Dispersion of Potato Leafroll Virus and Potato Y Virus in Potato Seed Production Fields of Hamedan Province

Potato (Solanum tuberosum L.) is widely grown in different environments, forming the fourth largest crop in the world, with a production of almost 321 million metric tons. Seed potato degeneration, the reduction in yield or quality caused by an accumulation of pathogens and pests in planting material due to successive cycles of vegetative propagation, has been a long-standing production challenge for potato growers around the world. In developed countries this problem has been overcome by general access to and frequent use of the seed, produced by specialized growers, that has been certified to have pathogen and pest incidence below established thresholds, often referred to as certified seed. Potato leaf roll virus (PLRV) and potato virus Y (PVY) are the most important viruses infecting potato crops and also reduce the size as well as a number of potato tubers with annual global yield losses of up to 20 million tonnes. In Iran, PLRV and PVY are widely distributed in most potato-growing areas in Iran and have caused severe yield losses of up to 40 percent.This study was carried out to evaluate the amount of potato seed field’s infection to potato leaf roll virus and potato virus Y in different regions of Hamedan province and to survey the sensitivity of cultivars to studied viruses.

Leaf samples were prepared from potato seed field (S seed class) which has a 3-years rotation and 400 meters isolated distance from other potato growing fields. Studied potato seed fields were located in three regions of Hamedan province included: KaboodarAhang, Goltappe and Razan. These regions are the main potato production areas in Hamedan province of Iran. Leaf samples infection to potato leafroll virus and potato virus Y was determined by DAS-ELISA test using specific antiserum (Patho Screen Kit, supplied by Agdia Incorporated, USA) following the fundamental protocol outlined by Clark and Adams (1977) ELISA assay. The yield of all studied fields was determined after harvesting. Meteorological information of three seed production areas included average temperature, rainfall and wind speed was collected during the studied period.

Results showed that infected potato plants by both studied viruses (potato leaf roll virus and potato virus Y) were seen in KaboodarAhang region, while potato plants infected by studied viruses were not seen in the other regions (Goltappe and Razan). The probable cause of higher virus infection in KaboodarAhang region could be due to the wider migration of carriers and their greater activity in the region which had higher average temperature and rainfall than the other two studied areas. In Goltappe region which was diseases free, the temperature means and the amount of rainfall was lower than the other regions during the growth period. Maximum wind speed (25 m.s-1) in the infected region (KaboodarAhang) was higher than regions which were free of diseases (Goltappe and Razan). The wind blowing provides the possibility of transmission of viral infection by aphids (especially Myzus persicae) from neighbor infected fields.  However, portable flight capacity such as the aphid Myzus persicae may rarely exceed 100 meters, but Wind-assisted flight can carry aphids for several hundred kilometers. Therefore, what matters more than the isolated distance between potato seed production fields is the health of the seed production area and the speed and direction of the wind.Among studied cultivars, Agria and Arinda cvs. were infected by both studied viruses, while the other studied cultivars (Sante, Banba and jelly) were not infected.In Agria cv. and in the range of infection between 1 and 3%, the relationship between yield and potato plants infection to PLRV and PVY was not found, but in Arinda cv., the yield of virus (PLRV and PVY) free fields were much higher than those of infected by PLRV and PVY.

Since the Agria and Arinda cvs. were infected by potato leaf roll virus and potato virus Y, this can be concluded that these cultivars are sensitive to potato leafroll virus and potato virus Y. It seems Goltappe and Razan regions are suitable for potato seed production in Hamedan province. In the low range of viral infection, no logical relation was seen between potato plant’s yield and viral infection of plants. Among studied meteorological parameters, temperature mean and the amount of rainfall in the free of diseases region are lower than infected region.