Co-inoculation of Bradyrhizobium japonicum and Azospirillum brasilense on the physiological quality of soybean seeds / Coinoculação de Bradyrhizobium japonicum e Azospirillum brasilense na qualidade fisiológica de sementes de soja

The success of the soybean crop depends on the physiological quality of seeds, which can be favored by beneficial microorganisms, however, it may be impaired by unfavorable environmental conditions. The aim of this study was to evaluate the effect of co-inoculation with Bradyrhizobium japonicum and Azospirillum brasilense on the physiological quality of soybean seeds obtained in the 2017/2018 crop season, from a field trial involving 23 cultivars submitted to co-inoculation (in-furrow) or without co-inoculation. Plants were assessed for nodulation at R1 and, after harvest at R8, seeds were assessed for concentration of proteins, mass of thousand seeds, and seed physiological quality [(Germination, emergence of seedlings in sand, and Emergence Speed Index (ESI)]. In the average of cultivars, the number of nodules per plant increased from 36.0 in the control to 44.4 nodules with co-inoculation. Increases in the concentration of proteins and in the mass of thousand seeds due to co-inoculation were 5.6% and 34.7%, respectively. Seeds originated from co-inoculated plants had higher germination rateat the first (50% vs. 45.3%) and at the final (87% vs. 79.8%) countings, in addition to higher rate of seedlings emergence in sand box (83.3% vs. 80%), and higher ESI (18.5 vs. 17.4). The benefits of co-inoculation were observed in 17 of 23 cultivars (74%) for at least two of the seven assessed variables. Considering only the minimal germination of 80%, the seeds originated from 10 non-inoculated cultivars could not be used, whereas for the co-inoculated plants this number fell to four.

O sucesso da cultura da soja depende da qualidade fisiológica das sementes, a qual pode ser favorecida por microrganismos benéficos, mas prejudicada por fatores ambientais desfavoráveis. O objetivo desse estudo foi avaliar o efeito da coinoculação com Bradyrhizobium japonicum e Azospirillum brasilense na qualidade fisiológica de sementes de soja obtidas na safra 2017/2018, em ensaio de campo com23 cultivares, submetidas à coinoculação via sulco de semeadura ou mantidas sem coinoculação. As plantas foram avaliadas quanto à nodulação em R1 e, após a colheita (R8), determinaram-se os teores de proteínas, massa de mil sementes e a qualidade fisiológica das sementes [Germinação, emergência em areia e índice de velocidade de emergência (IVE)]. Na média das cultivares, o número de nódulos aumentou de 36,9 no controle para 44,4 nódulos por planta com a coinoculação. Os aumentos nos teores de proteínas e na massa de mil sementes devido à coinoculação foram de 5,6% e 34,7%, respectivamente. As sementes das plantas coinoculadas apresentaram maior germinação na primeira contagem (50,0%vs. 45,3%) e na final (87,0% vs. 79,8%), além de maior taxa de emergência de plântulas em caixa de areia (83,3% vs. 80,0%) e maior IVE (18,5 vs. 17,4). Os benefícios da coinoculação foram observados em 17 das 23 das cultivares (74%), em pelo menos duas das sete variáveis avaliadas. Considerando apenas o critério de germinação mínima de 80%, as sementes de 10 cultivares não inoculadas não serviriam para uso, enquanto que para as coinoculadas esse número caiu para quatro.

Co-inoculation of Bradyrhizobium japonicum and Azospirillum brasilense on the physiological quality of soybean seeds / Coinoculação de Bradyrhizobium japonicum e Azospirillum brasilense na qualidade fisiológica de sementes de soja

