Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The blast and the yellow leaf spot are the major rice and wheat, respectively, both are commonly found as for its destructive potential. Because of this, proving the efficiency of control methods through experiences is of paramount importance, since these results will be used as reference for technicians and producers. The precision is related to the choice of suitable design (local control), the number of repetitions, the sample size in the field, among others. In the case of control experiments involving fungicides, which is the main method of controlling both diseases, leaf sampling in installments is necessary because measuring the entire population becomes unviable. Sampling generates a new error (sampling) within the plot, and this should be minimized by appropriate sampling strategy. Thus, this study aimed to determine sample sizes needed to assess the severity of rice leaf blast and the yellow spot of wheat. For this reason, results of chemical control experiments performed during harvests and 2009/2010 2010/2011 were used. The procedure for collection and analysis of data was identical in all experiments, regardless of culture. In all, the diseases were measured at seven, 14 and 21 days after application of fungicides by sampling 10 leaves in the plots. The variables were disease severity and area under the disease progress curve (AUDPC). Data were subjected to analysis of variance to obtain the experimental and sampling errors, and so, by hypothesis test to check whether the sample dimension and the number of repetitions were adequate. The departure from randomness of variable severity was tested in order to determine whether the methodology used to calculate the sample size was adequate. The departure from randomness test showed that both diseases behaved were distinct, both among treatments between assessments, sometimes distributing randomly in the field, sometimes not. Thus, the combination of theoretical distributions (indicating random or clustered distribution of the disease in the field) to the formula used to calculate the sample size is inadequate. The sample size necessary to measure the average disease severity in the plots was not the same in all treatments and between assessments. This result is expected since, in most of the experiments, the average of the disease was different between treatments and between evaluations. This result leads to a constant change in the relationship between the variance and the mean, which is indicative of the disease in the field of dispersion, this dispersion that is related to the sample intensity. Finally it was observed that, to measure the average AUDPC variable, it is necessary to evaluate fewer leaves in the plots. / A brusone da folha e a mancha amarela são as principais doenças do arroz e do trigo, respectivamente, tanto por serem comumente encontradas quanto pelo seu potencial destrutivo. Devido a isso, a comprovação da eficiência de métodos de controle através de experiências é de suma importância, uma vez que estes resultados serão usados como referência por técnicos e produtores. A precisão experimental está relacionada com a escolha adequada do delineamento (controle local), do número de repetições, do tamanho da amostra na parcela, entre outros. No caso de experimentos de controle envolvendo fungicidas, que é o principal método de controle de ambas as doenças, a amostragem de folhas nas parcelas é necessária, pois mensurar toda a população torna-se inviável. A amostragem gera um novo erro (amostral) dentro da parcela, e este deve ser minimizado através de um dimensionamento amostral adequado. Deste modo, o presente trabalho teve por objetivo determinar tamanhos de amostra necessários para avaliar a severidade da brusone da folha do arroz e da mancha amarela do trigo. Para isso, foram utilizados resultados de experimentos de controle químico realizados durante as safras 2009/2010 e 2010/2011. O procedimento de coleta e análise dos dados foi idêntica em todos os experimentos, independente da cultura. Em todos eles, as doenças foram mensuradas aos sete, 14 e 21 dias após a aplicação dos fungicidas através da amostragem de 10 folhas nas parcelas. As variáveis estudadas foram a severidade das doenças e a área abaixo da curva de progresso das doenças (AACPD). Os dados foram submetidos a análise de variância para a obtenção dos erros experimental e amostral, e assim, através do teste de hipótese, verificar se o dimensionamento amostral e o número de repetições foram adequados. O afastamento da aleatoriedade da variável severidade foi testado com o objetivo de determinar se a metodologia utilizada no cálculo do tamanho da amostra foi adequada. O teste de afastamento da aleatoriedade mostrou que ambas as doenças comportaram-se de foram distintas, tanto entre os tratamentos quanto entre as avaliações, ora distribuindo-se de forma aleatória no campo, ora não. Desse modo, a associação de distribuições teóricas (que indicam distribuição aleatória ou agregada da doença no campo) à formula utilizada no cálculo do tamanho da amostra é inadequado. O tamanho de amostra necessário para mensurar a média da severidade das doenças nas parcelas não foi o mesmo em todos os tratamentos e entre as avaliações. Este resultado era esperado, uma vez que, na grande maioria dos experimentos, a média das doenças foi distinta entre os tratamentos e entre as avaliações. Este resultado levou a uma constante mudança na relação entre a variância e a média, que é um indicativo da dispersão da doença no campo, dispersão esta que esta relacionada com a intensidade amostral. Por fim observou-se que, para mensurar a média da variável AACPD, é necessário avaliar menos folhas nas parcelas. Deste modo, recomenda-se que, sempre que possível, utiliza-se a variável AACPD como forma de comparação entre os tratamentos.

