03474naa a2200217 a 450000100080000000500110000800800410001910000170006024501210007726000090019830000160020749000370022350001800026052024570044070000180289770000240291570000230293970000240296270000240298677302460301014668172007-07-27       2004    bl uuuu     u00u1 u    #d1 aCAPELETI, I.  aLignin of soybean (Glycine max (L.) Merrill) seed coat and their relatiosnhips with resistance to mechanical damage.  c2004  ap. 236-237.  a(Embrapa Soja. Documentos, 228).  aEditado por Flávio Moscardi, Clara Beatriz Hoffmann-Campo, Odilon Ferreira Saraiva, Paulo Roberto Galerani, Francisco Carlos Krzyzanowski, Mercedes Concordia Carrão-Panizzi.  aLignin is, second to cellulose, the most abundant organic compound in the terrestrial biosphere. It is a complex polymer of hydroxylated and methoxylated phenylpropane units, linked via oxidative coupling catalyzed by peroxidases. It is a major constituent of cell walls and provides to these cells rigidity for structural support and impermeability to water. There is considerable interest in the lignin since its deposition in the seed coat tissue provides mechanical resistance and also protects the cell against microorganisms. Mechanical damage is the most important factor that reduces soybean (Glycine max (L.) Merr.) seed quality at harvest and processing. In this context, the seed coat lignin content was found to be high in soybean cultivars with high index of resistance against mechanical damage. Using the gravimetric method, researchers of the EMBRAPA-Soja classified cultivars as follows: resistant (Doko, FT-2, Paraná and IAS-5); moderately resistant (Santa Rosa, IAC-8; Bossier and FT-10), and susceptible (Savana, Paranagoiana and Davis). It is known that many methods have been developed for the isolation of lignin and its quantitative determination, but there is no perfect method. Lignothioglycolic acid (LTGA) preparations have been considered as best suited for the isolation and quantitative assay of lignin. In this procedure, thioglycolic acid derivatization displaces lignin from its normal covalent attachments to the cell wall and enables it to be extracted from cell walls by alkali. Acidification of the alkaline extract precipitates LTGA. After being resolubilized, LTGA can be determined quantitatively by measuring its absorbance at 280 nm. Based on this methodology, the present work was carried out to determine the lignin content of seed coats of those cultivars, and to correlate the results with the index of seed mechanical damage resistance obtained by the pendulum test. The results showed that: 1. the adopted method may be used to quantify lignin in seed coats of different soybean cultivars, 2. a proportionality between lignin content and mechanical damage resistance was observed (r2 = 0.79), and 3. a lignin content in the seed coats above 0.36 g% is proposed to be a reasonable indicator of resistance against mechanical damage for soybean seeds. In conclusion, the present method may be used for screening genotypes for resistance to mechanical damage in a breeding program for soybean seed quality.1 aBONINI, E. A.1 aFERRARESE, M. L. L.1 aTEIXEIRA, A. C. N.1 aKRZYZANOWSKI, F. C.1 aFERRARESE FILHO, O.  tIn: WORLD SOYBEAN RESEARCH CONFERENCE, 7.; INTERNATIONAL SOYBEAN PROCESSING AND UTILIZATION CONFERENCE, 4.; CONGRESSO BRASILEIRO DE SOJA, 3., 2004, Foz do Iguassu. Abstracts of contributed papers and posters. Londrina: Embrapa Soybean, 2004.