Agrobacterium Tumefaciens-mediated Transformation Of MdSPDS1 And HAL2 Genes In Citrus

Citrus is one of the most important fruit crops in the world, with the first cultivated area and production ranking among all the fruit crops. However, citrus industry is also threaten by diseases, destructive insects and natural disaster. Salinaty affect more than 20% of arable lands and half of the irrigation lands in the world, and salinization is rapidly increasing on a global scale. There are 30 million hm² halomorphic lands in China. Attempts to improve the salt tolerance of citrus through conventional breeding programmes have met with limited success, due to long juvenility, polyembryony, high genetic heterozygosity and parthenogenesis. Agrobacterium tumefaciens-mediated genetic transfer and cloning of a variety of stress-related genes provide an alternative for citrus cultival improvement with the intention of enhancing stress-tolerance.In this research, the MdSPDS1 and HAL2 were transformed into embryogenic callus and epicotyls of several citrus cultivars by Agrobacterium tumefaciens. The main results are as follows:1 The effects of Kanamycin on Skagg's Bonanza Navel orange and Florest navel orange callus were investigated. It showed that suitable concentration for selection of resistant callus was 50 mg/L.2 Efficient regeneration media for Ponkan and Jincheng orange epicotyl were optimized primarily. It showed that BA played an important role in the process of the regeneration and its appropriate concentration was 1.0 mg/L. The optimum regeneration media for Ponkan explants cultured horizontally and vertically were MT plus 1.0 mg/L of BA and 0.5 mg/L of IAA and MT plus 1.0 mg/L of BA and 1.0 mg/L of IAA respectively. The optimum medium for Jincheng orange epicotyl cultured horizontally was MT plus 1.0 mg/L of BA and 0.5mg/L of IAA.3 Several factors affecting transformation of Skagg's Bonanza Navel orange callus were initially optimized. The highest transformation efficiency was obtained when the explants were infected for 15 to 20 minutes at OD₆₀₀ of 0.8 and co-cultivated for 3 days.4 The resistant callus were obtained by transformation of Skagg's Bonanza Navel orange with the MdSPDS1 and HAL2 gene respectively. The resistant callus still grew...