Further investigations on colonization of Poncirus trifoliata by the Asian citrus psyllid

Authors: Hall, David; George, Justin; Lapointe, Stephen

Submitted to: Crop Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/13/2015
Publication Date: 3/17/2015
Citation: Hall, D.G., George, J., Lapointe, S.L. 2015. Further investigations on colonization of Poncirus trifoliata by the Asian citrus psyllid. Crop Protection. 72:112-118.

Interpretive Summary: The Asian citrus psyllid is an important insect pest of citrus because it vectors bacteria responsible for citrus greening disease. Growers apply insecticides as a tactic to manage the disease but with little success. Plant resistance might be a viable alternative management, and resistance to the psyllid has been reported in the genotype Poncirus trifoliata, which is cross compatible with citrus. The Citrus Research Center in Riverside, California, maintains a large number of accessions of P. trifoliata. We conducted experiments with 29 accessions, the results of which collectively showed that 12 accessions have resistance to the psyllid. However, the level of resistance in these accessions has been variable possibly due to environmental conditions, plant age, proximity of plants to susceptible germplasm, and other factors.

Technical Abstract: The Asian citrus psyllid (ACP), Diaphorina citri Kuwayama (Hemiptera: Liviidae) vectors a bacterium, ‘Candidatus Liberibacter asiaticus’ (CLas), associated with one of the world’s most serious diseases of citrus, huanglongbing (HLB) (also known as citrus greening disease). There is no known cure for this disease, which severely reduces tree productivity and fruit quality and promotes tree decline and death. Growers apply insecticides to control ACP as a tactic to prevent or reduce the incidence of HLB but with little or no success. Plant resistance to ACP might be a viable tactic for managing ACP and thus CLas, and resistance to colonization by ACP populations has been reported in the genotype Poncirus trifoliata L., which is cross compatible with citrus. The Citrus Research Center (CRC) in Riverside, California, maintains a large number of accessions of P. trifoliata. We conducted four free-choice experiments with a total of 29 CRC accessions of P. trifoliata and found that 19 were colonized by fewer eggs than a susceptible sweet-orange cultivar. Subsequent infestation densities of nymphs generally reflected reductions in oviposition but there were notable exceptions – some accessions might be susceptible to oviposition but contain traits that confer antibiosis to nymphs. In no-choice experiments with seedling plants representing eight P. trifoliata accessions, oviposition rates were reduced as compared to sweet orange and it appeared that factors associated with mature leaves could have been involved. In no-choice experiments with adult ACP confined to flush cuttings, large reductions were observed in numbers of eggs and nymphs on each of five P. trifoliata accessions. Based on these results in conjunction with published reports, accessions that have consistently shown resistance to oviposition include CRC 2554, 3206, 3207, 3209, 3218, 3338, 3412, 3486, 3547, 3548, 3588, and 3882. However, the level of resistance in these accessions has been variable possibly due to environmental conditions, plant age, proximity of plants to susceptible germplasm, and other factors.