Root mass vertical distribution of perennial cool-season grasses grown in pure or mixed swards

ABSTRACT: In this study we tested whether the root biomass of mixtures composed by grass species is greater than their respective monocultures. The treatments were monocultures of Arrhenatherum elatius, Festuca arundinacea, Dactylis glomerata, and a mixture of them, cultivated in a rich-soil environment. Root biomass was evaluated on a single evaluation per season at three soil depths (0-5, 5-10, and 10-20 cm). Mixed swards presented the greatest root biomass, and this was explained by a greater concentration in the topsoil layer (0-5 cm). These findings reinforce the need for permanent soil conservation practices to not jeopardize the benefits of the more abundant root biomass reported in the mixed swards.

Characterization of Root System Architecture Traits in Diverse Soybean Genotypes Using a Semi-Hydroponic System

Phenotypic variation and correlations among root traits form the basis for selecting and breeding soybean varieties with efficient access to water and nutrients and better adaptation to abiotic stresses. Therefore, it is important to develop a simple and consistent system to study root traits in soybean. In this study, we adopted the semi-hydroponic system to investigate the variability in root morphological traits of 171 soybean genotypes popularized in the Yangtze and Huaihe River regions, eastern China. Highly diverse phenotypes were observed: shoot height (18.7–86.7 cm per plant with a median of 52.3 cm); total root length (208–1663 cm per plant with a median of 885 cm); and root mass (dry weight) (19.4–251 mg per plant with a median of 124 mg). Both total root length and root mass exhibited significant positive correlation with shoot mass (p ≤ 0.05), indicating their relationship with plant growth and adaptation strategies. The nine selected traits contributed to one of the two principal components (eigenvalues > 1), accounting for 78.9% of the total genotypic variation. Agglomerative hierarchical clustering analysis separated the 171 genotypes into five major groups based on these root traits. Three selected genotypes with contrasting root systems were validated in soil-filled rhizoboxes (1.5 m deep) until maturity. Consistent ranking of the genotypes in some important root traits at various growth stages between the two experiments indicates the reliability of the semi-hydroponic system in phenotyping root trait variability at the early growth stage in soybean germplasms.

Humic acids impact on heavy metal phytoextraction in Tagetes patula L.

In a model study, we analysed the impact of humic acids (HAs, 500 ppm) on the accumulation of heavy metals (HMs; Pb, Cu, Ni and Zn) in roots and aboveground organs of the annual ornamental plant Tagetes patula (Scarlet variety) cultivated on the Terra Vita nutritive substrate used in modern cultural landscape mulching to imitate the upper fertile root layer (UR-RAT) of contaminated urban soils in megacities. Plants were grown in full photoculture (at no sunlight) in pots placed in a closed grow box, maintaining internal microclimate. A modern HLG Quantum Board QB288 V2 Rspec LED panel enabled with vegetation modes was used as light source. HMs were introduced in substrate as aqueous saline. Each setting was quadruplicated. Total experiment duration was 30 days. Tagetes patula was proved a particularly effective phytoextractor of Zn applied at 40 mg/kg (p<0.01). At the same time, the plants showed high tolerance to toxic growth inhibition (in biometry of the above- and underground organ length and mass) and preserved external aesthetics. Metals were further graded by phytomass accumulation as follows: Cu>Pb>Ni. Ni at 30 mg/kg had a major impact on plant weight and length, which sets off the variety as a sensitive phytoexcluder for this metal. HAs increased aboveground mass in all settings and decreased the HM mass impact. A sharp root mass reduction was observed in combinations of the two factors (HMs+HAs), which was clearly reflected in impaired root mass in zinc settings. A single metal addition reduced the mass by average 12.0 % (p<0.01) vs. control (no HAs or HMs), whilst a combined HAs+HMs administration induced its 65.0 % reduction (p<0.01). The results obtained indicate a good root buffering capacity for HM translocation from the rhizosphere to aboveground parts. In general, HA usage is promising for creating the green space and phytoremediation of urban HM-contaminated soils.

