Identified the factors that determine the seed transmission rate of plant viruses

More than 25% of all known plant viruses are transmitted through the seeds. This transmission mode allows viruses to persist for years over unfavorable conditions, and to disperse long distances even at a transcontinental scale. Consequently, seed transmission is central to understand disease emergence in crops and wild plants, which makes it of great biological, ecological and socio-economic relevance. However, current knowledge on the factors modulating seed transmission rate, and therefore the risk of seed transmitted viruses to start damaging epidemics, is very limited. Research conducted by Dr. Israel Pagán´s group has identified these factors using the plant viruses Turnip mosaic virus (TuMV) and Cucumber mosaic virus (CMV), and their natural host Arabidopsis thaliana, as model systems. In virus-infected A. thaliana plants, the researchers quantified the virus speed of within-host movement, its level of multiplication in plant growth and reproductive structures, and the effect of infection on seed production, seed germination rate and seed survival. Using advanced statistical methods, the authors analyzed how these factors explained the TuMV and CMV seed transmission rate, and the relative importance of each factor. Results showed that the faster the virus within-host movement (that is, the sooner the virus reaches the seeds) and the higher the virus multiplication in the reproductive structures (inflorescence, flowers and fruits), the higher the virus seed transmission rate. Other factors, such as the virus virulence and its effect on seed survival, played a secondary role in determining seed transmission rate. This wok provides novel insights on the mechanisms of seed transmission, which is a central but poorly understood aspect of plant-virus interactions. In addition, using the information derived from their work, the group of Dr. Pagán developed a mathematical model that accurately predicts the conditions in which the risk of seed transmission is higher. This tool could potentially contribute to develop more efficient control strategies of disease epidemics caused by seed transmitted viruses.