, less number of leaves, less number of productive branches, however resulted in shorter height of the pods insertion on the crop. Early sowing of E. heterophylla results in better development of the weed specie in relation to the sowing data were both, weed and crop are sowed at the same day, resulting on higher leaf area, higher dry matter production and soil cover by the weed species. Percentage of yield losses due to the weed plant presence could be adequately estimated through the different models used. Both the linear and the hyperbolic model indicate a higher percentage loss when the sowing of E. heterophylla occurs before than the common bean crop. The hyperbolic model overestimates the values of the critical level of damage in relation to the linear model. Increases on the yield losses per unit weed, lower crop yield, lower herbicide efficiency and lower value of the harvested product resulted in smaller values of the economic injury level. Although, as the E. heterophylla control cost increase, the economic injury level also increases.

CAPES / O crestamento bacteriano comum, causado por Xanthomonas axonopodis pv. phaseoli, é uma das principais doenças da cultura do feijoeiro. Em busca por alternativas no controle de doenças em plantas, o uso de eliciadores/indutores de resistência tem sido explorado. Desta forma, o objetivo deste trabalho foi verificar a eficiência dos eliciadores harpina e acibenzolar-S-metílico na indução de mecanismos de defesa em plantas de feijoeiro (Phaseolus vulgaris L.) ao crestamento bacteriano comum, causado por X. axonopodis pv. phaseoli, avaliandose possíveis alterações no processo de trocas gasosas e ativação das principais enzimas envolvidas na defesa vegetal - peroxidase, superóxido dismutase, além de proteínas e fenóis. Foram utilizadas sementes dos cultivares IAPAR 31 e IPR Colibri. Depois de emergidas as primeiras folhas trifoliadas na fase vegetativa (V3) as plantas, foram tratadas com os eliciadores acibenzolar-S-metílico, harpina e água destilada (controle). Sete dias após a primeira aplicação dos eliciadores, foi inoculado o patógeno nas folhas do feijoeiro. A avaliação da severidade foi realizada a cada 10 dias sendo a primeira avaliação realizada 15 dias após a inoculação do patógeno. As leituras de fotossíntese foram realizadas 40 dias após a inoculação quando os sintomas e danos da doença demonstravam-se estabelecidos. Para a realização das análises bioquímicas, amostras de tecidos foliares de cada tratamento foram coletadas 24 horas antes, 24, 48 e 72 horas após a aplicação dos eliciadores. Também, foram determinados o rendimento e seus componentes em ambas as cultivares.A aplicação de ASM e harpina proporcionou redução na severidade da doença do crestamento bacteriano comum nas plantas de feijoeiro da cultivar IPR-Colibri e a mesma tendência foi observada para a cultivar IAPAR 31 tratada com ASM. As plantas da cultivar IAPAR 31 tratadas com o eliciador ASM, apresentaram maiores taxas de assimilação de CO2 quando comparadas ao controle e a mesma tendência foi observada para a cultivar IPR-Colibri. A aplicação do ASM promoveu o aumento da atividade da enzima antioxidativa peroxidase e a indução da síntese de compostos fenólicos e especialmente na cultivar suscetível IPRColibri. Para o rendimento de grãos e seus componentes, não foram observadas diferenças significativas entre o controle e os eliciadores ASM e harpina. Os eliciadores ASM e harpina induziram os mecanismos de resistência em feijoeiro contra X. axonopodis pv. phaseoli, indicando a potencialidade do uso dos eliciadores na cultura do feijoeiro. / The common bacterial blight, caused by Xanthomonas axonopodis pv. phaseoli is one of the major diseases of the bean crops. In search for alternatives to control the plant diseases, the use of the elicitors / inductors of resistance has been explored. Thus, the objective of this work was to verify the effectiveness of the elicitors harpina and acibenzolar-S-methyl in the induction of the defense mechanisms in bean plants (Phaseolus vulgaris L.) against common bacterial blight caused by X. axonopodis pv. phaseoli, evaluating the possible changes in the process of gas exchange and the activation of the key enzymes involved in the plant defense - peroxidase, superoxide