The success of the soybean crop depends on the physiological quality of seeds, which can be favored by beneficial microorganisms, however, it may be impaired by unfavorable environmental conditions. The aim of this study was to evaluate the effect of co-inoculation with Bradyrhizobium japonicum and Azospirillum brasilense on the physiological quality of soybean seeds obtained in the 2017/2018 crop season, from a field trial involving 23 cultivars submitted to co-inoculation (in-furrow) or without co-inoculation. Plants were assessed for nodulation at R1 and, after harvest at R8, seeds were assessed for concentration of proteins, mass of thousand seeds, and seed physiological quality [(Germination, emergence of seedlings in sand, and Emergence Speed Index (ESI)]. In the average of cultivars, the number of nodules per plant increased from 36.0 in the control to 44.4 nodules with co-inoculation. Increases in the concentration of proteins and in the mass of thousand seeds due to co-inoculation were 5.6% and 34.7%, respectively. Seeds originated from co-inoculated plants had higher germination rateat the first (50% vs. 45.3%) and at the final (87% vs. 79.8%) countings, in addition to higher rate of seedlings emergence in sand box (83.3% vs. 80%), and higher ESI (18.5 vs. 17.4). The benefits of co-inoculation were observed in 17 of 23 cultivars (74%) for at least two of the seven assessed variables. Considering only the minimal germination of 80%, the seeds originated from 10 non-inoculated cultivars could not be used, whereas for the co-inoculated plants this number fell to four.(AU)

O sucesso da cultura da soja depende da qualidade fisiológica das sementes, a qual pode ser favorecida por microrganismos benéficos, mas prejudicada por fatores ambientais desfavoráveis. O objetivo desse estudo foi avaliar o efeito da coinoculação com Bradyrhizobium japonicum e Azospirillum brasilense na qualidade fisiológica de sementes de soja obtidas na safra 2017/2018, em ensaio de campo com23 cultivares, submetidas à coinoculação via sulco de semeadura ou mantidas sem coinoculação. As plantas foram avaliadas quanto à nodulação em R1 e, após a colheita (R8), determinaram-se os teores de proteínas, massa de mil sementes e a qualidade fisiológica das sementes [Germinação, emergência em areia e índice de velocidade de emergência (IVE)]. Na média das cultivares, o número de nódulos aumentou de 36,9 no controle para 44,4 nódulos por planta com a coinoculação. Os aumentos nos teores de proteínas e na massa de mil sementes devido à coinoculação foram de 5,6% e 34,7%, respectivamente. As sementes das plantas coinoculadas apresentaram maior germinação na primeira contagem (50,0%vs. 45,3%) e na final (87,0% vs. 79,8%), além de maior taxa de emergência de plântulas em caixa de areia (83,3% vs. 80,0%) e maior IVE (18,5 vs. 17,4). Os benefícios da coinoculação foram observados em 17 das 23 das cultivares (74%), em pelo menos duas das sete variáveis avaliadas. Considerando apenas o critério de germinação mínima de 80%, as sementes de 10 cultivares não inoculadas não serviriam para uso, enquanto que para as coinoculadas esse número caiu para quatro.(AU)

Azospirillum inoculation of Marandu palisade grass seeds: effects on forage production and nutritional status / Inoculação do Azospirillum em sementes de capim Marandu: efeitos na produção de forragem e estado nutricional

Plant-growth-promoting bacteria can be used for sustainable forage grass production while increasing nutrition and biomass. Most of the soils under pasture in the tropics have a degradation level that impairs the forage yield potential, especially because of mismanagement and lack of fertilization. The objective of this work was to evaluate the seed inoculation effects of Azospirillum brasilense on the shoot and root dry mass production and nutritional status of Urochloa brizantha cv. Marandu under field conditions for two years in a fertility soil. The experimental design was a randomized block design with four replications, arranged in a 2 × 3 factorial scheme, comprised of two doses of A. brasilense (0 and 200 mL ha-1) in combination with three doses of N (0, 25 and 50 kg ha-1). Seed inoculation increased shoot dry mass by 13% in the first year and by 6% in the second year, whereas N application increased dry mass by 27% and 35% in the first and second year, respectively. The concentration of nutrients in the shoots did not change due to the inoculation, but N fertilization affected P, Mg, Fe, Mn, and Zn in the first year and N, P and Cu in the second year. Root dry mass increased 36% with fertilization of 25 kg N ha-1 plus inoculation in relation to the other treatments in the first year. In the second year, the inoculation of A. brasilense increased by 17%. Therefore, seed inoculation of Urochloa brizantha cv. ‘Marandu with Azospirillum brasilense increased root and shoot dry mass production in some cuts without influencing tiller numbers. Nitrogen fertilization altered N, Mg, P, Fe, Mn, Zn, and Cu concentrations in shoot dry mass.(AU)

