Performance of Two Citrus Species Grafted to Different Rootstocks in the Presence of Huanglongbing Disease in Puerto Rico

Since Huanglongbing (HLB) disease was detected in 2009 in Puerto Rico, a steady drop in citrus production has been experienced, forcing farmers to abandon their land or switch to other crops. Between 2015 and 2016, we used grafted trees from two experimental orchards (Tahiti lime and Nova mandarin), each on five rootstocks, to collect soil and plant tissue samples from each scion‒rootstock combination to determine soil fertility, tissue nutrient content, and yield. The tree growth parameters (height, diameter, and canopy volume) and efficiency of the two orchards were also measured. These orchards, growing in Coto series (Typic Hapludox), were planted in 2009 and reported as heavily infested with HLB by 2011. Our results showed that soil and tissue samples from the Tahiti lime orchard exhibited benefits for tree growth parameters when grafted on Carrizo and Cleopatra rootstocks. Lower tree mortality (13%) was observed for Tahiti lime grafted on Carrizo, HRS 812, Carrizo and Rough lemon rootstocks, while 25% of the Nova mandarin trees perished on the same rootstocks. Yield was higher for Tahiti lime grafted on Swingle rootstock (35.6 fruit m−3) as compared to the other rootstocks. In general, HLB appears to have caused poor development and low production in the Nova mandarin orchard.