Half-sib Progenies Research Articles

Effects of high- vs. low-yield environments on selection for increased biomass yield in switchgrass

No information is available on the effects of different biomass yield environments on selection efficiency in switchgrass (Panicum virgatum L.) breeding improvement. This study was conducted to assess the effects of high- and low-biomass yield environments (HYE and LYE, respectively) on recurrent selection for general combining ability (RSGCA) in a lowland population of switchgrass (NL-94). The top 14 of 65 NL-94 C0 parent plants were selected based on biomass yield of half-sib (HS) progeny tested for one post-establishment year under HYE and LYE conditions. Nine of the 14 C0 parent plants were the same based on HS performance under HYE and LYE. Selected plants were intercrossed to produce NL-94 HYE and NL-94 LYE C1 populations. One hundred and twenty-five HS C1 progeny families (60 NL-94 HYE and 65 NL-94 LYE) were evaluated for biomass yield for 3 years (2002–2004) under HYE and LYE conditions. The HYE produced about 2.5 times higher biomass yields than the LYE in both C0 and C1 HS progeny tests. Estimated additive genetic variance and predicted gains from selection (ΔG) were high in the C1 populations indicating that RSGCA should achieve higher biomass yields. Mean biomass yields of C1 HS families originating from the LYE protocol were significantly higher than those of families originating from the HYE protocol in both HYE and LYE performance tests, suggesting greater selection response under LYE in the C0 population. The estimates of narrow-sense heritability ( \( h_{\hbox{n}}^2 \)) and ΔG from the C1 populations indicate that positive response to selection for biomass yield is possible in subsequent cycles of selection under either HYE or LYE, with a possible small advantage for HYE.

Initial evaluation of half-sib progenies of Norway spruce using the best linear unbiased prediction

The present paper deals with data obtained from fifteen years old Norway spruce (<i>Picea abies</i> [L.] Karst.) progeny test established at three sites in the Sázava River region. Parameter under the evaluation was a tree height in 15 years following the establishment of the trial. Genetic parameters were estimated using the REML (Restricted Maximum Likelihood) procedure followed by the BLUP (Best Linear Unbiased Prediction). Genetic parameters estimates were used to predict genetic gain in three alternative selection strategies. The value of gain depends on target value of gene diversity. 10−15% gain is due to selecting breeding population composed of 50 individuals. Based on these quantitative findings, current and future research orientation is discussed.

Relação entre características físicas e o rendimento de polpa de maracujá-amarelo

O trabalho foi realizado na Universidade Federal de Viçosa (UFV), com o objetivo de avaliar a relação entre características do fruto de maracujazeiro e seus desdobramentos em efeitos diretos e indiretos para obtenção de maior rendimento de polpa e peso de frutos, norteando o melhoramento genético. As avaliações foram feitas no primeiro ano de produção (safrinha). Retirou-se uma amostra aleatória de 200 frutos em um ensaio com 42 progênies de meios-irmãos de maracujazeiro. Os caracteres avaliados foram: comprimento e diâmetro equatorial do fruto, peso do fruto, peso da casca e da polpa, espessura da casca, rendimento e relação comprimento/diâmetro. Foram realizadas análises dos coeficientes de correlação de Pearson e análise de trilha. Verificaram-se correlações significativas entre os caracteres avaliados. O peso da polpa apresenta maior efeito direto em sentido favorável à seleção de peso de fruto. O diâmetro equatorial do fruto apresentou-se mais associado com o peso da polpa, em relação ao comprimento do fruto. A seleção dos frutos com maior diâmetro equatorial possibilita a obtenção de maracujás mais pesados e com maior rendimento. Não foi observada correlação entre a relação comprimento/diâmetro e rendimento de polpa.

