PVY efficiency of autoinfection of two potato (Solanum tuberosum L.) varieties, INIAP-Fripapa and Superchola, and its relationship with temperature and virus concentration in the Ecuadorian Andes

Potato (Solanum tuberosum L.) is the world's third most important food crop. Majority of the world's potato production occurs in developing countries, where instead of purchasing certified seed with lower incidences of potato virus Y (PVY) infection, smallholder potato farmers save a portion of their harvest for planting in subsequent seasons. This practice leaves seed stocks vulnerable to seed degeneration, defined as an increase in pest and/or pathogen incidence or severity associated with reduction of yield or quality of seed tubers over successive cycles of vegetative propagation. Efficiency of autoinfection is defined as the percentage of progeny tubers infected with the same virus as their virus-infected seed tuber, and was thought to be a main driver of seed degeneration in the Andean region of South America. This study seeks to quantify the PVY efficiency of autoinfection of two potato varieties, INIAP-Fripapa and Superchola, at altitudes 2468, 3050 and 3507 meters above sea level (masl) in the Ecuadorian Andes; while also determining the relationship between seed tuber virus concentration and efficiency of autoinfection. Seed tubers of each variety, one treatment infected with PVY and one free of virus as determined by DAS-ELISA, were planted at each of the three attitudes under 0.4 x 0.8 mm anti-aphid netting. Field plots were planted between February and March 2015 and harvested between July and August 2015. Absorbance of dried leaf samples homogenized at a 1:10 dilution by weight with extraction buffer were analyzed using a Tecan Sunrise(TM) microplate reader at 405 nm wavelength to estimate the virus concentration (ng mL-1). A field experiment was carried out as a randomized complete block design with altitudes representing blocks. A greenhouse experiment was carried out as a completely randomized design with 4 treatments and 15 replications. Neither PVY efficiency of autoinfection (p<0.96) nor tuber count (p<0.17) were significantly different at any of the three sites, but at altitude 3050 masl, tuber weight was significantly lower at 3050 masl (p<0.02). Treatment INIAP-Fripapa: PVY+ had a significantly higher efficiency of autoinfection in both the field and greenhouse experiments (75.29 and 83.29%, respectively) compared to the INIAP-Fripapa: PVY- treatment and both the PVY- and PVY+ Superchola treatments (p<0.0001). Superchola had a significantly higher per plant tuber count in both the field and greenhouse experiments (32 and 34 tubers, respectively) than the INIAP-Fripapa treatments (p<0.0001). In conclusion, PVY efficiency of autoinfection was affected by potato variety and virus status and not by temperature differences observed between 2468 and 3507 masl in the Ecuadorian Andes.