Analysis of r-genes in Australian limes in comparison to commercial citrus cultivars

Authors: LIU, JIANYANG - Department Of Energy; SINGH, K - University Of Tennessee; HUFF, M - Texas A&M University; PARK, J - University Of Tennessee; RICKMAN, T - University Of Tennessee; Keremane, Manjunath; Krueger, Robert; ZHENG, P - Washington State University; HUMANN, J - Washington State University; KUNTA, M - Texas A&M University; ROOSE, M - University Of California, Riverside; MAIN, D - Washington State University; STANTON, M - University Of Tennessee; RAMADUGU, C - University Of California, Riverside; Dardick, Christopher - Chris

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 11/8/2023
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Huanglongbing (HLB) is a devastating threat to the citrus industry, due to a lack of effective control measures and a lack of HLB resistant cultivars. Several species of Australian native limes have been recognized to have remarkable tolerance or resistance to HLB and are thus hypothesized to harbor unique genes that confer resistance against HLB. Therefore, identifying resistance (R) genes, which confer pathogen-specific responses, would help us better understand HLB pathogenesis and facilitate breeding for resistance in citrus. In this study, we identified putative R-genes in three Australian native limes (Citrus australasica, C. inodora and C. glauca) in comparison to two commercial cultivars C. clementina and C. sinensis. Our results showed there are 300-600 R-genes in the Australian limes, among which about half have either a Coiled Coil (CC) domain or a Toll-Interleukin receptor (TIR) domain. Despite their distinct evolutionary history, the total number and composition of R-genes in Australian limes are largely similar to those in C. clementina and C. sinensis. Phylogenetic analysis indicates R-genes from all the five genomes are largely grouped together according to R-gene types. R-gene clusters occurred in many of the same chromosomal locations, however, important differences were identified that indicate the potential presence of unique R-gene clusters in Australian native limes. Analyses in motifs, mutations and synteny revealed several distinct evolutionary patterns in Australian native limes, relative to their cultivated counterparts. This study shed light into the structure and organization of R-genes in Australian native limes and will thus potentially assist development of resistant varieties.