Reaction of some Persian lime genotypes to ‘Candidatus Phytoplasma aurantifolia’ under greenhouse condition

Lime witches' broom disease associated with ‘Candidatus Phytoplasma aurantifolia’ is one of the most serious threats to lime production in Oman, United Arab Emirates and Iranian southern provinces. In this study, under warm condition (35-37°C and 25-27°C day/night) the reaction of four genotypes of Persian lime including TLCR10, TLCRO, TLC876 (tolerant genotypes) and RA (sensitive genotype) to ‘Ca. P. aurantifolia’ was investigated via graft inoculation. Also, under cool condition (24-26°C and 18- 20°C day/night) using the same inoculation method, the reaction of RA genotype to this pathogen was evaluated. Quantitative PCR was used for detection and quantification of ‘Ca. P. aurantifolia’ in the inoculated plants. At 48 weeks post-inoculation, the copy numbers of ‘Ca. P. aurantifolia’ per 100 ng of total plant DNA in TLCRO, TLC876 and TLCR genotypes was very low (17, 10 and 12, respectively) and no disease symptoms were observed. In RA genotype under warm condition, the mean copy numbers of ‘Ca. P. aurantifolia’ per 100 ng of plant total DNA was higher than that of cool condition and showed significant differences (P < 0.01) . Furthermore, the disease symptoms were only appeared under the warm condition. The results of the present study showed that TLC10, TLC876 and TLCRO genotypes had high tolerance to ‘Ca. P. aurantifolia’ and can be introduced as tolerant or resistant cultivars to ‘Ca. P. aurantifolia’. These tolerant genotypes can be used in genetic breeding programs to produce resistant and tolerant cultivars. The results also indicated that higher temperature may change susceptibility of