As bactérias promotoras de crescimento de plantas podem ser usadas para a produção sustentável de gramíneas forrageiras, aumentando a nutrição e a biomassa. A maioria dos solos sob pastagem nos trópicos apresenta um certo nível de degradação que prejudica o potencial de produção de forragem, principalmente por causa de má gestão e falta de fertilização. O objetivo deste trabalho foi avaliar os efeitos da inoculação de sementes de Azospirillum brasilense na produção de massa seca da parte aérea e da raiz e o estado nutricional do Urochloa brizantha cv. Marandu sob condições de campo por dois anos em um solo de de baixa fertilidade. O delineamento experimental foi em blocos casualizados com quatro repetições, dispostos em esquema fatorial 2 × 3, composto por duas doses de A. brasilense (0 e 200 mL ha-1) em combinação com três doses de N (0, 25 e 50 kg ha-1). A inoculação das sementes aumentou a massa seca da parte aérea em 13% no primeiro ano e em 6% no segundo ano, enquanto a aplicação de N aumentou 27% e 35% no primeiro e segundo ano, respectivamente. A concentração de nutrientes na parte aérea não foi alterada devido à inoculação, porém a adubação nitrogenada afetou P, Mg, Fe, Mn e Zn no primeiro ano e N, P e Cu no segundo ano. A massa seca da raiz aumentou 36% com a adubação de 25 kg N ha-1 combinado com a inoculação em relação aos demais tratamentos, no primeiro ano. No segundo ano, a inoculação de A. brasilense aumentou em 17%. Portanto, a inoculação de sementes de Urochloa brizantha cv. ‘Marandu com o Azospirillum brasilense aumentou a produção de massa seca da raiz e da parte aérea em alguns cortes sem influenciar o número de perfilhos. A adubação nitrogenada alterou as concentrações de N, Mg, P, Fe, Mn, Zn e Cu da massa seca da parte aérea.(AU)

Outstanding impact of soil tillage on the abundance of soil hydrolases revealed by a metagenomic approach

The soil represents the main source of novel biocatalysts and biomolecules of industrial relevance. We searched for hydrolases in silico in four shotgun metagenomes (4,079,223 sequences) obtained in a 13-year field trial carried out in southern Brazil, under the no-tillage (NT), or conventional tillage (CT) managements, with crop succession (CS, soybean/wheat), or crop rotation (CR, soybean/maize/wheat/lupine/oat). We identified 42,631 hydrolases belonging to five classes by comparing with the KEGG database, and 44,928 sequences by comparing with the NCBI-NR database. The abundance followed the order: lipases > laccases > cellulases > proteases > amylases > pectinases. Statistically significant differences were attributed to the tillage system, with the NT showing about five times more hydrolases than the CT system. The outstanding differences can be attributed to the management of crop residues, left on the soil surface in the NT, and mechanically broken and incorporated into the soil in the CT. Differences between the CS and the CR were slighter, 10% higher for the CS, but not statistically different. Most of the sequences belonged to fungi (Verticillium, and Colletotrichum for lipases and laccases, and Aspergillus for proteases), and to the archaea Sulfolobus acidocaldarius for amylases. Our results indicate that agricultural soils under conservative managements may represent a hotspot for bioprospection of hydrolases.(AU)

Water restriction and physiological traits in soybean genotypes contrasting for nitrogen fixation drought tolerance

Biological nitrogen fixation (BNF) is essential to the economic viability of the soybean [Glycine max (L.) Merrill] crop in Brazil, but drought may impair the BNF processes. We evaluated physiological traits of nitrogen fixation drought-tolerant (NFDT) (R01-581F, R01-416F and R02-1325) and drought-susceptible (CD 215 and BRS 317) genotypes of soybean subjected to drought or regular water supply between 45 and 55 days after emergence, in an experiment under greenhouse conditions in pots containing non-sterile soil. R01-581F had more stable photosynthetic and transpiration rates, and higher intercellular CO2 levels under drought. Drought reduced the chlorophyll concentration in all genotypes, but with less intensity in R01-581F and R02-1325. The NFDT genotypes generally showed higher concentrations of N, K and Mn in shoots, irrespective of the water condition. Exposure to drought increased total soluble sugars in nodules in all genotypes, as well as the concentrations of ureides in leaves and nodules, whereas ureides in petioles increased only in the susceptible genotypes. Drought negatively affected photosynthetic and BNF attributes; however, R01-581F showed the best performance, with potential for use in breeding programs aiming at drought-tolerant varieties.

