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POSTERS: Abiotic interactions

Huanglongbing-irrigation pH interaction affects disease progression
Sadikshya Sharma - University of Florida. Lushan Ghimire- University of Florida, Evan Johnson- University of Florida, Tripti Vashisth- University of Florida, Davie Kadyampakeni- University of Florida

Huanglongbing (HLB), associated with ‘Candidatus Liberibacter asiaticus’, is the greatest limitation in citrus production with root loss as one of the first symptoms. Field observations indicated irrigation water quality and soil pH greatly affect fibrous root health signifying the possibility of a pH-HLB interaction. An experiment was set with the objective to evaluate the effect of irrigation water pH on performance of healthy and HLB-affected citrus plants. Healthy and HLB-affected ‘Midsweet’ sweet orange grafted on Kuharske citrange arranged in a randomized complete block design with 7 replicates and irrigated every 4-5 days with phosphate buffers at pH 5.8, 6.4, 7.0 and 8.0 were monitored for 6 weeks. HLB-affected plants at pH 5.8 showed greater increase in plant height with 100% survival rate compared to highest death rate at pH 8.0. Soil media of HLB-affected plants had higher electrical conductivity (EC) than healthy plants at pH 8.0 indicating poor nutrient uptake by roots, not just nutrient unavailability. At pH 8.0, HLB-affected plants had more leaf drop leaving just 0.25g leaf fresh weight on the plant compared to 15g on healthy plants. Among all treatments, HLB-affected plants at pH 8.0 had the most limited root growth and development pattern, leading to lowest root dry weight. In contrast, at pH 5.8, HLB-affected plants had the same root dry weight as healthy plants. HLB symptoms were more prominent at pH 8.0 suggesting irrigation water pH management as a potential option for minimizing HLB effects.