LIBRO-CONGRESO-CITRUS

or Huanglongbing (HLB) and its vector, the Asian Citrus Psyllid (ACP), has completely changed this scenario
and the industry now faces one of its worst nightmares. It is well know that Calcium is one of the most
important elements in the plant that generate signals to be transduced into response to counteract basically
any kind of biotic and abiotic stresses. No information is currently available on the effect that HLB has on
genes regulating calcium signals, however, nutrient leaf analysis shown that Calcium is one the elements that
is reduced upon CLas infection. The objective of this research is to study the effect of CLas infection on the
expression of genes involved in Calcium dynamic in HLB infected Valencia sweet orange young and mature
leaves, asymptomatic and symptomatic, compared to non-infected Valencia orange control. Results by realtime
PCR obtained to date shows strong reduction in expression of a calcium ion channel in young and mature
infected asymptomatic leaves compared to health control. Mature symptomatic leaves also had reduced
expression compared to control, but more expression than young and mature asymptomatic leaves. -Results
for expression of 15 genes involved in calcium signals will be presented.
S12O06
Transcriptional genomics and proteomics in citrus roots infected by Candidatus Liberibacter asiaticus.
Zhong Y.
Institute of Fruit Tree Research, Guangdong Academy of Agricultural Science (GAAS), Citrus Breeding, China. zhongyun99cn@163.com
Jiangxired tangerine root samples at 50 wpi were used in RNA-sequencing. Some DEGs were confirmed by
qPCR. Results showed that: 1) 3956 genes were differentially expressed, among which 1840 were up-regulated
and 2116 down-regulated. 65 DEGs were identified with more than 10-fold changes. 2) SA signal transduction
pathway related genes were up-regulated, the key gene of this pathway, NPR1 was up-regulated 1.6 times,
and the downstream PR1 gene was up-regulated 2.4 times. 3) JA signal transduction pathway related gene
didn’t have notable responses to HLB infection. 4) Sucrose invertase was up-regulated 1.7 times, while the
sucrose synthase were down-regulated 1.8 times. This may indicate that the sucrose level in HLB infected
roots decreased as result of plugged phloem. Furthermore, ferredoxin expression was down-regulated 2.2
times, which may be related to nutrition deficiency, that is commonly associated with HLB infected trees.
Comparative proteomic approach was also applied to decipher the pathogenic process of HLB in affected
red tangerine roots using iTRAQ technique. Results showed that: 1) The 1445 identified proteins mainly
ranged from 20 to 70kDa or larger than 100kDa. 2) plugged phloem related protein SEO was up-regulated by
1.67 times, and this protein may function in inhibiting infection of the HLB bacteria and hampering the long
distance transport of sucrose. Subtilisin-like protease was up-regulated with a fold change of 282.09 and the
gene of this protein was also up-regulated 3.14times, which suggested that the enzyme play important roles
in inhibiting the infection of HLB bacteria and protecting the root meristematic zone.
S12O07
Resistance and tolerance to Huanglongbing in citrus
Stover E. 1 , McCollum G. 1 , Driggers R. 1 , Duan Y.P. 1 , Shatters, Jr. R. 1 , and Ritenour M. 2
1 USDA/ARS, US Horticultural Research Laboratory (USDA/ARS, USHRL), USA; and 2 University of Florida, Indian River Research and
Education Center (U of F, IRREC), USA. ed.stover @ ars.usda.gov
Huanglongbing (HLB) is severely impacting Florida citrus. Productivity declines in many HLB-affected
genotypes, often with greatly thinned canopies. Fruit size and quality are often adversely affected as the
disease advances. HLB was assessed in diverse cultivars in commercial groves with high HLB-incidence.
Temple had the lowest HLB symptoms and Liberibacter (Las) titer, while Murcott and Minneola had the
highest. The USDA Ft. Pierce, FL farm is managed to reveal genotype responses to HLB. Some current cultivars
and hybrid seedlings demonstrate resistance/tolerance, at least to strain(s) of Las present. C. trifoliata is the
best documented citrus resistance source with Las titers suppressed even when C. trifoliata is grafted onto
severely-infected rootstocks. Some cultivars and hybrids have abundant foliage symptoms, but full canopies
and seemingly normal fruit set and size. In 3-years of data from a replicated trial of Triumph(T), Jackson(J),
Flame(F), and Marsh(M), HLB symptoms were severe in all trees and Liberibacter titers were similar. However,
F&M were almost completely defoliated in some years while T&J had full canopies. Cumulative fruit/tree was
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S12