O fungo Magnaporthe oryzae, agente causal da brusone em trigo e em várias outras gramíneas, desde o seu primeiro relato no Brasil tem sido alvo de inúmeras pesquisas. O entendimento da morfologia, fisiologia e parâmetros bioquímicos deste ascomiceto é o primeiro passo para a adoção de medidas eficientes de controle da doença. Os objetivos deste trabalho foram avaliar os aspectos morfológicos, fisiológicos e bioquímicos relativos à patogenicidade do fungo M. oryzae em trigo, além de determinar in vitro as condições ótimas de temperatura e fotoperíodo para o crescimento e esporulação dos isolados testados, quantificar a pressão de turgor exercida pelo apressório no momento da penetração do substrato, verificar a presença de enzimas extracelulares produzidas pelo patógeno e o papel de cada uma delas na degradação da parede celular e, também, demonstrar a possível produção e ação de metabólitos tóxicos do fungo em plântulas de trigo. Dois isolados do fungo, Py5003 e Py6017, foram repicados para os meios de cultivo cenoura, milho-cenoura, batata-dextrose-ágar (BDA), aveia e V8, incubados, de maneira independente, sob luz contínua, escuro contínuo e fotoperíodo de 12h, por 20 dias, sendo avaliados periodicamente quanto ao crescimento micelial total e esporulação do patógeno. Em seguida, conídios germinados e com apressórios formados foram submetidos a diferentes concentrações de PEG-8000 para a mensuração da pressão de turgor apressorial. Além disso, o teor de proteínas totais foi mensurado e a atividade celulolítica determinada, por espectrofotometria indireta para os isolados cultivados em meio Merlin-Norkrans Modificado (MNM), a partir das enzimas exo e endo-?-1,4-glucanase e ?-glicosidase. A produção de metabólitos tóxicos foi determinada por condutivimetria, após o cultivo dos isolados por 5 e 10 dias em batata-dextrose (BD) e obtenção dos filtrados após esse período, sendo que, a ação destes, foi observada em plântulas de trigo com 25 dias de idade. Os resultados evidenciaram melhor crescimento micelial e esporulação dos isolados em meio de cultivo composto de aveia, incubado a 25 °C e fotoperíodo de 12 h. A pressão de turgor apressorial, tanto para Py5003 quanto para Py6017, concentrouse na faixa dos 7,5 MPa. Não houve diferença estatística entre os teores de proteínas totais apresentados pelo isolados. Os dois isolados exibiram alta atividade celulolítica, com diminuição da atividade observada para endo-?-1,4-glucanase e ?- glicosidase na presença de glicose e celobiose, respectivamente. A exposição de plântulas de trigo aos filtrados dos isolados do fungo M. oryzae provocou alta liberação de eletrólitos, sendo, em termos absolutos, Py5003 maior do que Py6017. Plântulas expostas ao filtrado, autoclavado ou não, e ao extrato bruto obtido a partir da separação dos metabólitos tóxicos em acetato de etila, apresentaram-se cloróticas e/ou necróticas. Os resultados sugerem um mecanismo de parasitismo desenvolvido por M. oryzae no desenvolvimento da brusone em trigo, indo desde a fase de pré-penetração, passando pelo estabelecimento das relações parasitárias estáveis e o aparecimento de sintomas e sinais na planta hospedeira. / The fungus Magnaporthe oryzae, causal agent of blast in wheat and several other grasses, since its first occurrence in Brazil has been the subject of extensive research. The understanding of the morphology, physiology and biochemical parameters of this ascomycete is the first step for the adoption of efficient measures to control the disease. The objectives of this study were to evaluate the morphological, physiological and biochemical aspects related to the pathogenicity of the