TESTING RESISTANCE TO TSWV INTROGRESSED FROM LYCOPERSICON-PERUVIANUM BY ARTIFICIAL TRANSMISSION TECHNIQUES

Three lines of Lycopersicon esculentum (RDD, UPV 1 and UPV 32) with re sistance to TSWV introgressed from L. peruvianum have been tested. RDD is a carrier of the SW5 gene and the other two lines have been develo ped at the Universidad Politecnica de Valencia (UPV) from accessions c ollected in the Andean region. Two methods of artificial inoculation, mechanical and by Frankliniella occidentalis populations, and three hi ghly virulent Spanish isolates of TSWV have been used. Inoculation by populations of thrips proved to be more efficient than mechanical tran smission independently of the considered isolate. The three lines were completely resistant when mechanical transmission was used. Also RDD and UPV 1 showed high resistance levels by thrips inoculation method; the isolates had the same effect on these two genotypes. Nevertheless, UPV 32 shows a partial resistance depending on the isolate utilized. The inoculation of virulent isolates by thrips under a high pressure o f inoculum caused infection in a few plants of the three genotypes tes ted. In spite of being the most efficient at present for their unspeci ficity to isolates (and so the most used by breeders), resistance conf erred by SW5 does not guarantee the absence of infection depending on the prevailing crop conditions.