World’s ornamental plant market, including domestic market of several countries and its exports, is currently evaluated in 107 billion dollars yearly. Such estimate highlights the importance of the sector in the economy of the countries, as well as its important social role, as it represents one of the main activities, which contributes to income and employment. Therefore a well-structured plant breeding program, which is connected with consumers’ demands, is required in order to fulfill these market needs globally. Activities related to pre-breeding, conventional breeding, and breeding by biotechnological techniques constitute the basis for the successful development of new ornamental plant cultivars. Techniques that involve tissue culture, protoplast fusion and genetic engineering greatly aid conventional breeding (germplasm introduction, plant selection and hybridization), aiming the obtention of superior genotypes. Therefore it makes evident, in the literature, the successful employment of genetic breeding, since it aims to develop plants with commercial value that are also competitive with the ones available in the market.
ABSTRACT. Currently, one of the acclaimed alternatives for increasing maize yield is accomplished through utilization of heterosis in hybrid cultivars. However, upon performing crosses between related pairs, there are losses due to inbreeding depression. Thus, the aim of this study was to estimate inbreeding depression and the contribution of loci in heterozygosity in different types of maize hybrids. Eight treatments were evaluated, considering the F 1 and S 0 generations of four commercial hybrids. A randomized block experimental design was used, with three replications, and plots consisting of two three-meter long rows at a spacing of 0.50 m. The traits evaluated were plant height, first ear height and husked ear weight. For ear weight trait, there was a significant difference, where the treatments could be classified into three distinct groups. In this case, the single-cross hybrids AG7088 2 F.B.S. Botelho et al. Genetics and Molecular Research 15 (3): gmr.15035497 and 30F90Y exhibited greater depression through inbreeding due to the greater contribution of loci in heterozygosity and consequent predominance of deviations due to dominance.
Maize is one of the most harvested cereals on the planet. In Brazil, it is the country’s second largest grain production after soybean, with a large portion of production destined for animal feed. During the 2019/2020 harvest, 35% of total maize production was exported, 9.5% was destined for industrial processing and only 1.1% for human consumption. Specialty maize are those grains that are not destined for the dry grain commodities market, but have various other uses and are destined exclusively for human consumption. Specialty maize are also considered as an alternative profit source for farmers. From a plant breeding standpoint, maize is greatest example of success when it comes to the exploitation of heterosis and therefore most of the investment in genetic breeding done by private companies is in the development of simple GMO single-cross hybrids. In today’s market, there are rarely any specialty maize cultivars available, creating a niche for public funded research and development centers to exploit with their conventional type cultivars. This article discusses the relevance of the specialty maize market niches and the role of the Maize Genetic Breeding Program of Instituto Agronomico (IAC) in the development of innovations in São Paulo through the launch of conventional cultivars aimed at small and medium producers and niches of specialty maize.
RESUMO -A seca é a causa mais severa da redução da produção agrícola e o aquecimento global previsto agravará, consideravelmente, o impacto do déficit hídrico. Alterações climáticas e custos elevados da irrigação são outros fatores que podem afetar ainda mais os problemas ocasionados pela deficiência hídrica, aumentando a necessidade de melhoramento genético para tolerância à seca em milho. A estratégia mais efetiva é a obtenção de cultivares tolerantes que possam escapar do estresse hídrico durante os períodos mais críticos da cultura, com a seleção de germoplasma que possua variabilidade genética para os caracteres adaptativos relacionados à seca. A demanda por cultivares de milho é grande por parte dos agricultores e o mercado disponibiliza poucas cultivares que sejam adaptadas, tolerantes à seca e de alta produtividade. Um programa de Melhoramento Genético para tolerância à seca é um trabalho de médio a longo prazo, difícil por se tratar de um caráter complexo, controlado por vários genes, com grande influência do ambiente, requerendo conhecimentos multidisciplinares e um sistema confiável de experimentação de campo. Com esse enfoque, este artigo apresenta uma revisão de tópicos sobre estratégias de melhoramento para tolerância à seca, principais caracteres e métodos de melhoramento genético utilizados, bem como um histórico dos trabalhos para a obtenção de híbridos e populações de milho visando à tolerância ao déficit hídrico do Instituto Agronômico (IAC), em Campinas, SP. PALAVRAS-CHAVE -estresse, déficit hídrico, seleção I. INTRODUÇÃOA seca e a disponibilidade de água no planeta já estão entre as principais preocupações das diversas lideranças mundiais, havendo indicações de que a água será um produto raro futuramente. Estudos relacionados com tolerância à seca são estratégicos para o país, pois esse é o estresse abiótico mais complexo e de maior efeito sobre as culturas, sendo considerado um dos fatores que mais limita a produção mundial de alimentos [21]. Na cultura do milho, não é diferente. A seca é um dos fatores que causa grandes prejuízo ao desenvolvimento e rendimento da planta, causando redução severa na produtividade de grãos, reduzindo até 100% na produtividade do milho. Segundo Barker et al.[23], a perda média anual de produtividade de milho causada pela seca é de aproximadamente 15% em regiões temperadas e 17% em regiões tropicais. Essa situação é ainda mais agravada quando o milho é semeado durante a segunda safra, pois fica sujeito a maior instabilidade climática com maior probabilidade de ocorrência de períodos de déficit hídrico, já que a safrinha abrange o final do período chuvoso [24]. Assim, a avaliação de genótipos sob déficit hídrico deve ser destaque em programas de melhoramento.Um Programa de Melhoramento Genético para Tolerância à Seca é um assunto de médio a longo prazo, é um trabalho difícil por se tratar de um caráter complexo, controlado por vários genes, com grande influência do ambiente, requerendo conhecimentos multidisciplinares e um sistema confiável de experimentação de c...
