Nell’ambito della ricerca di colture alternative e di alimenti ad alto valore nutrizionale, presso il Dipartimento di Scienze delle Produzioni Vegetali Sostenibili, si è svolta un’attività di ricerca sull’adattabilità della quinoa in Italia Settentrionale. La sperimentazione è durata tre anni ed ha preso in considerazione areali pedo-climatici di pianura e di collina. Il primo obiettivo era quello d’identificare le varietà di quinoa più adatte alle condizioni ambientali del Nord Italia, e come secondo obiettivo individuare la tecnica di coltivazione appropriata per gli agrosistemi intensivi; come terzo obiettivo contribuire al miglioramento della tecnica di coltivazione della quinoa nei Paesi emergenti (Colombia). In Italia settentrionale le attività di ricerca sono iniziate nel 2014 con un confronto varietale di 24 ecotipi di quinoa. Per il ciclo colturale 2015, sono state scelte le migliori 11 cultivar delle prove precedenti, insieme ad altre 5 nuove cultivar. Per quanto riguarda invece il 2016, le prove sono state divise in due: 1. Due prove riguardanti alla scelta varietale 2. Una prova con lo scopo di studiare la risposta produttiva della quinoa alla fertilizzazione azotata. Per quanta riguarda la sperimentazione nei Paesi in Via di sviluppo sono state allestite due prove agronomiche nel dipartimento di Boyacà (Colombia). / With the aim of finding alternative crops and foods high in nutrients, at the Department of Sustainable Crop Production (DI.PRO.VE.S.), a research on the adaptability of quinoa in Northern Italy was carried out. This activity has continued for three years both in the plain and in the hills. The first aim of this work was to identify quinoa varieties most suitable for Northern Italy environmental conditions and as a second purpose to identify the appropriate cultivation technique to adopt the quinoa crop in the sustainable intensive farming systems; the third aim was to contribute to the improvement of quinoa cultivation technique in emerging countries (Colombia). In Northern Italy the research activities began in 2014 with a varietal comparison of 24 quinoa ecotypes. During 2015 crop cycle, the best 11 varieties out of the previous trials were selected, together with 5 new cultivars. In the third year (2016), the trials were divided into: 1. Regarding the varietal screening, two different trials 2. In order to study the response of quinoa to nitrogen fertilization, a trial a split-plot trial was arranged. Furthermore, regarding the research in the developing countries, two agronomic trials were established in the Department of Boyacà (Colombia).

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Swine production in southern Brazil is concentrated on small farms, seeking the recovery of waste as a source of nutrients crops of economic interest. The interaction between applications of pig slurry and soil management is common on small farms, however scarce information was found about the main responses of agricultural crops under this condition. Thus, the present work aimed to evaluate the use of pig slurry, associated with soil management in succession oat / maize and double purpose wheat / soybean. The experimental design was a factorial in a randomized complete block design, with four replications. The treatments consisted of doses of pig slurry (without manure, 20, 40, 80 m3 ha-1), and mineral fertilizer in three different soil management: no tillage, chiseling and chiseling + disking. The application of pig slurry was held before oat/maize and wheat crops sowing, and the soil management employed only before the establishment of winter crops. The application of pig slurry in succession oat / maize showed increases in dry matter yield, and in the accumulation of nitrogen, phosphorus and potassium, and in the grain yield. As for soil management, no-tillage favored the production of oat dry matter yield and soybean grain yield. However, the dual-purpose wheat proved to be low responsive to soil management employed. As for maize, the interaction between higher doses of pig slurry and with tillage managements promotes increases in grain yield. The application of pig slurry before the dual purpose wheat sowing promoted increases in dry matter production and grain yield. The residual effect of five applications of pig slurry does not alter the soybean grain yield. / A produção de suínos no Sul do Brasil concentra-se em pequenas propriedades rurais, que buscam o aproveitamento dos resíduos como fonte de nutrientes as culturas agrícolas de interesse econômico. Aplicação de dejeto líquido de suínos e manejos de solo diferenciados é comum em pequenas propriedades rurais, no entanto são escassas informações sob as repostas das principais culturas agrícolas frente a esta condição. Nesse sentido, o trabalho teve por objetivo avaliar a influência do uso de dejeto líquido de suínos, associado a manejos de solo na sucessão aveia/milho e trigo duplo propósito/soja. O delineamento experimental foi de blocos ao acaso em esquema fatorial, com quatro repetições. Os tratamentos constaram da interação de doses de dejeto líquido de suínos (sem dejeto, 20, 40, 80 m3 ha-1), e adubação mineral, em três diferentes manejos de solo: plantio direto, escarificado e escarificação + gradagem. A aplicação do dejeto líquido de suínos foi realizada antes da semeadura das culturas aveia, milho e trigo, os manejos de solo realizados antes do estabelecimento das culturas de inverno. A aplicação de dejeto líquido de suínos na sucessão aveia/milho promoveu incrementos na produção de matéria seca, no acúmulo de nitrogênio, fósforo e potássio, e na produtividade de grãos. Quanto aos manejos de solo, o plantio direto favoreceu a produção de matéria seca da aveia e a produtividade de grãos de soja. Já para o milho, a interação entre maiores doses de dejeto líquido de suínos e manejos com revolvimento do solo promove incrementos na produtividade de grãos. A aplicação do dejeto líquido de suínos antes da semeadura do trigo duplo propósito promove incrementos na produção de matéria seca e na produtividade de grãos. O efeito residual de cinco aplicações de dejeto líquido de suínos não altera a produtividade de grãos de soja.

