Validation of microsatellite markers for assisted selection of soybean resistance to cyst nematode races 3 and 14

The objective of this work was to validate microsatellite markers associated with resistance to soybean cyst nematode (Heterodera glycines Ichinohe) races 3 and 14, in soybean (Glycine max L.) genotypes, for use in marker-assisted selection (MAS) programs. Microsatellites of soybean linkage groups A2, D2 and G were tested in two populations, and their selection efficiencies were determined. The populations were 65 F2:3 families from Msoy8001 (resistant) x Conquista (susceptible) cross, and 66 F2:3 families of S5995 (resistant) x Renascença (susceptible) cross, evaluated for resistance to races 3 and 14, respectively. Families with female index up to 30% were considered moderately resistant. Markers of A2 and G linkage groups were associated with resistance to race 3. Markers Satt309 and GMENOD2B explained the greatest proportion of phenotypic variance in the different groups. The combinations Satt309+GMENOD2B and Satt309+Satt187 presented 100% selection efficiency. Resistance to race 14 was associated with markers of G linkage group, and selection efficiency in the Satt309+Satt356 combination was 100%. The selection differential obtained by phenotypic and marker assisted selection showed that both can result in similar gains.

Early selection in open-pollinated Eucalyptus families based on competition covariates

The objetive of this work was to evaluate the influence of intergenotypic competition in open-pollinated families of Eucalyptus and its effects on early selection efficiency. Two experiments were carried out, in which the timber volume was evaluated at three ages, in a randomized complete block design. Data from the three years of evaluation (experiment 1, at 2, 4, and 7 years; and experiment 2, at 2, 5, and 7 years) were analyzed using mixed models. The following were estimated: variance components, genetic parameters, selection gains, effective number, early selection efficiency, selection gain per unit time, and coincidence of selection with and without the use of competition covariates. Competition effect was nonsignificant for ages under three years, and adjustment using competition covariates was unnecessary. Early selection for families is effective; families that have a late growth spurt are more vulnerable to competition, which markedly impairs ranking at the end of the cycle. Early selection is efficient according to all adopted criteria, and the age of around three years is the most recommended, given the high efficiency and accuracy rate in the indication of trees and families. The addition of competition covariates at the end of the cycle improves early selection efficiency for almost all studied criteria.

Validation of microsatellite markers for assisted selection of soybean genotypes resistant to powdery mildew

Powdery mildew is one of the most serious diseases of soybean and is found in all producing countries. The purpose of this study was to validate microsatellite markers previously identified as associated with resistance to powdery mildew in soybean. The study was conducted in two F, parent populations with contrasting resistance to powdery mildew, In the analysis 10 SSR primers were used for the populations. and tour polymorphic markers were identified for cross I (MGBR95-20937 x IAC-Foscarin 31) and three for cross 2 (MGBR-46 x Empresa Brasileira de Pesquisa Agropecuária (EMBRAPA) 48). The Chi-square analysis of the phenotypic evaluation confirmed the expected segregation (3: 1) of a dominant gene related to resistance. The polymorphic markers also segregated as expected (1:2:1). The markers Sat 366 and Sat 393 in the crosses 1 and 2. respectively, located at 9.41 and 12.45 cM from the gene. were considered promising for marker-assisted selection for resistance to powdery mildew in soybean. at a selection efficiency of 92.7% and 60.3% respectively.

Test-day milk yield as a selection criterion for dairy buffaloes (Bubalus bubalis Artiodactyla, Bovidae)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Early selection in open-pollinated Eucalyptus families based on competition covariates

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

A genome-wide scan for selection signatures in Nellore cattle

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Strategies in identifying individuals in a segregant population of common bean and implications of genotype x environment interaction in the success of selection

The objective of this study was to compare the BLUP selection method with different selection strategies in F-2:4 and assess the efficiency of this method on the early choice of the best common bean (Phaseolus vulgaris) lines. Fifty-one F-2:4 progenies were produced from a cross between the CVIII8511 x RP-26 lines. A randomized block design was used with 20 replications and one-plant field plots. Character data on plant architecture and grain yield were obtained and then the sum of the standardized variables was estimated for simultaneous selection of both traits. Analysis was carried out by mixed models (BLUP) and the least squares method to compare different selection strategies, like mass selection, stratified mass selection and between and within progeny selection. The progenies selected by BLUP were assessed in advanced generations, always selecting the greatest and smallest sum of the standardized variables. Analyses by the least squares method and BLUP procedure ranked the progenies in the same way. The coincidence of the individuals identified by BLUP and between and within progeny selection was high and of the greatest magnitude when BLUP was compared with mass selection. Although BLUP is the best estimator of genotypic value, its efficiency in the response to long term selection is not different from any of the other methods, because it is also unable to predict the future effect of the progenies x environments interaction. It was inferred that selection success will always depend on the most accurate possible progeny assessment and using alternatives to reduce the progenies x environments interaction effect.