dismutase, besides proteins and phenols. It was used seeds from IAPAR 31 and IPR Colibri cultivars. After emerged the first trifoliate leaves in the vegetative stage (V3) the plants were treated with the elicitors Acibenzolar-S-methyl and harpina, and distilled water (control). Seven days after the first application of the elicitors, the pathogen was inoculated on the leaves of bean plants. The severity assessment was performed every 10 days and the first evaluation 15 days after the pathogen inoculation. The measurement photosynthesis were performed 40 days after the inoculation when the symptoms and the damages of the disease showed themselves established. To carry out the biochemical analysis, samples of leaf tissue from each treatment were collected 24 hours before, 24, 48 and 72 hours after the application of the elicitors. Also, it was determined the yield and its components in both cultivars. The application of ASM and harpina provided the reduction in the severity of the common bacterial blight disease of the bean plants of IPR-Colibri cultivars and the same trend was observed for the IAPAR 31 cultivars treated with the elicitor ASM. Plants by IAPAR 31 treated with the elicitor ASM showed higher rates of assimilation of CO2 when compared to the control and the same trend was observed for cultivar IPR-Colibri. The application of ASM promoted the increase of the antioxidative enzyme peroxidase activity, and the induction of the phenolic compounds synthesis and, especially in the susceptible cultivar IPR-Colibri. For grain yield and its components, significant differences were not observed between the control and the elicitors ASM and harpina. The elicitors ASM and harpina induced the resistance mechanisms in bean plant against X. axonopodis pv. phaseoli, indicating the potentiality of the elicitor utilization in bean crops.

Fundação Araucária, CNPQ / Plantas daninhas competem com as cultivadas e dentre as influências negativas desse convívio está a redução da produtividade das culturas. O controle químico é a principal forma de gestão das infestantes na cultura do feijão (Phaseolus vulgaris L.). Sua eficácia depende de uma série de fatores, entre eles: condições ambientais (em função dos horários de aplicação) no momento da aspersão do herbicida e doses utilizadas. Um programa de pesquisa foi desenvolvido no curso de Agronomia da UTFPR, Pato Branco, PR, durante a safra 2010/11 com os objetivos gerais de analisar o impacto de horários de aplicação (e por consequência das variáveis ambientais) e de doses de fluazifop-p-butyl e de fomesafen sobre: o desempenho desses herbicidas no controle de plantas daninhas mono e dicotiledôneas, respectivamente; a seletividade do feijoeiro ao fomesafen e; a lucratividade da lavoura de feijão. As variáveis ambientais, de acordo com o horário do dia ou a época do ano em que os produtos foram aplicados, influenciaram no controle das infestantes. Fluazifop-p-butyl teve atividade favorecida quando aspergido às 06:00h, com umidade relativa do ar e ângulo foliar das gramíneas influenciando de maneira mais significativa no resultado. Para esse mesmo herbicida, aplicação noturna foi eficaz em mitigar os efeitos negativos da aplicação vespertina. O desempenho de fomesafen no controle das plantas daninhas dicotiledôneas foi máximo quando o produto foi aspergido às 11:00h e às 16:00h. Nesse caso, a irradiância e a temperatura do ar foram os principais determinantes da eficácia do herbicida. As doses de fluazifop-p-butyl + fomesafen que propiciaram maior controle da infestação resultaram em aumento da produtividade do feijoeiro e da rentabilidade da produção. Em alguns casos, a maximização da renda líquida foi obtida com dose menor do que a recomendada no rótulo do produto e aquela necessária para a obtenção da máxima eficácia do produto. Fomesafen provocou toxicidade nas plantas de feijão, as quais recuperaram-se das injúrias com o decorrer do tempo. O grau de fitointoxicação foi mais acentuado com doses elevadas do produto e quando esse foi aspergido às 11:00h e às 16:00h. Nesses horários, a temperatura do ar e a irradiância estavam mais acentuadas. Pode-se sintetizar que a eficácia no controle das plantas infestantes e a toxicidade dos herbicidas ao feijoeiro foram