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SUMMARYSugarcane is considered a Si-accumulating plant, but in Brazil, where several soil types are used for cultivation, there is little information about silicon (Si) fertilization. The objectives of this study were to evaluate the silicon availability, uptake and recovery index of Si from the applied silicate on tropical soils with and without silicate fertilization, in three crops. The experiments in pots (100 L) were performed with specific Si rates (0, 185, 370 and 555 kg ha -1 Si), three soils (Quartzipsamment-Q, 6 % clay; Rhodic Hapludox-RH, 22 % clay; and Rhodic Acrudox-RA, 68 % clay), with four replications. The silicon source was Ca-Mg silicate. The same Ca and Mg quantities were applied to all pots, with lime and/or MgCl 2, when necessary. Sugarcane was harvested in the plant cane and first-and second-ratoon crops. The silicon rates increased soil Si availability and Si uptake by sugarcane and had a strong residual effect. The contents of soluble Si were reduced by harvesting and increased with silicate application in the following decreasing order: Q>RH>RA. The silicate rates promoted an increase in soluble Si-acetic acid at harvest for all crops and in all soils, except RA. The amounts of Si-CaCl 2 were not influenced by silicate in the ratoon crops. The plant Si uptake increased according to the Si rates and was highest in RA at all harvests. The recovery index of applied Si (RI) of sugarcane increased over time, and was highest in RA.Index terms: cultivar, nutrition, fertilization, monocotyledons.(

No abstract

Asian soybean rust is an important disease that has deeply troubled farmers and researchers since it was first reported. The causal agent, biotrophic fungus Phakopsora pachyrhizi Sydow & P. Sydow, has found extremely favorable conditions for its dissemination in Brazil. The most characteristic symptom of infection appears in the leaves, initially on the adaxial leaf surface, as small angular points less than 1mm in diameter, together with gray-colored uredospores (spores). Management involves a set of practices that guarantee coexistence between the plant and the pathogen without significant damage to the crop. The objective of this research was to evaluate tolerance to Asian rust by estimating losses caused by natural infection in the field. Experiments with generation F4 (2014/15) plants were established in a randomized blocks design with four replicates, with two types of genotypes (crosses and parents) and two schemes for disease management using fungicides. For analysis of the data, a test was applied on two dependent samples to verify the significance of the estimate of the rust effect. With regard to grain yield and tolerance, the most outstanding crosses were 104 (USP14-01-20 × EMGOPA313) and 149 (USP93-05.552 × EMGOPA313). Crosses 147 (USP93-05552 × PI153.282) and 137 (USP70.108 × PI153.282) were graded as tolerant in the evaluation of both yield reduction and seed size. We found evidence of tolerance to Asian rust in both crosses and parents. The statistical test revealed the significance of the rust effect estimates in soybean.

The white mold, caused by Sclerotinia sclerotiorum (Lib.) de Bary, is one of the most important diseases of soybean. The objective of the present work was to evaluate the soybean reaction to the fungus S. sclerotiorum, which causes white mold, in a partial diallel with 50 crosses. The Group I of parents was composed of ten experimental lines with high grain yield and the group II consisted in five genotypes with possible resistance to white mold. Ten plants of each cross in the F 4 generation and the parents were evaluated for reaction to fungus infection using the method of inoculation in detached leaves in order to assess the severity of the disease and to later estimate the combining abilities. Estimates of the specific combining ability (SCA) was a significant reaction to S. sclerotiorum, indicating that there is variability for fungus resistance due to non-additive genes action.

The diallel schemes comprise a powerful strategy for the genetic study of the characters and the ability to match the genotypes, as well as to obtain information at the different stages of a genetic breeding program involving artificial hybridizations. Moreover, it presents importance for the adequate selection of the parents in generations of endogamy after the hybridization. The objective was identifying the potential of soybean crosses to obtain progenies with high grain yield. A partial diallel was carried out, where group I was composed of ten experimental lines with high grain yield, and group II was composed of five genotypes with resistance to white mold, as indicated in literature. Two field experiments were installed to estimate the general and specific combining ability, the first one with the 50 crosses and the second one with the 15 parents (I and II groups). At the R8 stage, grain yield in kg ha -1 of the crosses and the parents was evaluated. The comparison of means between the genotypes and heterosis was also calculated. Broad-sense heritability was estimated considering phenotypic, environmental and genotypic variances. The results indicated superiority of the crosses in comparison to the parents. Heritability was considered high for most crosses evaluated. Diallel analysis was effective in identifying F2 populations with higher genetic gain potentials.Resumo: Os esquemas dialélicos de cruzamentos compreendem uma estratégia poderosa para o estudo genético dos caracteres e capacidade de combinação entre genótipos, bem como para se obter informações nas diferentes etapas de um programa de melhoramento genético envolvendo hibridações artificiais. Além disso, apresenta importância na escolha adequada dos genitores em gerações de endogamia após a hibridação. O objetivo foi identificar cruzamentos potenciais a fim de obter progênies altamente produtivas. Foi utilizado um dialelo parcial em que o grupo I envolveu dez genótipos representados por linhagens de soja experimentais com alta produtividade de grãos e o grupo II foi composto por cinco genótipos de soja com indicações na literatura de possível resistência ao mofo branco. A fim de estimar a capacidade geral e específica de combinação, foram instalados dois experimentos em campo, sendo o primeiro experimento representado por 50 cruzamentos e o segundo experimento pelos 15 genótipos (grupos I II). No estádio R8, foi avaliada a produtividade de grãos, em kg.ha -1 , dos dois experimentos. Foi realizado teste de média entre os genótipos e foi calculada a heterose. A herdabilidade no sentido amplo foi estimada com as variâncias fenotípicas, ambientais e genotípicas. Os resultados indicaram superioridade dos cruzamentos em comparação aos genitores. A herdabilidade foi considerada alta para a maioria dos cruzamentos. A análise dialélica foi eficaz em identificar populações F2 com maiores potenciais de ganho genético.Palavras-chaves: Glycine max, heterose, herdabilidade, dialelo parcial

