Biological nitrogen fixation in soybean under water restriction and exposed to 1-methylcyclopropene

Abstract

-The objective of this work was to assess the effects of 1-methylcyclopropene (1-MCP) on traits related with biological nitrogen fixation on 'BRS 268' soybean (Glycine max) subjected to water restriction. Plants were either exposed to drought between 32 (R 2 ) and 47 (R 3 ) days after sowing (DAS) or kept well-watered, in combination with exposure or not to 1-MCP. On the second day under drought (34 DAS), plants from both water conditions were exposed to 1-MCP in a hermetically sealed chamber for 15 hours. Control plants, dry or well-watered, that were not exposed to 1-MCP were kept in a separate chamber. At 36 (R 2 ) and 47 (R 3 ) DAS, shoot and root dry weights, leaf area index, number and dry weight of nodules, total ureides in sap, and N concentration in leaves were assessed. From 47 DAS on, extra plants were well watered until physiological maturity (R 8 ) and assessed for yield components. Water restriction increased ureides in sap and reduced N in leaves in R 2 ; reduced the number and mass of nodules, shoot dry weight, and leaf area index in R 3 ; and reduced the number of pods and seed mass of plants not exposed to 1-MCP. However, when plants are exposed to 1-MCP, there is an attenuation of water restriction effects.Index terms: Bradyrhizobium, Glycine max, inhibitor of ethylene, nodulation, water stress. Fixação biológica do nitrogênio em soja sob restrição hídrica e exposta ao 1-metilciclopropenoResumo -O objetivo deste trabalho foi avaliar os efeitos do 1-metilciclopropeno (1-MCP) em parâmetros relacionados à fixação biológica de nitrogênio em soja (Glycine max) 'BRS 268' submetida à restrição hídrica. As plantas foram submetidas à seca entre 32 (R 2 ) e 47 (R 3 ) dias após a semeadura (DAS) ou mantidas bem irrigadas, em combinação com exposição ou não ao 1-MCP. No segundo dia sob seca (34 DAS), as plantas de ambas as condições hídricas foram expostas ao 1-MCP em câmara hermeticamente fechada por 15 horas. As plantas-controle, sob restrição hídrica ou bem irrigadas, não expostas ao 1-MCP foram mantidas em câmara separada. Aos 36 (R 2 ) e 47 (R 3 ) DAS, foram avaliados massa seca da parte aérea e das raízes, índice de área foliar, número e massa seca de nódulos, ureídos totais na seiva e concentração de N foliar. A partir dos 47 DAS, as plantas remanescentes foram mantidas bem irrigadas até a maturação fisiológica (R 8 ) e os componentes de produção foram avaliados. A restrição hídrica aumentou os ureídos na seiva e reduziu o N foliar em R 2 ; reduziu o número e a massa de nódulos, a massa seca da parte aérea e o índice de área foliar em R 3 ; e reduziu o número de vagens e a massa de sementes em plantas sem exposição ao 1-MCP. No entanto, quando as plantas são expostas ao 1-MCP, há atenuação do efeito da restrição hídrica.Termos para indexação: Bradyrhizobium, Glycine max, inibidores de etileno, nodulação, estresse hídrico.

Genetic Analysis and Mapping of QTLs for Soybean Biological Nitrogen Fixation Traits Under Varied Field Conditions

“…Beyond rhizobial species, BNF capacity has also been associated with soil characteristics, such as high soil nitrate levels, which tend to reduce nitrogen fixation capacity (Nohara et al, 2005; Yang et al, 2009), and low available phosphorus, which not only limits legume growth, but also inhibits BNF capacity (Adelson et al, 2000; Ward, 2011). Furthermore, water stress also appears to affect BNF capacity (Nascimento et al, 2016; Jemo et al, 2017). In short, BNF is a complex process that is affected by host and symbiotic genotypes, along with the context of environmental conditions in which the symbiosis occurs.…”