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Suggested support mechanism: Presuming that there is more than one group seeking support for genome sequencing, funds should be awarded competitively.

Time to outcome: Significant sequence information, and perhaps even the entire genome sequence, could be accomplished in less than two years using current high-throughput methods.

Other sections of this report containing related information: Appendix K.


Given the urgency of the HLB situation in Florida, most investments in research and management are necessarily near-term. However, continuing investments in research aimed at longer term solutions remains important. In addition to the four long-term recommendations below, completing the citrus genome sequences and exploiting them to create usable breeding systems for commercial citrus (Recommendation NI-4) should be a priority. The genome sequence, when combined with high-throughput SNP genotyping and other additional information, can facilitate improvement of Florida citrus varieties.

TABLE 4-4 Long-Term Recommendations


Support development of transgenic HLB-resistant and ACP-resistant citrus.


Support development and testing of bactericides, therapeutics or SAR activators.


Support analysis of ACP behavior, ACP-plant interactions and ecology to enhance the knowledge base available for new ACP management strategies.


Explore possible control strategies based on release of modified psyllid males.

Recommendation L-1. Support development of transgenic HLB-resistant and ACP-resistant citrus, including creating suitable anti-CLas and anti-ACP genes.

It is generally agreed that CLas- or ACP-resistant citrus would provide the ideal long- term management tool for HLB. Currently, the most promising path to developing resistant citrus involves genetic engineering (GE). Advances in GE approaches include techniques to utilize mature tissue, to bypass the juvenile stage and accelerate the transformation and regeneration process (Cervera et al., 1998). Other research groups are exploring transgenes that may confer resistance to pathogens other than CLas or greater tolerance to low temperatures. To expedite rapid screening of candidate trait genes, Citrus tristeza virus (CTV)-derived vectors are available for stable transient expression in citrus (Folimonova et al., 2007) and can be used to provide a testbed for gene constructions designed to have anti-CLas or anti-ACP activity.

Although there are non-citrus plants that demonstrate resistance to CLas or ACP, such plants are not likely to be sources of genes useful in citrus because of inter-species incompatibility and difficulties in isolating such genes. Sequences encoding anti-CLas transgenes are more likely to be anti-microbial peptides and proteins (AMPs) of animal, plant, microbial or bacteriophage origin (Canny and Levy, 2008; Conesa et al., 2009; Soehnlein, 2009; Mao et al, 2010). Similarly, there are many possible sources for sequences that could encode anti-ACP proteins (Sauvion et

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