Thesis (M.Sc. (Agriculture Agronomy)) -- University of Limpopo, 2020 / Pigeonpea (cajanus cajan [L] Millsp.) is a legume crop which is grown mainly in the Semi-Arid Tropical (SAT) regions and it is mostly cultivated for its edible seeds. It has been identified as a possible substitute crop which can be bought by all people and it can also provide an acceptable amount of nutrition and protein in particular as it is not an expensive source of protein when compared to animal protein. Its ability to tolerate drought and fix atmospheric nitrogen makes it suitable for marginal areas with low rainfall and poor fertility. However, it remains one of the underutilized crops due to limited research on the crop’s diversification and adaptation. Smallholder farmers in the Limpopo Province cultivate landraces pigeonpea varieties that are characterized by late maturity, low grain yield and are sensitive to photoperiod and this makes it difficult for the cultivars to flower early and produce reasonable yield. The objectives of the study were to evaluate the nitrogen fixation, yield and yield components of exotic elite pigeonpea genotypes. The experiment was conducted at the University of Limpopo Experimental farm (Syferkuil) in Mankweng during the 2017/18 growing seasons. The trial was carried out in a Randomized Complete Block Design (RCBD) consisting of three replications. A total of 18 elite pigeonpea breeding lines obtained from ICRISAT in Kenya were planted at an inter-row and intra-row spacing of 1m and 0.5m respectively, in a row of 5m length with an alley way of 2m between the blocks. The standard management practices for pigeonpea were used for weed and insect control. The agronomic data collected included the number of days to first and 50% flowering, the number of days to 90% maturity, canopy width (m), plant height (m), peduncle length (m), number of primary branches, number of pods per plant, pod length (cm), hundred seed weight (g), calcium content, sodium content, magnesium content, phosphorus content, potassium content, iron content, zinc content, proportion of legume N derived from the fixation of atmospheric N2 (%Ndfa), amount of nitrogen fixed and the grain yield (kg.ha-1 ). The generated data was subjected to an analysis of variance using the Statistix 10.0 software. The Least Significance Difference (LSD) was used to separate the means that showed significant differences at an alpha level of 0.05. The results revealed significant differences in nearly all the pigeonpea variables (pod length, number of seed per pod, nutrient elements and the number of primary branches). Across genotypes, the number of days to 50% flowering ranged from 95 to 130 days, while the number of days to 90% maturity ranged from 172 to 220 days, with variety ICEAP 01154-2 being the earliest to flower and mature. Tall plants were observed by variety ICEAP 01541 (2.01m) followed by ICEAP 00902 (1.99m) and ICEAP 00850 (1.90m). Breeding line ICEAP 00673-1 recorded long peduncles with a mean of 0.94m. The number of pods per plant had a range between 56 and 482, while the pod length varied from 2.03 to 8.82cm. Variety ICEAP 00673-1 exhibited the highest number of pods per plant and with longest pods. The 100 seed weight varied from 9.43 to 16.97g among the genotypes. The higher calcium amount was observed in verities ICEAP 00979-1 with an average of 556 mg/L and the highest iron content was observed in ICEAP 01172-2 (14 mg/L). The potassium content ranged between 24 mg/L to 110 mg/L, with the variety ICEAP 00540 having the highest and the variety ICEAP 00850 having the lowest content. The sodium content ranged from 15 to 85.1 mg/L, with the variety ICEAP 01154-2 being the highest and the variety ICEAP 01147-1 having the lowest sodium content. The highest magnesium content was observed in ICEAP 00673-1 (141 mg/L). The phosphorus content ranged from 24.5 to 3.77 mg/L and the highest zinc content was observed in ICEAP 01541 and in ICEAP 00979-1 that had an average of 2.36 and 2.26 mg/L, respectively. The amount of nitrogen fixed from all the varieties ranged from 73.547 to 154.254 kg.ha-1 . The grain yield among the genotypes ranged from 89.24 to 785.29 kg.ha-1 . The top yielding varieties were ICEAP 01159 and ICEAP 00557 with grain yields of 785.29 and 661.51 kg.ha-1 . ICEAP 01159 and ICEAP 00557 are the varieties that produced the highest grain yields and they are recommended for cultivation and breeding purposes. / NRF (National Research Foundation)

Thesis (M.Sc. (Agronomy)) -- University of Limpopo, 2021 / Soybean (Glycine max L.) is one of the valuable leguminous crops with grain used for human consumption, livestock feeding, bio-fuel (bio-diesel) production, vegetable oil and is a protein resource. The crop also fixes atmospheric nitrogen. The study aimed to evaluate the performance of two soybean varieties to a combination of inoculation and seaweed extract. The research trial was conducted at Syferkuil farm during 2017/2018 summer season in which two soybean varieties (TGx 1937-1F promiscuous) and (PAN 1583R specific-nodulating) were evaluated for their growth, nodulation and yield responses to rhizobium inoculation and seaweed extract (0 % rate (0ml/12L), 50 % rate (30ml/12L) and 100 % (60ml/12L). The research trial was laid out as a split-split plot arrangement fitted in RCBD with four replications. Inoculation significantly influenced grain yield at P≤0.05, seed nutrient content and total above-ground biomass, except for seed potassium. No inoculation significantly achieved higher primary branches per plant at P≤0.05, pod number per plant, stem diameter (P≤0.05), grain yield (P≤0.05), harvest index and total above-ground biomass at P≤0.001. The variety TGx 1937-1F had significantly (P≤0.001) higher nodule number per plant, effective nodules per plant, nodule dry weight, dried shoot biomass, leaf number per plant, pod number per plant, primary branches per plant, stem diameter, plant height, leaf chlorophyll content, total above-ground biomass, grain yield and seed iron (Fe) content. Application of full rate seaweed extract significantly (P≤0.001) increased primary branches per plant, stem diameter, leaf number per plant, plant height, shelling percentage, total above-ground biomass, grain yield, and seed content of calcium (Ca), potassium, magnesium (Mg), manganese (Mn) and sodium (Na) all at P≤0.05. Seaweed extract rate at 0 % obtained the highest harvest index (P≤0.001). Inoculation and variety TGx 1937-1F interaction exhibited a significant increase on leaf number per plant at P≤0.001, primary branches per plant at P≤0.001 and plant height at P≤0.001. Variety TGx 1937-1F, without inoculation, obtained significantly higher pod number per plant (P≤0.001), stem diameter at P≤0.001, grain yield at P≤0.05 and total above-ground biomass at P≤0.001. Variety PAN 1583R, without inoculation, obtained significantly higher harvest index and shelling percentage at P≤0.001. Interaction of vi inoculation and seaweed extract showed that no inoculation × 100 % rate of seaweed extract significantly (P≤0.001) increased primary branches per plant, leaf number per plant, stem diameter, pod number per plant and plant height. Interaction of inoculation × 100 % rate of seaweed extract increased grain yield (P≤0.001) and total above-ground biomass at P≤0.001. Inoculation × 50 % rate of seaweed extract interaction increased shelling percentage at P≤0.001. No inoculation × 0 % rate of seaweed extract interaction obtained significantly higher harvest index (P≤0.001). Interaction of variety and seaweed extract showed that variety TGx 1937-1F × 100 % rate of seaweed extract significantly increased primary branches per plant (P≤0.001), pod number per plant at P≤0.001, grain yield at P≤0.001 and total above-ground biomass at P≤0.001. The variety TGx 1937-1F × 50 % rate of seaweed extract significantly raised the size of stem diameter (P≤0.01) and plant height (P≤0.001). Three-way interactive effects of inoculation × variety TGx 1937-1F × 100 % rate of seaweed extract obtained significantly higher number of shelling percentage at P≤0.001, leaf number per plant at P≤0.05 and primary branches per plant at P≤0.001. Interaction of no inoculation × variety TGx 1937-1F × 100 % rate of seaweed extract obtained significantly high pod number per plant at P≤0.001, grain yield at P≤0.05, total above-ground biomass at P≤0.001 and plant height at P≤0.001. No inoculation × PAN 1583R × 100 % rate of seaweed extract interaction had a higher harvest index at P≤0.001. The study showed that inoculation, seaweed extract, or their combination generally enhanced seed nutrient content, especially in variety TGx 1937-1F. The study further showed that promiscuous soybean (TGx 1937-1F) had higher grain yield, under stressful growing conditions as compared to PAN 1583R variety. This implies that soybean variety TGx 1937-1F, with 50 % or 100 % application rate of seaweed extract could be recommended to smallholder farmers. Key words: Soybean, inoculation, seaweed extract, phenological development, growth, nodulation, grain yield and seed nutrient content. / National Research Foundation (NRF)

In multiple species, genome-wide association (GWA) studies have become an increasingly prevalent method of identifying the quantitative trait loci (QTLs) that underlie complex traits. Despite this, relatively few GWA analyses using high-density genomic markers have been carried out on highly quantitative traits in wheat. We utilized single-nucleotide polymorphism (SNP) data generated via a genotyping-by-sequencing (GBS) protocol to perform GWA on multiple yield-related traits using a panel of 329 soft red winter wheat genotypes grown in four environments. In addition, the SNP data was used to examine linkage disequilibrium and population structure within the testing panel. The results indicated that an alien translocation from the species Triticum timopheevii was responsible for the majority of observed population structure. In addition, a total of 50 significant marker-trait associations were identified. However, a subsequent study cast some doubt upon the reproducibility and reliability of plant QTLs identified via GWA analyses. We used two highly-related panels of different genotypes grown in different sets of environments to attempt to identify highly stable QTLs. No QTLs were shared across panels for any trait, suggesting that QTL-by-environment and QTL-by-genetic background interaction effects are significant, even when testing across many environments. In light of the challenges involved in QTL mapping, prediction of phenotypes using whole-genome marker data is an attractive alternative. However, many evaluations of genomic prediction in crop species have utilized univariate models adapted from animal breeding. These models cannot directly account for genotype-by-environment interaction, and hence are often not suitable for use with lower-heritability traits assessed in multiple environments. We sought to test genomic prediction models capable of more ad-hoc analyses, utilizing highly unbalanced experimental designs consisting of individuals with varying degrees of relatedness. The results suggest that these designs can successfully be used to generate reasonably accurate phenotypic predictions. In addition, multivariate models can dramatically increase predictive accuracy for some traits, though this depends upon the quantity and characteristics of genotype-by-environment interaction. / Ph. D.