dependentes dos herbicidas utilizados, das condições ambientais em função do horário do dia em que os herbicidas foram aplicados e das doses utilizadas. A escolha correta do horário e da dose de aplicação favorece a eficiência do controle das plantas daninhas, minimiza os prejuízos à cultura em função da competição e eleva a lucratividade da lavoura. / The weeds compete with the cultivated crops and among the negative effects of this interaction is the reduction of the crop yields. The chemical method is the main weed control technic in the common bean crop (Phaseolus vulgaris L.). The efficacy of the herbicides depends on a number of factors, including: environmental conditions (in function of the time of application) at the moment of spraying of the herbicide and doses used. A research program was developed on the Agronomy course of UTFPR, Pato Branco, PR, during the 2010-11 with the main objectives to evaluate the impact of the application time (and therefore environmental variables) and doses of fluazifop-p-butyl and fomesafen on the: performance of these herbicides in the control of mono and dicotyledonous weeds, respectively; selectivity of bean crop to fomesafen; and the lucrativity of the common bean crop. The environmental variables, according to the time of day or season of year in which herbicides were applied, influence the control of weeds. Fluazifop-p-butyl activity has been favored when sprayed at 06:00h. The relative humidity and grass leaf angle were the factors most important affecting this herbicide performance. For this same compound, night application has been effective to mitigate the negative effects of the afternoon application. The performance of fomesafen to control broadleaf weeds has been maximum when the product was sprayed at 11:00h and 16:00h. In this case, the irradiance and the air temperature have been the main factors to affect the herbicide efficacy. The doses of fluazifop-p-butyl + fomesafen which allowed best weed control have increased grain yield and profitability of the common bean crop production. In some cases, the maximum net return has been obtained with a dose lower than that needed for maximum herbicide efficacy. Fomesafen has injured the common bean plants, but they have recovered with time. The degree of phytointoxication has increased at high fomesafen doses and when it has been sprayed at 11:00h and 16:00h. During these times, the air temperature and irradiance were the highest. It can be summarized that the efficacy on weed control and on the common bean injury was dependent on the herbicide used, on the environmental conditions during the time of the herbicide spray, and on the rates applied. The selection of the correct time of the day and rate of application can optimize the weed control, can reduce the crop yield losses due to competition, and can optimize the crop profitability.

A crescente procura por alimentos mais saudáveis demanda um aumento na produção isenta de agrotóxicos. O feijão-de-vagem é uma das principais olerícolas cultivadas no Brasil. Dentre as principais doenças que afetam essa cultura está o oídio, podendo ocasionar perdas de produção em até 69%, sendo de ocorrência comum em cultivos protegidos especialmente em períodos tardios. O uso do leite tem demonstrado boas perspectivas no controle desta doença em diversas culturas. Foram desenvolvidos na Universidade Tecnológica Federal do Paraná – Campus de Pato Branco – PR, nos anos de 2007 e 2008, trabalhos com o objetivo de avaliar o efeito do leite de vaca in natura e seus possíveis mecanismos de ação sobre o controle de oídio em feijão-de-vagem sob ambiente protegido. Conduziu-se experimento com aplicação de leite de vaca in natura nas concentrações de 0%, 5%, 10%, 15% e 20% em freqüência semanal e quinzenal, com e sem espalhante adesivo. Foi avaliada a severidade da doença e a produtividade. O delineamento foi em blocos ao acaso, com 4 repetições. Em outro experimento avaliou-se o efeito dos componentes químicos do leite, com aplicações foliares de Nitrato de Potássio (0,79 g L-1), Cloreto de Amônio (0,82 g L-1), Nitrato de Cálcio (0,96 g L-1), Fosfato de Amônio Monobásico (0,51 g L-1), Carbonato de Sódio (0,23 g L-1), mistura destes componentes, leite (200 ml L-1) e água. O delineamento foi