Wide- versus specific-adaptation strategy for lucerne breeding in northern Italy

This study is aimed at comparing wide- versus specific-adaptation strategies for lucerne in northern Italy on the basis of actual dry matter yield gains over 12 harvests from phenotypic selection, assessing the value of specific genetic bases and selecting environments for the contrasting subregion A (no drought stress/sandy-loam soil) and subregion C (summer drought stress/silty-clay soil). A second aim is to investigate the adaptive responses of five sets of 18 half-sib progenies. The following selected populations were evaluated along with five cultivars: GW-SW, GA-SA, GA-SC, GC-SC and GC-SA (where GW, GA and GC are the genetic bases for wide adaptation, subregions A and C; SW, SA and SC are the selection environments for wide adaptation, subregions A and C). The selection and test environments were four artificial environments created by the factorial combination of two drought stress levels by two soil types. Two environments represented the subregions A and C whereas the combination of the other two environments represented the intermediate subregion B. Genotype x environment interaction (P < or = 0.001) due to both environmental factors and implying cross-over interaction between the contrasting subregions occurred for the populations and the five selections. Specific genetic bases (GA and GC) implied gains in their target subregions of 5.2% for subregion A and 2.9% for subregion C compared with the widely adapted one (GW). The gain of SA ('no stress/sandy-loam soil') over SC ('stress/silty-clay soil') decreased from subregion A (10.6%) through subregion C (1.7%) but exhibited an advantage per se across environments of 5.4%. The best specific selections (GA-SA for subregions A and B; GC-SA for subregion C) implied higher yields of 9.8% in subregion A and 6.5% in subregion C, and over twofold greater selection efficiency across the region, relative to GW-SW. Half-sib progeny x artificial environment interaction (P < or = 0.05) occurred in three sets of progenies whose parents belonged to cultivars with different or similar adaptation.

Genetic Variation for and Correlations Among Seed Yield and Seed Components in Tall Fescue

Abstract To study the genetic variation, heritability and genetic correlations for seed yield and its components (panicles emergence date, anthesis date, panicle number, plant height, panicle length, 1000-grain weight, seed number and seed weight per panicle, harvest index, seed yield, dry matter (DM) yield and fertility index) in tall fescue (Festuca arundinace Schreb), 20 parents were randomly chosen from a genetically broad-based population, and their respective half-sib families were generated. Clonally propagated parents and their half-sib family seeds were grown as individual spaced plants using a randomized complete-block design with two replications in Alborz Research Center, Karaj, Iran, during 2002–2004. The estimates of broad-sense heritability (h b 2) were moderate to high for all traits (h b 2 = 0.46–0.82), except harvest index, seed number and seed weight per panicle. Narrow-sense heritability (h n 2) estimates from analyses of progenies and from regression of half-sib (HS) progenies on pare...

Variation in lignin and cell wall digestibility in caffeic acid O-methyltransferase down-regulated maize half-sib progenies in field experiments

Lignin content and structure were examined in seven caffeic acid O-methyltransferase antisense (COMT-AS) maize progenies and their corresponding normal inbred lines in relation to cell wall digestibility. The seven parental inbreds were chosen for their highly divergent in vitro wall digestibility. Maize plants were grown under field conditions to determine (i) if the positive effect of COMT down-regulation on wall chemistry and digestibility was similar to that previously observed for COMT-AS maize grown in the greenhouse and (ii) to what extent the genetic background was a factor in determining the effect of the transgene. All COMT-AS progenies displayed a significant reduction in endogenous COMT activity (14-43% residual activity). In all but one genetic background (F4), the COMT-AS gene resulted in an expected increase in wall digestibility accompanied by chan- ges in lignin composition. These effects varied greatly among parental lines, and independently of the inherent digestibility values in the correspond- ing non-transformed lines. Curiously, in the highly digestible F4 background, the typical decrease in syringyl (S) unit lignin and a higher frequency of 5-OH guaiacyl lignin resulting from the introduc- tion of the COMT-AS transgene were not observed. Our results indicate that COMT down-regulation via an antisense strategy is an efficient tool for forage maize improvement in the field.

Estimates of genetic parameters in Mimosa scabrella populations by random and mixed reproduction models

Heritabilities and expected selection gains were estimated in nine provenances of Mimosa scabrella Bentham by means of random and mixed reproduction models. In the random model, the relationship coefficient was considered as half-sibs, and in the mixed, relatedness was estimated based on parameters of the mating system. The trait height was measured six months after planting in the field and a progeny sample of each provenance was analyzed by isoenzyme electrophoresis to estimate parameters of the mating system. The mean inbreeding coefficient was 0.392, which is 56.8% higher than expected in half-sib progenies (0.25). The mean estimates of the additive genetic variance, heritability within progenies and gains expected with selection among and within progenies, calculated by the underlying random reproduction model were overestimated, respectively, by 36%, 48% and 41%, when compared to estimates obtained based on the mixed reproduction model.

