NOVEL RESISTANCES TO 4 POTYVIRUSES IN TUBER-BEARING POTATO SPECIES, AND TEMPERATURE-SENSITIVE EXPRESSION OF HYPERSENSITIVE RESISTANCE TO POTATO-VIRUS-Y

Novel potyvirus resistance specificities were found in eight tested wi ld potato species (clones): hypersensitive resistance (HR) to potato Y potyvirus (PVY) strain groups PVYO in Solanum megistacrolobum and S. polyadenium and PVYN in S. stoloniferum; HR to potato V potyvirus (PVV ) in S. maglia, S. polyadenium, S. stoloniferum, S. sparsipilum and S. sucrense, HR to potato A potyvirus (PVA) strain group 1 in S. sucrens e, and extreme resistance (ER) to PVA in S. polyadenium. S. commersoni i and S. stoloniferum expressed HR to tobacco etch potyvirus (TEV) whi ch has not been reported previously in potato species. The studied clo ne of S. stoloniferum expressed HR to all potyviruses and potyvirus st rains tested. The clone of S, stoloniferum (2n = 48; nuclear DNA conte nt (2C) = 3.6 pg) and S. chacoense (2n = 24; 2C = 1.9 pg) were crossed and one hybrid (2n = 36; 2C = 2.9 pg) was obtained. The hybrid expres sed HR to all tested potyviruses except PVA, which indicated that HR t o PVA was controlled gene which is different from the genes (or gene) controlling HR to PVYO, PVYN, PVV and TEV in S. stoloniferum. On the o ther hand, S. chacoense and the hybrid expressed ER to cucumber mosaic cucumovirus (CMV), whereas S. stoloniferum was susceptible to CMV. Al l tested wild species and the six tested potato cultivars (S. tuberosu m subsp. tuberosum) expressed HR to PVV. Expression of HR following in fection with PVYN induced systemic acquired resistance (SAR) in S. cha coense. HR to PVYN in S. sparsipilum and S. sucrense and to PVYO in po tato cv. Pito was efficiently expressed at lower temperatures (16/18 d egrees C) indicated by the development of distinct necrotic lesions an d/or vein necrosis in inoculated leaves, whereas the HR was rendered l ess effective at higher temperatures (19/24 degrees C) which was indic ated by the development of systemic infection with leaf-drop and mosai c symptoms.