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Dr. Maher Al Rwahnih

Maher Al Rwahnih was born in Jordan and received his Bachelor of Science degree in Plant Protection from the University of Jordan, Amman in 1994. He then worked for the Jordanian Ministry of Agriculture as a Plant Protection agent where he implemented integrated pest management and outreach programs for growers. He developed an interest in plant virology and earned a Master’s Degree in Plant Virology from the International Center for Advanced Mediterranean Agronomic Studies in Bari, Italy. His dissertation focused on the sanitary status of stone fruits in Jordan. He was the first to identify Sharka disease in Jordan and was involved in monitoring disease spread and the removal of all the Plum pox virus infected trees in the country. Continuing his work in Italy, he earned a PhD in Plant Virology from the University of Bari in 2004. Thereafter, he accepted a post-doctoral fellowship at the University of California-Davis where his research focused on fruit tree, nut tree, and grapevine viral diseases. In 2009, he was appointed to the position of assistant project scientist at the Department of Plant Pathology/Foundation Plant Services (FPS) at University of California-Davis.

While working at FPS, Dr. Al Rwahnih has implemented the application of a novel technology for the identification of viral diseases in grapevines and other crops. He has adapted the technology of Next Generation Sequencing (NGS) as a diagnostic technique for the characterization of the entire cohort of viruses infecting individual grapevines. Dr. Al Rwahnih was the lead author of the first publication to describe the application of NGS analysis to the census of the complete virome of an infected grapevine. The use of this technology has since spread across the grapevine industry. There have been more than 90 citations to his initial paper from world-wide sources since it was published in 2009 (Virology, 387:395–401). That work lead directly to the recent manuscripts in APS journals (described below).

NGS analysis is a laboratory procedure that requires relatively little time and expense to produce its comprehensive lists of all the pathogens present in infected vines. Dr. Al Rwahnih is the lead author of a manuscript (2015) “Comparison of Next Generation Sequencing vs. Biological Indexing for the Optimal Detection of Viral Pathogens in Grapevine” Phytopathology 105: 758-763. In this paper, he proposed a practical application of his 2009 work and suggested a modernization of the grapevine virus screening process for both quarantine and certification. This supports the proposition that classical diagnostic procedures be replaced by NGS analysis for registration and certification programs of clean-stock grapevine materials. This paper also documents the improvements to be realized and the savings of grower expense and time. It presents a two-year study that compares detection of grapevine viruses using the industry standard biological indexing panel versus the analysis of the same infected vines by NGS assay. The data clearly show that the NGS technique is more comprehensive, precise and accurate. Additionally, NGS is less costly in terms of materials, labor and land use than is the classical bioassay analysis. The data has been taken under appraisal by the regulatory agencies as they consider the possibility of incorporating this technology into the standard protocols for grapevine quarantine and clean stock certification.

Dr. Al Rwahnih has taken a lead in the characterization of NGS analysis as an improved diagnostic tool for the discovery of phytopathological viruses. He was the lead author of “Association of a DNA virus with Grapevines affected by Red Blotch disease in California” (Phytopathology 103:1069-76). In this 2013 manuscript, Dr. Al Rwahnih and his team characterize a leafroll-like infection of grapevines with red blotches along leaf margins and red veins under leaf surfaces, originally described in 2008. Red blotch disease is now of major concern to the grape growing industry due to its association with negative fruit quality. Dr. Al Rwahnih has used the DNA sequence data that was derived from his discovery of this virus to design a PCR probe specific for it. That probe has been used for field survey analysis of the distribution of this Grapevine red blotch-associated virus (GRBaV), which was shown to be widely distributed in the U.S. The data that was generated in this work has been part of the decision process whereby GRBaV will be added to the viruses on the certification list for California grapevines. Dr. Al Rwahnih has published a further study that showed that this virus is not an emerging threat, but is endemic in California. That study was published as: Al Rwahnih et al. (2015) “First Report of Grapevine red blotch-associated virus in Archival Grapevine Material from Sonoma County, California” Plant Disease 99: 895.

Dr. Al Rwahnih is pursuing a program to use biological observations to establish the agronomic relevance of NGS findings. Biological observations are needed to characterize the diseases that may be associated with viruses newly described by NGS analysis and to analyze the distributions and agronomic impact such newly described infections. Dr. Al Rwahnih is a participant in the regulatory process and is active in the California Department of Food and Agriculture Registration and Certification program and the U.S. National Clean Plant Network (NCPN). He serves as a Tier II member in the NCPN Fruit Trees and Roses sections. He has authored/coauthored more than 39 peer-reviewed research papers (nine of which appeared in APS journals). He has been an active member of APS: reviewing manuscripts, serving on the virology committee, and co-organizing the special session on NGS ‘Virus Fishing with Chips: Plant Virus Microarrays and Next Generation Sequencing’. He has presented more than 37 seminar and poster presentations at professional conferences and has given talks at more than 32 producer and technical meetings.