Heritability of Resistance to Verticillium Wilt in Alfalfa.

Verticillium wilt of alfalfa, caused by Verticillium albo-atrum, may reduce forage yields by up to 50% in alfalfa-producing areas of the northern United States and Canada. It has been suggested that cultivars require at least 60% resistant plants to afford maximum protection against disease. Our objective was to calculate heritability estimates of resistance to Verticillium wilt in alfalfa. Estimates were generated for two alfalfa populations developed from the cvs. Affinity + Z and Depend + EV. Heritability on a half-sib progeny means basis was calculated based on data from greenhouse pathogenicity tests. Estimates based on repeated experiments conducted for single years (2004 and 2005) were high for both populations, ranging from 0.86 to 0.92. The heritability estimate based on data collected over 2 years was 0.26 for Affinity + Z and 0.66 for Depend + EV. Disease was more severe in 2005 than in 2004. However, the Spearman rank correlation between mean disease severity index values for half-sib families over 2 years was positive and significant for both populations. Results of pathogenicity tests suggested that neither cultivar had resistance levels approaching 60%. The heritability estimates suggest that resistance levels in both Affinity + Z and Depend + EV could be improved further through selection.

Improvement of seed yield potential in tall fescue

Modest and unreliable seed yield limits the usefulness of some forage tall fescue cultivars. In preliminary experiments, significant correlations for seed weight per panicle but not panicle number were established between spaced plants and sown rows of half-sib progeny derived from them. However, seed yield of the sown rows in the second year was not correlated with first year values. Half-sibling families of an elite breeding pool were sown in rows at three contrasting sites in autumn 1999. The following spring, panicle numbers were counted and in summer seed was harvested and weight per panicle calculated. Families varied significantly for seed yield and yield components, and family values were correlated between sites. Seedlings were raised from remnant seed of the best performing families (based on first year data at the 3 sites) and assessed pre-anthesis for panicle number. Selected plants were isolated and seed harvested. After progeny tests, three sub-sets of elite plants were isolated to produce improved selections. Plot trials sown at Lincoln (New Zealand) and at Pergamino (Argentina), showed significant seed yield improvements from the selections compared with "Grasslands Advance," a standard cultivar derived from the same breeding pool

Avaliação genética de indivíduos de erva-mate (&lt;i&gt;Ilex paraguariensis&lt;/i&gt; St. Hil.) na região de Caarapó, MS, pelo procedimento reml/blup.

O presente estudo objetivou estimar parâmetros e valores genéticos para os caracteres altura e diâmetro de indivíduos de erva-mate Ilex paraguariensis (St. Hil.) pela metodologia de modelos mistos (procedimento REML/BLUP). As progênies de meios-irmãos foram plantadas na Reserva Indígena Kaiowá e Guarani, em Caarapó/MS, sob delineamento de blocos ao acaso, com seis tratamentos (progênies), seis repetições e vinte plantas por parcela. Aos 9 meses de idade, foram avaliados os caracteres: altura total das mudas e diâmetro do coleto. Ganhos genéticos preditos de 4,16% foram obtidos para o caráter altura e 7,20% para o caráter diâmetro, com a seleção dos dez melhores indivíduos. Embora os ganhos genéticos não sejam elevados para a idade avaliada, estimulam a utilização desses germoplasmas e a continuidade das avaliações em idades mais avançadas, explorando-se a variabilidade dentro das progênies.

Genetic Gain and Gene Diversity Following Thinning in a Half-Sib Plantation

Abstract Status number, gene diversity, inbreeding coefficient and genetic gain were calculated following phenotypic rogueing of different intensities in a half-sib progeny plantation of Scots pine (Pinus sylvestris L.). Across most selection intensities the status number, gene diversity and genetic gain remained favorably high while the inbreeding coefficient was remarkably stable. It is suggested that phenotypic selection in half-sib progeny tests or plantations with unknown pedigrees, can be used to manage seed collection areas or as a component in low-input breeding without a fast build up of coancestry or inbreeding, provided the initial number of progenies of unrelated parents is sufficiently high and that a high number of these families are retained with a few individuals per family.

