| Texas citrus has been constantly challenged by many biotic and abiotic threats and has so far survived. Currently major diseases attacking US citrus and causing detrimental economic loss are Huanglongbing (HLB), Citrus Canker, Citrus Tristeza Virus (CTV), as well as disease caused by fungal pathogens. The production of disease resistant cultivars through genetic transformation can tremendously benefit the industry. Genetically modified 'Hamlin' and 'Valencia' sweet orange cultivars overexpressing CSM-1 gene, a calcium signal modified gene, were produced through Agrobacterium-mediated genetic transformation in an attempt to create broad-spectrum disease resistance in sweet orange plants. Overexpression of the CSM-1 gene in the transgenic plants was confirmed through quantitative polymerase chain reaction (qPCR). Southern blot hybridization determined all 'Hamlin' and 'Valencia' transgenic plants to contain more then the two CSM-1 gene copies displayed by 'Hamlin' and 'Valencia' non-transgenic plants. Transgenic plants displayed resistance to Phytophthora nicotianae and Xanthomonas citri subsp. citri (Xcc) as evaluated through pathogenicity tests. Lethal freezing temperature (LT50) in 'Hamlin' and 'Valencia' proved no significant difference in 'Hamlin' and 'Valencia' transgenic and non-transgenic. The physiology tests conducted displayed an increase in the amount of photosynthesis, stomatal conductance, and transpiration rates coordinated with a lower rate of WUE in 'Hamlin' and 'Valencia' transgenic plants, when compared to 'Hamlin' and 'Valencia' non-transgenic plants. However, gas exchange in transgenic plants was not altered negatively after transformation. |
