Selection in early generations to shift allele frequency for seminal root angle in wheat

A current challenge for plant breeders is the limited ability to phenotype and select for root characteristics to enhance crop productivity. The development of a high-throughput phenotyping method has recently offered new opportunities for the selection of root characteristics in breeding programs. Here, we investigated prospects for phenotypic and molecular selection for seminal root angle (SRA), a key trait associated with mature root system architecture in wheat (Triticum aestivum L.). We first investigated genetic diversity for this trait in a panel of 22 wheat lines adapted to Australian environments. The angle between the first pair of seminal roots ranged from 72 to 106°. We then evaluated selection gain via direct phenotypic selection in early generations by comparing the resulting shift in population distribution in tail populations selected for “narrow” and “wide” root angle. Overall, two rounds of selection significantly shifted the mean root angle as much as 10°. Furthermore, comparison of allele frequencies in the tail populations revealed genomic regions under selection, for which marker-assisted selection appeared to be successful. By combining efficient phenotyping and rapid generation advance, lines enriched with alleles for either narrow or wide SRA were developed within only 18 mo. These results suggest that there is a valuable source of allelic variation for SRA that can be harnessed and rapidly introgressed into elite wheat lines

Hétérogénéité spatiale de l'activité des microorganismes décomposeurs des matières organiques dans les sols. Mise en évidence, paramètres explicatifs

AIP Ecosol 1995-1998 : rapport final de projet *INRA Unité de Science du Sol Versailles Diffusion du document : INRA Unité de Science du Sol VersaillesNational audienc

Comparação de métodos de determinação de carbono orgânico total no solo Comparison of determination methods of total organic carbon in soils

O teor de C orgânico total do solo (COT) pode ser determinado por métodos que se baseiam nos princípios de combustão a seco e combustão úmida. Ambos apresentam inconvenientes, principalmente o de combustão úmida, que exige grande quantidade de reagentes, gerando, por conseqüência, alta quantidade de resíduos tóxicos que contêm Cr. O método denominado Mebius no bloco de digestão (Mebius no bloco) permite a diminuição do uso de dicromato de potássio em análises de solo. Nesse sentido, o presente estudo objetivou verificar a precisão e exatidão do método Mebius no bloco em relação a outros de combustão úmida e o de combustão a seco. O trabalho foi realizado na Universidade Federal de Santa Maria, em duas etapas: os teores de COT foram determinados em 18 amostras de duas camadas (0-5 e 5-10 cm) de um Latossolo Vermelho distrófico típico com diferentes usos. Os métodos usados foram Walkley-Black, Mebius modificado, Mebius no bloco e por captura de CO2; os teores de COT foram determinados por combustão a seco e Mebius no bloco em 75 amostras coletadas nos horizontes A1 (0-7,5 e 7,5-15 cm), A2, E e Bt de um Argissolo Vermelho-Amarelo distrófico abrúptico submetido a cinco sistemas de manejo e três repetições. A precisão apresentada pelos métodos de combustão úmida é similar e com coeficiente de variação abaixo de 10 %, com exceção do método de captura de CO2, que apresentou valores de COT inferiores aos dos demais e com maior coeficiente de variação. O método Mebius no bloco permite processar maior número de amostras por tempo, com menor consumo de reagentes, e seus resultados apresentam boa precisão (coeficiente de variação menor que 2,60 %) entre os métodos de combustão úmida testados. Um fator de correção de 1,14 deverá ser aplicado aos resultados obtidos pelo método Mebius no bloco para equivaler aos obtidos por combustão a seco (analisador elementar de carbono).<br>The total organic carbon (TOC) in soils can be estimated by dry and humid combustion methods. Both have some drawbacks, mainly the humid combustion, which demands high reagent quantities and generates toxic waste containing chromium. The Mebius in Block method was developed to decrease the quantity of Na dichromate used in analyses. The objectives of this study were to verify the precision and accuracy of the Mebius in Block compared with other wet and dry combustion methods. The study was performed in two phases at the Universidade Federal de Santa Maria: (a) TOC contents of 18 soil samples of a Rhodic Ferralsol were determined in the 0-5 and 5-10 cm layers, by different practices. The methods evaluated were Walkley-Black, modified Mebius, Mebius in digestion block, and by CO2 capturing; (b) The TOC contents were determined by Mebius in Block and an elementary analyzer of carbon and nitrogen in 75 samples collected in A1 (0-7.5 and 7.5-15 cm layers), A2, E and Bt horizons of a Rhodic Acrisol with five management practices and three replicates. The data precision of the humid combustion methods was similar, with a coefficient of variation (CV) below 10 %, except for the CO2 capturing method, where the TOC contents were lower, while the variation coefficient was higher. The Mebius-in-block processes a larger number of samples with lower reagent consumption and a greater precision (CV < 2.60 %) than the other methods. A factor of correction of 1.14 should be applied to Mebius-in-Block values for an adjustment to those obtained by dry combustion (elementary analyzer)

Fracionamento densimétrico com politungstato de sódio no estudo da proteção física da matéria orgânica em solos Densimetric fractionation with sodium polytungstate to investigate physical protection of soil organic matter

