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ARS Home » Research » Publications at this Location » Publication #296682
Title: Breeding for resistance/tolerance to HLB within citrus

Author
item Stover, Eddie
item McCollum, Thomas
item Driggers, Randall
item Lee, Richard
item Shatters, Robert - Bob
item Duan, Ping
item RITENOUR, MARK - University Of Florida
item CHAPARRO, JOSE - University Of Florida
item Hall, David

Submitted to: Acta Horticulturae
Publication Type: Proceedings
Publication Acceptance Date: 1/20/2013
Publication Date: N/A
Citation: N/A

Interpretive Summary: Huanglongbing (HLB) disease is now widespread across the southern half of the Florida peninsula, and is found in every citrus producing county and has now been found in California and Texas as well. The disease greatly debilitates trees and sometimes contributes to tree death. Development of citrus cultivars resistant to HLB is the best long-term control solution for diseases such as HLB in Florida. Compared to other tested cultivars in experiments outside the U.S., lower susceptibility to HLB associated with Candidatus liberibacter asiaticus (CLas), has been reported for limes, pummelos, lemons, some mandarin types and various non-cultivated Citrus or related species. Because of this continued evidence of HLB resistance in C. trifoliata, several trials are now underway using diverse trifoliates and their hybrids, including some advanced material with near commercial fruit quality. The hope is that molecular markers can be identified to facilitate resistance through conventional breeding and/or genes can be used to generate HLB-resistant standard cultivars using biotechnology. Results also suggest useful resistance or tolerance to HLB may be found in conventional scion cultivars and further work is needed to assess this potential and its commercial value, and to mobilize such resistance into the range of commercial fruit types necessary to satisfy consumer demands. The USDA citrus breeding program has used a large genetic base to create unique hybrids, many of which are exposed to HLB in our Florida farms. In addition to the studies described, a number of hybrids and even a few cultivars appear to have useful tolerance or resistance to HLB. A major focus of our breeding program is to characterize this resistance/tolerance and use it to breed new citrus which also have outstanding fruit quality in a range of fruit types (oranges, grapefruits, tangerines etc.).

Technical Abstract: Huanglongbing (HLB) disease is now widespread across the southern half of the Florida peninsula, and is found in every citrus producing county and has now been found in California and Texas as well. The disease greatly debilitates trees and sometimes contributes to tree death. Development of citrus cultivars resistant to HLB is the best long-term control solution for endemic diseases such as HLB in Florida. Compared to other tested cultivars in experiments outside the U.S., lower susceptibility to HLB associated with Candidatus liberibacter asiaticus (CLas), has been reported for limes, pummelos, lemons, some mandarin types and various non-cultivated Citrus or related species. Because of this continued evidence of HLB resistance in C. trifoliata, several trials are now underway using diverse trifoliates and their hybrids, including some advanced material with near commercial fruit quality. The hope is that molecular markers can be identified to facilitate introgression of resistance through conventional breeding and/or genes can be used to generate HLB-resistant standard cultivars using transgenic methods. Results also suggest useful resistance or tolerance to HLB may be found in conventional scion cultivars and further work is needed to assess this potential and its commercial value, and to mobilize such resistance into the range of commercial fruit types necessary to satisfy consumer demands. The USDA citrus breeding program has used a large genetic base to create unique hybrids, many of which are exposed to HLB in our Florida farms. In addition to the studies described, a number of hybrids and even a few cultivars appear to have useful tolerance or resistance to HLB. A major focus of our breeding program is to characterize this resistance/tolerance and incorporate it into genotypes which also have outstanding fruit quality in a range of market phenotypes.