Heritability of morphophysiological traits and inbreeding effects in grazing-type lucerne

To estimate heritability and inbreeding in grazing-type lucerne, 14 parent genotypes and their half-sib and selfed progeny were grown under spaced-plant conditions. Dry-matter weight (four cuts), plant height, basal plant diameter, stem density, and late-autumn vegetation were recorded on a plant basis. Genetic coefficients of variation for the three germplasm groups, and broad-sense heritability on a plot basis for parents were computed from variance component estimates; narrow-sense heritability was estimated from progeny-parent regression. Genetic variation was generally greater among selfed than half-sib progeny. Broad-sense heritability was high, while narrow-sense heritability was much lower for all traits except plant diameter. Inbreeding effects, assessed with comparison between parents and selfed progeny, were notable for plant weight and late-autumn vegetation only. The high correlation coefficients computed between parents and either progeny suggested the equivalent value of self- and polycross-progeny tests for selecting superior parents.

The effect of low plant density on response to selection for biomass production in switchgrass

Switchgrass (Panicum virgatum L.) is a model bioenergy species with a high biomass production from which renewable sources of fuel and electricity can be generated. The objective of this study was to perform divergent single-plant selection for biomass yield at low plant density, intermate the selected plants in polycrosses, and evaluate the performance of their half-sib (HS) progenies in sward and row plots. One thousand plants from ‘Alamo’ and ‘Kanlow’ populations were planted in unreplicated honeycomb trials with a plant spacing of 120 cm. Moving-ring selection was applied to select 15 high- and 15 low-yielding plants from each population. These were grown in separate polycrosses to create HS-families. Four HS-families from high- and 4 from low-yielding parents of Alamo and Kanlow, along with their bulks were evaluated for 3 years in sward plots with row spacing of 18 cm. Five HS-families from high- and five from low-yielding parents of Alamo and Kanlow were evaluated for 2 years in row plots spaced 76 cm along with their bulks. Overall, the row-plots had 20% higher biomass per unit area than the sward-plots. Across populations and plant densities, the highest-yielding HS-families produced between 2.0 and 9.3 t/ha more biomass than the lowest-yielding HS-families. The mean biomass of the HS-families from parents selected for high-yield was between 0.34 and 4 t/ha higher than the mean of the HS-families from the low-yielding parents. The annual response to selection for the mean and the bulk of the HS-families from the high yielding parents was 19 and 27% higher than the check. These results indicate that on average, high- and low-yielding parental genotypes were effectively selected from the two populations under low plant density.

Germinação de sementes de genótipos de maracujazeiro

O objetivo deste trabalho foi avaliar a germinação de sementes de 22 progênies de meios-irmãos e duas cultivares de maracujazeiro (Passiflora edulis Sims f. flavicarpa Degener) e submeter 6 desses genótipos a diferentes tempos de embebição. Foram conduzidos dois experimentos, sendo que no primeiro foi utilizado o delineamento inteiramente casualizado, com quatro repetições, considerando-se cada genótipo como um tratamento. No segundo experimento, utilizou-se o mesmo delineamento experimental, num fatorial 6x4 (genótipo x tempo de embebição), com quatro repetições. Cada grupo de 50 sementes foi considerado como uma unidade experimental. No primeiro experimento, aos 28 dias, avaliaram-se a porcentagem de germinação e velocidade de emergência e aos 45 dias, a porcentagem de sobrevivência, o comprimento total das plântulas, a altura das plântulas, o comprimento de raiz, o número de folhas e a massa total das plântulas. No segundo experimento, aos 28 dias, as mesmas variáveis do experimento anterior foram avaliadas, com exceção da porcentagem de sobrevivência e número de folhas. A porcentagem de germinação das sementes e o índice de velocidade de emergência não são influenciados pelos diferentes tempos de embebição, mas pelo genótipo das plantas, indicando que estas características podem ser utilizadas para seleção, no melhoramento genético.

