Abstract The induction of polyploidy in Eucalyptus can lead to higher-yielding and more adapted clones, with better wood quality. After artificial polyploidization, it is necessary to certify the effectiveness of the process through cytogenetic analyses and anatomical trait evaluations. Thus, the aim of this study was to certify the chromosome duplication in artificially polyploidized clones of Eucalyptus grandis × Eucalyptus urophylla using cytogenetic analysis, flow cytometry, and leaf anatomy measurements. Chromosomal counts and DNA content estimation allowed the identification of artificially polyploidized clones and mixoploids. Polyploid clones had larger stomata diameter than diploids. The increase in stomata size was accompanied by lower stomatal density in most polyploid clones. The typical gigas effect of polyploidized plants was demonstrated by the expressive increase in leaf area in polyploid individuals compared to diploids. Our findings indicate that the use of polyploidy in Eucalyptus breeding is promising, allowing the discrimination of diploid, tetraploid, and mixoploid plants.

Abstract The viability of using inbred progenies, i.e., S1 or S2, in recurrent selection programs for perennial plants was evaluated in comparison with full sibs using the expression of gain from selection. Populations with different genetic properties, were considered in obtaining the estimates, with the population genetic variance always equal to 1 used as reference, as well as different experimental strategies. The estimates of genetic covariances between average additive effects of the alleles and the dominance effects of homozygotes, which occur when S1 or S2 is used, although negative for the lower values of the average allele frequencies, were always smaller than the additive genetic variance. Per unit of time, the total gain from selection with S1 was greater than with S2 and full sibs. However, it is argued that the best strategy is a cycle with S1, followed by a cloned progeny test with full sibs.

ABSTRACT Background: One of the biggest challenges for breeders, especially for perennial plants, is to have strategies to reduce the risk of recommending new clones. One of the alternatives would be to use a mixture of clones, clonal compounds (CC), instead of monoclones (MC). This strategy has not yet been properly proven from experiments involving CC and MC simultaneously in different environments. Results: The CC’s contribution to the interaction was significant, although associated with a high MAI estimate (m³. ha-1. year-1). The CC’s took better advantage of environmental stimuli than most MC’s. The rick estimates in the CC recommendation were, in most situations, lower than those of the different monoclones. Conclusion: The use of CC proved to be more efficient than the use of MC in mitigating the effects of the interaction of genotypes by environments, in recommending clones for forest exploitation.

ABSTRACT: The development and recommendation of single cross maize hybrids (SH) to be used in extensive land areas (mega-environments), and in different crop seasons requires many experiments under numerous environmental conditions. The question we asked is if the data from these multi-environment experiments are sufficient to identify the best hybrid combinations. The aim of this study was to critically analyze the phenotype data of experiments of yield, established by a large seed producing company, under a high level of imbalance. Data from evaluation of 2770 SH were used from experiments conducted over four years, involving the first and second crop seasons, in 50 locations of different years and regions of Brazil. Different types of analysis were carried out and genetic and non-genetic components were estimated, with emphasis on the different interactions of the SH with the environments. Results showed that the coincidence of common hybrids in these experiments is normally small. The estimates of the correlations between of the hybrids coinciding in the environments two by two is of low magnitude. The hybrid × crop season interaction was always expressive; however, the interactions of hybrids and other environmental variables were also important. Under these conditions, alternatives were discussed for making with the information obtained from the experiments, can be more efficient on the process to obtain new hybrids by companies.

ABSTRACT. In Brazil, there is an increasing demand for common bean (Phaseolus vulgaris L.) cultivars having Carioca-type (cream-colored seed coat with brown stripes) beans which have a light color that persists for a longer time combined with the most possible upright plant architecture. However, plant breeders are finding it difficult to combine these two traits in the same cultivar. The aim of this study was to compare success in the selection of new common bean lines that combine the two traits in segregating populations with 25%, 50%, or 75% of the alleles from the parents contrasting in upright plant architecture or in bean grains with persistent light color. A biparental cross was performed between a parent with light-colored beans (P1) and another with upright plants (P2). Three populations were obtained from the F1 seeds, with allelic frequencies of 75%, 50%, and 25% of P1. Subsequently, progenies were evaluated in a similar number in each population in the F2:3, F2:4, F2:5, and F2:6 generations. The plant architecture (PA) and grain darkening (GD) traits were visually evaluated using a scoring scale. Genetic and phenotypic parameters were estimated for all generations. There was no expressive advantage in using populations with a greater allele proportion of the parent favorable to upright plant architecture or slow grain darkening either in releasing of variability or in the occurrence of progenies with favorable phenotypes for the two traits.

