Germination of Crotalaria and Lupinus (Fabaceae) seeds submitted to different pre-germination treatments and their effect on enzymatic activity during early germination / Germinação de sementes de Crotalaria e Lupinus (Fabaceae) submetidas a diferentes tratamentos pré-germinativos e o efeito da atividade enzimática na fase inicial da germinação

Abstract Most of the wild and native legume seeds has a hard and impermeable testa, which causes physical dormancy and prevents them from germinating even when environmental conditions are favorable. The study evaluated the effect of scarification treatments on germination and enzymatic activity of Crotalaria longirostrata (Cl) and Lupinus exaltatus (Le) seeds. After scarification treatments, germination percentage (GP) and rate (GR) were assessed during 30 days after seeding (DAS); and water absorption (WA) and specific enzymatic activity (SEA) during early germination (0, 6, 18, 36, 72, 120 h) in a growing chamber at 25 °C and photoperiod of 12 h. Scarification with 98% H2SO4 15 min increased GP and GR in both species. At 30 DAS, GP and GR of Le seeds were 34% and 0.97 seeds day-1, respectively. In Cl seeds, GP was 64% and GR 0.90 seeds day-1. Scarification with H2O at 80 °C 1 min also promoted germination in Cl (52%). At 120 h after seeding, Le and Cl seeds showed already a high GP with acid scarification (31% and 48%, respectively). In seeds of both species, scarification treatments affected WA and SEA during early germination. During this period, scarification treatments that increased GP also showed a higher α-D-galactosidase activity. The maximum enzyme activity was observed 72 h after hot water scarification in Cl (82.6 U/mg total protein), followed by acid scarification (54.5 U/mg total protein). In Le, the activity peak was 36 h after acid scarification (9.5 U/mg total protein). No relationship was observed between β-glucosidase activity and GP in both species. In conclusion, during early germination of both species, the increase in GP is accompanied by a rise in α-D-galactosidase activity between 36 and 72 h after seeding; and in Cl seeds, an alternative scarification treatment to increase GP may be the use of hot water.

Resumo A maioria das sementes de leguminosas nativas e selvagens têm um tegumento rígido e impermeável, ​​o que causa dormência física e impede a germinação, mesmo se as condições ambientais forem favoráveis. O estudo avaliou o efeito de tratamentos de escarificação sobre a germinação e a atividade enzimática de sementes de Crotalaria longirostrata (Cl) e Lupinus exaltatus (Le). Após os tratamentos de escarificação, a percentagem (PG) e a velocidade de germinação (VG) foram avaliadas durante 30 dias após a semeadura (DAS); absorção de água (AA) e atividade enzimática específica (AEE) na fase inicial da germinação (0, 6, 18, 36, 72 e 120 h) em uma câmara de crescimento a 25 °C e fotoperíodo de 12 h. A escarificação com 98% de H2SO4, durante 15 min aumentou PG e VG nas duas espécies. Aos 30 DDS, PG e VG de sementes de Le foram de 34% e 0,97 sementes dia -1, respectivamente. Em sementes de Cl, PG foi de 64% e VG 0,90 sementes dias-1. A escarificação com H2O a 80 °C 1 min também promoveu a germinação em Cl (52%). A 120 h após a semeadura, as sementes de Cl e Le já tinha atingido uma alta PG com escarificação ácida (31% e 48%, respectivamente). Nas sementes das duas espécies, os tratamentos de escarificação afetaram a AEE e a AA nafase inicial da germinação. Durante este período, os tratamentos de escarificação que aumentaram PG, também mostraram a atividade mais elevada de α-D-galactosidase. A atividade enzimática máxima foi observada 72 h após o tratamento com água quente em Cl (82,6 U/mg de proteína total), seguido por escarificação ácida (54,5 U/mg de proteína total). Em Le, o pico de atividade foi de 36 h após a aplicação do tratamento ácido (9,5 U/mg de proteína total). Em contraste, não foi observado nenhuma relação entre a actividade β-glicosidase e PG. Em conclusão, durante a germinação precoce das duas espécies, o aumento da GP é acompanhado por um aumento da atividade da α-D-galactosidase entre 36 e 72 h após a semeadura; e em sementes de Cl, um tratamento de escarificação alternativo para aumentar GP pode ser o uso de água quente.

