Characterization of the alfalfa pollen virome

Abstract Vertical transmission of plant pathogenic viruses is an important component of viral persistence, survival, and spread in agricultural production systems. This type of transmission is of considerable economic significance as it can cause major crop losses by serving as the initial focus of infection for future epidemics. Vertical transmission occurs when a virus is passed on to offspring either by direct invasion of the developing seed embryo from infected mother plants or through infected pollen grains after fertilization. We have recently demonstrated by high throughput sequencing that mature seeds of the agriculturally important forage crop alfalfa (Medicago sativa L.) are associated with a broad range of viruses some of which could potentially spread over long distances via seed. Aside from alfalfa mosaic virus, little is currently known about viral transmission via alfalfa pollen and its role in the epidemiology in this crop. This research was conducted to screen the pollen obtained from unique alfalfa genotypes for the presence of pathogenic viruses and their potential for dissemination. The plants from which the pollen was collected were alfalfa genotypes selected for fungal plant disease resistance and agronomic performance in a USDA ARS pre-breeding program in Prosser, WA. Competing Interest Statement The authors have declared no competing interest. List of abbreviations - AVS - alfalfa virus S - ACRV - alfalfa cytorhabdovirus - ANRV - alfalfa nucleorhabdovirus - BCV - beet cryptic virus - BLRV - bean leafroll virus - HTS - High-throughput sequencing - MsAV - Medicago sativa amalgavirus - MsAPV - Medicago sativa alphapartitivirus - NPGS - National Plant Germplasm System - PAPLV - pepper-associated picorna-like virus - PeSV - pea streak virus - RCVMV - red clover vein mosaic virus - SRAV - Snake River alfalfa virus - RT-PCR - reverse transcription-polymerase chain reaction