O fracionamento físico densimétrico é uma técnica que permite estudar a proteção física da matéria orgânica (MO) no solo, sendo utilizadas, de forma indistinta, soluções densas de iodeto de sódio (NaI) e de politungstato de sódio (PTS). O objetivo deste estudo foi avaliar (a) o efeito de soluções de NaI (1,8 g cm-3) e de PTS (1,8, 2,0 e 2,2 g cm-3) no rendimento de carbono (C) nas frações leve-livre (FLL) e leve-oclusa (FLO) da MO na camada de 0-5 cm de um Argissolo Vermelho [PVd, Eldorado do Sul (RS)] e de um Latossolo Vermelho [LVdf, Dourados (MS)] e (b) a magnitude da proteção física da MO em agregados no acúmulo de C orgânico nesses solos submetidos, respectivamente, ao sistema plantio direto por 18 anos (PD) e pastagem (Brachiaria decumbens) por nove anos, em comparação à sua condição em preparo convencional (PC). Em ambos os locais, blocos indeformados de solo foram coletados em experimentos de longa duração; os agregados foram separados nos planos de fraqueza e passados em peneira de 9,51 mm; esse material foi submetido ao fracionamento densimétrico da MO do solo. O uso da solução de PTS 1,8 g cm-3 aumentou de 176 a 727 % o rendimento de C na FLO em comparação à solução de NaI na mesma densidade, mas não teve efeito no rendimento de C da FLL da MO do solo. O aumento da densidade da solução de PTS de 1,8 g cm-3 para 2,0 g cm-3 incrementou de 30 a 99 % o rendimento de C da FLO; contudo, o aumento da densidade para 2,2 g cm-3 resultou em aumento pouco expressivo (< 18 %) no rendimento de C na FLO nos diferentes solos e sistemas de manejo. O uso de NaI no fracionamento densimétrico leva à conclusão errônea de que a proteção física não é um mecanismo importante de estabilização da MO no solo. Por outro lado, a utilização da solução de PTS 2,0 g cm-3, a qual é recomendada para o fracionamento densimétrico devido à sua alta eficiência na recuperação do C da FLO, permitiu constatar que a proteção física da MO em agregados de solo foi responsável por 54 e 23 % do acúmulo de C orgânico no PVd e LVdf, respectivamente, sob plantio direto e pastagem.<br>Through the densimetric fractionation it is possible to study the physical protection of soil organic matter (SOM). High density solutions of sodium iodide (NaI) or sodium polytungstate (SPT) have been indistinctively used for this purpose. This study aimed to assess: (a) the capacity of these two solutions at a density of 1.8 g cm-3 (NaI-1.8 and SPT-1.8) and of SPT at densities of 2.0 (SPT-2.0) and 2.2 g cm-3 (SPT-2.2) to increase C recovery in the free light fraction (FLF) and occluded light fraction (OLF) of the organic matter contained in soil aggregates of the 0-5 cm layer of an Acrisol [PVd, Eldorado do Sul (RS)] and of a Ferralsol [LVdf, Dourados (MS)]; and (b) the magnitude of the physical protection in promoting soil organic matter accumulation in these soils under no-tillage for 18 years and pasture (Brachiaria decumbens) for 9 years, respectively, both in comparison to conventional-tilled soil. Soil blocks were collected and < 9.51 mm soil aggregates were separated and submitted to density fractionation of soil OM. The SPT-1.8 increased OLF-C by 176 to 726 % in comparison to NaI-1.8, but no effect was observed on FLF-C recovery. By using SPT-2.0, the OLF-C recovery increased by 30 to 90 % in comparison with SPT-1.8, but a lower increment (< 18 %) was observed when SPT-2.0 was substituted by SPT-2.2. Density fractionation of OM with NaI solution (low OLF and high FLF) may lead to the erroneous conclusion that physical protection is not an important stabilizing mechanism of SOM in soils under no-tillage or pasture. On the other hand, when using SPT-2.0, which was most efficient in recovering OLF-C, the physical protection within aggregates was responsible for 54 % (PVd) and 23 % (LVdf) of the total SOM accumulation in soils under no-tillage and pasture, respectively

The European/International Fibromuscular Dysplasia Registry and Initiative (FEIRI)-clinical phenotypes and their predictors based on a cohort of 1000 patients.

Since December 2015, the European/International Fibromuscular Dysplasia (FMD) Registry enrolled 1022 patients from 22 countries. We present their characteristics according to disease subtype, age and gender, as well as predictors of widespread disease, aneurysms and dissections. All patients diagnosed with FMD (string-of-beads or focal stenosis in at least one vascular bed) based on computed tomography angiography, magnetic resonance angiography, and/or catheter-based angiography were eligible. Patients were predominantly women (82%) and Caucasians (88%). Age at diagnosis was 46 ± 16 years (12% ≥65 years old), 86% were hypertensive, 72% had multifocal, and 57% multivessel FMD. Compared to patients with multifocal FMD, patients with focal FMD were younger, more often men, had less often multivessel FMD but more revascularizations. Compared to women with FMD, men were younger, had more often focal FMD and arterial dissections. Compared to younger patients with FMD, patients ≥65 years old had more often multifocal FMD, lower estimated glomerular filtration rate and more atherosclerotic lesions. Independent predictors of multivessel FMD were age at FMD diagnosis, stroke, multifocal subtype, presence of aneurysm or dissection, and family history of FMD. Predictors of aneurysms were multivessel and multifocal FMD. Predictors of dissections were age at FMD diagnosis, male gender, stroke, and multivessel FMD. The European/International FMD Registry allowed large-scale characterization of distinct profiles of patients with FMD and, more importantly, identification of a unique set of independent predictors of widespread disease, aneurysms and dissections, paving the way for targeted screening, management, and follow-up of FMD