O conhecimento dos diferentes fatores genéticos que afetam os caracteres quantitativos de importância agronômica é um pré-requisito importante para o planejamento dos programas de melhoramento genético que visam explorar de maneira eficiente a variabilidade genética disponível nas populações. A importância da epistasia no melhoramento genético das populações de milho ainda não é bem entendida, sendo assim ignorada na maioria dos estudos de herança dos caracteres de interesses para os melhoristas. Os objetivos deste trabalho foram: (i) verificar a importância da epistasia para produção de grãos e seus componentes em milho; (ii) estimar os efeitos epistáticos em cada planta F2 para estes caracteres; e (iii) verificar a importância da interação epistasia x ambientes. A geração F1 obtida do cruzamento entre as linhagens endogâmicas L08-05F e L38-05D foi autofecundada para dar origem à população F2. Uma amostra de 100 plantas F2 foi autofecundada originando 100 progênies F2:3, que foram retrocruzadas com ambas as linhagens genitoras e sua geração F1, seguindo o esquema de cruzamento do delineamento triple test cross (TTC). As 300 progênies de retrocruzamentos foram avaliadas em 11 ambientes no município de Piracicaba/SP, em delineamento alfa-látice 15 x 20, no esquema fatorial com duas repetições por ambiente. As análises de variância seguindo o modelo TTC mostraram que a epistasia total foi altamente significativa para todos os caracteres e que os efeitos epistáticos não aditivos (epistasia aditiva x dominante e/ou dominante x dominante) foram mais importantes que a epistasia aditiva x aditiva. Os efeitos epistáticos estimados em cada planta F2 para a produção de grãos e seus componentes não foram unidirecionais e, além disso, sugerem a presença de epistasia pleiotrópica para PG e a maioria dos componentes da produção. A interação epistasia x ambientes foi verificada apenas para o caráter número de fileiras espigas-1. A presença de efeitos epistáticos positivos poderiam estar contribuindo significativamente para a elevada heterose reportada para o cruzamento entre as linhagens L08-05F x L38-05D. Os resultados sugerem que a epistasia é um componente importante na arquitetura genética dos caracteres estudados, o que significa que o modelo aditivo dominante não é suficiente para descrever a variação genética da produção de grãos e seus componentes na população. Diante disso, os efeitos epistáticos não deveriam continuar sendo ignorados e sua consideração nos modelos de predição da performance dos genótipos e na seleção assistida por marcadores moleculares poderia aumentar significativamente a eficiência da seleção nos programas de melhoramento genético de plantas. / Knowledge of different genetic factors that affect quantitative traits of the agronomic importance, is an relevant prerequisite to plant breeding programs aiming to efficiently explore the genetic variability available in populations. The importance of epistasis in breeding populations of maize is still not well understood, being ignored in most inheritance studies of characters important to plant breeders. This study aimed (i) to verify the role of epistasis in grain yield and its components in maize, (ii) to estimate the epistatic effects in each F2 plant for these characters, and (iii) to verify the role of epistasis x environment interaction. The F1 generation was developed from the cross between the inbred lines L-08-05F and L-38-05D and the F2 population from the selffecundated of F1. A sample of 100 F2 plants was self-fecundated resulting in 100 F2:3 progenies, which were backcrossed with both parental lines and their F1 generation, according to the triple test cross (TTC) design. The 300 backcross progenies were evaluated in 11 environments at the municipality of Piracicaba-SP, Brazil, using an alpha-lattice 15 x 20 design in a factorial arrangement with two replications per environment. Analysis of variance based on the TTC model showed that the total epistasis was highly significant for all characters and that non-additive epistatic effects (additive x dominant and / or dominance x dominance) were more important than the additive x additive epistasis. The epistatic effects estimated in each F2 plant for grain yield and its components were not unidirectional and these estimates suggest the presence of pleitropic epistasis for yield and major yield components. The epistasis x environment interaction was observed only for the number of row eras-1. The presence of positive epistatic effects could contribute significantly to the high heterosis reported for the crossing between the inbred lines L08-05F x L38-05D. Results suggest that epistasis is an important component in the genetic architecture of the traits considered, which means that the additive - dominant model is not enough to describe the genetic variation of grain yield and its components in the population. Thus, the epistatic effects should not remain ignored and its account in the models for predicting performance of the genotypes and in the molecular marker-assisted selection would significantly increase the efficiency of selection programs in plant breeding.

