The use of rhizobium and mycorrhizae in soil containing rhizobiophage to improve growth and nodulation of cowpea

The interaction between leguminous plants and rhizosphere microorganisms is essential because it can either enhance or inhibit the beneficial effects of individual species. Phages are one of the biotic factors with a negative impact on the beneficial bacteria in soil rhizosphere. In the current study, phage showed lytic activity against Bradyrhizobium sp. Vigna (tal16) with an icosahedral head at a 43.44 nm diameter and a long non-contractile tail, measuring 99.85 nm. This phage belongs to the Siphoviridae family, found in the Met El-Ez area of Dakalia Governorate in Egypt. The results revealed that the presence of phage in soil affected nodulation and growth parameters. Mycorrhizal inoculation aggravated the negative effects of this phage. Cowpea grown in soil containing phage VB_BrV_SD4 showed a reduction in the nodule number, nitrogenase activity, and total N of 40-50 %; however, mycorrhizal inoculation augmented this negative effect with a reduction percentage to 20-28 %. Mycorrhizal inoculation also improved total chlorophyll, carotenoids, legume amount, and the seed protein content.

Seed size influences the promoting activity of rhizobia on plant growth, nodulation and N fixation in lima bean / O tamanho da semente influencia a atividade promotora dos rizóbios sobre o crescimento de plantas, nodulação e fixação de N em feijão-fava

This study evaluated the activity of rhizobia isolates inoculated in large (18 mm) and small (11 mm) seeds on lima bean growth, nodulation and N fixation. Selected rhizobia isolates were compared with a reference strain CIAT899 and two controls without inoculation. Large seeds contributed for highest plant growth, nodulation and N fixation than small seeds. The isolates UFPI-59, UFPI-18 and UFPI-38 promoted the highest values of shoot and root dry weight, respectively. The isolates UFPI-32 promoted the highest values of nodule number, while UFPI-59 promoted the highest values of nodule dry weight. The isolates UFPI-38 and UFPI-59 promoted the highest accumulation of N. This study showed that seed size really influences lima bean growth, nodulation and BNF. Considering rhizobia isolates, UFPI-59, UFPI-38, and UFPI-18 contributed for plant growth, promoted better nodulation and effectiveness on biological N fixation.(AU)

Este estudo avaliou a atividade de isolados de rizóbios inoculados em sementes pequenas (11 mm) e grandes (18 mm) sobre o crescimento, nodulação e fixação de N de feijão-fava. Isolados selecionados de rizóbios foram comparados com uma estirpe de referência CIAT899 e dois controles sem inoculação. Sementes grandes contribuíram para maior crescimento de plantas, nodulação e fixação de N do que sementes pequenas. Os isolados UFPI-59, UFPI-18 e UFPI-38 promoveram os maiores valores de massa seca de parte aérea e raízes. Os isolados UFPI-32 e UFPI-59 promoveram os maiores valores de número e massa de nódulos, respectivamente. Os isolados UFPI-38 e UFPI-59 promoveram maior acúmulo de N. Este estudo mostrou que o tamanho de sementes influencia o crescimento, nodulação e fixação de N em feijão-fava. Considerando os isolados de rizóbios, UFPI-59, UFPI-38 e UFPI-18 contribuíram para o crescimento de plantas, promoveram melhor nodulação e eficiência na fixação de N.(AU)

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)

Stimulation of adhesiveness, infectivity, and competitiveness for nodulation of Bradyrhizobium japonicum by its pretreatment with soybean seed lectin.

Soybean seed lectin stimulates adsorption of Bradyrhizobium japonicum to its host roots. Pretreatment of the rhizobia with soybean seed lectin for at least 6-12 h previous to their interaction with the plants was required to detect the stimulatory effect. This activity could be observed with as few as 1000 soybean seed lectin molecules per bacterium, and required specific carbohydrate binding. Infectivity and competitiveness for nodulation were also stimulated by preincubation of the rhizobia either with soybean seed meal extract or soybean seed lectin, the extract being more effective in enhancing competitiveness.