Abstract This study estimated the general and specific combining abilities and mean heterosis of tobacco lines of the varietal groups Flue-Cured Virginia (FCV) and Air-Cured Burley (BY). In addition, possible advantages and an improved strategy of using hybrids in tobacco breeding in the tropics were discussed. Ten BY and 13 FCV lines were crossed in a diallel mating design. The hybrids and parental lines were evaluated at two locations in Southern Brazil. The mean heterosis was 5.37% for FCV and zero for BY lines, although higher than 15% in some combinations. The occurrence of heterosis indicates dominance in the control of tobacco yield. Tobacco breeding programs must focus primarily on improving the performance of lines per se and then on the identification of the best hybrid by testing combinations.

ABSTRACT Background: This review aims to discuss alternatives for obtaining new clones of eucalyptus ( Eucalyptus spp.) with greater efficiency than current methods, as well as the feasibility of obtaining hybrid seeds. The commercial-scale use of eucalyptus hybrid seeds may reduce implantation costs and bring other advantages for forest exploitation. The proposal focuses on using inbred progenies (S 1, S 2...S g) to improve the species. Self-fertilization releases a greater proportion of undesirable alleles hidden in heterozygotes, increasing selection success. Results: From the best individuals of the inbred progenies, full-sibling (FS) progenies will be developed, allowing the selection of new clones and conduct recurrent selection programs. The hybrid seeds must be obtained, also from the FS evaluations, in each selfing generation (S g x S g). Simultaneously with the conduction of inbreeding generations, information must be gathered aiming to implement the strategy for obtaining hybrid seeds, such as verifying the feasibility of generating double haploid lines and looking for alternatives to facilitate the large-scale production of hybrid seeds. Conclusion: this review of research results can serve as an initial basis for obtaining new clones of eucalyptus with greater efficiency than current methods, as well as the feasibility of obtaining hybrid seeds.

Abstract This study aimed to compare recombinant inbred lines (RIL) obtained via the bulk method with doubled haploid lines (DHL). For comparison, 190 DHL and 194 RIL were evaluated simultaneously at two different locations. Phenotypic and genetic parameters were estimated for the traits green leaf yield (GLY) and alkaloid content (ALK). The results of the RIL and DHL evaluations were similar for ALK. Conversely, estimates of genetic variation and heritability in the DHL were higher than those in the RIL for GLY. However, the mean estimate of the RIL was 13.3% higher than that of the DHL and thus, the annual gain with selection was higher for the RIL. The use of DHL in a recurrent selection program will be efficient in comparison to RIL if a large number of lines are obtained, which must undergo a preliminary selection before the most intensive evaluation to identify the lines to be recombined.

RESUMO Várias características devem ser consideradas simultaneamente na seleção de cultivares de tabaco para atender às necessidades dos agricultores, fabricantes e consumidores. Nesse contexto os melhoristas devem conhecer as correlações entre as características de importância econômica, a fim de adotar a melhor estratégia de seleção para elas. A utilização de índices de seleção tem se mostrado uma das estratégias mais eficientes para selecionar caracteres correlacionados. No caso do tabaco, nenhum relato foi encontrado na literatura para a seleção de múltiplas características. Neste estudo, demonstramos a eficiência da Soma do Índice de Variáveis Padronizadas (SSV) para a seleção de múltiplas características em tabaco. O método foi avaliado usando uma coleção de treze linhagens parentais e seus híbridos oriundos de um esquema dialélico. Os híbridos, as linhagens parentais e as testemunhas foram avaliados em dois locais. As características avaliadas foram produtividade (YLD), índice geral de qualidade (IGQ), relação talo/lâmina, porcentagem total de alcalóides e porcentagem total de açúcares. Consideramos os pesos para o indíce de acordo com a importância econômica de cada característica: 0,4 para YLD, 0,3 para GQI e 0,1 para os demais caracteres. O índice SSV mostrou-se eficiente e fácil de interpretar, podendo ser utilizado para se ter ganho genético para quase todos os caracteres na direção desejada. A capacidade geral de combinação (CGC) explicou a maior parte da variação do índice na análise dialélica. A estimativa de heterose média foi de 2,02%. Algumas combinações de híbridos exibiram níveis de heterose maiores que 10%, indicando que uma maior atenção pode precisar ser dada à comercialização de híbridos F1.