Purple nutsedge (Cyperus rotundus L.) extract as carrot growth and production inducer

There is evidence that the purple nutsedge (Cyperus rotundus L.) aqueous extract can induce the plants rooting due to the high auxin concentrations. This study aimed to evaluate the effect of application seasons and concentrations of purple nutsedge aqueous extract application on the growth and production of carrot, cultivar Brasília. The experimental design was in randomized blocks, in a 2 x 5 factorial scheme in two seasons of the extract application (25 and 50 days after sowing) and five concentrations of (0%, 10%, 20%, 30% and 40%) with four replicates. Harvesting was carried out at 90 days after sowing, being evaluated the following morphological parameters: root diameter (cm); root fresh mass (g plant-1); plant height (cm); aerial part fresh mass (g plant-1); root dry mass (g plant-1); aerial part dry mass (g plant-1); plant dry mass (g plant-1); ratio between root dry mass and aerial part dry mass; root length (cm); commercial productivity (t ha-1); defective root mass (t ha-1); total productivity (t ha-1); commercial yield (roots kg-1); and root classification by length. The extract application at 50th day was more efficient for the root diameter (3.37 cm); fresh root mass (120.7 g plant-1); root length (15.4 cm); commercial productivity (68.2 t ha-1); total productivity (73.6 t ha-1); and commercial roots (8.8 roots kg-1). Root classification by length showed a higher percentage in the 14 cm classification range. The parameters did not present significant differences in both seasons, at 25th and 50th days, respectively, for root dry mass (12.0 and 12.8 g plant-1), ratio between dry mass of roots and aerial part (1.66 and 1.57), and defective root mass (1.3 and 1.5 t ha-1).

Genotype-Dependent Effect of Silencing of TaCKX1 and TaCKX2 on Phytohormone Crosstalk and Yield-Related Traits in Wheat

The influence of silenced TaCKX1 and TaCKX2 on coexpression of other TaCKX gene family members (GFMs), phytohormone regulation and yield-related traits was tested in awned-spike cultivar. We documented a strong feedback mechanism of regulation of TaCKX GFM expression in which silencing of TaCKX1 upregulated expression of TaCKX2 genes and vice versa. Additionally, downregulation of TaCKX2 highly upregulated the expression of TaCKX5 and TaNAC2-5A. In contrast, expression of these genes in silenced TaCKX1 was downregulated. Silenced TaCKX1 T2 lines with expression decreased by 47% had significantly higher thousand grain weight (TGW) and seedling root mass. Silenced TaCKX2 T2 lines with expression of TaCKX2.2.1 and TaCKX2.2.2 decreased by 33% and 30%, respectively, had significantly higher chlorophyll content in flag leaves. TaCKX GFM expression, phytohormone metabolism and phenotype were additionally modified by Agrobacterium-mediated transformation. Two novel phytohormones, phenylacetic acid (PAA) and topolins, lack of gibberellic acid (GA) and changed phytohormone contents in the 7 days after pollination (DAP) spikes of the awned-spike cultivar compared to a previously tested, awnless one, were detected. We documented that major mechanisms of coregulation of the expression of TaCKX GFMs were similar in different spring wheat cultivars, but, depending on content and composition of phytohormones, regulation of yield-related traits was variously impacted.

Effect of Soil Water on GPR Estimation of Bulked Roots, Methods, and Suggestions

Background: Root phenotyping methods are of increasing importance as researchers seek to understand belowground productivity and breeders work to select for root traits. Effective non-destructive root phenotyping methods do not exist for bulked-root and tuber crops such as potato and cassava. Cassava is a tropical crop widely grown by subsistence farmers throughout the tropics and is the fourth most important staple food crop in the world, yet lags in research. It has an extensive growth period sometimes exceeding 12 months. Early maturity is a major goal for breeders, but the ability to select for it is hampered by the lack of non-destructive yield estimation methods. GPR is a tool with potential to aid in bulked root selection, but standard methods have yet to be developed. In this study, we demonstrate good practice in GPR estimation of root mass, which was used as a proxy for cassava root mass, and investigate the effect of soil water content on measurement.Results: Significant correlation between GPR data and daikon root mass was found for three of the five irrigation treatments. Correlation strength improved with increased soil water content and decreased variation of soil water content between plots. Pearson correlation coefficient varied from 0.53 – 0.79.Conclusions: GPR can be used to estimate bulked root mass. Wet soil can improve the predictive quality of GPR data, but water content needs to be homogeneous throughout the study site and period. Determining the optimal soil water content will require further research.