Caracteres de produção da cebola associados à resistência a tripes

A variabilidade existente para caracteres de produção associados à resistência a Thrips tabaci (Thysanoptera: Thripidae) foi estimada em 62 progênies de meios irmãos da cv. de cebola ValeOuro IPA-11. As testemunhas foram as cvs. ValeOuro IPA-11 e os seus genitores Roxa IPA-3 e Belém IPA-9. O experimento foi conduzido em condições de campo, em Juazeiro (BA), utilizando delineamento experimental de blocos ao acaso, com três repetições, 65 tratamentos. As estimativas dos parâmetros para as progênies de ValeOuro IPA-11 indicaram forte interferência ambiental para todos os caracteres. As maiores estimativas das herdabilidades e o ganhos esperados com 20% de pressão de seleção foram, respectivamente, de 35,74% e 10,39% para produção de bulbos comerciais (PBC), de 31,33% e -24,48% para porcentagem de plantas improdutivas (%I), de 33,92% e -16,80% para produção de bulbos não comerciais (PBNC) e de 30,31% e -13,18% para porcentagem de bulbos não comerciais (%BNC). Estes caracteres indicaram maior possibilidade de sucesso com a seleção. O caráter ninfas de T. tabaci nas duas folhas centrais completamente desenvolvidas (NINFA), apresentou coeficientes de herdabilidade de 18,24 e 21,34% e ganho esperado de seleção de -11,22 e -7,41% aos 48 e 69 dias após o transplante (DAT), respectivamente, indicando ganhos superiores em seleções efetuadas aos 69 DAT. Apesar da infestação média de 31,96 NINFA, 45,16% das progênies de ValeOuro IPA-11 apresentaram PBC acima da média, sugerindo que o tipo de resistência envolvida venha a ser por tolerância.

Accuracy of Single- and Multiple-Trait REML Evaluation of Data Including Non-Random Missing Records

AbstractWe examined the accuracy of single- and multiple-trait REML procedures by studying estimates of within-individual genetic correlations between an ordered categorical trait and a continuous trait. The traits were derived from simulated bivariate, normally distributed data including selectively deleted records. Ten thousand data sets were generated for each partially factorial combination of two levels of genetic correlation (0.3 and 0.6), and environmental correlation (0.3 and 0.6), and three levels of narrow-sense individual heritability (0.05, 0.15 and 0.25) and mortality (0, 10, 30 and 50%). All data sets consisted of data on 200 unrelated parents, each with 20 halfsib progenies. The accuracy of the evaluations was illustrated in terms of average bias and variation of derived correlation estimates. The average bias values generated by multiple-trait REML were generally low. In contrast, single-trait REML was sensitive to selective deletion of records and systematically underestimated the genetic correlations. For both methods, especially at low heritabilities, the magnitude of the variation was generally high, showing that there is a substantial probability of obtaining seriously misleading genetic correlation estimates if the analysis is based on a single experiment and data include non-random missing records.

Genetic variation and heritability of phosphorus uptake in Alamo switchgrass grown in high phosphorus soils

Developing crop cultivars with high P uptake may prevent the accumulation of phosphorus in the soil and its escape to streams and water reservoirs. The purpose of this investigation was to assess the potential for P uptake in switchgrass ( Panicum virgatum L.), an important bioenergy and forage crop, and to determine the nature of genetic variation and heritability of this trait. Thirty genotypes from a population of ‘Alamo’ switchgrass were evaluated in the greenhouse [Tifton loamy sand (fine, loamy, siliceous thermic Plinthic Paludults)] and the field [Wedowee coarse sandy loam (fine, kaolinitic, thermic family of the Typic Kanhapludults)] at a rate of 450 mg P kg −1 and 200 mg N kg −1 soil. Significant genetic variation was observed among the parental genotypes for P concentration, biomass production, and P uptake. Genotype × location interaction was significant for all three traits. Nevertheless, rank correlation of the genotypes between the two locations was high for P uptake ( r = 0.83, P < 0.01) indicating that little of the genotype × location interaction is associated with changes in ranking. Narrow sense heritability based on individual plant and family means were 2 and 13% for P concentration, 60 and 69 for biomass production, and 67 and 73 for P uptake, respectively. Expected genetic gain based on individual plant selection were <1, 51, and 65% of the parental means for P concentration, biomass production, and P uptake, respectively. Expected gain from selection based on half-sib progeny testing was slightly higher (2, 55, and 68% for P concentration, biomass, and P uptake). Although little gain from selection is predicted for P concentration, the magnitude of heritability values for biomass production and P uptake indicate that substantial genetic progress in increasing P uptake can be achieved through breeding for higher biomass production.