The aim of this study was to identify inbred progenies of S maize (Zea mays L.) plants that were efficient at a low level of technology and responsive at a high level of technology through the use of topcrosses. Two contrasting environments were created using two levels of base fertilization and topdressing, so that the levels of nitrogen, phosphorus, and potassium were applied four times higher in one environment than in the other. We used S progenies derived from commercial hybrids in topcrosses with two testers (an elite line from the flint heterotic group and an elite line from the dent heterotic group). The progenies and three controls were evaluated in an augmented block design in Nossa Senhora das Dores, SE, Brazil in the 2010 crop season. The average grain yield in the high-technological level was 21.44% greater than that in the low-technological level. There were no changes in progeny behavior in the two technological levels for grain yield. The testers did not differ in the average grain yield of the progenies at the two technological levels. Therefore, it is possible to select progenies derived from commercial hybrids that have an efficient response to fertilization.
ABSTRACT. Despite the benefits of crop rotation, occurrence of nematodes is a common problem for almost all crops within the Cerrado biome, especially for rice. The use of resistant cultivars is one of the main methods for control of nematodes. Thus, the present study aimed to evaluate the reaction of 36 upland-rice lines, with desirable agronomic characteristics, according to their resistance to root-knot nematodes (Meloidogyne incognita). The experimental design was entirely randomized with four replications. Each plot of land consisted of two rice plants in a 3-L vase. The plants were inoculated with 1000 eggs and eventual juveniles of the respective nematodes. Fifty-five days after the inoculation, the roots and the aerial part of the plant were weighed and the egg mass (EM) as well as the reproduction factor (Rf) were estimated. It was determined that the isolated use of EM was not beneficial in selecting rice lines resistant to the root-knot nematode. This procedure must, therefore, take into account the egg counting and the Rf, in order to improve the reliability of the selection. In our study, 30 evaluated lines were observed to be resistant. Among 17385Resistance of upland-rice lines to root-knot nematodes ©FUNPEC-RP www.funpecrp.com.br Genetics and Molecular Research 14 (4): 17384-17390 (2015) the recommended cultivars, only BRS Monarca had its performance susceptible to the studied nematode species.
O melhoramento do milho branco visa, além da produtividade de grãos, maior rendimento em canjica. Devido ao processo de obtenção de canjica por via seca ser o mais utilizado, a obtenção de híbridos que apresentem grãos duros é mais desejada, pois esse tipo de grãos tem maior rendimento e qualidade de canjica. O objetivo com este desse trabalho foi avaliar híbridos intervarietais de milho branco e identificar os que apresentarem grãos do tipo duro e alta produtividade de grãos para serem destinados à alimentação humana. Foram avaliados 40 híbridos intervarietais, resultantes do cruzamento de progênies S1derivadas de híbrido comercial com a variedade Murano e duas testemunhas comerciais, IAC 8019 e F2IPR 127. O experimento foi realizado em Mococa/SP, na Unidade de Pesquisa e Desenvolvimento do Instituto Agronômico, na safra 2018/2019. O delineamento experimental foi o de blocos casualizados com 3 repetições e parcelas constituídas de 2 linhas de 5 metros, avaliando-se a produtividade de grãos e classificando o tipo de grãos. Foi realizada a análise de variância e o teste de Scott-Knott a 5% de probabilidade foi utilizado para agrupamento de médias. O efeito dos híbridos intervarietais foi significativo. Destacaram-se híbridos com elevada produtividade de grãos, mas por serem classificados como dentados foram considerados inadequados para a produção de canjica. Apenas 20 por cento dos híbridos avaliados apresentaram grãos do tipo duro, destacando-se HI 8, HI 29, HI 16, HI 5, HI 38 e HI 35, que obtiveram produtividade de grãos variando de 6589 a 4087 kg.ha-1, com desempenho superior à das testemunhas comerciais. Conclui-se que os híbridos HI 29 e HI 35, por apresentarem alta produtividade e serem classificados como grãos duros, podem ser indicados como cultivares comerciais promissores para alimentação humana.
In the context of plant breeding programs, it is necessary to evaluate the efficiency of genotype selection over successive years. However, evaluating the genotype selection efficiency is not an easy task, since there is not just a single way to precede it. Besides that, the programs need to be dynamic; that is, they should be able to track the introduction and discard of genotypes each year. As a result, the available data is quite unbalanced, leading to difficulties in certain analyses. Thus, the present study aims to propose some approaches to verify the genetic progress in the preliminary trial of the Federal University of Lavras (UFLA) upland rice breeding program. We utilized mixed models for grain yield and plant height. Trials were performed with a total of 120 genotypes in seven environments, defined by the interaction between locations and years. Due to the imbalance in the available data, the mixed model approach, i.e., Restricted Maximum Likelihood/Best Linear Unbiased Prediction (REML/BLUP), was adopted for the joint analysis. Besides the genetic and phenotypic parameters, the expected gains were also obtained with the selection, genetic progress, renewal rate (RR%), and dynamism of preliminary trials. The efficiency of the selection of superior genotypes per year was verified, with genetic progress favorable for reducing the medium-sized plants associated with high yield.
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