Fertilizantes de liberação controlada como a ureia revestida com polímeros podem propiciar melhor sincronia entre a disponibilidade de nitrogênio (N) no solo e as exigências do nutriente pela cultura de milho (Zea mays L.). Para avaliar o efeito de diferentes estratégias de uso da ureia revestida com polímeros na disponibilização de nitrogênio inorgânico, nitrato (NO3-) e amônio (NH4+) no solo durante o ciclo da cultura de milho, e na produtividade final de grãos, foram conduzidos experimentos na safra 2012/2013, em duas condições edafoclimáticas no município de Piracicaba, Estado de São Paulo. Os solos dos experimentos foram: Latossolo Vermelho Distrófico (LVd) e Latossolo Vermelho Amarelo Distrófico (LVAd). O delineamento experimental foi de blocos completos ao acaso com quatro repetições e os tratamentos constaram da aplicação da dose de 180 kg ha-1 de N, utilizando-se duas fontes de N, ureia revestida com polímeros e ureia convencional, aplicadas, respectivamente, nas proporções de 100:0, 90:10, 80:20, 70:30, 60:40, 50:50 e 0:100%, além de um tratamento com ureia em manejo convencional com aplicação parcelada (20% na semeadura e 80% em cobertura entre os estádios V4-V6), e o controle sem aplicação de N. Foi semeado híbrido de milho com elevado potencial de produtividade. Os fertilizantes aplicados na semeadura foram incorporados a 5 cm de profundidade e 10 cm ao lado da linha de milho. Para determinar o teor de nitrogênio inorgânico no solo, nas camadas de 0-0,1, 0,1-0,2, 0,2-0,4 e 0,4-0,6 m, foram realizadas amostragens na semeadura e em V4, V12 e R3 no LVd e na semeadura e em V6, V14 e R4 no LVAd. Produtividade de grãos, massa seca da parte aérea, acúmulo de N na parte aérea, exportação de N nos grãos, e a eficiência de utilização interna de nitrogênio foram avaliados na maturidade fisiológica da cultura. Os resultados foram submetidos à análise de variância e quando observado efeito significativo de tratamentos, foram realizadas análises de contraste de médias (p<=0,1). A produtividade máxima nos dois experimentos foi da ordem de 10 Mg ha-1 de grãos de milho. Nos dois experimentos a ureia revestida com polímeros disponibilizou nitrogênio mineral no solo ao longo de todo o ciclo da cultura de milho, o que resultou no LVAd em produtividade de grãos mais elevada em relação à utilização de ureia convencional, diferentemente do ocorrido no LVd, onde não foram observados efeitos de tratamentos. A utilização de misturas de URP e U na adubação da cultura do milho, com proporções variando de 100% a 50% da fonte de liberação controlada, mostrou-se eficiente e pode ser considerada uma estratégia que fornece N conforme a exigência da cultura, o que resulta em maior produtividade de grãos em condições edafoclimáticas favoráveis. / Controlled release fertilizers such polymer coated urea can provide better synchrony between nitrogen (N) availability in the soil and its requirements by maize (Zea mays L.). To evaluate the effect of different use strategies of polymer coated urea on the availability of inorganic nitrogen, nitrate (NO3-) and ammonium (NH4+) throughout the crop cycle, and the grain yield, field experiments were carried out in the 2012-2013 growing season, in two soil-climatic conditions, in Piracicaba, São Paulo State. The soils were a clayey and a sandy Oxisol. The experimental design was randomized blocks with four replications, and the treatments consisted of 180 kg N ha-1, using two sources of N, polymer coated urea and conventional urea, respectively, in proportions of 100:0, 90:10, 80:20, 70:30, 60:40, 50:50% and 0:100%, besides a treatment with urea in conventional management, split-applied (20% at seeding and 80% side-dressed in V4-V6 corn growth stage) and a control (without N). Maize hybrid with high productivity potential was used. The fertilizers applied at seeding were placed in bands 5 cm depth and 10 cm aside the corn row. To determine the inorganic nitrogen content in the soil at 0-0.1, 0.1-0.2, 0.2-0.4 and 0.4-0.6 m soil layers, samples were collected at seeding, V4, V12 and R3 corn growth stage in the clayey Oxisol, and at sedding, V6, V14 and R4 in the sandy Oxisol. Grain yield, aerial biomass, nitrogen uptake by the aerial biomass, grain nitrogen uptake and internal utilization efficiency of nitrogen were evaluated. Data were analyzed using analysis of variance and when differences were detected, means where separated using contrast test (p<=0.1). The maximum maize grain yield in the experiments was approximately 10 Mg ha-1. In the two experiments, polymer coated urea led to a greater inorganic nitrogen availability throughout the maize cycle, which resulted in higher yield comparing to the use of conventional urea in the sandy Oxisol, not thus in the clayey Oxisol, where no effects of treatments in grain yield were observed. The use of blends of polymer coated urea and conventional urea in maize fertilization, with ratios ranging from 100 to 50% of the controlled release source, was efficient and can be considered a strategy that supplies N as the crop demands it, and thus lead to a greater maize grain yield under agro-climatic favorable conditions.