Parceria público x privada no desenvolvimento de pesquisa em melhoramento genético animal

O melhoramento genético animal é, normalmente, pesquisado e desenvolvido nas universidades e instituições públicas de pesquisa do Brasil. No entanto, os rebanhos de exploração zootécnica, verdadeiros objetivos desses estudos, pertencem à iniciativa privada. O melhoramento genético animal e as parcerias público-privadas constituem-se em um caso especial de grande sucesso, que é analisado no presente texto, com ênfase especial ao Grupo de Melhoramento Animal e Biotecnologia da Faculdade de Zootecnia e Engenharia de Alimentos da Universidade de São Paulo, instituição de origem dos autores. O sucesso desse grupo, medido em atividades de pesquisa e suas conseqüentes publicações, de ensino e formação de recursos humanos e de extensão de serviços à comunidade, é apresentado como incentivo aos pesquisadores das mais diversas áreas ligadas à produção animal.

Selective ingestion of pelagic versus benthic algae by the cockle Cerastoderma edule (Linne, 1758)

The pre-ingestive selection of microphytobenthic algae by the cockle Cerastoderma edule was studied in comparison with diets containing the pelagic diatom Phaeodactylum tricomutum. Treatments with the different diets covered a range of seston concentrations and organic content similar to field conditions. Rejection rates of C. edule exposed to the different treatments were significantly correlated with the concentration of total particulate matter. No significant differences in total rejection rates were found between pelagic and benthic diets. Organic rejection rate was significantly correlated with particulate organic matter of the treatments and no significant differences were found between both diets. Selection efficiency was significantly correlated with particulate organic matter concentration in both diets and no significant differences were found between the diets. Analysis of the pseudofeces composition by flow cytometry from cockles exposed to a mixed diet of microphytobenthic algae and P. tricornutum, showed a preferential ingestion of the pelagic diatom. Benthic species, such as small pennates and Navicula sp., were preferentially ingested in comparison to larger microphytobenthic species. The largest microphytobenthic species, Cylindrotheca sp., was significantly rejected. In general, C. edule is an opportunistic filter feeder that takes advantage of both pelagic and benthic algal cells.

Opportunity cost of ad hoc marine reserve design decisions: an example from South Australia

Like many states and territories, South Australia has a legacy of marine reserves considered to be inadequate to meet current conservation objectives. In this paper we configured exploratory marine reserve systems, using the software MARXAN, to examine how efficiently South Australia's existing marine reserves contribute to quantitative biodiversity conservation targets. Our aim was to compare marine reserve systems that retain South Australia's existing marine reserves with reserve systems that are free to either ignore or incorporate them. We devised a new interpretation of irreplaceability to identify planning units selected more than could be expected from chance alone. This is measured by comparing the observed selection frequency for an individual planning unit with a predicted selection frequency distribution. Knowing which sites make a valuable contribution to efficient marine reserve system design allows us to determine how well South Australia's existing reserves contribute to reservation goals when representation targets are set at 5, 10, 15, 20, 30 and 50% of conservation features. Existing marine reserves that tail to contribute to efficient marine reserve systems constitute 'opportunity costs'. We found that despite spanning less than 4% of South Australian state waters, locking in the existing ad hoc marine reserves presented considerable opportunity costs. Even with representation targets set at 50%, more than halt of South Australia's existing marine reserves were selected randomly or less in efficient marine reserve systems. Hence, ad hoc marine reserve systems are likely to be inefficient and may compromise effective conservation of marine biodiversity.

Heritability at family mean level

Based on a polygenic system of a diploid species, without epistasis, and a population in Hardy-Weinberg equilibrium, without inbreeding and under linkage equilibrium, it can be shown that: (1) the narrow sense heritability at half-sib family level is equal to the square of the correlation coefficient between family mean and the additive genetic value of its common parent; (2) the narrow sense heritability at full-sib family level is equal to the square of the correlation coefficient between family mean and the mean of the additive genetic values of its parents; (3) the narrow sense heritability at Sn family level is exactly equal to the square of the correlation coefficient between family mean and the additive genetic value of its parent only in absence of dominance or when allele frequencies are equal; and (4) the broad sense heritability at full-sib or Sn family level can be used to analyze selection efficiency, since the progeny genotypic mean is, in general, a good indicator of parents, or Sn-1 plant superiority with respect to the frequency of favorable genes.

