RESISTANCE OF WILD NICOTIANA SPECIES TO DIFFERENT PVY ISOLATES

摘要

Veinal necrosis of tobacco leaves caused by Potato virus Y (PVY) is a disease of major economic importance. The appearance of new virus isolates, capable of breaking the resistance of tobacco, prompts the investigators to search for sources of resistance among wild species of the genus Nicotiana.A total of 96 entries, including 68 species, autotetraploid forms and botanical varieties were screened for resistance. The tests comprised six isolates which belonged to three groups, PVYNW, PVYNZ and PVYNTN, that differed for their serological characteristics and for their ability to break resistance from different sources. The plants were mechanically inoculated in the greenhouse. Records were taken of developing disease symptoms and DAS-ELISA tests were performed using two kinds of antibodies manufactured by Bioreba.The Nicotiana species varied extensively for their resistance to the isolates used. The highest number of resistant species was found within the section Paniculatae. Nicotiana raimondii, diploid and tetraploid forms of N. knightiana, as well as tetraploid N. glauca were found completely resistant. Nicotiana benavidesii, N. wigandioides and N. noctiflora were also highly resistant. Among the species of the subgenus Petunioides only N. africana showed resistance to all isolates. The other species became infested to various degree depending on the isolate used and they developed symptoms that varied in appearance and intensity.