A bacterial disease of saffron caused by Burkholderia gladioli and Pseudomonas spp.

Symptoms of a disease of possible bacterial origin were observed
in the leaves and corms of some saffron plots in Sardinia
since October 2003. The leaves had reddish brown spots, that
were either isolated or coalescing and were surrounded by a large chlorotic halo. The corms had yellowish-brown rounded spots,
which tended to become black with time. Isolation on nutrient
agar from corms and leaves produced numerous cream to yellowish-
brown and white-cream bacterial colonies mixed with others
characterized by a yellow hue. Based on their frequency, ten
colonies were selected, four of which were cream to yellowishbrown,
four white-cream, and two yellowish. In pathogenicity
tests, only four of ten isolates reproduced the symptoms on saffron
leaves and corms, and three could also infect tomato plants.
These four virulent isolates were identified with conventional
tests and the computerised system BIOLOG. One isolate was
identified as Burkholderia gladioli, one as Pseudomonas corrugata
while the remaining two were P. fluorescens biotype F. The latter
three isolates reacted positively with a serum to P. corrugata anti
IPVSS-6FP. Fatty acid profiles of two representative isolates confirmed
that one was Burkholderia sp., and the other Pseudomonas
sp. (P. fluorescens/P. marginalis/P. putida). We suggest that isolates
of B. gladioli and Pseudomonas spp. are responsible for the
saffron disease found in Sardinia. B. gladioli has only been reported
once in the literature. Genomic characterization of the other
three pseudomonads is underway.