Host-Associated Distribution and Mycological Characteristics of Fusarium sambucinum Species Complex and Other Fusarium Species in Rice, Maize, and Weeds in Korea.

Fusarium asiaticum and Fusarium graminearum, belonging to the Fusarium sambucinum species complex (FSAMSC), are primary causal agents of Fusarium head blight (FHB) and associated mycotoxin contamination in cereal crops worldwide. In this study, we performed a nationwide survey of Fusarium populations in rice, a staple crop in Korea, and examined the distribution of trichothecene genotypes and the mycological characteristics of dominant species. A total of 1,008 Fusarium isolates were obtained from rice (375) and plants surrounding rice paddy fields, including maize (133) and gramineous weeds (500). FSAMSC members accounted for the majority (59-70%) of Fusarium isolates from the three plants, with F. asiaticum predominating in both rice (57%) and weeds (44%), whereas F. graminearum was dominant in maize (41%). Trichothecene genotype analysis revealed that the nivalenol (NIV) type of F. asiaticum predominated in rice (82%) and weeds (70%), whereas the 15-acetyldeoxynivalenol (15ADON) type of F. graminearum was more common in maize (83%). A comparison of the mycological traits of two dominant species highlighted that F. asiaticum NIV type strains exhibited significantly higher pathogenicity in rice than F. graminearum 15ADON type strains (P = 0.01), despite lower growth and reproductive capacity (P < 0.05). By integrating this largescale distribution survey with mycological analyses, we showed that F. asiaticum is a major contributor to FHB and trichothecene risks in the rice cultivation system in Korea.