L. Galipienso et al., Host range and symptomatology of a graft-transmissible pathogen causing bud union crease of citrus on trifoliate rootstocks, PLANT PATH, 49(2), 2000, pp. 308-314
A graft-transmissible pathogen causing bud union crease of Nagami kumquat S
RA-153 on Troyer citrange was characterized for host range and symptomatolo
gy. Buds of Marsh grapefruit, Nules clementine, Eureka lemon and Pineapple
sweet orange preinoculated with kumquat SRA-153 were propagated on citrange
rootstocks. Some plants of Nules clementine and Eureka lemon had developed
bud union crease six months after propagation, whereas all Marsh grapefrui
t and Pineapple sweet orange plants still showed normal bud union after one
year. On indexing these preinoculated species, Nules clementine and Eureka
lemon caused vein clearing in Pineapple sweet orange and Dweet tangor, chl
orotic blotching in Dweet tangor and stem pitting in Etrog citron, whereas
Marsh grapefruit and Pineapple sweet orange caused only chlorotic blotching
in Dweet tangor and stem pitting in Etrog citron. Following shoot-tip graf
ting in vitro of kumquat SRA-153, kumquats 38-1 and 497-2 obtained from it
caused chlorotic blotching in Dweet tangor and stem pitting in Etrog citron
, but not vein clearing in Pineapple sweet orange and Dweet tangor or bud u
nion crease when propagated on citrange. These results suggest the presence
of at least two pathogens or pathogen strains in kumquat SRA-153 and the e
limination of one of them after shoot-tip grafting in vitro or inoculation
on Marsh grapefruit or Pineapple sweet orange. They also indicate that the
pathogens in kumquat SRA-153 can be detected by indexing on Dweet tangor or
Etrog citron.