Assessment of pear decline prevalence and phytoplasma infection in major commercial orchards of Al-Mafraq, Jordan

Authors: ABU ALLOUSH, ASEM - National Center For Agricultural Research And Extension (NCARTT); Bottner-Parker, Kristi; QUAGLINO, FABIO - University Of Milan; Wei, Wei

Submitted to: Phytopathogenic Mollicutes
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/15/2024
Publication Date: 3/5/2025
Citation: Abu Alloush, A.H., Bottner-Parker, K.D., Quaglino, F., Wei, W. 2025. Assessment of pear decline prevalence and phytoplasma infection in major commercial orchards of Al-Mafraq, Jordan. Phytopathogenic Mollicutes. 15(1):71-72. https://doi.org/10.5958/2249-4677.2025.00040.4.
DOI: https://doi.org/10.5958/2249-4677.2025.00040.4

Interpretive Summary: Pear decline (PD) is a severe disease caused by a phytoplasma, a small bacterium that harms pear trees by causing curled leaves, stunted growth, and reduced fruit yields. This disease presents a significant threat to pear production, potentially leading to major economic losses for farmers if left unmanaged. In 2023, ARS scientists in Beltsville, Maryland, in collaboration with Jordanian researchers, conducted a survey in commercial pear orchards across Al-Mafraq, Jordan, to assess the spread of PD. Typical PD symptoms were observed in 70%-95% of trees across four locations. Among the 213 samples collected (200 from diseased trees and 13 from healthy ones), a molecular diagnosis called nested PCR confirmed infection in all symptomatic trees, while healthy trees showed no infection. This study highlights the need for improved PD management strategies, including further research, enhanced monitoring, and the development of resistant pear varieties. The findings benefit plant scientists, breeders, farmers, and policymakers working to reduce PD’s impact on pear production globally.

Technical Abstract: Pear decline (PD), associated with 'Candidatus Phytoplasma pyri' (16SrX-C), is one of the most destructive phytoplasma diseases globally. In 2023, a four-month-long survey was conducted in commercial pear orchards across the Al-Mafraq region, Jordan. PD-like symptoms, including leaf curling, reddening, and stunted growth, were observed, with a disease incidence ranging from 70% to 95%. A total of 200 symptomatic and 13 asymptomatic samples were collected from pear trees in four locations. Molecular detection using nested PCR with specific primers targeting the 16SrX group revealed a 100% infection rate in all tested symptomatic samples. No infection was detected in asymptomatic samples. The results highlight the widespread presence of 'Ca. P. pyri' in commercial pear orchards in Al-Mafraq, indicating the need for further molecular characterization and the development of management strategies to mitigate the disease's impact.