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Poster: Diseases of Plants: Disease Detection & Diagnosis


Relative post-inoculation detection frequencies of ‘Candidatus Liberibacter solancearum’ haplotypes in three solanaceous hosts
C. RUSH (1), L. Paetzold (1), F. Workneh (1) (1) Texas A&M AgriLife Research, Bushland, TX, U.S.A.

Candidatus Libreibacter solanacearum’ (Lso), vectored by the potato psyllid (Bactericera cockerelli), is a putative bacterial pathogen, which causes potato zebra chip disease. The pathogen also infects all known solanaceous plants including peppers and tomatoes. Currently there are two haplotypes (A and B) of the pathogen identified from potatoes, and individual psyllids can carry either A or B or both. Greenhouse experiments were conducted to investigate post-inoculation relative incidences of the haplotypes in host plants (pepper, potato, and tomato) and in successive psyllid generations reared on the hosts. Plants were infested with psyllids in 5 cages each (12 psyllids/cage) with each cage containing 2 plants. Psyllids were obtained from a colony in which nearly 90% were positive for A+B (the rest B). Plant and psyllid samples from the cages were collected 3 times (about every 2 weeks) beginning 6 weeks after infestation and tested for Lso haplotypes using qPCR and SYBR analysis. There was a highly significant difference among the hosts in incidence of the haplotypes (Chisq=15.3, P<0.0001). In peppers, 70% of the haplotypes were A, and 30% A+B. Haplotype B by itself was not detected. In potatoes, 75, 18, and 7% of haplotypes were A+B, B, and A, respectively. However, nearly all samples from tomatoes (96.7%) had haplotype A+B (the rest B) but A as a single haplotype was not detected. Haplotype frequencies in psyllids followed a similar detection pattern.