Effects of Light, N and Defoliation on Biomass Allocation in Poa annua

Plants allocate biomass to above- and below-ground organs in response to environmental conditions. While the broad patterns are well-understood, the mechanisms by which plants allocate new growth remain unclear. Modeling approaches to biomass allocation broadly split into functional equilibrium type models and more mechanistically based transport resistance type models. We grew Poa annua plants in split root boxes under high and low light levels, high and low N supplies, with N supplied equally or unequally. Our data suggest that light level had the strongest effect on root mass, with N level being more important in controlling shoot mass. Allocation of growth within the root system was compatible with phloem partitioning models. The root mass fraction was affected by both light and N levels, although within light levels the changes were primarily due to changes in shoot growth, with root mass remaining relatively invariant. Under low light conditions, plants exhibited increased specific leaf area, presumably to compensate for low light levels. In a follow-up experiment, we showed that differential root growth could be suppressed by defoliation under low light conditions. Our data were more compatible with transport resistance type models.

AVALIAÇÃO AGRONÔMICA DE NOVOS CLONES DE Manihot esculenta Crantz NO SEGUNDO CICLO VEGETATIVO

O presente trabalho teve como objetivo avaliar as características agronômicas no segundo ciclo vegetativo de novos clones de mandioca de mesa oriundos de um programa de melhoramento, nas condições edafoclimáticas do município de Santarém, Oeste do Pará. O delineamento experimental utilizado foi em blocos casualizados com 13 tratamentos (novos clones de macaxeira) e três repetições. As parcelas foram constituídas por 10 plantas distribuídas em duas linhas de 5 metros, com espaçamento de 1,0 x 1,0 m. Os resultados obtidos denotam que a produtividade apresentou correlação significativa e positiva com a massa de raízes comerciais (r= 0,98), massa fresca da parte aérea (r= 0,61) e diâmetro médio das raízes (r= 0,63), com destaque para o clone C5 que obteve maiores rendimentos em relação a estas características, e consequentemente apresentou maior média de produtividade 44,70 t ha-1. Em relação ao tempo de cozimento das raízes, de treze clones testados, doze materiais obtiveram tempo médio de cozimento inferior a trinta minutos, sendo classificados como tempo de cozimento bom, com destaque para o clone C11, que apresentou média de 12,30 minutos. Todos os clones avaliados apresentam características agronômicas desejáveis tornando-se promissores para o mercado do município de Santarém, no baixo Amazonas. Palavras-chave: melhoramento; baixo amazonas; produtividade; mandioca de mesa. Agronomic evaluation of new Manihot esculenta Crantz clones in the second vegetative cycle ABSTRACT: The present work aimed to evaluate the agronomic characteristics in the second vegetative cycle of new macaxeira clones from a breeding program under the edaphoclimatic conditions of the municipality of Santarém, Western Pará. The experimental design was randomized blocks with 13 treatments (new clones of cassava) and three repetitions. The plots consisted of 10 plants distributed in two rows of 5 meters, with 1.0 x 1.0 m spacing. The results show that yield was significantly and positively correlated with commercial root mass (r = 0.98), fresh shoot mass (r = 0.61) and mean root diameter (r = 0.63). highlighting clone C5 that obtained higher yields in relation to these characteristics, and consequently presented higher average yield 44.70 t ha-1. Regarding the root cooking time, of thirteen clones tested, twelve materials had an average cooking time of less than thirty minutes, being classified as good cooking time, especially clone C11, which presented an average of 12.30 minutes. All evaluated clones have desirable agronomic characteristics making them promising for the lower Amazon market. Keywords: breeding; low amazons; productivity; table cassava.

CARACTERÍSTICAS ESTRUTURAIS E ACÚMULO DE FITOMASSA DO MILHETO SOB DIFERENTES REGIMES DE IRRIGAÇÃO COM ÁGUA RESIDUÁRIA E ADUBAÇÃO ORGÂNICA