fungus M. oryzae on wheat. Thus, it were determined in vitro the optimal conditions of temperature and photoperiod for growth and sporulation of the isolates tested, quantified the pressure exerted by appressorium at the time of substrate penetration, verified the presence of extracellular enzymes produced by the pathogen and their role in the degradation of cell wall and also demonstrated the possible production and action of toxic metabolites of the fungus in wheat seedlings. Two isolates of the fungus, Py5003 and Py6017, were grown on carrot, maize-carrot, PDA, oat and V8 media and measure periodically for 20 days and after that period, being evaluated the total mycelia growth and sporulation of the pathogen. Then, germinated conidia and appressoria were subjected to different concentrations of PEG-8000 for the measurement of appressorial turgor pressure. In addition, the concentration of total proteins was measured and enzyme activity (exo and endo-?- 1,4-glucanase, ?-glucosidase) was determined by indirect spectrophotometry, for the isolates grown in Modified Melin-Nokrans (MMN) medium. The production of toxic metabolites was determined after growing the isolates for 5 and 10 days in potatodextrose medium (PD) and obtaining the filtrate. The toxic action was evaluated in wheat seedlings (25 days old) by measuring electrolyte leakage. The results showed better mycelial growth and sporulation of the isolates in oat medium incubated at 25 °C and under a photoperiod of 12 h. Appressorial turgor pressure for both isolates were at the range of 7.5 MPa.There were no statistical differences between the levels of total protein presented by the isolates. The two isolates showed high cellulolytic activity, with decreased activity observed for endo-?-1,4-glucanase and ?- glucosidase in the presence of glucose and celobiose, respectively. The exposure of wheat seedlings to the filtrates of the fungus M. oryzae caused high electrolyte release, being, in absolute terms, Py5003 greater than Py6017. Seedlings exposed to the filtrate, autoclaved or not, and the crude extract obtained from the separation of the toxic metabolites in ethyl acetate, exibited clorotic and/or necrotic. These results suggest a mechanism of parasitism developed by M. oryzae on wheat, ranging from pre-penetration through the establishment of stable parasitic relationships and the appearance of symptoms and signals in the host plant.

Submitted by MARCOS LEANDRO TEIXEIRA DE OLIVEIRA (marcosteixeira@ufv.br) on 2018-08-15T18:29:36Z No. of bitstreams: 1 texto completo.pdf: 1510730 bytes, checksum: 754986579a43c0d4c754880228c9a25d (MD5) / Made available in DSpace on 2018-08-15T18:29:36Z (GMT). No. of bitstreams: 1 texto completo.pdf: 1510730 bytes, checksum: 754986579a43c0d4c754880228c9a25d (MD5) Previous issue date: 2016-08-25 / A brusone, causada por Pyricularia oryzae, é considerada uma doença economicamente importante para trigo na América do Sul. Uma das estratégias de manejo para minimizar as perdas causadas por essa doença é o uso de cultivares resistentes. Alternativamente, pode-se utilizar indutores de resistência para aumentar o nível basal de resistência do trigo à brusone. O presente estudo teve como objetivos: i) determinar as alterações fisiológicas e bioquímicas em plantas de trigo pulverizadas com uma concentração não fitotóxica do ácido α-picolinico (AP), o qual é uma toxina não seletiva produzida por P. oryzae e ii) verificar a manipulação metabólica exercido por P. oryzae quando infectando cultivares de trigo com diferentes níveis de resistência basal à brusone. Nas folhas de trigo pulverizadas com uma concentração não fitotóxica