A interação QTL por ambientes (QE) têm sido relatada como uma das principais causas de insucesso da seleção assistida por marcadores moleculares (SAM). Estudos que visam o melhor entendimento da interação QE podem contribuir para o aumento da eficiência dos programas de SAM. O objetivo deste trabalho foi mapear QTL para produção de grãos (PG), prolificidade (PROL), peso de 500 grãos (P500), comprimento (CE) e diâmetro de espiga (DE), profundidade de grão (PROF), número de fileiras (NFil) e de grãos por fileira (NGFil) em uma população de milho tropical, verificar a importância da interação QE para estes caracteres e avaliar a estabilidade dos efeitos genéticos dos QTL mapeados. Uma população de 256 progênies F2:3 obtida do cruzamento entre duas linhagens de grupos heteróticos distintos e contrastantes para diversos caracteres foi avaliada em 13 ambientes. Os ambientes foram alocados em grupo de ambientes utilizando um método de agrupamento e o modelo AMMI, sendo que ambos os métodos levaram a identificação de três grupos de ambientes. O mapeamento de QTL foi realizado considerando um mapa genético com 177 marcadores microssatélites e mapeamento por intervalo composto expandido para múltiplos ambientes (mCIM). As médias de grupo de ambientes para cada caráter foram utilizadas nas análises. Foram mapeados 87 QTL, sendo 9 para PG, 9 para PROL, 14 para P500, 7 para CE, 9 para DE, 14 para PROF, 17 para NFil e 8 para NGFil. A maioria dos QTL mapeados localizou-se em regiões genômicas que ainda não foram reportados QTL, tanto para germoplasma temperado quanto tropical. A interação QTL por grupo de ambientes foi significativa para PG e não significativa para os componentes de produção. Para PG, as metodologias QQE biplot e AMMI foram utilizadas para estudar a interação QE dos efeitos genéticos dos QTL. As estimativas dos efeitos aditivos e de dominância dos QTL foram influenciadas pela interação QTL por grupo de ambientes, sendo que o padrão de interação foi específico para cada efeito genético. A expressiva interação QTL por grupo de ambientes para PG e o padrão específico de interação dos efeitos genéticos dos QTL impõe desafios adicionais à incorporação da SAM nos programas de melhoramento que visam o desenvolvimento de genótipos produtivos e com estabilidade de produção. / QTL by environment (QE) interaction has been reported as one of the main reasons for the unsuccessful of marker-assisted selection (MAS). Studies aimed to a better understanding of QE interaction could contribute to increase the efficiency of MAS programs. The objectives of this study were to map QTL for grain yield (GY), prolificacy (PROL), 500 Kernels weight (W500), ear length (EL), ear diameter (ED), kernel depth (KD), row number per ear (RN) and kernels per row number (KRN) in a tropical maize population, to assess the importance of QE interaction for these traits and to evaluate the stability of the genetic effects of mapped QTL. A population of two-hundred and fifty-six progenies obtained from the cross between two inbred lines, which belong to different heterotic groups and divergent for different traits, was evaluated in 13 environments. The environments were jointed into groups using a cluster method and an AMMI model. Both methods led to the identification of three groups of environments. The QTL mapping was performed considering a genetic map with 177 microsatellites markers and the multiple-environment composite interval mapping analysis (mCIM). The means from each group of environments of each trait were used in the analyses. Eighty seven QTL were mapped: 9 for GY, 9 for PROL, 14 for W500, 7 for EL, 9 for ED, 14 for KD, 17 for RN and 8 for KRN. Most of the mapped QTL was located in genomic regions that have not been reported QTL in both temperate and tropical germplasm. The QTL by group of environments interaction was significant for GY and not significant for yield components. For GY, QQE biplot and AMMI methodologies were used to study the QE interaction of the genetic effects of the QTL. The estimates of additive and dominance effects of QTL were affected by QTL by group of environments interaction and the interaction pattern was specific for each genetic effect. The large QTL by group of environments interaction for GY and the specific interaction pattern of the genetic effects of QTL impose additional challenges for the incorporation of MAS in breeding programs that aim to develop high yielding genotypes with grain yield stability.