CARACTERÍSTICAS ESTRUTURAIS E ACÚMULO DE FITOMASSA DO MILHETO SOB DIFERENTES REGIMES DE IRRIGAÇÃO COM ÁGUA RESIDUÁRIA E ADUBAÇÃO ORGÂNICA JOSÉ RALIUSON INÁCIO SILVA1; EDUARDO SOUZA1; MAURÍCIO LUIZ DE MELLO VIEIRA LEITE1; GENIVAL BARROS JUNIOR1; JOSE ROMUALDO DE SOUSA LIMA2 E ALDO TORRES SALES1 1Universidade Federal Rural de Pernambuco, Unidade Acadêmica de Serra Talhada, Programa de Pós-Graduação em Produção Vegetal, Avenida Gregório Ferraz Nogueira, s/n, José Tomé de Souza Ramos – CEP: 56909-535, Serra Talhada –PE, Brasil, [email protected], [email protected], [email protected], [email protected], [email protected] 2Universidade Federal do Agreste de Pernambuco, Avenida Bom Pastor, s/n, Boa Vista – CEP:55292-270, Granhuns-PE, [email protected] 1 RESUMO A utilização de água residuária pode aumentar a oferta hídrica e de alimentos em regiões semiáridas. Assim, objetivou-se estudar a dinâmica temporal das características estruturais e acúmulo de fitomassa do milheto irrigado com diferentes lâminas de água cinza, com e sem adubação orgânica. A pesquisa foi conduzida em ambiente protegido em esquema fatorial (4 x 2) + 1, com três repetições, sendo os fatores: níveis de água disponível do solo (25, 50, 75 e 100%) e doses de esterco (0 e 34 Mg ha-1), mais o tratamento controle (irrigação com água potável e sem adubação). Foram realizadas avaliações semanais das características estruturais: comprimento e diâmetro do colmo e número de perfilhos, folhas totais, folhas vivas e folhas mortas, sendo ajustados modelos matemáticos para descrever o comportamento dessas características ao longo do ciclo da cultura. Após 60 dias de aplicação dos tratamentos o milheto foi colhido e determinou-se o acúmulo de fitomassa e massa de raízes. O modelo sigmoidal é o que melhor explica a dinâmica da maioria das características estruturais. A irrigação com águas cinzas não afetou as características estruturais, massa de raízes e o acúmulo de fitomassa do milheto, sendo indicado adubação a fim de melhorar o seu desempenho. Palavras-chave: Pennisetum glaucum, águas cinzas, dinâmica do crescimento, manejo de irrigação SILVA, J. R. I.; SOUZA, E.; LEITE, M. L. M. V.; BARROS JUNIOR, G.; LIMA, J. R. S; SALES, A. T. STRUCTURAL CHARACTERISTICS AND PHYTOMASS ACCUMULATION OF MILLET UNDER DIFFERENT IRRIGATION REGIMES WITH WASTEWATER AND ORGANIC FERTILIZATION 2 ABSTRACT The use of wastewater can increase the water and food supply in semi-arid regions. Thus, the objective was to study the temporal dynamics of structural characteristics and the accumulation of phytomass in millet irrigated with different depths of greywater, with and without organic fertilization. The research was conducted under greenhouse conditions in a factorial scheme (4 x 2) + 1 with three replications, the factors being levels of water available from the soil (25, 50, 75 and 100%) and manure doses (0 and 34 Mg ha-1), plus control treatment (irrigation with drinking water and without fertilization). It was performed weekly evaluations of structural characteristics: stem length and diameter, and number of tillers, total leaves, live leaves and dead leaves. Mathematical models were adjusted to describe the behavior of these characteristics throughout the cycle. After 60 days of the application of the treatments, millet was harvested and the accumulation of phytomass and root mass was determined. The sigmoidal model best explains the dynamics of most structural features. The irrigation with greywaters did not affect the structural characteristics, root mass and phytomass accumulation of millet, and fertilization is indicated to improve its performance. Keywords: Pennisetum glaucum, greywaters, growth dynamics, irrigation management

Microorganisms in the biological control of root-knot nematode: A metanalytical study

Nematodes can cause annual losses in the order of 100 billion dollars in crops worldwide. Its control using chemical nematicides proves to be quite aggressive to the environment. For this reason, the management of microorganisms has been promising. However, it is essential to know the control potential of each organism. Thus, the objective of this study was to verify the efficiency of different microorganisms in the biological control of Meloidogyne sp. A systematic review of the literature was carried out from 2000 to 2020 with the keywords “Meloidogyne and biology control", resulting in 659 articles, of which 51 were pre-selected and, after the more detailed evaluation, was selected ten published articles. These ten articles generated a total of 83 studies for meta-analyses. Each study included a treatment group using some microorganisms (bacteria, fungus, actinomycetes) for nematode biocontrol, a control group without using biocontrol agents. From this meta-analysis, we can observe that the use of microorganisms decreased the number of galls (42.05%), the number of eggs (57.77%), the gall index (28.58%) and the eggs mass (53.48%). The use of microorganisms was also positive in increasing root mass (832.89%). We can conclude that the use of microorganisms proved to be efficient in controlling nematodes M. javanica and M. incognita. The fungi Pleurotus ostreatus and Phanerochaete chrysosporium have more significant potential for biocontrol for these species.