Tests for transmission of four potato viruses through potato true seed

The Andean potato calico strain of tobacco ringspot virus (TRSV-Ca) was detected in 2–9% of potato seedlings grown from true seed from plants of cv. Cara and clone G5998(6) infected with TRSV-Ca. Similarly, a potato isolate of the oca strain of arracacha virus B (AVB-O) was detected in 4–12% of progeny seedlings of cv. Cara and clone D42/8 infected with AVB-O. Potato virus T (PVT) passed through 33–59% of seed from PVT-infected cv. Cara, but only 0–2% infection was detected in seedlings from seed of PVT-infected clone D42/8. By contrast, no infection was detected in seedlings grown from seed from plants of G5998(6), D42/8 or cv. Cara infected with Andean potato latent virus strains Hu (APLV-Hu) or Caj (APLV-Caj), although both strains passed through seed of Nicotiana clevelandii. AVB-O, PVT and TRSV-Ca were detected in all tests of pollen from flowers of infected potato plants, but APLV-Hu and APLV-Caj were detected less frequently. AVB-O and PVT were transmitted through 2% and 8% respectively, of seed from healthy potato plants pollinated with pollen from infected plants. However, no transmission through seed was detected when pollen from TRSV-Ca infected plants was used. None of the four viruses were transmitted to healthy potato plants pollinated with pollen from infected plants. APLV-Hu caused exceptionally severe symptoms in the cv. Cara plants used for seed production, but the Bolivian strain of PVT induced only mild symptoms rather than the severe systemic necrosis previously reported for the type of strain of PVT in this cultivar. No symptoms developed in potato seedlings infected with TRSV-Ca, AVB-O or PVT through the seed.