Estudo comparativo de dellineamentos experimentais para estimativas de parâmetros genéticos em erva-mate (Ilex paraguariensis A. St. - Hil.)

O presente trabalho teve por objetivo comparar a eficiência do látice em relação aos delineamentos em blocos casualizados (DBC) e inteiramente casualizados (DIC) quanto aos caracteres altura e produção de massa verde em erva-mate (Ilex paraguariensis A. St. - Hil.). O experimento, conduzido na Fazenda Experimental do Canguiri, da Universidade Federal do Paraná, em Pinhais, PR, foi composto de cinco procedências, quatro com 13 e uma com 12 progênies de meias-irmãs. Cada progênie continha 54 plantas (nove parcelas de seis plantas). O experimento seguiu o modelo látice 8 x 8 com nove repetições balanceadas. As análises foram conduzidas usando-se tanto este modelo quanto os modelos DBC e DIC. Com relação ao caráter altura, a estimativa da eficiência do DBC em relação ao DIC (Êb/i) foi de 48,6%; do látice em relação ao DBC (Êl/b), de 61%; e do látice em relação ao DIC (Êl/i), de 139%. A estimativa da correlação intraclasse entre plantas dentro das parcelas (c²) foi de 9,4% para o DBC e zero para o látice. Para o caráter produção de massa verde, Êb/i, Êl/b e Êl/i foram de 14,3; 81,7; e 108%, respectivamente; e c², 16,9% para o DBC e 3,1% para o látice. Essas estimativas, associadas a uma estimativa de F de Snedecor altamente significativa dos dois caracteres, permitiram concluir que a capacidade de teste do DBC foi satisfatória para o caráter altura de plantas, mas insatisfatória para o caráter produção de massa verde.

Correlações entre caracteres agronômicos associados à resistência a tripes em cebola

Foram determinadas as correlações genotípicas, fenotípicas e ambientais entre caracteres agronômicos e resistência a Thrips tabaci em 62 progênies de meio-irmãos da cultivar ValeOuro IPA-11 de cebola. O experimento foi conduzido em campo, em Juazeiro (BA), com avaliações aos 48; 69 e 93 dias após o transplantio (DAT). A produção de bulbos comerciais (PBC) apresentou correlações genotípicas com comprimento de folhas (CF) (0,63**); número total de folhas (NTF) (0,74**); número de folhas danificadas (NFD) (0,74**); peso médio de bulbos comerciais (PMBC) (0,54**); porcentagem de bulbos comerciais (%BC) (0,61**); e porcentagem de bulbos não comerciais (%BNC) (-0,63**). Foram observadas correlações genotípicas do número de ninfas de T. tabaci entre as duas folhas centrais completamente desenvolvidas (NINFA), aos 69 DAT com ângulo entre as folhas centrais (ANG) (-0,76**); NTF (0,46**); %BC (-0,35**); e porcentagem de plantas improdutivas (%I) (0,39**). Estas correlações indicam que menos ninfas ocorre em plantas com menor NTF e maior ANG. Por sua vez, plantas com menor NTF apresentam maior ANG (-0,92**). Porém, ressalta-se que o NTF correlacionou-se positivamente com PBC, PMBC (0,45**) e %BC (0,43**). As correlações genotípicas positivas de NFD com PBC, PMBC (0,40**) e %BC (0,51**), sugerem que esta população apresenta resistência por tolerância.

Alterations in heterosis of maize populations derived from single-cross hybrids after reciprocal recurrent selection

One hundred and sixty-nine interpopulational half sib progenies were obtained from maize populations derived from the commercial single-cross hybrids AG9012 (1) and C333 (2) to investigate the efficiency of reciprocal recurrent selectio n (RRS). Fifteen progenies with highest hulled ear yield were obtained. Two recombination trials were sown with remnant S 1