First Detection of the Perithecial Stage of Eutypa lata in Chilean Vineyards

The sexual stage of Eutypa lata, the causal agent of Eutypa dieback of grapevine, has not been documented previously in Chile, limiting understanding of its epidemiology and disease cycle in this region. The objective of this study was to investigate the occurrence of E. lata perithecia in Chilean vineyards and to confirm the pathogenicity of ascospores. Between 2022 and 2025, surveys were conducted in 36 commercial vineyards in the Maule Region, and perithecia of E. lata were detected on dead grapevine wood in one vineyard. Morphological characterization revealed globose black perithecia containing cylindrical, long-stalked asci and allantoid, hyaline, aseptate ascospores typical of E. lata. Molecular analyses based on ITS and β-tubulin sequences confirmed the identity of isolates obtained from ascospores. Ascospore discharge from perithecia was observed under moist laboratory conditions, and pathogenicity was evaluated under greenhouse and field conditions. In both assays, ascospores induced necrotic lesions in grapevine wood, and the pathogen was successfully reisolated and reidentified, fulfilling Koch’s postulates. The detection of perithecia and the completion of Koch’s postulates using ascospores provide evidence that E. lata completes its sexual cycle in Chilean vineyards and demonstrate that ascospores produced from naturally occurring perithecia are pathogenic to grapevine. These findings have important implications for disease management, particularly highlighting the need to protect pruning wounds during periods favorable for ascospore release.