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Genetic Transformation of Passionflower and Evaluation of R₁ and R₂ Generations for Resistance to Cowpea aphid borne mosaic virus

We report on the production and evaluation of passionflower transgenic lines for resistance to Cowpea aphid borne mosaic virus (CABMV). Genetic transformation was done using Agrobacterium tumefaciens and transgene integration was confirmed by Southern blot analyses, resulting in nine transgenic lines for ‘IAC 275’ and three for ‘IAC 277’. Transgenic lines were clonally propagated and evaluated for resistance to CABMV. After the third inoculation, under higher inoculum pressure, only propagated plants of the transgenic line T16 remained asymptomatic, indicating a high resistance to infection with CABMV. This transgenic line was self-pollinated and the R₁ generation was evaluated together with the R₁ generation of another resistant transgenic line (T2) identified previously. Plants were inoculated with CABMV by means of viruliferous Myzus nicotianae. All 524 T2R₁ plants became infected, whereas 13 of 279 T16R₁ remained asymptomatic after four successive inoculations. A T16R₂ generation was obtained and plants were inoculated with CABMV mechanically or by aphids. After successive inoculations, 118 of 258 plants were symptomless, suggesting that the resistance to CABMV was maintained in the plant genome as the homozygous condition was achieved. Five selected resistant T16R₂ plants which contained the capsid protein gene are being crossed for further analyses.