Title: Conventional and transgenic resistance/tolerance to Huanglongbing in citrus Authors
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: September 1, 2012
Publication Date: N/A
Technical Abstract: Huanglongbing (HLB) is severely impacting Florida citrus, and has been found in California and Texas. Citrus researchers are immersed in extensive and broad-ranging efforts to identify solutions to HLB. Previous research indicates susceptibility to HLB throughout cultivated citrus: in FL none are immune and many are extremely adversely affected. Numerous transgenic strategies are underway to develop HLB/psyllid resistance in established cultivars, some show promise, and new ideas are added regularly. With HLB widespread in Florida, it is clear that not all cultivars are affected equally. HLB was assessed in commercial groves with high HLB-incidence: Temple had the mildest HLB symptoms and lowest Liberibacter (Las) titer, while Murcott and Minneola had the most severe symptoms and highest titer. The USDA Fort Pierce farm is managed to reveal genotype HLB responses. Some current cultivars and conventional hybrid seedlings demonstrate resistance/tolerance, at least to strain(s) of Las present. Some have abundant foliage symptoms, but full canopies and seemingly normal fruit set and size. For example, in a 3-year replicated trial of the grapefruit types Triumph(T), Jackson(J), Flame(F), and Marsh(M), all trees had HLB symptoms and similar Liberibacter titers. However T&J maintained full canopies and had fruit with normal size, yield and quality while F&M fruit were fewer and unacceptable. C. trifoliata is the best documented citrus resistance source, and its hybrids are being evaluated, with some already showing near-commercial fruit quality. Useful resistance/tolerance to HLB is present in cultivated citrus and more distant relatives, while transgenic methods offer tremendous potential for greater resistance. All are being investigated by the USDA citrus breeding program and collaborators, as well as other researchers.