Production of transgenic tomato plants with enhanced resistance against the fungal pathogen Fusarium oxysporum

ABSTRACT

Tomato [Lycobersicum esculentum Mill] cultivar CastleRock was used to produce fungal resistant plants by introducing an antimicrobial chitinase gene. Hypocotyl with a part of cotyledon [hypocotyledonary] of young tomato seedlings were used as explant material. The transformation performed by delivering the vector pGL2 harbouring a class I rice chitinase gene [chi11] under the control of the CaMV 35S promoter and hygromycin resistant gene as a plant selectable marker, using biolistic bombardment mediated transformation system. Shoots were regenerated onto selective regeneration medium supplemented with 1 mg/l BAP, 1 mg/l Zeatin ripozide, 5mg/l AgNO[3] and 25mg/l hygromycin, then subjected to rooting medium for developing roots. Putative transgenic plantlets of R0 were confirmed by PCR analysis using specific primers for the transgene, and most regenerated plants showed positive results. However, PCR and dot blot analyses were conducted using R1 seedlings to confirm the stable integration of transgenes in R1 progeny. Bioassay for transgenic plants was performed on the transgenic R1 young seedlings and non-transgenic controls by challenging with a vigorous isolate of the fungal pathogen Fusarium oxysporum f. sp. Lycopersici to assay for the resistance against fusarium wilt disease among individuals. Data from transgenic plants showed lower percentages of infection ranging from 11 to 60% in lines 8 and 5 respectively compared to the control plants [80% infected]. The percentage of resistance ranged from 11 to 77.7% in lines 7 and 8, respectively compared to 10% in non-transgenic control plants. In addition, the average percent of the tolerant seedlings were19.69% that had been infected but showed delayed symptoms and suppression in symptom extension. The obtained results indicated that expression of the chitinase protein [Chi 11] in transgenic tomato plants acquired them antifungal activity against Fusarium