Importance of the lignin content in the pod wall and seed coat on soybean seed physiological and health performances

The effects of lignin on soybean seed quality have been studied since the early 1990s. Initially, higher lignin content in the seed coat was associated with greater resistance to mechanical damage by the seeds. Later, positive relationships of lignin content in the seed coat were associated with tolerance to stresses caused by weathering in pre-harvest, resulting in improved seed quality. Additional studies have shown that higher lignin content in the pod wall of soybean is also related to production of seeds with high physiological and sanitary qualities. Colored soybean seeds (black or brown) are known to have higher seed quality due to higher lignin content in the seed coat; in addition, the presence of anthocyanin in the seed coat of colored seeds also contributes to improve seed quality. Finally, the effects of boron on lignin synthesis are also highlighted in this review article. As demonstrated in this review article, lignin content in the seed coat and pod wall of soybean plays an important role in relation to physical, health, and physiological seed qualities. These parameters should be considered in studies related to evaluation of the quality of soybean seeds as affected by genetic factors. These parameters should also be strongly considered for inclusion in breeding programs to improve soybean seed and grain quality.