First Report of Rhodococcus Isolates Causing Pistachio Bushy Top Syndrome on ‘UCB-1’ Rootstock in California and Arizona

摘要: 'UCB-1' (Pistacia atlantica × Pistacia integerrima) rootstock is a hybrid cultivar widely used by the U.S. pistachio industry. In last three years, large number of micropropagated UCB-1 rootstocks planted in California and Arizona orchards exhibited shortened internodes, stunted growth, swollen lateral buds, bushy/bunchy stem galls with multiple twisted roots minimal branching. Field T-budding success affected was reduced to approximately 30% unusual bark cracking often observed around bud-union. The percentage abnormal within varied from 10 90%. We have termed cumulative symptoms "pistachio bushy top syndrome" (PBTS) describe these trees. Two isolates, both containing virulence factors phytopathogen Rhodococcus fascians, were identified on symptomatic trees field nursery samples. Micropropagated inoculated isolates internode length, sylleptic branching, differences root morphology, compared control To our knowledge, this first report related causing disease commercial tree crop results presented indicate that organism responsible at least part for PBTS Arizona.