Prioritisation of native legume species for further evaluation as potential forage crops in water-limited agricultural systems in South Africa.

In the face of climate change, identification of forage species suitable for dryland farming under low rainfall conditions in South Africa is needed. Currently, there are only a limited number of forage species suitable for dryland farming under such conditions. The objective of this study was to identify and prioritise native legume species that could potentially be used in dryland farming systems in water-limited agro-ecosystems in South Africa. Using a combination of ecological niche modelling techniques, plant functional traits, and indigenous knowledge, 18 perennial herbaceous or stem-woody legume species were prioritised for further evaluation as potential fodder species within water-limited agricultural areas. These species will be evaluated further for their forage quality and their ability to survive and produce enough biomass under water limitation and poor edaphic conditions.

Soybeans inoculated with root zone soils of Canadian native legumes harbour diverse and novel Bradyrhizobium spp. that possess agricultural potential.

An assessment was made of the evolutionary relationships of soybean nodulating bacteria associated with legumes native to eastern Canada to identify potential new sources of soybean inoculant strains. Short season soybeans were used to selectively trap bacteria from root zone soils of four native legume species. Screening of more than 800 bacterial isolates from soybean root nodules by analysis of recA gene sequences followed by analyses of selected genotypes using six core and two symbiosis (nodC and nifH) gene sequences permitted identification of diverse taxa that included eight novel and four named Bradyrhizobium species as well as lineages attributed to the genera Afipia and Tardiphaga. Plant tests showed that symbionts related to four named species as well as a novel Bradyrhizobium lineage were highly efficient with regard to nitrogen fixation on soybeans relative to an inoculant strain. A new symbiovar (sv. septentrionalis) is proposed based on a group of four novel Bradyrhizobium spp. that possess distinctive nodC and nifH gene sequences and symbiotic characteristics. Evidence is provided for horizontal transfer of sv. septentrionalis symbiosis genes between novel Bradyrhizobium spp., a process that rendered recipient bacteria ineffective on soybeans. Diverse lineages of non-symbiotic and symbiotic Bradyrhizobium spp. co-occured within monophyletic clusters in a phylogenetic tree of concatenated core genes, suggesting that loss and/or gain of symbiosis genes has occurred in the evolutionary history of the bacterial genus. Our data suggest that symbiont populations associated with legumes native to eastern Canada harbour elite strains of Bradyrhizobium for soybean inoculation.

Germination of Crotalaria and Lupinus (Fabaceae) seeds submitted to different pre-germination treatments and their effect on enzymatic activity during early germination

Abstract Most of the wild and native legume seeds has a hard and impermeable testa, which causes physical dormancy and prevents them from germinating even when environmental conditions are favorable. The study evaluated the effect of scarification treatments on germination and enzymatic activity of Crotalaria longirostrata (Cl) and Lupinus exaltatus (Le) seeds. After scarification treatments, germination percentage (GP) and rate (GR) were assessed during 30 days after seeding (DAS); and water absorption (WA) and specific enzymatic activity (SEA) during early germination (0, 6, 18, 36, 72, 120 h) in a growing chamber at 25 °C and photoperiod of 12 h. Scarification with 98% H2SO4 15 min increased GP and GR in both species. At 30 DAS, GP and GR of Le seeds were 34% and 0.97 seeds day-1, respectively. In Cl seeds, GP was 64% and GR 0.90 seeds day-1. Scarification with H2O at 80 °C 1 min also promoted germination in Cl (52%). At 120 h after seeding, Le and Cl seeds showed already a high GP with acid scarification (31% and 48%, respectively). In seeds of both species, scarification treatments affected WA and SEA during early germination. During this period, scarification treatments that increased GP also showed a higher -D-galactosidase activity. The maximum enzyme activity was observed 72 h after hot water scarification in Cl (82.6 U/mg total protein), followed by acid scarification (54.5 U/mg total protein). In Le, the activity peak was 36 h after acid scarification (9.5 U/mg total protein). No relationship was observed between -glucosidase activity and GP in both species. In conclusion, during early germination of both species, the increase in GP is accompanied by a rise in -D-galactosidase activity between 36 and 72 h after seeding; and in Cl seeds, an alternative scarification treatment to increase GP may be the use of hot water.

