Molecular, Cultural and Pathogenic Characterization of Neopestalotiopsis rosae from Strawberry in Mexico

Leaf spot and crown rot caused by Neopestalotiopsis spp. are relevant emerging diseases of strawberries worldwide. This study aimed to: i) identify and characterize isolates of Neopestalotiopsis spp. recovered from different strawberry plant organs; ii) determine the pathogenic variation of those isolates; and iii) determine the response of 13 strawberry varieties against N. rosae. Four hundred ninety-eight isolates were obtained from leaves, roots and crowns of strawberry in central Mexico from 2020 to 2021. A subsample of 160 isolates was selected for characterization using a previously developed High-Resolution Melting (HRM) assay. The incubation period (IC) and the time to reach 100% leaf severity (LS) on a strawberry variety was recorded. Twenty-six isolates were further identified by multilocus phylogenetic analysis (MLPA) based on ITS, tef1 and β-tubulin tub2 partial genes along with morphological characterization. The response of 13 varieties to detached leaflet inoculation was assessed. Aggressive isolates (11%) had a 12-h IC and reached 100% severity between 6-7 days after inoculation, whereas moderately aggressive isolates (57%) had a 24-h IC lasting 8-10 d, and low-aggressive isolates (32%) with IC longer than 48 h took 11-14 d. HRM results showed 159 of 160 isolates were N. rosae and one Neopestalotiopsis sp. MLPA reveled 22 of the isolates of N. rosae, 1 Neopestalotiospsis spp., 1 Pestalotiopsis sp., and 2 related to N. iranensis. Marisol was the least susceptible whereas Fortuna Albion, Festival and Fronteras were the most susceptible. These findings will aid in developing effective management strategies and contribute to breeding resistant varieties.