IMPROVEMENT OF FUNGAL DISEASE TOLERANCE IN TOMATO PLANTS, USING GENE TRANSFER TECHNOLOGY

Abstract

Tomato yield is severely affected by Fusarium fungal disease. In order to investigate the influence of the genetic background on fungal resistance, 30-day old seedlings from four tomato cultivars (namely; Pomodora, Castle Rock, Super strain B, and Red star) were subjected to artificial infection with Fusarium oxysporum lycopersici sp. The data showed that the cultivars differ genetically for their response to fungal resistance. Based on fusarium specific ITS marker early diagnosis of fungal infection was detected. The disease severity data indicate that the cultivar Castle rock proved to be tolerant to Fusarium infection followed by the cv. Pomodora. Plant defense enzymes were increased under fungal infection. The regeneration capacity among the tested cultivars was investigated. The data indicate that, embryogenic calli were formed within 7 days in MS medium containing 1 mgl-1 2,4-D. Adventitious shoots emerged from the embryonic calli in the presence of 2 mgl-1 BA. Shoot regeneration frequencies varied between tomato cultivars according to their genetic makeup. Regeneration frequency was higher in the cultivar Pomodora 48% compared with the other cultivars tested. The optimum condition of transformation was determined for the cultivars CastleRock and Super Strain B. The hypocotyl explants isolated from both cultivars were co-cultivated with A. tumefaciens strain LBA4404 harboring a binary vector pBI-121 containing the neomycin phosphotransferase-II gene (npt-II). The successful integration of the transgene was confirmed by PCR analyses. The gus gene expression can be detected only in the transgenic plants. To improve fungal resistance, cultivars Castle Rock and Super Strain B were transformed with E.coli katE genes. The transformation efficiency was 5.6 and 3.5% for cultivars Castle Rock and Super Strain B , respectively. PCR and DNA Dot blot techniques confirmed the integration of the katE genes into transgenic tomato genome. RT-PCR analysis confirmed that kat-E could be expressed normally in the transgenic plants. Green house experiment was conducted to investigate the effect of the introduced kat-E gene on tomato fungal tolerance. The data showed that the transgenic lines expressed different levels of fungal tolerance as expressed by the performance of plants disease severity and catalase concentration. These results sho