Identifying Disease Resistant Pummelos for Citrus Improvement

Citrus canker and Huanglongbing (HLB) remain scourges of the citrus industry. While citrus canker largely affects the physical appearance of the fruit, it blemishes the fruit such that it becomes unmarketable. Huanglongbing, or citrus greening disease, is lethal to trees in the long term, and while the tree is in decline produces malformed and bitter fruits. Genetic analyses of citrus have shown that the pummelo (Citrus maxima Burm.) is one of the ancestors of the grapefruit as well as other citrus varieties. Identifying a disease resistant variety of pummelo would be useful to breed new, disease resistant varieties of grapefruit or other citrus. Mature, seed grown pummelo trees were examined in the field for evidence of disease in groves where both citrus canker and HLB are present. Trees found to be symptom free of HLB and citrus canker were replicated and subjected to canker inoculation under greenhouse conditions, and in process for HLB positive psyllid inoculation. Identified disease resistant varieties are being used to generate new citrus varieties.