Resistance of Poncirus and Citrus × Poncirus Germplasm to the Asian Citrus Psyllid

The Asian citrus psyllid (ACP), Diaphorina citri Kuwayama, has spread to citrus growing regions nearly worldwide and transmits phloem‐limited bacteria (Candidatus Liberibacter spp.) that are putatively responsible for citrus greening disease. Host plant resistance may provide the most effective control, but ACP has a broad host range and resistance in Citrus spp. and relatives to ACP has not been widely documented. Very low abundances of ACP were found on two accessions of Poncirus trifoliata (L.) Raf. (hardy‐orange) in a field survey. Therefore, we tested whether 81 accessions of P. trifoliata and ×Citroncirus spp. (hybrids of P. trifoliata and Citrus spp.) from the USDA‐ARS National Clonal Germplasm Repository for Citrus and Dates were resistant to ACP by determining whether these accessions influence oviposition and lifespan of adults in no‐choice tests. There was a higher abundance of eggs on the control (Citrus macrophylla Wester [alemow]) than nearly all accessions of P. trifoliata, and zero eggs were laid on 36% of the accessions. Additionally, more eggs were laid on the control than 10 of 34 accessions of ×Citroncirus spp. Lifespan of adults was approximately 2.5 to 5 times longer on 11 of the 17 trifoliates and trifoliate hybrids we tested. Poncirus trifoliata appears to have antixenosis and antibiosis resistance to ACP, but we must next identify the traits that promote resistance to create commercial varieties of citrus that reduce the population of ACP and lower the incidence of citrus greening disease.