RELATIONSHIP BETWEEN SOYBEAN SEED COAT LIGNIN CONTENT AND RESISTANCE TO MECHANICAL DAMAGE

Mechanical damage is the most important factor that reduces soybean se ed quality at harvest and processing. Careful handling of the seed dur ing those phases may prevent the occurrence of mechanical injury. Some cultivars have shown certain genetic resistance to mechanical abuse, which is a desirable characteristic for seed quality. The causes of me chanical damage as well the procedures to evaluate it are well known. The objective of this research was to investigate the genetic mechanis m of the observed resistance to mechanical damage so that soybean bree ders may screen for the character. Twelve cultivars of known performan ce related to mechanical damage were used: resistant - Doko, FT-2, IAS -5 and Parana: moderately resistant - Santa Rosa, IAC-8, FT-10 and Bos sier; susceptible - Davis, Paranagoiana, Savana and IAC-2. Lignin cont ent of the seed coat was determined and its results correlated with th e index of resistance to seed mechanical damage obtained by the pendul um rest. The coefficient of determination (r(2)) between these two par ameters was 0.90, which was highly significant, meaning that the highe r the level of lignin content in the seed coat, the higher the level o f resistance to mechanical damage. These results directly implicate li gnin content of the seedcoat as the genetic trait that should be used to screen for genotypes that will resist to mechanical damage.