inteiramente casualizado com 3 repetições. No terceiro experimento avaliou-se a atividade metabólica em tecidos foliares de feijão-de-vagem tratado com aplicações semanais de leite de vaca in natura nas concentrações do primeiro experimento. O cultivo foi em vasos, em casa de vegetação com ambiente controlado. O delineamento foi inteiramente casualizado com 4 repetições. Para realização das análises bioquímicas (proteínas, açúcares totais e redutores, peroxidases e FAL) foram coletados discos foliares de 0,2 g de cada unidade experimental, 24, 48 e 72 horas após a aplicação do leite de vaca in natura. O leite aplicado em freqüência semanal promoveu controle do oídio de 37,94 a 79,96%. Em freqüência quinzenal o controle variou de 22,32 a 28,59%, sendo mais efetivo no início da infestação. Sua aplicação não requer uso de espalhante adesivo. As concentrações mais viáveis foram entre 10 e 15%. Aplicação dos diferentes componentes químicos de forma combinada controlou a doença de forma semelhante à aplicação do leite de vaca in natura. Aplicações de concentrações crescentes de leite de vaca in natura interferiu nos parâmetros bioquímicos foliares de proteínas, açúcares totais e redutores, atividade de peroxidase e FAL, demonstrando ser um elicitor capaz de induzir a uma resposta de resistência, alterando a atividade de enzimas relacionadas com a defesa do feijão-de-vagem. / The rising search for healthier food demands a rising in the production without fertilizers. The bean pod is one of the main plants from the vegetable gardens grown in Brazil. Among the main diseases which affect this culture is the powdery mildew which can cause losses in the production up to 69%, being a common occurrence in protected cultures especially in late periods. The usage of milk has shown good perspectives in this disease control in different cultures. Works with the aim of evaluate the effect of in natura milk and its possible mechanisms of action in the powdery mildew control in bean pods under a protected environment were developed during 2007 and 2008. In the Federal Technological University of Paraná – campus in Pato Branco- PR. The experience was conducted with the application of in natura milk in the concentrations of 0%, 5%, 10%, 15% and 20% every week or every fifteen days with or without the adhesive spreader. The severity of this disease was evaluated as well as the productivity. The design was in blocks at random, with four repetitions. In other experiment it was evaluated the milk chemical components effect with application leaf of Potassium Nitrate (0.79 g L-1), Ammonium Chloride (0.82 g L-1), Calcium Nitrate (0.96 g L-1), Ammonium Phosphate Monobasic (0.51 g L-1), Sodium Carbonate (0.23 g L-1), mixture of these components, milk (200 ml L-1) and water. The design was entirely developed with three repetitions. In the third experiment the metabolic activity was evaluated in the follicular tissue in bean pods treated with weekly applications of cow milk in natura in the concentrations of the first experiment. The cultivation was in vases in a vegetation house with controlled environment. The design was entirely developed with four repetitions. In order to make the biochemical analysis (proteins, total sugar and reductors, peroxidasis e PAL) Follicular disks of 0.2g were collected from each experimental unity, 24, 48 e 72 hours after the application of cow milk in natura. The milk applied weekly promoted the powdery mildew control of 37.94 to 79.96%. Being used every fifteen days the control varied from 22.32 to 28.59%, being more effective in the beginning of the infestation. Its application does not require the usage of adhesive spreader. The most variable concentrations were between 10 e 15%. The application of different chemical components in a combined form controlled the disease in a similar way to the application of cow Milk in natura. The applications of rising concentrations of cow milk in natura interfered in the follicular biochemical patterns of proteins, total sugar and reductors, activity of peroxidasis and PAL demonstrating to be an elicitor which is able to induct to an answer of resistance, alternating the enzymatic activity related to the bean pod defense.

No description available.

No description available.