Resumo A maioria das sementes de leguminosas nativas e selvagens têm um tegumento rígido e impermeável, o que causa dormência física e impede a germinação, mesmo se as condições ambientais forem favoráveis. O estudo avaliou o efeito de tratamentos de escarificação sobre a germinação e a atividade enzimática de sementes de Crotalaria longirostrata (Cl) e Lupinus exaltatus (Le). Após os tratamentos de escarificação, a percentagem (PG) e a velocidade de germinação (VG) foram avaliadas durante 30 dias após a semeadura (DAS); absorção de água (AA) e atividade enzimática específica (AEE) na fase inicial da germinação (0, 6, 18, 36, 72 e 120 h) em uma câmara de crescimento a 25 °C e fotoperíodo de 12 h. A escarificação com 98% de H2SO4, durante 15 min aumentou PG e VG nas duas espécies. Aos 30 DDS, PG e VG de sementes de Le foram de 34% e 0,97 sementes dia -1, respectivamente. Em sementes de Cl, PG foi de 64% e VG 0,90 sementes dias-1. A escarificação com H2O a 80 °C 1 min também promoveu a germinação em Cl (52%). A 120 h após a semeadura, as sementes de Cl e Le já tinha atingido uma alta PG com escarificação ácida (31% e 48%, respectivamente). Nas sementes das duas espécies, os tratamentos de escarificação afetaram a AEE e a AA nafase inicial da germinação. Durante este período, os tratamentos de escarificação que aumentaram PG, também mostraram a atividade mais elevada de -D-galactosidase. A atividade enzimática máxima foi observada 72 h após o tratamento com água quente em Cl (82,6 U/mg de proteína total), seguido por escarificação ácida (54,5 U/mg de proteína total). Em Le, o pico de atividade foi de 36 h após a aplicação do tratamento ácido (9,5 U/mg de proteína total). Em contraste, não foi observado nenhuma relação entre a actividade -glicosidase e PG. Em conclusão, durante a germinação precoce das duas espécies, o aumento da GP é acompanhado por um aumento da atividade da -D-galactosidase entre 36 e 72 h após a semeadura; e em sementes de Cl, um tratamento de escarificação alternativo para aumentar GP pode ser o uso de água quente.

Microevolution of symbiotic Bradyrhizobium populations associated with soybeans in east North America.

Microevolution and origins of Bradyrhizobium populations associated with soybeans at two field sites (A and B, 280 km apart in Canada) with contrasting histories of inoculation was investigated using probabilistic analyses of six core (housekeeping) gene sequences. These analyses supported division of 220 isolates in five lineages corresponding either to B. japonicum groups 1 and 1a or to one of three novel lineages within the genus Bradyrhizobium. None of the isolates from site A and about 20% from site B (the only site with a recent inoculation history) were attributed to inoculation sources. The data suggest that most isolates were of indigenous origin based on sequence analysis of 148 isolates of soybean-nodulating bacteria from native legumes (Amphicarpaea bracteata and Desmodium canadense). Isolates from D. canadense clustered with B. japonicum group 1, whereas those from A. bracteata were placed in two novel lineages encountered at soybean field sites. One of these novel lineages predominated at soybean sites and exhibited a significant clonal expansion likely reflecting selection by the plant host. Homologous recombination events detected in the 35 sequence types from soybean sites had an effect on genetic diversification that was approximately equal to mutation. Interlineage transfer of core genes was infrequent and mostly attributable to gyrB that had a history of frequent recombination. Symbiotic gene sequences (nodC and nifH) of isolates from soybean sites and native legumes clustered in two lineages corresponding to B. japonicum and B. elkani with the inheritance of these genes appearing predominantly by vertical transmission. The data suggest that soybean-nodulating bacteria associated with native legumes represent a novel source of ecologically adapted bacteria for soybean inoculation.