Transgenic Resistance Confers Effective Field Level Control of Bacterial Spot Disease in Tomato

Abstract

We investigated whether lines of transgenic tomato (Solanum lycopersicum) expressing the Bs2 resistance gene from pepper, a close relative of tomato, demonstrate improved resistance to bacterial spot disease caused by Xanthomonas species in replicated multi-year field trials under commercial type growing conditions. We report that the presence of the Bs2 gene in the highly susceptible VF 36 background reduced disease to extremely low levels, and VF 36-Bs2 plants displayed the lowest disease severity amongst all tomato varieties tested, including commercial and breeding lines with host resistance. Yields of marketable fruit from transgenic lines were typically 2.5 times that of the non-transformed parent line, but varied between 1.5 and 11.5 fold depending on weather conditions and disease pressure. Trials were conducted without application of any copper-based bactericides, presently in wide use despite negative impacts on the environment. This is the first demonstration of effective field resistance in a transgenic genotype based on a plant R gene and provides an opportunity for control of a devastating pathogen while eliminating ineffective copper pesticides.

Tomato (Solanum lycopersicum L.) in the service of biotechnology

“…For example AvrBs2 (an effector that is highly conserved in a number of Xanthomonas species) is recognized by Bs2 R protein in pepper (a close relative of tomato). Horvath et al (2012) investigated whether the obtained Bs2 transgenic tomato lines are resistant to different bacterial strains. Their results showed that all tested genotypes from the Bs2 lines had developed high resistance to bacteria as compared to the control group.…”

Synthetic Botany

“…Selective breeding still plays a major role in the production of new varieties but the emergence of modern plant biotechnology has led to a more targeted approach to increasing crop yields. Traits of agricultural importance successfully introduced to plants using recombinant DNA technology include herbicide resistance (Comai et al 1985), drought resistance (Kumar et al 2014), pest resistance (Bates et al 2005), pathogen resistance (Brunner et al 2011;Horvath et al 2012;Jones et al 2014), abiotic stress resistance (Jaglo-Ottosen et al 1998), enhanced photosynthetic capacity (Ku et al 2001), im-proved nitrogen use efficiency (Yanagisawa et al 2004), and added nutritional value (Ye et al 2000). However, although plants hold a unique promise for bioproduction at the gigatonne scale, efforts in genetic engineering of plants are lagging compared with microbial systems (Antunes et al 2009(Antunes et al , 2011Liu et al 2011Liu et al , 2013Koschmann et al 2012;Wend et al 2013;Zurcher et al 2013;Fethe et al 2014;Mül-ler et al 2014).…”

Application of Genetic Engineering in Plant Breeding for Biotic Stress Resistance

“…The R protein Bs2 has been identified in pepper, and is able to recognize a highly conserved Xanthomonas effector named AvrBs2, thus triggering HR. The evidence shows that trials have shown that transgenic tomato plants expressing the Bs2 gene show high disease resistance and significant increased yield (Horvath et al, 2012) Although very promising, resistance based on the deployment of a single R gene can be rapidly overcome by the pathogen due to the emergence of resistant strains (Dangl et al, 2013). Moreover, Bs2 specifically recognizes a single effector in a specific species, limiting the use of these resistant tomato lines.…”