Common bean (Phaseolus vulgaris L.) is an important legume crop in Kenya and is a cheap source of proteins. The small scale farmers in Kenya produce common bean under low agricultural input systems and this predisposes the crop to pests and diseases. Among the diseases, angular leaf spot (ALS) is a major constraint to common bean production and contributes to yield losses as high as 80%. The causative pathogen Pseudocercospora griseola (Sacc.) Crous & Braun is highly variable and several races have been reported. There are few common bean genotypes with resistance to this disease. Therefore breeding for resistance to ALS is important for the country. This study was carried out to; i) evaluate the common bean production systems, constraints and farmer varietal preferences in Kenya, ii) evaluate local landraces and selected introductions of common bean for yield performance and reaction to ALS, iii) study the genetics of resistance to ALS in common bean and iv) develop a breeding method for durable resistance to ALS in common bean. To determine the common bean production systems, farmers’ preferred traits and their knowledge on common bean constraints including ALS, a survey was conducted in Kiambu county using a semi-structured questionnaire, interviews, and focus group discussions. The study revealed that farmers cultivate common beans during the short and long rain seasons. However, they experience better yields in the short rains due to reduced disease incidence. The majority of the farmers (71%) intercrop common bean and this ensures maximum utilisation of space. A high percentage (70%) of the farmers utilise their retained seed for production. The farmers identified ALS as one of the most important constraints to production. The only preventative measure they undertake to control the disease is weeding. The farmers reported that they would prefer improved varieties that were resistant to ALS. Farmers have a preference for particular common bean traits that include high yield (80%), resistance to insect-pests and diseases (72%), type I growth habit (52%), early maturity (68%), seed size and colour (21%) and cooking time (20%). These should be incorporated in breeding programmes. Two hundred common bean landraces and market class varieties were evaluated for ALS resistance in a nethouse at University of Nairobi, Kabete Field Station and for ALS resistance and yield in the field in KARI-Tigoni. The results showed that disease severity scores for the genotypes were similar in the two locations, with the top three resistant genotypes being Minoire, GBK 028123 and Murangazi with disease severity scores of 2.9, 2.9 and 3.2 in Kabete and 2.6, 2.8, and 2.9 in Thika respectively. These resistant genotypes can be used as sources of resistance in a breeding programme or they can be used as resistant varieties. All the market class varieties were susceptible to ALS (disease severity score 6.7-8.0). There was a non-significant correlation between disease and yield most likely because most of the resistant genotypes were exotic and hence not adapted to the local conditions. There was also a non-significant correlation between disease and seed size. The two hundred common bean genotypes were evaluated for yield at University of Nairobi, Kabete Field Station and KARI-Thika. The results indicated that the 2011 and 2012 seasons had similar mean yields and that yields at Kabete were higher than at KARI-Thika. The highest yielding genotypes across the two locations were; GLP 2 (766 kg ha-1), Nyirakanyobure (660 kg ha-1), GBK 028110 (654 kg ha-1), GLP 585 (630 kg ha-1) and Mukwararaye (630 kg ha-1). There was a significant genotype x environment interaction and hence it is important for breeders to carry out stability analysis, so as to recommend varieties for a wide range of environments. To study the genetics of ALS resistance in common bean, three inter-gene pool crosses: Super-rosecoco x Mexico 54, Wairimu x G10909 and Wairimu x Mexico 54 were made. The resistant genotypes were Mexico 54 and G10909, while Super-rosecoco and Wairimu were susceptible. The generations F1, F2, BC1P1 and BC1P2 for each of the crosses were developed. The parents P1, P2 and the five generations of each cross were evaluated for resistance to ALS in Kabete Field Station. Results showed that both dominance and additive gene action were important in the expression of resistance to ALS. However, additive gene action was predominant over dominance gene action. There was a moderately high narrow sense heritability estimate (52.9-71.7%). The minimum number of genes controlling resistance to ALS was between 2 and 3. The predominance of additive gene effects and the moderately high narrow sense heritability estimates recorded imply that progress in resistance to ALS could be made through selection in the early segregating generations. A double cross followed by selection against resistant genotypes was used to develop a method to breed for durable resistance to ALS in common bean. The method was used to accumulate minor genes of ALS resistance into single genotypes. Four intermediate resistant landraces were used to develop a double cross population that was screened using a mixture of ALS races. Selection in F1 and F2 population was done on the basis of intermediate resistance (disease severity score 4.0-6.0), while selection from F3 population was based on resistance (disease severity score 1.0-3.0). Ten advanced F4 lines along with their parents were evaluated for ALS resistance. The F4 advanced lines had a significantly improved resistance to ALS compared to their parents. Hence the method was successful in accumulating minor genes for resistance thus showing significant breeding progress in breeding for durable resistance. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2013.