ABSTRACT Several traits must be simultaneously considered in selection of tobacco cultivars for meeting the requirements of farmers, manufacturers and consumers. Breeders should have an understanding of associations between economically-important traits in order to devise the best strategy to have response to selection for all them. Utilization of selection indices has been shown to be one of the most efficient strategy for selecting for correlated characters. In tobacco, no reports can be found within the academic literature for multiple trait selection. In this study we demonstrate the efficiency of the Sum of the Standardized Variables Index (SSV) for multi-trait selection in tobacco. The method was evaluated using a collection of thirteen inbred lines and hybrids derived using a diallel scheme. The hybrids, parental lines, and checks were evaluated in two field locations. The traits assessed were yield (YLD), general quality index (GQI), leaf stem to lamina ratio, percent total alkaloids, and percent total sugars. We considered weights according to the economic importance of each trait: 0.4 for YLD, 0.3 for GQI and 0.1 for the remaining characters. The SSV index proved to be efficient and easy to interpret, and could be used to generate genetic gain for almost all characters in the desired direction. General combining ability (GCA) explained the larger part of the variation of the index in the diallel analysis. The mean heterosis estimate was 2.02%. Some hybrid combinations exhibited heterosis levels greater than 10%, indicating that increased attention might need to be given to commercialization of F1 hybrids.

Abstract: The importance of plant breeding in Brazilian agriculture has grown a lot in the last 50 years. This occurred mainly because of the: increase in graduate programs, which qualified hundreds of professionals; creation of EMBRAPA and other research institutes or state companies, with an emphasis on the production of new cultivars and; promulgation of the cultivar protection law, which stimulates investments in seed production. The retrospective of what happened, enabling the country to move from being an importer of grains, fruits, and fibers to one of the largest exporters of these products worldwide, was the focus of this work. Taking as reference some agricultural products, this article highlights the significant contribution of plant breeding in recent years. Also, some of the enormous challenges that still have to be overcome, in which the participation of Brazilian breeders will be fundamental to continue the progress of agriculture in the coming years.

RESUMO A mancha angular, causada pelo fungo Pseudocercospora griseola, é uma das doenças mais importantes do feijoeiro. A utilização de cultivares resistentes é uma das estratégias mais eficaz para o controle de ALS. O controle genético é quantitativo e envolve desde genes maiores como genes de pequeno efeito. Uma estratégia para a obtenção de linhas com resistência durável é a seleção recorrente, que visa aumentar gradativamente a frequência de alelos favoráveis. Neste estudo, avaliou-se a eficiência da inoculação artificial de P. griseola em feijão comum cultivado em casa de vegetação em um programa de seleção recorrente visando à resistência à mancha angular, com o objetivo de acelerar os programas de melhoramento. A partir da população inicial, três ciclos de avaliação, seleção e cruzamento foram realizados em casa de vegetação e as plantas mais resistentes foram selecionadas fenotipicamente. Plantas no estágio V2 foram inoculadas usando um isolado de P. griseola raça 63-63. As plantas selecionadas foram transplantadas para vasos e intercruzadas para formar o próximo ciclo de seleção. As progênies obtidas da população base (C0) e dos ciclos subsequentes (CI, CII e CIII) da geração S0: 2 foram avaliadas quanto à severidade da mancha angular em casa de vegetação e campo. As estimativas dos ganhos genéticos obtidos foram de -14,8% e -5,3%, para casa de vegetação e campo, respectivamente. A inoculação artificial com P. griseola permitiu três ciclos de seleção recorrentes por ano, representando um método promissor para a obtenção de linhagens de feijão resistentes a ALS em curto período.

ABSTRACT The angular leaf spot (ALS), caused by the fungus Pseudocercospora griseola, is one of the most notable diseases of common beans (Phaseolus vulgaris). The most effective strategy to control ALS is quantitative disease resistance provided by major and minor genes. One breeding strategy for obtaining lines with durable resistance to P. griseola is a recurrent selection that aims to gradually assemble favorable alleles. In this study, common beans were artificially inoculated with P. griseola and grown in a greenhouse under a recurrent selection program that aims to accelerate the breeding cycle and assimilate resistant conferring genes per generation. From the initial population, three cycles of evaluation, selection, and intercross were carried out in a greenhouse and the most resistant plants were phenotypically selected. Plants at the V2 stage were inoculated with an isolate of P. griseola, race 63-63. Selected plants were transplanted into pots and intercrossed to reap the next cycle of selection. Progenies obtained from the base population (C0) and subsequent cycles (CI, CII, and CIII) were assessed for the degree of the symptoms for ALS under greenhouse and field conditions. The rate of genetic progress per breeding cycle was - 14.8% and - 5.3% for the plants grown in greenhouse and field, respectively. Artificial inoculation with P. griseola allowed three recurrent selection cycles per year, signifying a promising method to obtain ALS-resistant common bean lines in a short period.

