In planta transformation of three Bangladeshi tomato varieties with a vacuolar antiporter

Abstract

Salinity is one of the major obstructions in Bangladesh towards achieving maximum crop production. Being a consequence of climate change, soil salinity has rapidly increased over the years without any remedy in sight. Along with other major crops, tomato, an economically important and nutritionally wholesome crop, is being affected adversely. On top of that, demand of tomato in the country is on the rise. Hence, research on developing salinity tolerant tomato has been given considerable priority. Although a large number of studies have been carried out for salinity tolerance in rice, studies on tomatoes are not that prominent. In this study, an attempt was made to transform tomato seeds of three varieties: BINA Tomato 2, BINA Tomato 3 and Bahar. The gene of interest was AtNHX1 (under the constitutive promoter CaMV35S), a vacuolar antiporter from Arabidopsis thaliana which has been shown to possess significant potential to confer tolerance against salinity. For transformation, in planta method was chosen to attain a sizeable percentage of putatively transformed seedlings after selection. In this method, seeds were infected with Agrobacterium strain LBA 4404 carrying plasmid pK7WG2_AtNHX1_1.6 for 15 and 30 minutes in an optimized bacterial density of 0.8-1.2 at OD600. The various morphological parameters of infected and non-infected plants were documented both for in vitro stage and mature stage in natural environment. Though some striking features of the putatively transformed plants in the early stages such as: higher time requirement for germination, lower height and root strength were observed, no significant differences were seen in overall survival percentages between control and putatively transformed plants of BINA Tomato 3 and Bahar. In mature stage, putatively transformed plants of all the varieties showed similar height to controls but higher total average leaf surface area (at a larger extent in BINA Tomato 3 and Bahar). Though time periods needed for flowering and fruiting were lower in controls (in most cases), the fruiting percentages were considerably higher in putatively transformed plants. Finally, in leaf bioassay of one putatively transformed plant, tolerance to 100 mM salt for 12 days was observed. Though it is a long way to commercial release, this study presents the potential of in planta method and AtNHX1 to attain a salinity tolerant tomato variety without any marked morphological or reproductive disadvantages.