A soja é a cultura de grãos mais importante no Brasil. Na safra de 2010/11 ocupou uma área de 24 milhões de hectares, se destacando como principal oleaginosa produzida e consumida no mundo. Alguns fatores podem limitar a produção da soja, entre eles as doenças. A mancha- alvo (Corynespora cassiicola) é frequente nas em todas as regiões produtoras de soja no Brasil e nos últimos anos tem se atribuído prejuízos crescentes à doença. Os objetivos deste trabalho foram: determinar a faixa ideal de temperatura para o crescimento micelial de diferentes isolados de C. cassiicola; verificar a esporulação em função do meio de cultura; avaliar a germinação de conídios sob diferentes períodos de molhamento foliar; estudar o efeito da temperatura e molhamento foliar nos componentes monocíclicos e realizar estudos de quantificação de danos. Para avaliar o efeito da temperatura no crescimento micelial, diferentes isolados foram mantidos nas temperaturas de 5°C, 10°C, 15°C, 20°C, 25°C, 30°C e 35°C. A temperatura mínima e máxima estimada pela função beta generalizada para o crescimento micelial foi de 6,9°C e 33°C, respectivamente. A esporulação foi estudada nos meios de cultura BDA e Czapek. Os dados obtidos foram comparados por meio do teste Scott-Knott (P<0,05). A produção de conídios foi variável em função do isolado, tanto em meio BDA como Czapek. O ensaio de germinação foi feito em folhas de soja utilizando-se diferentes períodos de molhamento foliar (2, 6, 12, 24, 48 e 72 horas). A contagem de conídios germinados foi feita em microscópio eletrônico de varredura. A germinação de conídios na superfície das folhas foi verificada a partir do período de 6 horas. Para o estudo dos componentes monocíclicos as temperaturas testadas foram 10ºC, 15ºC, 20ºC, 25 ºC e 30ºC e os períodos de molhamento foliar foram 12, 24, 48 e 72 horas. As variáveis quantificadas foram a severidade, o número e o diâmetro das lesões. Os dados foram ajustados às funções beta generalizada e monomolecular. A temperatura mínima, máxima e ótima capazes de promover o desenvolvimento da mancha-alvo foram de 18°C, 32°C e 27°C, respectivamente. O período de molhamemto foliar de 48 horas resultou em maior desenvolvimento da doença. No ensaio de quantificação de danos, cultivares comerciais foram semeadas em duas épocas. Os componentes avaliados em campo foram: a severidade, a área foliar, o indice vegetativo da diferença normalizada (NDVI) e a produtividade (kg ha-1). Com o uso destes dados foram calculadas a área abaixo da curva de progresso da doença (AACPD), a área abaixo da curva de progresso do índice de área foliar (AULIAPC), o indice de área foliar (LAI), o indice de área foliar sadia (HLAI), a duração da área foliar sadia (HAD) e a absorção da área foliar sadia (HAA). Neste ensaio verificou-se que valores de severidade de até 37% no dossel inferior não causam danos no patossistema C.cassicola - soja. As variáveis HLAI e AULAIPC se correlacionaram com a produtividade e podem ser úteis para estudos futuros de quantificação de danos para este patossistema. / Soybean is the most important grain crop in Brazil. The production of 2010/11 occupied an area of 24 million hectares, becoming the most important oilseed produced and consumed worldwide. Some factors, such as diseases, may limit soybean production. The target spot caused by Corynespora cassiicola is frequent in all soybean producing regions in Brazil and in the past years, an increasing loss has been assigned to it. The aims of the present study were to determine the ideal temperature range for mycelial growth of different isolates of C. cassiicola; verify the sporulation in relation to the culture medium; evaluate the conidia germination under different periods of leaf wetness; study the effect of the temperature and the leaf wetness on the monocyclic components and carry out studies of crop loss in the field. In order to evaluate the effect of the temperature on the mycelial growth, different isolates were cultivated at the temperatures of 5°C, 10°C, 15°C, 20°C, 25°C, 30°C and 35°C. The minimum and maximum estimated temperature by the beta function to provide C.cassiicola mycelial growth was 6.9 °C and 33 °C, respectively. The sporulation was analyzed in PDA and Czapek culture media. The results obtained were compared through the Scott-Knott test (P <0.05). The conidia production varied according to each isolate on both PDA and Czapek medias. The germination test was carried out in soybean leaves using different leaf wetness periods (0, 12, 24, 48 and 72 hours). The germinated conidia measurement was done in a scanning electron microscope. The conidia germination on the leaves surface was observed from 6 hours. The temperatures used to study the monocyclic components were 10 º C, 15 º C, 20 º C, 25 º C and 30 º C and the leaf wetness periods were 12, 24, 48 and 72 hours. The variables quantified were severity, number and diameter of lesions. The data were adjusted to the generalized beta and monomolecular functions. The minimum, maximum and optimum temperature able to promote the development of target spot in soybean leaves were 18 ° C, 32 ° C and 27 ° C, respectively. The 48- hour leaf wetness resulted in greater development of the disease. For damage quantification, commercial cultivars were sown in two sowing times. The components evaluated in the field were: severity, leaf area, normalized difference vegetation index (NDVI) and grain yield (kg ha-1). Using these data, it was calculated the area under disease progress curve (AUDPC), area under the leaf area index progress curve (AULIAPC), leaf area index (LAI), healthy leaf area index (HLAI), healthy area duration (HAD) and healthy area absorption area (HAA). The severity values up to 37% in the lower canopy do not cause crop loss in C.cassicola - soybean pathosystem .The variables HLAI and AULAIPC correlated with grain yield and may be useful for future studies of crop loss for this pathosystem.