Water restriction and physiological traits in soybean genotypes contrasting for nitrogen fixation drought tolerance

Biological nitrogen fixation (BNF) is essential to the economic viability of the soybean [Glycine max (L.) Merrill] crop in Brazil, but drought may impair the BNF processes. We evaluated physiological traits of nitrogen fixation drought-tolerant (NFDT) (R01-581F, R01-416F and R02-1325) and drought-susceptible (CD 215 and BRS 317) genotypes of soybean subjected to drought or regular water supply between 45 and 55 days after emergence, in an experiment under greenhouse conditions in pots containing non-sterile soil. R01-581F had more stable photosynthetic and transpiration rates, and higher intercellular CO2 levels under drought. Drought reduced the chlorophyll concentration in all genotypes, but with less intensity in R01-581F and R02-1325. The NFDT genotypes generally showed higher concentrations of N, K and Mn in shoots, irrespective of the water condition. Exposure to drought increased total soluble sugars in nodules in all genotypes, as well as the concentrations of ureides in leaves and nodules, whereas ureides in petioles increased only in the susceptible genotypes. Drought negatively affected photosynthetic and BNF attributes; however, R01-581F showed the best performance, with potential for use in breeding programs aiming at drought-tolerant varieties.(AU)

Reclamation status of a degraded pasture based on soil health indicators

Pasture degradation is a concern, especially in susceptible sandy soils for which strategies to recover them must be developed. Microbiological and biochemical soil health indicators are useful in the guindace of soil management practices and sustainable soil use. We assessed the success of threePanicum maximum Jacq. cultivars in the reclamation of a pasture in a sandy Typic Acrudox in the northwest of the state of Paraná, Brazil, based on soil health indicators. On a formerly degraded pasture withUrochloa brizantha (Hochst. ex A. Rich.) R.D. Webster, a trial with threeP. maximum (cv. Massai, Tanzânia, or Mombaça) was conducted. Lime and phosphate were applied at set-up, and mineral N and K as topdressing. A remnant of degraded pasture adjacent to the trial was used as control. Twenty-three chemical, physical, microbiological and biochemical attributes were assessed for the 0-10 cm topsoil. The procedures for reclamation improved most of the indicators of soil health in relation to the degraded pasture, such as soil P, mineral N, microbial biomass C, ammonification rate, dehydrogenase activity and acid phosphatase. CO2 evolution decreased, whereas microbial biomass C increased in the pasture under reclamation, resulting in a lower metabolic quotient (qCO2) that points to a decrease in metabolic stress of the microbial community. The reclamation of the pasture withP. maximum, especially cv. Mombaça, were evidenced by improvements in the microbiological and biochemical soil health indicators, showing a recovery of processes related to C, N and P cycling in the soil.

Reclamation status of a degraded pasture based on soil health indicators

Pasture degradation is a concern, especially in susceptible sandy soils for which strategies to recover them must be developed. Microbiological and biochemical soil health indicators are useful in the guindace of soil management practices and sustainable soil use. We assessed the success of threePanicum maximum Jacq. cultivars in the reclamation of a pasture in a sandy Typic Acrudox in the northwest of the state of Paraná, Brazil, based on soil health indicators. On a formerly degraded pasture withUrochloa brizantha (Hochst. ex A. Rich.) R.D. Webster, a trial with threeP. maximum (cv. Massai, Tanzânia, or Mombaça) was conducted. Lime and phosphate were applied at set-up, and mineral N and K as topdressing. A remnant of degraded pasture adjacent to the trial was used as control. Twenty-three chemical, physical, microbiological and biochemical attributes were assessed for the 0-10 cm topsoil. The procedures for reclamation improved most of the indicators of soil health in relation to the degraded pasture, such as soil P, mineral N, microbial biomass C, ammonification rate, dehydrogenase activity and acid phosphatase. CO2 evolution decreased, whereas microbial biomass C increased in the pasture under reclamation, resulting in a lower metabolic quotient (qCO2) that points to a decrease in metabolic stress of the microbial community. The reclamation of the pasture withP. maximum, especially cv. Mombaça, were evidenced by improvements in the microbiological and biochemical soil health indicators, showing a recovery of processes related to C, N and P cycling in the soil.(AU)