In the genus Fusarium are many important plant pathogens. The diversity of hosts the genus attacks, the number of pathogenic taxa and the range of habitats in which they cause disease are the greatest in plant pathology. One important species complex within the genus Fusarium is Fusarium oxysporum Schlecht. This species complex consists more than 80 pathogenic forma specialis and is particularly difficult to control. The fungi can survive in soil for decades as specialized spores, known as chlamydospores. Interestingly, however, this species complex also contains beneficial non-pathogenic forms that can be exploited to manage Fusarium wilt diseases. In this study, the ability of non-pathogenic F. oxysporum strains, Trichoderma harzianum Rifai Eco-T®, soluble silicon, and their combination was evaluated on two important crops, banana (Musa sp. L.) and beans (Phaseolus vulgaris L.), for their potential to suppress pathogenic strains of F. oxysporum. The ability of these crops to take up and accumulate silicon in their organs, and its effect on low temperature stress was also investigated. Several endophytic fungi, mainly Fusarium spp. and bacteria, were isolated from healthy mature banana plants. After preliminary and secondary in vivo screening tests against F. oxysporum f.sp. phaseoli on beans (Phaseolus vulgaris L.) cv. Outeniqua, two non-pathogenic F. oxysporum strains were selected for further testing. These two non-pathogenic F. oxysporum strains were found to colonize banana (Musa sp.) cv. Cavendish Williams and bean plants, and to suppress Fusarium wilt of these crops. In order to improve the efficacy of these biocontrol fungi, soluble silicon was introduced. The relationship between plant mineral nutrition and plant diseases have been reported by several authors. Plants take up silicon equivalent to some macronutrients, although it is not widely recognized as an essential element. In this study, we established that roots, the target plant organ for soilborne plant pathogens, accumulated the greatest quantity of silicon of any plant organs when fertilized with high concentrations of silicon. On the other hand, the corm and stem accumulated the least silicon. Such observations contradict the concept of passive uptake of silicon via the transpiration stream in these plants as the only uptake mechanism. The prophylactic properties of silicon have been documented for many crops against a variety of diseases. In vitro bioassay tests of silicon against these wilt pathogens showed that silicon can be toxic to Fusarium wilt fungi at high concentrations (>7840 mg .-1), resulting in complete inhibition of hyphal growth, spore germination and sporulation. However, low concentrations of silicon (<490 mg .-1) encouraged hyphal growth. Silicon fertilization of banana and beans significantly reduced disease severity of these crops by reducing the impact of the Fusarium wilt pathogens on these crops. However, it could not prevent infection of plants from the wilt pathogens on its own. Synergistic responses were obtained from combined applications of silicon and non-pathogenic F. oxysporum strains against Fusarium wilt of banana. Combinations of silicon with the non-pathogenic F. oxysporum strains significantly suppressed disease severity of Fusarium wilt of banana, caused by F. oxysporum f.sp. cubense (E.F. Smith) Snyder & Hansen, better than applications of either control measure on their own. Banana production in the subtropical regions frequently suffer from chilling injury, and from extreme variations between night and day temperatures. Such stress predisposes banana plants to Fusarium wilt disease. Silicon, on the other hand, is emerging as important mineral in the physiology of many plants, ameliorating a variety of biotic and abiotic stress factors. We established that silicon fertilization of banana plants significantly reduced chilling injury of banana plants. Membrane permeability, lipid peroxidation (MDA level) and proline levels were higher in silicon-untreated plants than the treated ones, all of which demonstrated the stress alleviating effect of silicon. Low temperatures damage the cell membrane of susceptible plants and cause desiccation or dehydration of these cells. Levels of sucrose and raffinose, recognized as cryoprotectants, were significantly higher in silicon-amended banana plants than unamended plants. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2008.