de AP (0.1 mg mL -1 ), os sintomas da brusone desenvolveram menos em associação com um melhor desempenho fotossintético, melhoria do metabolismo antioxidante e redução nas concentrações de H 2 O 2 , O 2 ●- e MDA. As cultivares BR-18 e EMBRAPA- 16 foram mais resistentes à brusone do que a cultivar BRS-Guamirim. O desempenho fotossintético das plantas infectadas foi alterado devido a limitações de natureza difusiva e bioquímica para uma eficiente fixação do CO 2 . Durante a fase assintomática da infecção por P. oryzae, mudanças drásticas no metabolismo de carboidratos e nos níveis de aminoácidos, compostos intermediários do ciclo de Krebs e poliaminas ocorreram nas plantas das três cultivares sugerindo, assim, uma manipulação metabólica exercida por P. oryzae. No entanto, um metabolismo antioxidativo mais eficiente foi importante para neutralizar os efeitos deletérios da infecção por P. oryzae em associação com maiores atividades da fenilalanina amônia liase e polifenoloxidase e maiores concentrações de compostos fenólicos e lignina. Com base nesses resultados e possível concluir que a concentração não fitotóxica de AP foi capaz de potencializar a defesa das plantas de trigo e reduzir a severidade da brusone. A infecção do trigo por P. oryzae ocasionou distúrbios no metabolismo primário das plantas e alguns deles foram semelhantes entre as cultivares independentemente do nível basal de resistência delas. / Blast, caused by Pyricularia oryzae, has become an economically important disease in wheat in South America. One of the management strategies for minimizing the losses caused by blast includes the use of resistant cultivars. Alternatively, the use of inducers of resistance showed the potentiation to increase wheat resistance to blast. This study aimed: i) to determine the physiological and biochemical alterations in wheat plants sprayed with a non-phytotoxic concentration of α-picolinic acid (PA), which is a non-host selective toxin produced by P. oryzae and ii) to establish the degree of metabolic manipulation exerted during the infection by P. oryzae on plants from cultivars with different levels of basal resistance to blast. The spray of leaves of plants with a non-phytotoxic concentration of PA (0.1 mg mL -1 ) resulted in less blast symptoms in association with a better photosynthetic performance, an improvement on the antioxidant metabolism and reduced concentrations of H 2 O 2 , O 2 ●- and malondialdehyde. The cultivars BR-18 and EMBRAPA-16 were more resistant to blast in comparison to cultivar BRS-Guamirim. The photosynthetic performance of the infected plants was altered due to diffusional and biochemical limitations for CO 2 fixation. During the asymptomatic phase of P. oryzae infection, drastic changes in the carbohydrates metabolism and on the levels of amino acids, intermediates compounds of Krebs cycle and polyamines occurred on plants from the three cultivars suggesting a metabolic manipulation exerted by the pathogen. However, amore efficient antioxidant metabolism was able to help the wheat plants to counteract against the deleterious effects of P. oryzae infection in association with great phenylalanine ammonia lyases and polyphenoloxidases activities and high concentrations of phenolics and lignin. Based on this information, it is possible to conclude that a non- phytotoxic concentration of PA elicited the activation of host defense mechanisms that reduced blast severity. Likewise, the infection of leaves by P. oryzae induced remarkable disturbances in the primary metabolism and some of them were conserved among the cultivars regardless of their basal level of resistance to blast.