Abstract The success of bean (Phaseolus vulgaris L.) crops in Brazil is due to the development of new cultivars. The aim of the present study was to critically analyze the fifty years of a bean breeding program at the Universidade Federal de Lavras (UFLA) and estimate the genetic progress (GP) achieved for grain yield. The estimated genetic progress for grain yield was 0.35% per year, which is associated with visible improvement in plant architecture, resistance to some pathogens, and better carioca bean grain quality. The program was found to be efficient, generating 119 theses and 43 dissertations during the period under study. In addition, hundreds of articles have been published, especially studies aimed at improving the efficiency of genetic breeding programs. Over the past few years, partnerships with other public institutions in performing Value for Cultivation and Use tests have resulted in 12 recommended cultivars.

RESUMO A exploração florestal é conduzida em milhares de hectares e apresenta ampla variação nas condições ambientais em termos de solo, clima e até mesmo manejo, assim, identificar clones que possam ser recomendados para essas diversas condições é um grande desafio. Nesta recomendação, um caráter importante é o incremento médio anual em celulose (IMACEL). Este estudo teve como objetivo avaliar a interação de diferentes clones e ambientes para o IMACEL com a finalidade de verificar se a origem da seleção dos clones afeta seu desempenho em outras regiões e identificar clones com base na adaptabilidade. Foram utilizados dados de IMACEL referente à avaliação de clones de Eucalyptus da empresa Suzano S.A. em cinco ambientes, nos estados do Espírito Santo, São Paulo e Mato Grosso do Sul. Os testes clonais foram instalados no delineamento de blocos casualizados com parcelas de uma planta. Dados referentes ao IMACEL das árvores, aos cinco anos, foram submetidos à análise de variância por ambiente e, posteriormente, à análise conjunta. A interação clones x ambientes foi expressiva para o IMACEL, porém, a origem de seleção dos clones não afeta o seu desempenho quando utilizados em outras regiões. Alguns clones se destacaram quanto à adaptabilidade, permitindo maior segurança à empresa na recomendação para diferentes ambientes.

ABSTRACT Forest exploitation is conducted in thousands of hectares in Brazil and presents a wide variation in environmental conditions in terms of soil, climate and even management, so identifying clones that may be recommended for these various conditions is a major challenge. In this recommendation, one important character is the mean annual increment in cellulose (MAICEL). This study aimed to evaluate the interaction of different clones and environments for MAICEL in order to verify whether the origin of clone selection affects their performance in other regions and to identify clones based on adaptability. MAICEL data were used for the evaluation of clones from Suzano S.A. in five environments distributed in the states of Espírito Santo, São Paulo, and Mato Grosso do Sul. Clonal tests were arranged in a randomized block design with plots of one plant. Data on MAICEL of the trees at five years were submitted to analysis of variance per environment and, subsequently, to the joint analysis. The clones x environments interaction was expressive for MAICEL, however, the origin of selection does not affect the performance of clones when grown in other regions. Some clones stood out for their adaptability, allowing more security to the company on the recommendation for different environments.

Abstract Our aim in this study was to evaluate common bean progenies for water use efficiency (WUE) and verify if selection carried out under conditions without water limitation reflects the selection carried out under stress conditions. Eighty progenies from the BRSMG Talismã x G4280 cross and 80 from the BRSMG Talismã x G6492 cross were evaluated with high water availability (HWA) and low water availability (LWA) in two locations and two years. Genetic variance, heritability, accuracy, expected gain from selection, correlated response to selection, genetic correlation between HWA and LWA and between the two traits evaluated, and risk index in the recommendation (RI) were estimated. Some progenies had a RI close to zero, were tolerant in LWA, and were responsive in HWA. Progenies with high grain yield and WUE could be identified. The two conditions of evaluation were equally efficient for selection, as verified by estimates of expected gains from selection.

ABSTRACT: When breeding the common bean in Brazil, the best progenies are chosen, normally, from solely the generation under analysis at the conclusion of the evaluation, without considering what occurred in the past. However, a number of recently published studies show that if an evaluation were to consider all relevant generations, the gain from selection could be higher, especially when an index that involves information from the population that gave rise to the progenies is used. Thus, the aim of this study was to compare three selection procedures in the evaluation of successive generations and to discuss the implications of the progeny × environment interaction in terms of success of selection. Cycle XV progenies from a bean recurrent selection program were used. The traits evaluated were grain yield, plant architecture and grain type. Analysis of variance was carried out and the variance components and heritabilities were estimated. The same analyses were made using mixed models. A selection index weighted by the effect of populations and progenies within populations (WSI) was also obtained. We estimated the correlations between the classification of the progenies using the three procedures and the coincidence of the best progenies evaluated in S0:4 with the progenies in the previous generations. We found that the classification of the progenies by the BLUP's and WSI did not expressively differ from that obtained when using only the mean, even when a number of generations were considered in the selection. None of the procedures used effectively mitigated the effect of the progeny × environment interaction.