Tracking Foliar Symptoms Caused by Tuber-Borne Potato Yellow Vein Virus (PYVV) in Solanum Phureja (Juz et Buk) Cultivar “Criolla Colombia”

Abstract

Potato yellow vein virus (PYVV) causes vein yellowing in leaves and reduces potato yield by 50 %. In Andigena potato varieties, PYVV infections result in both symptomatic (S) and symptomless (NS) plants. The present study tracked PYVD symptoms over two field generations (G1 and G2) derived from mother plants (G0) of the Solanum phureja cultivar “Criolla Colombia.” PYVV was detected in the leaves of G0 plants by RT-PCR. The experiment began with tubers of 39 S plants from a commercial crop and 94 certified NS plants (PLRV, PVY, PVX, PVS free), yielding a total of 3561 plants analyzed over the two generations. The greenhouse whitefly vector Trialeurodes vaporarioum was controlled chemically. S plants produced large proportions of NS plants, 62 % and 84 % in G1 and G2, respectively. NS plants, whether RT-PCR positive or negative, generated greater than 96 % NS plants, but in some cases, produced a proportion of S plants ranging between 0.2 % and 3.4 %. The presence of PYVV was evaluated by RT-PCR and qPCR with Taqman probes in sprouts of the tubers of S and NS plants. One to 6 sprouts were analyzed per tuber. In 113 sprouts of the tubers of S RT-PCR positive/ negative plants and 36 of NS RT-PCR positive/negative plants, the viral RNA copies ranged between 3.42 × 102 to 6.01 × 108 copies/mg of plant extract. These results show that PYVV is present not only in symptomatic plants but also in some symptomless plants. PYVV is passed from symptomless mother plants to some of its tubers along with unknown putative silencing or latency mechanisms that prevent the virus from expressing in most of the infected progeny. Late vector transmission, heterogeneous viral concentration in tubers and virus latency are also discussed.