Diseases can cause negative impacts during all stages of development of soybean [Glycine max (L.) Merr.] Asian soybean rust (ASR) (caused by Phakopsora pachyrhizi) is the most destructive. The impact of ASR on vegetable soybean (consumed when the seeds are still immature) have not been studied rigorously. Thus, in a 2-yr study, we assessed 42 F 6 lines from crosses of soybean vegetable genotypes and three commercial cultivars ('BRS 257', 'BRS 267' and 'IAC 100') in two sites. During the R 6 and R 8 development stages, the genotypes were evaluated for 10 traits.The joint analysis showed that the interactions were significative for the most traits. The significance of the rust effect allowed us to identify the genotypes in which the losses were nonsignificant. We observed that ASR affected two stages of plant development. However, information about ASR losses quantified by the rust reaction rate (RRR) enabled the researchers to select lines that could be used in breeding programs aiming towards ASR tolerance. We found three lines that were superior to one of the cultivar checks. Furthermore, cluster analysis for RRR was useful in establishing the most promising groups of vegetable soybean genotypes for use in hybridization aiming to expand the genetic base for vegetable soybeans and integrate new genetic resources of vegetable soybean in the Brazilian genetic pool to ensure genetic gain.

AGRADECIMENTOS"A Deus, pela proteção, por ser meu guia nesta jornada e por sempre providenciar conquistas em minha vida. Aos meus pais, Eloy Alves de Freitas Filho e Zildinéa Rocha Freitas, pelo amor, pela confiança, pela dedicação, por todos os valores que me ensinaram e, acima de tudo, por acreditarem nos meus sonhos. As minhas irmãs, Manuela de Lurdes Rocha Freitas Nunes, Ana Flávia de Freitas Rocha e Graziela Maria de Freitas Rocha, pela amizade e apoio nos momentos difíceis. Aos meus sobrinhos, Júlia Agnes Freitas Nunes e Arthur Hiero Freitas Nunes, pelo carinho e pela torcida. Ao meu namorado Pedro Henrique Rodrigues de Moraes Martinez pelo incentivo, paciência e amor. Aos meus familiares pelo apoio. Às amigas de república pela amizade durante essa trajetória. Aos meus amigos por sempre me apoiarem e torcerem pelo meu sucesso.Ao meu orientador Natal Antonio Vello pela orientação, confiança e oportunidade de aprendizado. À Universidade de São Paulo, por meio da Escola Superior de Agricultura "Luiz de Queiroz" e do Departamento de Genética, por uma excelente estrutura de ensino e pesquisa que fizeram parte e foram de suma importância para a minha formação acadêmica durante o doutorado. Aos professores do Departamento de Genética, em especial do Programa de Pós-Graduação em "Genética e Melhoramento de Plantas" (PPG-GMP) RESUMO Potencial de cruzamentos de soja em gerações iniciais de endogamia para produtividade de grãos e reação à ferrugemA utilização de genótipos de soja tolerantes é uma alternativa muito promissora no manejo da ferrugem asiática da soja (FAS), uma vez que a resistência qualitativa mostra-se instável devido à grande variabilidade do patógeno. Este estudo objetivou avaliar o potencial de populações formadas por 64 cruzamentos biparentais (gerações F 2 , F 3 e F 4 ) de um dialelo parcial 8 x 8 para produtividade de grãos (PG) e tolerância à ferrugem. Quinze genitores compreenderam linhagens experimentais desenvolvidas pelo Departamento de Genética/ESALQ/USP e um genitor envolveu uma cultivar comercial. Em 2012/13, dois experimentos foram conduzidos: o primeiro com as populações dos 64 cruzamentos (geração F 2 ) e três testemunhas comuns, enquanto que o segundo envolveu os 16 genitores e as mesmas três testemunhas comuns. Em 2013/14 e 2014/15, a fim de se estimar o efeito ferrugem (EF), ou seja, o nível de tolerância dos genótipos, por meio da diferença entre as médias ajustadas de PG e peso de cem sementes (PCS), foram conduzidos quatro experimentos, sendo dois com as populações dos 64 cruzamentos (gerações F 3 e F 4 ) e outros dois com os 16 genitores; cada dupla de experimentos compreendeu dois manejos distintos de doenças com fungicidas. No manejo O&P foram feitas duas aplicações sucessivas de Opera e uma de Priori Xtra, para o controle da ferrugem e outras doenças de fim de ciclo (DFC); no manejo D foram feitas aplicações de Derosal para controle de DFC, exceto a ferrugem. No estádio R 5 , cinco plantas competitivas de cada parcela foram avaliadas para a severidade, enquanto que no ...