O fungo Magnaporthe oryzae, agente causal da brusone em trigo e em várias outras gramíneas, desde o seu primeiro relato no Brasil tem sido alvo de inúmeras pesquisas. O entendimento da morfologia, fisiologia e parâmetros bioquímicos deste ascomiceto é o primeiro passo para a adoção de medidas eficientes de controle da doença. Os objetivos deste trabalho foram avaliar os aspectos morfológicos, fisiológicos e bioquímicos relativos à patogenicidade do fungo M. oryzae em trigo, além de determinar in vitro as condições ótimas de temperatura e fotoperíodo para o crescimento e esporulação dos isolados testados, quantificar a pressão de turgor exercida pelo apressório no momento da penetração do substrato, verificar a presença de enzimas extracelulares produzidas pelo patógeno e o papel de cada uma delas na degradação da parede celular e, também, demonstrar a possível produção e ação de metabólitos tóxicos do fungo em plântulas de trigo. Dois isolados do fungo, Py5003 e Py6017, foram repicados para os meios de cultivo cenoura, milho-cenoura, batata-dextrose-ágar (BDA), aveia e V8, incubados, de maneira independente, sob luz contínua, escuro contínuo e fotoperíodo de 12h, por 20 dias, sendo avaliados periodicamente quanto ao crescimento micelial total e esporulação do patógeno. Em seguida, conídios germinados e com apressórios formados foram submetidos a diferentes concentrações de PEG-8000 para a mensuração da pressão de turgor apressorial. Além disso, o teor de proteínas totais foi mensurado e a atividade celulolítica determinada, por espectrofotometria indireta para os isolados cultivados em meio Merlin-Norkrans Modificado (MNM), a partir das enzimas exo e endo-?-1,4-glucanase e ?-glicosidase. A produção de metabólitos tóxicos foi determinada por condutivimetria, após o cultivo dos isolados por 5 e 10 dias em batata-dextrose (BD) e obtenção dos filtrados após esse período, sendo que, a ação destes, foi observada em plântulas de trigo com 25 dias de idade. Os resultados evidenciaram melhor crescimento micelial e esporulação dos isolados em meio de cultivo composto de aveia, incubado a 25 °C e fotoperíodo de 12 h. A pressão de turgor apressorial, tanto para Py5003 quanto para Py6017, concentrouse na faixa dos 7,5 MPa. Não houve diferença estatística entre os teores de proteínas totais apresentados pelo isolados. Os dois isolados exibiram alta atividade celulolítica, com diminuição da atividade observada para endo-?-1,4-glucanase e ?- glicosidase na presença de glicose e celobiose, respectivamente. A exposição de plântulas de trigo aos filtrados dos isolados do fungo M. oryzae provocou alta liberação de eletrólitos, sendo, em termos absolutos, Py5003 maior do que Py6017. Plântulas expostas ao filtrado, autoclavado ou não, e ao extrato bruto obtido a partir da separação dos metabólitos tóxicos em acetato de etila, apresentaram-se cloróticas e/ou necróticas. Os resultados sugerem um mecanismo de parasitismo desenvolvido por M. oryzae no desenvolvimento da brusone em trigo, indo desde a fase de pré-penetração, passando pelo estabelecimento das relações parasitárias estáveis e o aparecimento de sintomas e sinais na planta hospedeira. / The fungus Magnaporthe oryzae, causal agent of blast in wheat and several other grasses, since its first occurrence in Brazil has been the subject of extensive research. The understanding of the morphology, physiology and biochemical parameters of this ascomycete is the first step for the adoption of efficient measures to control the disease. The objectives of this study were to evaluate the morphological, physiological and biochemical aspects related to the pathogenicity of the fungus M. oryzae on wheat. Thus, it were determined in vitro the optimal conditions of temperature and photoperiod for growth and sporulation of the isolates tested, quantified the pressure exerted by appressorium at the time of substrate penetration, verified the presence of extracellular enzymes produced by the pathogen and their role in the degradation of cell wall and also demonstrated the possible production and action of toxic metabolites of the fungus in wheat seedlings. Two isolates of the fungus, Py5003 and Py6017, were grown on carrot, maize-carrot, PDA, oat and V8 media and measure periodically for 20 days and after that period, being evaluated the total mycelia growth and sporulation of the pathogen. Then, germinated conidia and appressoria were subjected to different concentrations of PEG-8000 for the measurement of appressorial turgor pressure. In addition, the concentration of total proteins was measured and enzyme activity (exo and endo-?- 1,4-glucanase, ?-glucosidase) was determined by indirect spectrophotometry, for the isolates grown in Modified Melin-Nokrans (MMN) medium. The production of toxic metabolites was determined after growing the isolates for 5 and 10 days in potatodextrose medium (PD) and obtaining the filtrate. The toxic action was evaluated in wheat seedlings (25 days old) by measuring electrolyte leakage. The results showed better mycelial growth and sporulation of the isolates in oat medium incubated at 25 °C and under a photoperiod of 12 h. Appressorial turgor pressure for both isolates were at the range of 7.5 MPa.There were no statistical differences between the levels of total protein presented by the isolates. The two isolates showed high cellulolytic activity, with decreased activity observed for endo-?-1,4-glucanase and ?- glucosidase in the presence of glucose and celobiose, respectively. The exposure of wheat seedlings to the filtrates of the fungus M. oryzae caused high electrolyte release, being, in absolute terms, Py5003 greater than Py6017. Seedlings exposed to the filtrate, autoclaved or not, and the crude extract obtained from the separation of the toxic metabolites in ethyl acetate, exibited clorotic and/or necrotic. These results suggest a mechanism of parasitism developed by M. oryzae on wheat, ranging from pre-penetration through the establishment of stable parasitic relationships and the appearance of symptoms and signals in the host plant.