O principal desafio para o desenvolvimento de híbridos contendo alto teor de óleo é a correlação negativa entre este caráter e a produção de grãos. O conhecimento da herança do caráter teor de óleo e da produção de grãos e seus componentes conjuntamente podem auxiliar a condução de programas de melhoramento que visam ao desenvolvimento de genótipos produtivos e com alto teor de óleo. Assim, os objetivos desta pesquisa foram: estimar parâmetros genéticos; mapear QTL e a congruência destes para os caracteres teor de óleo (OL), produção de grãos (PG) e seus componentes. Duzentas e cinquenta e seis progênies F2:3 obtidas do cruzamento de duas linhagens endogâmicas contrastantes para teor de óleo foram avaliadas em experimentos com repetições. O mapeamento de QTL foi realizado considerando um mapa genético com 139 marcadores microssatélites e mapeamento por intervalo composto expandido para múltiplos ambientes (mCIM). As estimativas de variância genética de progênies e coeficientes de herdabilidade diferiram de zero para todos os caracteres. Os coeficientes de herdabilidade apresentaram magnitudes elevadas para todos os caracteres. A estimativa de variância progênies por ambientes foi significativa para PG e seus componentes. As correlações entre OL e os caracteres PG e seus componentes não foram significativas. Os caracteres prolificidade (PROL), diâmetro de espiga (DE), profundidade de grãos (PFG), comprimento de espiga (CE) e número de grãos por fileira (NGF) apresentaram valores altos de coeficientes de correlação com PG. Foram mapeados 13 QTL para OL, 16 para PG, 17 para PROL, 12 para peso de 500 grãos (P500), 19 para CE e para DE, 18 para PFG, 15 para número de filerias NFI e 13 para NGF. Os QTL não estão uniformemente distribuídos ao longo do genoma para OL e a maioria dos componentes da produção. O grau médio de dominância foi de dominância parcial para PG, dominância para PROL e P500 e sobredominância para OL, CE, DE, PFG, NFI e NGF. A maioria dos QTL mapeados para PG e seus componentes interagiu significativamente com ambientes, indicando que experimentos conduzidos em vários locais e anos são necessários para identificar genótipos e QTL estáveis. A proporção da variância genética explicada pelos QTL foi de 52,22% para OL, 42,49% para PG e para seus componentes variou de 25,69% para NGF a 55,03% para PROL. Foram identificadas 34 regiões genômicas contendo QTL mapeados para os diferentes caracteres, não sendo, portanto identificadas regiões congruentes entre OL e PROL. A maioria dos QTL foi mapeada em regiões genômicas distintas, indicando que é possível aumentar o teor de óleo e a produção de grãos simultaneamente, utilizando os QTL independentes. Os resultados obtidos indicam que o desenvolvimento de híbridos produtivos com alto teor de óleo pode ser obtido por retrocruzamento assistido por marcadores envolvendo OL, PG e seus componentes e, devido ao reduzido número de QTL estáveis para a PG e seus componentes, os programas de melhoramento devem ser direcionados para regiões específicas. / The main challenge for the development of hybrids with high oil content is a negative correlation between this trait and grain yield. The knowledge of the inheritance of kernel oil content and grain yield and its components together can assist breeding programs for the development of productive genotypes with high oil content. The objectives of this research were to: estimate genetic parameters, map QTL and their congruence to oil content (OC), grain yield (GY) and its components. Two-hundred and fifty-six F2:3 progenies obtained from the cross between two inbred lines contrasting for oil content were evaluated in experiments with repetitions. The QTL mapping was performed considering a genetic map with 139 microsatellites markers and the multiple-environment composite interval mapping analysis (mCIM). Estimates of genetic variances of progenies and heritability coefficients differed significantly from zero for all traits. The heritability coefficients showed high magnitudes for all traits. The estimate of progenies by environments variance was significant for GY and for yield components. The correlations between the OC, GY and its components were not significant. The traits prolificacy (PROL), ear diameter (ED), kernel depth (KD), ear length (EL) and kernels per row number (KRN) showed high values of correlation coefficients with GY. Thirteen QTL were mapped for OC, 16 for GY, 17 for PROL, 12 to 500 kernels weight (W500), 19 for EL and for ED, 18 for kernel depth (KD), 15 for row number per ear (RN) and 13 for KRN. The QTL are not evenly distributed in the genome for OC and most of yield components. The average level of dominance was partial dominance for GY, dominance for PROL and W500 and overdominance for OC, EL, ED, KD, RN and KRN. Most of QTL mapped for GY and its components interacted significantly with environments, indicating that the experiments conducted in several locations and years are required to identify genotypes and QTL stable. The proportion of genetic variance explained by all QTL was 52.22% for OC, 42.49% for GY and for its components ranged from 25.69% for KRN to 55.03% for PROL. We identified 34 genomic regions containing QTL mapped for different traits, and therefore, we did not identify congruent regions between OC and PROL. Most of QTL were mapped in different genomic regions, indicating the possibility to increasing oil content and yield simultaneously, using the independent QTL. The results indicate that the development of high-oil hybrid with high yields can be obtained by marker-assisted backcrossing involving OC, GY and its components and due to the small number of stable QTL for GY and its components, the breeding programs should be directed towards specific areas.