The common bean (Phaseolus vulgaris L.) is an important crop grown widely in Uganda. It is also an important source of income for smallholder farmers particularly women. Despite its importance, production in the cool highland regions is constrained by anthracnose disease which causes losses in both the quantity and the quality of beans produced. The principal aim of this research was to elucidate on the status of dry bean anthracnose and the genetics governing its resistance. A participatory rural appraisal study was conducted to explore farmers' knowledge, experience, problems and cultivar preferences in association with managing dry bean anthracnose disease. This study revealed that anthracnose is an important constraint to production which is not controlled in any way. Although farmers have varying cultivar preferences, they use mostly home saved seed and only 1% could access improved seed. The study suggested the need for practical approaches in the provision of quality anthracnose resistant seed in consideration of farmers' preferences and the dynamics of their rural livelihoods. A study was conducted to determine the variability of the anthracnose (Colletotrichum lindemuthianum) pathogen in some of the major bean growing regions of Uganda. Use was made of a set of 12 internationally accepted anthracnose differential cultivars to identify the physiological races present. The results obtained indicated the presence of eight races with one race (767) being dominant and most aggressive. Differential cultivars AB 136 and G2333 were resistant to all the eight races, and can be utilised as potential sources of resistant genes. A germplasm collection of mostly Ugandan accessions was screened for anthracnose resistance. Using the area under disease progression curve as the tool for assessing disease severity, eleven accessions were identified that posses good levels of anthracnose resistance. The yield loss attributed to the anthracnose disease was determined on three susceptible Ugandan market-class dry bean cultivars and two resistant cultivars. The results showed that the yield of susceptible cultivars was reduced by about 40% and an almost equivalent yield was lost due to poor quality seed. In comparison, the yield lost by the resistant cultivars was not significant. The study suggested the use of resistant cultivars as the best solution in combating anthracnose resistance. Three susceptible Ugandan market class dry bean cultivars and six resistant cultivars were used for the study of the inheritance of resistance to the anthracnose pathotype 767 in a complete 9x9 diallel design. The results clearly indicated that the resistance was predominately conditioned by additive gene action. It was also established that epistatic gene action was important. More than one pair of genes displaying partial dominance were responsible for determining resistance and the maternal effect did not have an influence on resistance. Additionally, the result showed that some of susceptible cultivars combined very well with the resistant cultivars and that anthracnose resistance heritability estimates in both the narrow and broad sense were high. These results suggested that the use of simple pedigree breeding procedures such as backcross selection could be useful in improving anthracnose resistance levels in the Ugandan market class varieties. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2006.

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 (DT) agro-ecology and at 18% in the dry mid-altitude (DM) 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 landraces, bean fly resistant lines and local checks. The experiment was done under drought stressed (DS) 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 (DS) 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 to1704 kg ha-1 under natural infestation and from 591 to 2659 kg ha-1 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 DS. 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 A 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. Low to moderate narrow sense heritability values ranging from 0.22 to 0.45 were obtained for pupae in stem. Such heritability estimates indicate that although additive gene components were critical in the inheritance of resistance for the trait, non-additive gene action was also important in addition to the environmental effects. A major disadvantage in screening for resistance to bean fly in common bean by controlled means in net cages has been the lack of a method to use for raising adequate fly populations for screening. Due to this problem, a simple procedure for raising sufficient numbers of adult bean flies required for screening was described. Through this method, up to 62 % emergence of the adult flies was achieved. Moreover, the flies retained their ability to infest bean plants. To determine the presence of antibiosis and antixenosis mechanisms of resistance in common bean, five genotypes [CC 888 (G15430), GBK 047821, GBK 047858, Ikinimba and Macho (G22501)] and two local check varieties (Kat B1 and Kat B9) were screened under free-choice in outdoor net cages and no-choice conditions in net cages placed in a shadehouse. All the five resistant genotypes tested had relatively long internodes. It was established that long internode was a morphological trait associated with reduced pupation rate in bean stems, hence an antixenosis component of resistance. Both ovipositional non-preference and antibiosis mechanisms were found to exist in three genotypes namely CC 888 (G45430), GBK 047858 and Macho (G22501). These genotypes were resistant when they were subjected to bean fly under both free-choice and no-choice conditions. They had fewer feeding/oviposition punctures, low number of pupae in the stem, reduced damage to the stems and low percent plant mortality. The remaining genotypes, Ikinimba and GBK 047821 only expressed antixenosis. To maximize the effectiveness of host-plant resistance against bean fly, multiple insect resistances should be incorporated into a single bean genotype in order to ensure durability. However, this should be within the background of integrated pest management strategy. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2010.