The blast rice, caused of fungus Pyricularia oryzae is the most important rice crop disease and can cause up to 100% crop damage. The cultural, varietal and chemical management at the field level and the monitoring and knowledge of in vitro blast isolates sensitivity are essential tools for better understanding and control of this disease. The objective of this project was to evaluate the effect of the fungicides most used in blast control in three cultivars of irrigated rice in two sowing seasons and to determine in vitro the sensitivity of the mycelial growth of two isolates of P. oryzae to the same fungicides: Triciclazole, Tebuconazole, Azoxystrobin, Trifloxystrobin + Tebuconazole and Casugamycin. For that, an experiment was carried at the field level in the 2015/2016 cropseason in Santa Maria-RS and another experiment in the laboratory. In the first experiment the cultivars used were Guri INTA CL, Puitá INTA CL and IRGA 424 RI sown in the beginning and end of the recommended period and submitted to the same fungicides. The second experiment tested the fungicides at concentrations of 0, 0.01, 0.1, 1, 10 and 100 ppm in two isolates of blast. It was concluded that the cultivar IRGA 424 IR showed to be resistant to blast and that for the maintenance of productive levels in the cultivars susceptible to P. oryzae, especially in the second sowing season, the adoption of more efficient fungicides is indispensable. In relation to mycelial growth in vitro, the first insensitivity of a P. oryzae isolate to the active ingredients Triciclazol and Azoxystrobin was verified at the national level. / A brusone, causada pelo fungo Pyricularia oryzae, é a doença mais importante da cultura do arroz, podendo causar até 100% de prejuízos à cultura. O manejo cultural, varietal e químico a nível de campo bem como o monitoramento e conhecimento da sensibilidade in vitro de isolados de brusone, são ferramentas imprescindíveis para o melhor entendimento e controle desta doença. O objetivo deste projeto, foi avaliar o efeito dos fungicidas mais utilizados no controle de brusone, em três cultivares de arroz irrigado, em duas épocas de semeadura e determinar in vitro a sensibilidade do crescimento micelial de dois isolados de P. oryzae aos mesmos fungicidas: Triciclazol, Tebuconazole, Azoxistrobina, Trifloxistrobina + Tebuconazole e Casugamicina. Para tal, foi realizado um experimento em nível de campo na safra 2015/2016 em Santa Maria-RS e outro experimento em laboratório. No primeiro experimento foram utilizadas as cultivares GURI INTA CL, PUITÁ INTA CL e IRGA 424 RI, semeadas no início e no final da época recomendada e essas submetidas aos mesmos fungicidas. O segundo experimento, testou os fungicidas anteriormente citados nas concentrações de 0, 0.01, 0.1, 1, 10 e 100 ppm em dois isolados de brusone. Concluiu-se que a cultivar IRGA 424 RI mostrou-se resistente à brusone e que para a manutenção dos patamares produtivos nas cultivares suscetíveis a P. oryzae, principalmente na segunda época de semeadura, torna-se necessário a adoção de fungicidas mais eficientes. Em relação ao crescimento micelial in vitro, constatou-se à nível nacional, a primeira insensibilidade de um isolado de P. oryzae aos ingredientes ativos Triciclazol e Azoxistrobina.