Mapping of QTLs related with wood quality and developmental characteristics in hybrids (Eucalyptus grandis x Eucalyptus urophylla)

The present work aimed to characterize and identify QTLs for wood quality and growth traits in E. grandis x E. urophylla hybrids. For this purpose a RAPD linkage map was developed for the hybrids (LOD=3 and r=0.40) containing 52 markers and 12 linkage groups. Traits related to wood quality and growth were evaluated in the QTL analyses. QTL analyses were performed using chi-square tests, single-marker, interval mapping and composite interval mapping analyses. All approaches led to the identification of similar QTLs associated with wood density, cellulose pulp yield and percentage of extractives, which were detected and confirmed by both the interval mapping and composite interval mapping methodologies. Some QTLs regions were confirmed only by the composite interval mapping methodology: percentage of soluble lignin, percentage of insoluble lignin, CBH and total height. Overlapping QTLs regions were detected, and these, can be the result of major genes involved in the regulation and control of the growth traits by epistatic interactions. In order to evaluate the effect of early selection using RAPD molecular data, molecular markers adjacent to QTLs were used genotype selection. The analysis of selection differential values suggests that for all the traits the phenotypic selection at seven years should generate larger genetic gains than early selection assisted by molecular markers and the combination of the strategies should elevate the selection efficiency.

JUVENILE-MATURE GENETIC CORRELATIONS IN Pinus taeda CLONES PROPAGATED VIA SOMATIC EMBRYOGENESIS

ABSTRACT This study aimed to estimate the genetic correlation among selection ages (juvenile - adult) and efficiency of early selection for the height, diameter, and volume traits of individuals from Pinus taeda families propagated via somatic embryogenesis. This study was carried out by genetic-statistical analysis, estimation procedure of variance (Reml), and prediction components of breeding values (Blup), using the Selegen-Reml/Blup software. Genetic correlations among juvenile ages and rotation age were performed by applying the linear model developed by Lambeth (1980). In accordance with results of the established model, the early selection can be performed in clones of Pinus taeda with high selection efficiency. Ages from 4 to 6 years old are enough to select Pinus taeda clones propagated via somatic embryogenesis for harvesting at 8 and 12 years old; and 6 to 10 years old are enough to select them for harvesting at 20 years old. On the basis of the genetic correlations estimates from the environments, the clones' selection of Pinus taeda propagated via somatic embryogenesis should be developed specifically for each environment. The clones' selection can be performed considering the diameter due to the high correlation between volume and diameter.

Viabilidade de aplicação da seleção precoce em testes clonais de Eucalyptus spp

Com o objetivo de avaliar a eficiência da seleção precoce em Eucalyptus spp. foram usados dados de dois testes clonais avaliados quanto ao crescimento em altura (ALT), diâmetro à altura do peito (DAP) e volume individual de madeira (VOL) aos 25, 50 e 72 meses de idade. O delineamento experimental nos dois testes clonais foi o de blocos casualizados, com trinta tratamentos (clones), seis repetições, sendo um deles com seis e o outro com dez plantas em linha por parcela, no espaçamento de 3,0 m x 3,0 m. Foi feita a análise de variância para cada caracter e idade. Foram obtidas as estimativas de coeficiente de determinação genotípico e de correlações genotípicas entre os caracteres nas idades juvenis e na idade de rotação. Para verificar a viabilidade da aplicação da seleção precoce, foi simulada a seleção de 30% dos clones nas idades juvenis e na idade de rotação para cada um dos caracteres e idades avaliadas, obtendo-se as estimativas de ganhos genéticos com a seleção direta e indireta. Houve diferenças significativas entre os clones avaliados nos dois experimentos para todos os caracteres e idades. Com base nos resultados obtidos, é possível efetuar a seleção precoce aos 2 anos de idade sobre o caracter DAP em testes clonais de eucalipto.

Eficiência da seleção recorrente para redução da estatura de plantas em mamoneira (Ricinus communis L.)

Realizou-se, o presente trabalho, com o objetivo de avaliar a eficiência da seleção recorrente para a redução da estatura de plantas de mamona da cultivar Guarani (Ricinus communis L.), tornando-a com porte adequado para facilitar a colheita manual e/ou mecânica. Foram realizados quatro ciclos de seleção recorrente com a utilização de progênies autofecundadas na cultivar Guarani para redução da estatura das plantas, nas condições edafoclimáticas dos municípios de São Manuel - SP, Botucatu - SP e Penápolis - SP. As avaliações de estatura das plantas e de produtividade de grãos (kg.ha-1), dos quatro ciclos de seleção e do ciclo original foram realizadas nos municípios de São Manuel - SP, Botucatu - SP e Penápolis - SP na safra 2005/2006, sob um delineamento de blocos casualizados com cinco repetições e parcela útil de 30 m². A análise de variância para as características avaliadas foi feita separadamente para cada local e conjuntamente para os três locais e, posteriormente, realizada a comparação das médias pelo teste de Tukey, a 5%. Foram estimados, para as três localidades, por análise de regressão, os ganhos genéticos dos quatros ciclos de seleção para estatura de plantas. A partir dos resultados obtidos pôde-se concluir que a seleção recorrente foi eficiente para a redução da estatura de plantas e que a cultivar de mamona Guarani apresenta variabilidade genética para essa característica e que a produtividade não foi influenciada pela redução da estatura de plantas.