Azospirillum inoculation of Marandu palisade grass seeds: effects on forage production and nutritional status / Inoculação do Azospirillum em sementes de capim Marandu: efeitos na produção de forragem e estado nutricional

Plant-growth-promoting bacteria can be used for sustainable forage grass production while increasing nutrition and biomass. Most of the soils under pasture in the tropics have a degradation level that impairs the forage yield potential, especially because of mismanagement and lack of fertilization. The objective of this work was to evaluate the seed inoculation effects of Azospirillum brasilense on the shoot and root dry mass production and nutritional status of Urochloa brizantha cv. Marandu under field conditions for two years in a fertility soil. The experimental design was a randomized block design with four replications, arranged in a 2 × 3 factorial scheme, comprised of two doses of A. brasilense (0 and 200 mL ha-1) in combination with three doses of N (0, 25 and 50 kg ha-1). Seed inoculation increased shoot dry mass by 13% in the first year and by 6% in the second year, whereas N application increased dry mass by 27% and 35% in the first and second year, respectively. The concentration of nutrients in the shoots did not change due to the inoculation, but N fertilization affected P, Mg, Fe, Mn, and Zn in the first year and N, P and Cu in the second year. Root dry mass increased 36% with fertilization of 25 kg N ha-1 plus inoculation in relation to the other treatments in the first year. In the second year, the inoculation of A. brasilense increased by 17%. Therefore, seed inoculation of Urochloa brizantha cv. ‘Marandu’ with Azospirillum brasilense increased root and shoot dry mass production in some cuts without influencing tiller numbers. Nitrogen fertilization altered N, Mg, P, Fe, Mn, Zn, and Cu concentrations in shoot dry mass.

As bactérias promotoras de crescimento de plantas podem ser usadas para a produção sustentável de gramíneas forrageiras, aumentando a nutrição e a biomassa. A maioria dos solos sob pastagem nos trópicos apresenta um certo nível de degradação que prejudica o potencial de produção de forragem, principalmente por causa de má gestão e falta de fertilização. O objetivo deste trabalho foi avaliar os efeitos da inoculação de sementes de Azospirillum brasilense na produção de massa seca da parte aérea e da raiz e o estado nutricional do Urochloa brizantha cv. Marandu sob condições de campo por dois anos em um solo de de baixa fertilidade. O delineamento experimental foi em blocos casualizados com quatro repetições, dispostos em esquema fatorial 2 × 3, composto por duas doses de A. brasilense (0 e 200 mL ha-1) em combinação com três doses de N (0, 25 e 50 kg ha-1). A inoculação das sementes aumentou a massa seca da parte aérea em 13% no primeiro ano e em 6% no segundo ano, enquanto a aplicação de N aumentou 27% e 35% no primeiro e segundo ano, respectivamente. A concentração de nutrientes na parte aérea não foi alterada devido à inoculação, porém a adubação nitrogenada afetou P, Mg, Fe, Mn e Zn no primeiro ano e N, P e Cu no segundo ano. A massa seca da raiz aumentou 36% com a adubação de 25 kg N ha-1 combinado com a inoculação em relação aos demais tratamentos, no primeiro ano. No segundo ano, a inoculação de A. brasilense aumentou em 17%. Portanto, a inoculação de sementes de Urochloa brizantha cv. ‘Marandu’ com o Azospirillum brasilense aumentou a produção de massa seca da raiz e da parte aérea em alguns cortes sem influenciar o número de perfilhos. A adubação nitrogenada alterou as concentrações de N, Mg, P, Fe, Mn, Zn e Cu da massa seca da parte aérea.