Finger millet is the second most important cereal in Uganda after maize. The yields however, have remained low due to several constraints, such as finger millet blast disease and limited technology options. Therefore breeding investigations were conducted to determine farmer preferred traits, genetic variation, combining ability and genetic effects for head blast disease and head shapes, and other quantitative traits in finger millet. Among other traits, farmers preferred high grain yield potential, brown seed colour, compact head shape, tolerance to blast disease, high tillering ability, medium plant height, early maturity, tolerance to shattering and ease of threshing in new finger millet varieties. Path coefficient analysis indicated that the most important traits were grain mass head-1, tillering ability and reaction to head blast disease. Overall, the high heritabilities and genetic advance (GA) as a percentage of mean revealed the existence of variability which can be utilised through selection and/or hybridisation. The genotype x environment interaction (GEI) and stability analysis showed significant differences due to genotypes (58%), environments (10%) and GEI (32%). Twelve genotypes that combined high yield potential and stability were identified for advancement in the program. Both general (GCA) and specific combining ability (SCA) were significant for most traits, but GCA effects were more important for all the traits except for number of fingers head-1, finger width and panicle width. The Hayman genetic analysis confirmed importance of additive gene action for most of the traits and that additive-dominance model was adequate for explaining genetic variation in finger millet. The results also indicated that yield was controlled by recessive genes whereas blast resistance was controlled by dominant genes. At least two genes, probably three gene pairs and their interactions seemed to control head shape in finger millet. The interactions observed suggest recessive and dominant epistasis, and probably an inhibitor were involved. Seemingly, the gene for curving of fingers, when present in a dominant form prohibits opening of the heads; whereas the recessive form leads to open head shape irrespective of the gene conditions in the other loci. This study forms the baseline for future investigations and the basis for devising breeding strategy on finger millet head shapes. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2013.

Finger millet (Eleusine coracana) productivity in East Africa has remained low in all production agro-ecologies for decades owing to the low yielding potential of existing that are susceptible to the blast disease caused by the fungus Magnaporthe grisea (Hebert) Barr. and the limited research on the crop. The region holds large finger millet germpasm collections whose value is not yet been fully exploited. However, with the ongoing breeding efforts through hybridization, there is a need to comprehensively characterize the germplasm to identify valuable traits to address biotic and abiotic stresses that affect finger millet productivity. Studies on gene action and inheritance of key traits that contribute to yield improvement are also required to help formulate an effective breeding strategy for finger millet improvement. The objectives of this study were to (i) determine the genetic diversity in a set of germplasm from East Africa (ii) determine association between grain yield and its component traits (iii) identify genotypes for target production agro-ecologies (iv) identify blast resistant finger millet genotypes for use in breeding and production and (v) generate information on the inheritance of blast, grain yield and yield components for the development of an effective breeding strategy. A total of 340 finger millet accessions were collected from three countries in East Africa: Kenya, Tanzania and Uganda and 80 global minicore accessions sourced from ICRISAT-India. High phenotypic variability in the germplasm was recorded for 23 quantitative traits, blast reaction and five qualitative traits. Both morphological and molecular characterization (using SSR markers) of the 340 accessions revealed higher diversity within than among the countries Kenya, Tanzania and Uganda. Seven morphological clusters and three major genetic clusters were detected. Morphological diversity delineation was largely influenced by leaf sheath length, plant height, peduncle length, panicle exertion and grain yield. The mean polymorphic information content (PIC) of 19 polymorphic markers was 0.606 with mean alleles of 195 with sizes that ranged from 148-474 base pairs. The Kenyan and Tanzanian accessions had higher diversity than the Ugandan with the Kenyan and Ugandan, and the Kenyan and Tanzanian accessions being closely related than the Tanzanian and Ugandan. The low diversity in the Ugandan accessions could be attributed to higher research intervention in the country leading to the promotion and use of improved cultivars. Efforts have to be directed towards collection and conservation of valuable diversity before it is