Growth and root lignification of susceptible and glyphosate-resistant soybean

Glyphosate resistance is conferred to soybean (Glycine max L. Merril) by incorporating a gene encoding a glyphosate-insensitive enzyme (CP4-EPSP synthase) that acts in the shikimate/chorismate pathway, an important metabolic route in the lignification process. The aim of this work was to investigate the root growth and lignin contents of susceptible (CD 201 and OC 14) and glyphosate-resistant (CD 214RR and CD 213RR) soybean cultivars. To this end, three-day-old seedlings were cultivated in half-strength Hoagland nutrient solution (pH 6.0) in a growth chamber (25[degrees]C, 12-h photoperiod, irradiance of 280 [micro]mol [m.sup.-2] [s.sup.-1]) for 24 to 96 hours. The results revealed that glyphosate-resistant (CD 213RR and CD 214RR) cultivars showed high root growth when compared to the conventional (OC-14 and CD 201) cultivars. CD 213RR showed high root lignin content and reduced root weight compared to the conventional (OC 14) cultivar, although CD 214RR and CD 201 did not follow the same trend. Based on these results, it is possible to conclude that (1) the different form of EPSP synthase encoded in RR soybean may interfere in phenylpropanoid pathway and further in lignin biosynthesis, and (2) other genetic characteristics inherent to each cultivar may affect roots lignin content in soybean seedlings since lignification in CD 214 RR was not affected of similar manner than cultivar CD 213 RR. Keywords: glyphosate-resistant soybean, lignin, root growth, soybean. Crescimento e lignificacao de raizes de soja suscetivel e resistente ao glifosato. A resistencia ao glifosato e conferida a soja (Glycine max L. Merrill) pela incorporacao de um gene que codifica a enzima CP4-EPSP sintase, uma variante da EPSP sintase, insensivel ao glifosato, que atua na via do chiquimato/corismato, importante rota metabolica envolvida na lignificacao. O objetivo deste trabalho foi o de investigar o crescimento e os teores de lignina nas raizes de cultivares de soja, suscetiveis (CD 201 e OC 14) e resistentes (CD 214RR e CD 213RR) ao glifosato. Para isso, plantulas com tres dias de desenvolvimento foram cultivadas em solucao nutritiva de Hoagland, meia-forca (pH 6,0), em camara de crescimento (25[degrees]C, fotoperiodo de 12 h, irradiancia de 280 [micro]mol [m.sup.-2] [s.sup.-1]) de 24 a 96h. Os resultados revelaram que as cultivares resistentes ao glifosato (CD 213RR e CD 214RR) apresentaram elevado crescimento das raizes quando comparadas com as cultivares convencionais (OC-14 e