The influence of peanut stunt virus infection on black soybean seed quality

Some viruses, including the peanut stunt virus (PSV), have been reported to cause mottling of the soybean seed coat. In addition, the seed coat pigmentation phenomenon in yellow soybean has been reported to occur via spontaneous mutation of the I gene, which inhibits seed coat pigmentation by environmental factors such as chilling temperature. The pigmented seeds frequently show multiple defective cracks in the seed coat. Senda et al. (2017) suggested that lignin deposition might affect the physical properties of buff seed coats and lead to defective cracking. In this study, the incidence of seed coat mottling depended on PSV infection, as previously reported, and lignin accumulation in the mottled parts of the seed coat was assessed using phloroglucinol-HCl reagent for histological analysis. PSV was detected in the mottled parts of the immature seed coat. The infectious PSV was also present when the soybeans (Enrei) were inoculated with sap from the mottled parts of the immature seed coat. These results suggest that PSV infection is closely related to the mottling and cracking of the soybean seed coat.