Improvement of soybean cultivars for natto production through the selection of seed morphological and physiological characteristics and seed compositions: A review

Natto, a traditional soyfood fermented by Bacillus subtilis (natto), is prepared by steaming/cooking of soaked soybean seeds followed by inoculation with the bacteria and incubation. Natto soybean has increased in popularity due to its nutritional value and health benefits. Thus, the natto soybean market provides additional opportunities for farmers. The development of soybean cultivars with improved natto quality characteristics is crucial for maintaining and increasing the natto soybean market. Good-quality characteristics of natto are determined by soybean cultivar, processing conditions and bacteria strain. Natto quality evaluation generally determined by sensory panels is time consuming. Therefore, indirect selection for natto quality based on seed traits is preferred. Seed morphological and physiological characteristics and seed compositions play an important role in producing natto of good quality. In this review, we have summarized natto processing conditions, natto quality characteristics, seed traits involved in natto quality and their genetic variation, as well as the genetic diversity in food-grade soybean germplasms and B. subtilis strains. Information presented will be helpful for natto soybean cultivar development and natto manufacture.