Regeneration and transformation of a maize elite inbred line via immature embryo culture and enhanced tolerance to a fungal pathogen Exserohilum turcicum with a balsam pear class I chitinase gene

Abstract

Maize is one of the most important food crops worldwide and is subject to many diseases. Genetic engineering offers unique way to improve the current elite line via introduces single or multiple traits. In this report, we transformed an elite maize line, Jiao 51, with a balsam pear class I chitinase gene (Mcchit 1) driven by the maize ubiquitin-1 (ubi1) promoter. Conditions for callus induction from immature embryos were optimized using a Jiao 51 by culture on induction medium. The highest Type-I and Type-II callus induction efficiency of 91.33 and 89.10% were obtained on N6 media supplemented with 2.5 mg L-1 2, 4-D. Both types of calli grew fast. Type-I callus could easily change to Type-II callus. Agrobacterium-mediated transformation was used to generate eight transgenic lines that expressed the chitinase transgene. Assessing the functionality of the Mcchit1 protein in the transgenic plants was conducted using an excised leaf challenge assay. The transgenic maize expressing a balsam pear class I chitinase gene exhibited enhanced tolerance toExserohilum turcicum in greenhouse conditions. After 5 days inoculation, the number of lesions was significantly fewer, and the size of lesions was significantly smaller compared to the controls. Key words: Maize (Zea mays. L.), chitinase gene, transformants, fungal disease tolerance, Northern corn leaf blight, Exserohilum turcicum