lost. The diversity in plant height, maturity, yield and blast reaction and the cluster groups detected in the germplasm should provide a basis for finger millet improvement through hybridization and selection. Higher genotypic than phenotypic correlations were recorded for most of the traits studied with grain yield having high positive correlations with finger width, grains per spikelet, threshing percent, peduncle length and panicle exertion. Both grain yield and days to flowering had negative correlations with all three blast types (leaf, neck and finger). Path coefficient analysis revealed that productive tillers per plant, 1000 grain mass, grains per spikelet and threshing percent had positive direct genetic effects on grain yield with strong indirect effects from several of the other traits which necessitates simultaneous selection for those traits with strong direct effects and those with strong indirect effects for grain yield improvement. High broad sense heritability estimates and high genetic advance as percent of mean were recorded in fingers per panicle, flag leaf sheath length, 1000 grain mass, finger length, peduncle length, panicle exertion, number of leaves per plant and leaf sheath length probably indicating the predominance of additive gene effects in controlling these traits hence the potential for improvement through selection. Adaptation and stability analysis using the GGE biplot model identified Lanet 2012 long rains, Serere 2012 long rains and Miwaleni 2012 long rains as the most discriminating environments for the low temperature, sub-humid mid altitude and dry lowland areas, respectively. Alupe 2012 long rains was the ideal environment for genotype discrimination for blast while Lanet 2012 long rains was best for grain yield. Genotypes G3, G5, G17, G25, G28, G36 and G71 were identified as being stable across environments and G1, G18, G19, G37, G54, G61, G74, G75, and G77 were found ideal for specific adaptation. Disease severity scores were highly negatively (P<0.01) correlated with days to flowering and grain yield suggesting that early lines suffered more disease damage leading to reduced yield. Resistant genotypes were slow blasting (probably associated with horizontal resistance) which may enable them to withstand blast pathogen variability for longer periods. Nine genotypes were identified with high resistance to blast and will be useful for breeding as blast resistance sources. Resistant genotypes had low AUDPC values and disease severity rating for the three blast types and vice-versa for susceptible genotypes. Further investigations need to be carried out to determine the possibility of the three blast types being controlled by the same genes. Early maturing blast susceptible genotypes with good yield potential could be utilized in areas with low blast prevalence. To understand the gene action for inheritance of the various traits 16 F2 families plus their four female and four male parents were evaluated at Alupe and Kakamega western Kenya under artificial blast inoculation. Significant additive genetic effects were recorded for all traits (except for finger width and grains per spikelet) meaning that improvement for these traits would be possible through the common selection methods for self pollinating crops. Parent lines KNE 392, and KNE 744 and IE 11 were found to be suitable for blast resistance breeding while Okhale 1 was found to be suitable for high grain yield and blast resistance improvement due to their high desirable GCA effects. Most of the F2 families showed transgressive segregation for the three blast types in either direction which gives hope for the development new pure lines with better blast resistance than the parents. Crosses IE 3104 x KNE 796, KAT FM 1 x Okhale 1, IE 11 x Okhale, IE 11 x P 224 and KNE 744 x KNE 392 have potential to generate lines with blast resistance due to their high desirable SCA effects. The F2 segregation distributions for blast indicated quantitative inheritance. However the one to four minimum number of genes (effective factors) detected for resistance control in all the three blast types was not in sync with the segregation patterns in the F2 families and further investigations are required. There were differences in segregation patterns between crosses which may suggest the presence of different resistance genes in the different parents used. This would call for gene pyramiding for durable resistance. These results confirm the potential of sourcing valuable parental stocks in the local germplasm for the development of genotypes to improve finger millet productivity in East Africa. Already some of the high yielding and blast resistant genotypes identified here have been incorporated in the regional cultivar trials. The diversity information generated will facilitate effective conservation and utilization of this germplasm. Results of gene action for inheritance of the various traits from this study will enable breeders to develop sound breeding strategies for finger millet improvement in the region. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2013.