Project Number: 6034-21000-014-09-R
Project Type: Reimbursable Cooperative Agreement
Start Date: Jul 1, 2012
End Date: Jun 30, 2015
To produce citrus scion genotypes which are resistant to huanglongbing (HLB) using conventional plant breeding and on-transgenic biotechnology.
In the USDA breeding program several hybrids display tolerance to huanglongbing (HLB), with plants testing positive for Liberibacter but continuing to grow and crop well. Among commercial cultivars, Temple has the best HLB-resistance in initial tests. In this study, we will quantify the HLB-resistance/tolerance of priority material to determine its value in commercial Florida citrus production. We will also develop tissue culture derived material in which resistant genotypes form the vascular system and standard varieties produce the fruit quality layers. Such chimeras exist as commercial cultivars in China. Like scions on rootstocks, these chimeras use genotypes for their best traits in each plant portion, with proven methodology. The tissue culture "internal grafting" procedure to produce periclinal chimeras was developed by Ohtsu (Ann. Phytopath. Soc. Japan 60:82-88) and further demonstrated by Sugawara et al. (HortScience 30:1276 -1278) in Japan. Since the tissue layer forming the phloem and xylem contribute little to the juice vesicles, use of an HLB-resistant internal layer may provide a rapid and sustainable solution to HLB using established fruiting types. Material displaying promise will be further tested for fruit quality and other characteristics, while being field tested against standards to assess HLB resistance.